co2 and nh3 operation manual

_551511_om_kas_gbr_1_.doc 1

CO /NH2 3 Cascade unit 250 - 1000 kW

Operating Instructions

OPERATING INSTRUCTIONS

CO2/NH3 CASCADE UNIT 250 - 1000 KW

2 _551511_om_kas_gbr_1_.doc

COPYRIGHT

All Rights reserved. No part of this publication may be copied or published by means of printing, photocopying, microfilm or otherwise without prior written consent of Grasso. This restriction also applies to the corresponding drawings and diagrams.

LEGAL NOTICE

This publication has been written in good faith. However, Grasso cannot be held responsible, neither for any errors occurring in this publication nor for their consequences.




SYMBOLS USED IN THIS MANUAL

Danger!

This is an important warning. Non-observance these warnings can cause accidents with relevant damages on persons or serious damages on the compressor or refrigerating plant.

Warning!

Attention! Caution! Important!

Hint!

Tip! Note!




TABLE OF CONTENTS

1 Operating instructions.......................................................................................................................... 10 1.1 Delivery.................................................................................................................................... 10 1.2 Transport and storage ............................................................................................................ 10 1.3 Transport instructions ............................................................................................................. 10 1.4 Installation............................................................................................................................... 10 1.5 Assembly.................................................................................................................................. 11 1.6 Start-up instructions............................................................................................................... 11

1.6.1 Basics ........................................................................................................................... 11 1.6.2 First commissioning..................................................................................................... 11

1.6.2.1 Leak test....................................................................................................... 11 1.6.2.2 Drying, vacuum............................................................................................ 12 1.6.2.3 Oil charge..................................................................................................... 12 1.6.2.4 Checking the direction of rotation of the driving motor ........................... 15 1.6.2.5 Checking the direction of rotation of the oil pump motor........................ 15 1.6.2.6 Adjustment of oil pressure .......................................................................... 15 1.6.2.7 Mounting the coupling................................................................................ 16 1.6.2.8 Refrigerant charging.................................................................................... 16 1.6.2.9 Operating position of valves ....................................................................... 17 1.6.2.10 Checking the water circuits ....................................................................... 19 1.6.2.11 Initial startup.............................................................................................. 19 1.6.2.12 Setting the setpoint / limit values and safety devices .............................. 20 1.6.2.13 Switching on the CO2 refrigerant pumps.................................................. 20 1.6.2.14 Switching on the compressor .................................................................... 20 1.6.2.15 Checking the adjustment of the control slide........................................... 20 1.6.2.16 Checking the control slide adjustment times............................................ 20 1.6.2.17 Automatic mode........................................................................................ 21

1.7 Shutdown in the event of dangerous situations.................................................................... 21 1.8 Switching off ........................................................................................................................... 21

1.8.1 Normal shutdown ....................................................................................................... 22 1.8.2 Shutting down for a lengthy period .......................................................................... 22 1.8.3 Measures during stoppages ....................................................................................... 22

1.8.3.1 Monthly........................................................................................................ 22 1.8.3.2 Four weeks before putting back into service ............................................. 22

1.8.4 Putting back into service after approx 1 year............................................................ 22 2 Start-up / Operation of GSC ................................................................................................................ 23

2.1 General Information ............................................................................................................... 23 2.2 Description of the Grasso System Control.............................................................................. 23

2.2.1 View............................................................................................................................. 23 2.2.2 Lamps/ Push buttons .................................................................................................. 23 2.2.3 Operator terminal....................................................................................................... 24

2.2.3.1 Key assignment............................................................................................ 24 2.2.3.2 Open table of contents ............................................................................... 26

2.2.4 Status messages .......................................................................................................... 27 2.3 System description GSC........................................................................................................... 29

2.3.1 Explanation of the system LED................................................................................... 30 2.4 Alarms ..................................................................................................................................... 31

2.4.1 View active alarms and warnings............................................................................... 31 2.4.2 No alarm signal and the compressor will not start.................................................... 31 2.4.3 Restart following Alarms ............................................................................................ 31

3 Description of Design and Function .................................................................................................... 34 3.1 Brief Description...................................................................................................................... 34



6 _551511_om_kas_gbr_1_.doc

3.1.1 Use ...............................................................................................................................34 3.1.2 Design ..........................................................................................................................34

3.2 Refrigerant circuit ....................................................................................................................35 3.2.1 CO2 low temperature stage.........................................................................................35 3.2.2 NH3 high temperature stage .......................................................................................36

3.3 Oil return system......................................................................................................................36 3.3.1 CO2 circuit oil return system ........................................................................................36 3.3.2 NH3 circuit oil return system........................................................................................36

3.4 Auxiliary refrigeration unit for CO2 separator ........................................................................36 3.5 Safety devices...........................................................................................................................37

3.5.1 CO2 circuit ....................................................................................................................37 3.5.2 NH3 circuit ....................................................................................................................38

3.6 Monitoring devices ..................................................................................................................38 3.6.1 CO2 circuit ....................................................................................................................39 3.6.2 NH3 circuit ....................................................................................................................39

4 Maintenance Instruction.......................................................................................................................40 4.1 General Information ................................................................................................................40 4.2 Servicing/maintenance and safety ..........................................................................................41 4.3 Searching for leaks on refrigerant side / leak test .................................................................41 4.4 Vacuating, charging and draining refrigerant and oil............................................................42

4.4.1 Evacuating the refrigerant (see also initial start-up) ..................................................42 4.4.2 Charging with refrigerant (see also initial startup; initial charge with refrigerant) ..42 4.4.3 Charging characteristics...............................................................................................43 4.4.4 Draining the refrigerant ..............................................................................................43

4.4.4.1 General notes on draining refrigerant.........................................................43 4.4.4.2 Charging refrigerant.....................................................................................43 4.4.4.3 Connections for draining refrigerant...........................................................44

4.4.5 Venting the refrigerant circuits ...................................................................................44 4.5 Charging and draining oil (see also putting into service).......................................................44

4.5.1 General notes on handling refrigerator oil.................................................................44 4.5.2 Check oil level ..............................................................................................................44 4.5.3 Oil filling.......................................................................................................................44 4.5.4 Draining, changing, checking oil .................................................................................44 4.5.5 Used oil ........................................................................................................................45

4.6 Maintenance Work ..................................................................................................................45 4.6.1 General notes...............................................................................................................45 4.6.2 Opening the compressor (see also compressor maintenance instructions)...............45 4.6.3 Dismantling the compressor suction filter (see the compressor maintenance instructions) .............................................................................................................................46 4.6.4 Replacing the suction filter..........................................................................................46 4.6.5 Changing the suction filter before refrigerant pump - CO2 circuit.............................46 4.6.6 Oil change....................................................................................................................46

4.6.6.1 Meaning........................................................................................................46 4.6.6.2 Maintenance Work.......................................................................................47 4.6.6.3 Changing the oil ...........................................................................................47

4.6.7 Replace oil filter ...........................................................................................................47 4.6.8 Changing the filter driers - CO2 circuit ........................................................................48 4.6.9 Clutch maintenance.....................................................................................................48 4.6.10 Oil pump maintenance (for external oil pump)......................................................48 4.6.11 Checking the pull-in torques at fastener of fixing base ...........................................48 4.6.12 Changing the oil fine separation cartridges .............................................................48 4.6.13 Finding and fixing leaks.............................................................................................49 4.6.14 Cleaning the heat exchangers (heat-carrier / cooling agent sides) .........................49




4.6.14.1 Chemical cleaning ...................................................................................... 49 4.6.14.2 Mechanical cleaning .................................................................................. 49

4.7 Steps to be followed before starting the system after major repairs ................................... 50 4.7.1 Repair information...................................................................................................... 50 4.7.2 Pressure test, leak test ................................................................................................ 50 4.7.3 Vacuum Test................................................................................................................ 50

4.8 Repair work............................................................................................................................. 50 4.9 Guide to disturbances, their causes and remedies................................................................. 51




TABLE OF FIGURES

fig. 1: Vacuum required to remove moisture from refrigerating plants .................................................... 12fig. 2: Motor direction of rotation ............................................................................................................... 15fig. 3: Stop valve opened ............................................................................................................................. 17fig. 4: Stop valve closed................................................................................................................................ 17fig. 5: Check valve......................................................................................................................................... 17fig. 6: Combined stop/ check valve.............................................................................................................. 17fig. 7: Control valve ...................................................................................................................................... 17fig. 8: Combined stop/ check valve with integrated control function........................................................ 17fig. 9: Solenoid valve .................................................................................................................................... 18fig. 10: Change-over valve............................................................................................................................ 18fig. 11: oil pressure regulating valve ............................................................................................................ 18fig. 12: Overflow valve, safety valve ............................................................................................................ 18fig. 13: Pressure controlled check valve ....................................................................................................... 18fig. 14: Quick acting valve, spring-held ........................................................................................................ 18fig. 15: Charging valve, draining valve......................................................................................................... 18fig. 16: Service valve ..................................................................................................................................... 18fig. 17: Oil temperature limiter .................................................................................................................... 19fig. 18: Temperatur controlled valve ........................................................................................................... 19fig. 19: Thermostatic expansion valve.......................................................................................................... 19fig. 20: Solenoid valve plate with throttle screws ....................................................................................... 20fig. 21: Exterior view GSC............................................................................................................................. 23fig. 22: GSC operator terminal ..................................................................................................................... 24fig. 23: "Status messages" display................................................................................................................. 28fig. 24: Restart following Alarms ................................................................................................................. 32fig. 25: Diagram of the main components of the CO2/NH3 cascade, Part 1............................................... 34fig. 26: Diagram of the main components of the CO2/NH3 cascade, Part 2............................................... 35fig. 27: Oil fine separation cartridge............................................................................................................ 49



10 _551511_om_kas_gbr_1_.doc

At the same time, check the nitrogen filling and recharge to the specified overpressure of 0.3 bar ... 0.5 bar, if required. Dry nitrogen with a residual moisture of ≤ 300 ppm is used for this purpose.

1 OPERATING INSTRUCTIONS

1.1 Delivery

CO /NH2 3-cascade units are delivered with an inert gas charge (nitrogen) in the refrigerant circuit. The heat exchanger connections are closed. Check on arrival for possible transport damage and report damage in writing.

Warning!

Cascades are to be adequately protected from external influences during transport and storage.

This usually concerns lengthy standing times outdoors before installation and putting into service of the refrigeration plant.

Protect cascades from damage, dirt and moisture during longer periods of storage prior to setup/installation.

(check inert gas charge) Grasso recommends the use of plastic sheeting to cover the whole product. The compressors of the cascade unit are not charged

with oil, therefore the cascade must not be started unless properly installed and commissioned. The venting slots of the electric motors

must always be covered! Dispatch is effected in the type of packing stipulated in the order. The cascade unit is generally supplied without packing. 1.3 Transport instructions

Use the four carrier eyes on the base frame as slinging points for crane transport. 1.2 Transport and storage

Cascades are high-quality products which must be handled with due care. Protect the equipment from impacts and put it down carefully.

To prevent damage on piping and components attach crossbeams to the ropes.

Hint! When transported by crane, the cascade must have the same position as in operation. Do not use attaching points other than those provided for this purpose.

Pushing and pulling on components or climbing on the cascade unit or pipes easily causes damage and should be avoided at all costs. All the information needed to manipulate the

cascade is indicated in the "Transport Instructions".

After completion of erection on the foundation, and prior to starting up the cascade remove the transport safety devices installed in the works.

Warning!

It is prohibited to sling cascade units to any fittings or piping or at the eye screws/carrying ears on compressor, electric motor or switch cabinet.

The cascade unit should only be stored in closed, dry rooms if possible. Storage in the open air under a roof is only permissible for short periods.

Take special care not to attach the ropes near to small diameter tubing or to damage the same. Use spacers if necessary.

1.4 Installation

Select the installation site with care so that any possibly leaking substances do not penetrate the ground or enter the surface or ground water (Water Supply Law WHG).

Position the cascade on the transport vehicle such that it is prevented from sliding and tilting. The competent staff member or the company is responsible for ensuring transport safety. The cascade units have to be installed in closed

machine rooms and on a level surface. Provide enough space for maintenance work. The storage area of cascades shall be roofed, plain

and paved and secured against access of unauthorized persons. The cascade must be protected against knocks and impacts.

Rigid installation

The frame of the cascade unit is placed on foundation bolts on a prepared foundation. Turn the shaft of the compressor at least every four

weeks (approx. 1/8 revolutions). The frame must be levelled with suitable shims such that the coarse alignment (radial and angular



_551511_om_kas_gbr_1_.doc 11

• COmisalignment ≤ 0.25 mm) at the coupling is attained again.

- vent line 2

• NH3 - safety vent line Then tighten the foundation bolts.

• Electrical connection cable (see electrical connection diagram) Installation with anti-vibration mounts

The frame of the cascade unit shall be aligned with the levelling bolts until the coarse alignment (radial and angular misalignment ≤ 0,25 mm) at the coupling is attained again.

1.6 Start-up instructions

1.6.1 Basics

The cascade may only be operated by trained and qualified personnel who are familiar with the contents of the user manual for Grasso CO

Unless otherwise required by local conditions, the permissible ambient temperatures for operation are +15 to +40°C.

/NH2 3 cacades.

The safety regulations for refrigerating plants must always be correctly complied with in order to prevent operating personnel injuries and damage to the cascade.

All foundation calculations, the selection of materials and the soil analysis are owner’s responsibility.

Outside influences (vibrations, jolts) must be avoided. The cascade is operated from the control panel of

the compressor control. The unit may only be lifted for alignment by the mounting rails or by a crane. See to it in this connection that the cascade is evenly lifted by two respective small�hoists in the transverse direction when small hoists are used (e.g. hydraulic hoists).

After the setpoint values have been entered, both automatic and manual mode are possible.

The compressor control equipment's software and operating via the terminal are described elsewhere.

1.5 Assembly 1.6.2 First commissioning

Cascades dismantled in the factory for transport and positioning purposes must be carefully reassembled at the installation site according to the drawing and the PID.

The following procedures should be completed in the sequence in which they are described:

1.6.2.1 Leak test The separation points (flanged connections) of cold pipes must be insulated. The necessary safety precautions must be taken

before carrying out the leak test. The leak test is performed with dried, oil-free air or with dry nitrogen.

All pipes and electrical cables must be connected so that no mechanical stresses or strain occurs.

Connecting the pipes To check for leaks, a 3-hour test is carried out with dry air or dry nitrogen at any overpressure, but not higher than the allowable operating overpressure of the cascade.

• Before connecting the pipes, drain the cascade's nitrogen filling by opening the vent valves.

• All pipe connections are to be made so as to limit transmission of thermal expansion and vibration to the cascade as far as possible.

During the 3 hours a pressure drop of 2% is allowed, whereby fluctuations in the ambient temperature must be taken into account.

• Rubber expansion joints can be used for water connections. Warning!

Control devices which may be damaged at the given test pressure must be removed or blocked off before the leak test is performed.

• All pipe connections are to be fitted with fixed points directly on the cascade.

The following are to be connected

• NH3 connection to condenser

• Cooling water for oil cooler A record should be kept of the leak test, in which the the pressure in the lines to be tested, the ambient temperature and the temperature outside in the shade must be entered at hourly intervals.

• Connections for refrigerant-cooled oil cooler

• CO pump discharge line 2

• CO - return line 2



12 _551511_om_kas_gbr_1_.doc

After the leak test has finished and it has been established that the cascade is free of leaks, reinstall any instrumentation and control devices removed.

Warning!

Check the oil grade to be charged. See contract / project or Grasso recommendation. 1.6.2.2 Drying, vacuum

After the leak test has been completed, the system is evacuated and subjected to a vacuum test for 3 hours. Evacuation is used to remove air and moisture from the system.

The quantity of oil to be charged for the respective compressor is given in the compressor documentation.

During the 3 hour period the vacuum reached may rise by maximum 5 torr. Warning!

Due to the use of selected components, the refrigerator oils tend to absorb more moisture. Therefore, when charging a compressor the oil should be allowed to come into contact with air for a short time only. The contents of an opened drum have to be used up within one working day, provided the drum is properly closed between charging.

fig. 1: Vacuum required to remove moisture from

refrigerating plants

A Vacuum

B Room or wall temperature

After the required vacuum has been reached measured values must be logged hourly. After the negative pressure (vacuum) value, the temperatures in the machine house and the outdoor temperatures in the shade must be entered in the log. After the vacuum test the pressure must be equalized with refrigerant.

Warning!

Shut off the oil pump during evacuation!

1.6.2.3 Oil charge

The compressor is filled (charged) with oil in the NH3 or CO2 circuit according to the compressor's user instructions.

The vacuum present in the cascade unit before pressure compensation can be utilized for the first oil charge. A separate oil recharging pump is required after the pressure compensation and for refilling with oil.

1.6.2.3.1 Oil charge - NH3 side

The connection of the oil draining/oil charging shut-off valve (090) must be connected with the oil charging tank.

Switch the valves to the operating position before charging with oil.

Open the shut-off valve (090) until the oil level has reached the top third of the oblong sight glass in the oil separator sump.

The oil separator is generally charged with oil via the oil cooler.

When charging with oil for the first time, oil must be charged via the service valve (135) too. To this end the shut-off valve (065) must then be closed.

1.6.2.3.2 Oil charge - CO2 side

The connection of the oil draining/oil charging shut-off valve (5720) must be connected with the oil charging tank.

Before charging with oil, switch the valves to the operating position.

Open the shut-off valve (5720) until the oil level has reached the top third of the oblong sight glass in the oil separator sump.

The oil separator is generally charged with oil via the oil cooler.

When charging with oil for the first time, oil must be charged via the service valve (5710) too. To this end the shut-off valve (5305) must then be closed.



_551511_om_kas_gbr_1_.doc 13

1.6.2.3.3 Permissible oil grades

Special refrigerator oils must be used. The choice of oil grade does not only depend on its viscosity and chemical properties but on the cascade's operating conditions.

The choice of oil depends on the coolant, viscosity (at least 7 cSt at oil temperature before entering the compressor), evaporation temperature (pour point) and the oil separation performance requirements.

Hint!

When choosing an oil grade the compatibility of the sealing material for O-rings (elastomer quality) used in the compressor must be taken into account in addition to the refrigerant used (see overview).

Not all the oil grades listed can be used in an existing compressor. It is absolutely necessary to assign the oil grade depending on the elastomer used, even if the refrigerant is the same.

Oil grades are not always compatible with each other (cannot be mixed).

Changing from one oil grade to another can lead to faults in the compressor's operation and to leaks at the sealing points. The compressor manufacturer must always be asked before changing the oil grade.

If other oils are used without the compressor manufacturer's written approval, the cascade's guarantee cover expires.

circuit NH3

Viscosity Cooling medium outlet Flash Pour point Manufacturer Oil grade Basis at 40°C in temp in °C point in °C in °C cSt

1> -20,0 Fuchs-DEA Reniso S68 AB 68 190 -33

> -20,0 Fuchs-DEA Reniso S68 AB 68 190 -33

2> -20,0 Castrol Icematic 299 M 56 180 -34

> -20,0 Esso Zerice S46 AB 46 172 -36

> -20,0 Shell Shell Clavus G68 M 65 205 -36

> -30,0 Elf Elfrima FR46 M 46 171 -37

> -30,0 Shell Shell Clavus G46 M 44 195 -39

Gargoyle Arctic SHC 424 > -30,0 Mobil AB 32 157 -39

> -30,0 Esso Zerice S32 AB 32 157 -39

3> -30,0 CPI CP 1009-68 M* 68 226 -40

1 Alkylbenzenr

2 Mineral oil

3 Mineral oil with special treatment (hydrotreated oil)



14 _551511_om_kas_gbr_1_.doc

Cooling medium outlet temp in °C Manufacturer Oil grade Basis

Viscosity at 40°C in cSt

Flash point in °C

Pour point in °C

> -30,0 Mobil Gargoyle Arctic Oil 300 M 64 202 -40

> -30,0 Esso Zerice 46 M 46 204 -41

> -20,0 Petro-Canada Reflo 68A M* 58 236 -42

> -20,0 TEXACO Capella Premium M* 67 262 -42

> -40,0 Mobil Gargoyle Arctic Oil C Heavy

M 44 187 -50

> -40,0 CPI CP 4600-46 PAO4 46 268 -51

> -40,0 Mobil Gargoyle Arctic SHC 226E

PAO 67 266 -54

> -40,0 Mobil Gargoyle Arctic SHC 326 (NH68 also) AB + PAO 61 211 -54

> -40,0 Castrol Icematic 2294 PAO 69 233 -60

< -40,0 on request only

The screw compressors are fitted in the factory with suitable O-ring elastomers at the sealing points; these are selected depending on the refrigerant and lubricant.

Refrigerant / oil M AB PAO, M* AB/ PAO

R717 (ammonia CR CR HNBR CR

CO2 circuit

Manufacturer Trademark Oil grade O-ring material

Fuchs Reniso TRITON C 170 HNBR

The screw compressors are fitted in the factory with suitable O-ring elastomers at the sealing points; these are selected depending on the refrigerant and lubricant.

4 Polyalphaolefin



_551511_om_kas_gbr_1_.doc 15

1.6.2.4 Checking the direction of rotation of the driving motor

1.6.2.5 Checking the direction of rotation of the oil pump motor

The oil pump is started with the driving motor electrically blocked (service). The stop valves are in the operating position.

Warning!

The coupling must not yet connect motor and compressor!

The direction of the arrow given for the oil pump must correspond to the direction of rotation of the electric motor. • Secure the electric switchgear so as to prevent

the compressor driving motor from being switched on accidentally.

Caution!

Since the slide ring shaft seal of the oil pump is dependent on the direction of rotation and can be damaged when this direction is wrong, checking must be reduced to a very short running period (less than 2 seconds).

• With the control slide in the MIN or MAX position, it should be possible to rotate the compressor shaft easily and smoothly by hand. When checking the direction of rotation of the compressor driving motor pay attention to the conditions for switching the compressor on.

The adjusted differential pressure between the oil pump discharge side and the suction side of the oil pressure control valve is checked with the oil pump rotating in the correct direction. It must not be lower than the specified setpoint of 3.5 + 0.5 bar.

While the compressor is not running and the oil has not yet reached the operating temperature, the differential pressure can be slightly higher than the indicated value.

The differential pressure can be changed by rotating the spindle on the oil pressure control valve. (The differential pressure is increased by turning it inwards and vice versa).

fig. 2: Motor direction of rotation

A Compressor 1.6.2.6 Adjustment of oil pressure B Motor

Before the compressor drive motor and therefore the unit can be started, the oil pressure must be set correctly by adjusting the oil pressure regulating valve (075).

• The compressor driving motor is operated in star-delta connection for a short period in the operating mode "1 (manual + manual)". After that the compressor driving motor has to switch off.

For adjustment only the oil pump must be started. For units equipped with a Grasso System Control (GSC) please select operation mode “service mode”. • If the direction of rotation of the motor is

wrong, it should be corrected while the electric switchgear is secured to prevent the motor from being switched on accidentally. The motor must then idle for at least 1h.

The set value of the oil differential pressure should be taken from the P+I-diagram of the specific project. Normally the set value is Δp = 2-3 bar (oil pressure Pos (110) – discharge pressure Pos (105)).

• The coupling protection must be in place during this running-in period as required in the labour safety regulations.

The differential pressure can be changed by rotating the spindle on the oil pressure regulating valve (the differential pressure is increased by turning it inwards and vice versa). • After checking the direction of rotation of the

driving motor the coupling may be connected with the motor.



16 _551511_om_kas_gbr_1_.doc

Danger! Circuit Item No. charging valve

An oil pressure adjusted too high or too low can lead also after short operation time to serious compressor damages or even to a total breakdown of the compressor!

NH 2865 3

CO 6865 2

The location of these charging valves is given in the P+I flow diagram. In comparison to normal operation conditions the oil

differential pressure can be (at identical opening level of the valve) slightly higher if only the oil pump is operated (service mode) or in case the operating temperature is not reached yet.

Caution!

Mixing even the smallest quantities of NH and CO3 2 in the refrigerant cycles must be avoided under all circumstances! In this case the oil differential pressure should be

readjusted (according to the value in the P+I diagram) after start of the unit and reaching of the operation temperature.

Use top quality (specially cleaned and dried) NH and CO only! 3 2

1.6.2.7 Mounting the coupling Whenever work is carried out on the parts of the refrigerating system carrying refrigerant or oil, extreme caution is required as leaking refrigerant can cause hazards. Note and observe the refrigerant safety data sheets.

1. The electric switchgear is secured to prevent it from being switched on accidentally.

2. Mount the coupling, observe instructions of separate documentation.

For health and safety reasons, safety goggles and protective gloves must be worn. 3. The values for radial and angular deviations

given in the coupling documentation must be checked and if necessary corrected. Refrigerant charging procedure

Equipment required: 4. The real values have to record at data sheet of coupling documentation. Please send back a copy of the filled data sheet to:

— Refrigerant filling cylinder with liquid connection

— Weighing scales for refrigerant cylinder Grasso GmbH RT

— Special filling hose with cylinder connection Holzhauser Straße 165

— Shut-off valve with connection adapter for the charging valve 13509 Berlin, GERMANY

Fax: +49 (0)30 - 43 592 759 When charging for the first time, weigh the quantity of refrigerant given on the cascade's name plate. To do this, place the refrigerant cylinder with sufficient refrigerant on weighing scales. Before starting to charge, determine the weight of the cylinder.

Caution!

Pay attention to maintenance instructions!

Regreasing the coupling (if provided for in the maintenance instructions for the coupling)!

Connect the filling hose to the refrigerant cylinder.

Warning!

The compressor must be ready for refrigerant charging!

1.6.2.8 Refrigerant charging

After evacuating the refrigerant circuits, the system can be charged with refrigerant via the refrigerant charging valve and then the vacuum can be broken.

1. Connect the refrigerant reservoir to the charging valve.

2. Open the charging valve. The refrigerant circuits are only charged via the charging valves of the respective circuit. 3. Carefully open the reservoir valve and equalize

the pressure.

4. Close the valve.



_551511_om_kas_gbr_1_.doc 17

5. Check the system again for leakages. Caution! 6. Start the compressor. Flow direction: from A to B and C 7. Open the reservoir valve.

8. Draw refrigerant into the circuit at a low compressor delivery rate. stop valve

Valve opened during normal operation At the same time, continuously check the weight change in the filling cylinder.

Warning! fig. 3: Stop valve opened Only fill the quantity specified,

otherwise there is risk of overcharging the circuit.

Valve closed during normal operation

9. Close reservoir valve when the suction pressure nears the required values. Let the compressor continue to run until the refrigerant has been completely distributed in the circuit. Based on the values, you can now assess whether additional refrigerant has to be charged or not.

fig. 4: Stop valve closed

Check valve

Check valve during normal operation Hint!

If necessary, repeat the "refrigerant charging" process until the suction pressure reaches the required value.

fig. 5: Check valve

10. After the charging process has been completed, close the charging valve and cylinder valve. Combined stop/ check valve

Combined stop/check valve opened during normal operation

11. Drain and dismantle the charging line.

Now lift the hose to make liquid refrigerant flow back into the cylinder.

Before dismantling the charging line, carefully drain the gaseous contents of the hose into a water receiver in accordance with the safety regulations.

fig. 6: Combined stop/ check valve

Control valve Small quantities of refrigerant gas may escape.

Control valve adjusted at:

1.6.2.9 Operating position of valves — Commissioning

For the positions of the manually controllable fittings for the operation of the CO

— changed operating conditions /NH2 3-cascade unit see

P&I diagram.

The layout and symbols used in the R+I flow charts comply with the specifications of EN 1861, Issue April 1998.

fig. 7: Control valve

Combined stop/ check valve with integrated control function

Danger!

The valve positions must match the specifications given in the R+I flow chart to ensure trouble free operation!

Combined stop/ check valve with integrated control function opened during normal operation

fig. 8: Combined stop/ check valve with integrated control

function



18 _551511_om_kas_gbr_1_.doc

Solenoid valve Pressure controlled check valve

Controlled by Grasso System Control (GSC) controlled self-sufficient

fig. 9: Solenoid valve

Change-over valve

fig. 13: Pressure controlled check valve

Quick acting valve, spring-held

manually operated if necessary

fig. 10: Change-over valve

oil pressure regulating valve fig. 14: Quick acting valve, spring-held

Δp x,x ± x bar setted control pressure from reference pressure Charging valve, draining valve

— ½“ and ¾“ connections

— with cap

fig. 15: Charging valve, draining valve

fig. 11: oil pressure regulating valve

Service valve Danger! — Connection Rp ¼“ An oil pressure adjusted too high or too

low can lead also after short operation time to serious compressor damages or even to a total breakdown of the compressor!

— For pressure gauges and transducers

Overflow valve, safety valve fig. 16: Service valve

fig. 12: Overflow valve, safety valve



_551511_om_kas_gbr_1_.doc 19

6. The oil heater has sufficiently heated the oil Oil temperature limiter

Voltage connection controlled self-sufficient by control element

Before switching on the main switch, all motor protection switches and bridge fuses within the cascade must be switched on.

The cascade must be put into service in accordance with the operating instructions for the compressor control.

1. Switch on the control voltage of the compressor control.

2. Acknowledge existing fault indications. fig. 17: Oil temperature limiter

3. Select operating mode ”1 (manual + manual)”. Temperatur controlled valve

4. Switch on the cascade. controlled self-sufficient Switching on the main switch on the switch cabinet

supplies power to all the connected electrical loads and equipment and the SPC (programmable control) system, including the control and display unit.

Hint!

We advise switching on the voltage in good time before an intended startup.

fig. 18: Temperatur controlled valve

Thermostatic expansion valve The oil-fired heating requires a lead time in order to heat the oil in the compressor's crankcase to temperatures above the refrigerant's saturation temperature. This is intended to prevent refrigerant condensing in the compressor and to ensure any refrigerant already in the oil is evaporated. This ensures sufficiant viscosity for bearing lubrication while the compressor starts.

controlled self-sufficient

fig. 19: Thermostatic expansion valve

1.6.2.10 Checking the water circuits

Check whether the cooling and cold water pumps are running and the shut-off fittings in the cooling water circuit are in their operating positions.

Special features of operating mode 1 "Manual + Manual"

Manual mode can only be realised under the supervision of the operating personnel. The control cycles are to be specified by the owner on their own responsibility in compliance with the system-specific control response.

While the unit/ chiller is operating under project conditions, adjust the cooling water control so that the condensing and oil temperature lies within the permissible range.

Caution! 1.6.2.11 Initial startup

The following prerequisites must be fulfilled for the initial start-up:

The cascade is operated manually!

The cascade operates independent of the temperature and pressure control! 1. Main current supply available and switched on Safety and monitoring devices are fully functional!

2. Heat transfer medium and cooling water pumps are switched on

3. Media flows through the heat exchangers.

4. The valves are in their "operating position"

5. Sufficient refrigerant and oil charge



20 _551511_om_kas_gbr_1_.doc

3. The maximum end position (100%) must be reached and signalled on operating pushbutton switch (capacity increasing).

1.6.2.12 Setting the setpoint / limit values and safety devices

The setpoint and limit values are set according to the details given in the Control Manual and the project-related data.

4. The minimum end position (0%) must be reached and signalled on operating pushbutton switch (capacity decreasing).

Check the safety device settings. 5. Vent the adjusting device by moving the control

slide to and for about ten times. Hint!

See parameter list/ list of set values! 1.6.2.16 Checking the control slide adjustment times

While the cascade is running, determine the adjustment times needed when the control slide is continually moved from the maximum end position to the minimum end position and back. For the automatic system to run smoothly, the adjustment times in either direction must be approximately the same.

refrigerant pumps 1.6.2.13 Switching on the CO2

refrigerant pump ON" pushbutton Press the "CO2

1.6.2.14 Switching on the compressor

Start NH compressor 3

Minimum adjustment time 30 sec. Press the "Compressor ON" button

The following switching operations are automatically realised with the compressor startup:

Optimum adjustment time 60 sec.

— Oil-fired heating switched off. The adjustment times are matched by means of throttle screws mounted on the solenoid valve plate. — "Oil pressure bypass" timer starts up.

— Minimum output level after reduced-load startup

While the compressor is starting up the following readings are to be observed on the cascade:

— Suction pressure, final compression pressure and oil pressure

— Heat transfer medium temperature

— Sign glasses in the evaporator or in the liquid line and compressor's housing

compressor Start CO2

The switching operations are analogous to those of the NH3 compressor.

The "Increase output" and "Reduce output" pushbuttons can be used to reach the project values and run the cascade in steady state condition.

fig. 20: Solenoid valve plate with throttle screws

The NH3 and CO2 compressor output levels should be alternately switched on and off so that, as far as possible, both run under the same load.

adjustment time ↓ Rotate in clockwise direction

adjustment time ↑ Rotate in anti-clockwise direction The refrigerant charge must be checked and recharged if necessary! Influencing towards Maximum DS5

1.6.2.15 Checking the adjustment of the control slide Influencing towards Minimum DS6

1. Cascade is running.

2. Select operating mode ”1 (manual + manual)”.



_551511_om_kas_gbr_1_.doc 21

— “Switch on pause" timer starts up 1.6.2.17 Automatic mode

6. If the NHThe system is designed for automatic chilling; it is controlled by the compressor being switched on and off and its output adjustment.

3 compressor is in minimum output and the value falls further below the setpoint value the compressor switches off.

Continuous operation and observation of the machine is not necessary in automatic mode. The necessary information on starting up the system is given in the documentation for the compressor control.

1.7 Shutdown in the event of dangerous situations

The safety equipment of the CO2/NH3 cascade conforms to EN378 and UVV BGV4.

Danger! Due to the automatic monitoring of the individual operating parameters, the control detects hazardous situations in good time and automatically switches off the cascade.

Do not carry out any work on the cascade during an "Automatic shutdown"!

The cause of the fault is then displayed on the control unit and can then be corrected.

Special features of automatic mode The cascade concept is based, among other things, on the most tight, low-maintenance refrigerant circuits possible. However, residual risks remain, especially due to possible leaks or escaping refrigerant or rotating drive parts.

1. Fulfilment of the following requirements:

— Release signal issued by GSC

— Switching on conditions for the compressor drive motors are fulfilled

Hint! — There are no queued faults

The cascade can be switched off at any time via the EMERGENCY STOP button on the switch cabinet.

— System signals output requirements (temperature setpoint is smaller than actual value)

2. NH3 compressor drive motor starts up The auxiliary refrigeration unit has its own supply and can be taken out of service via a separate EMERGENCY STOP button.

— Oil heater is switched off

— "EHB" (starting frequency limiter) timer starts up When the cascade is switched off, taking the

auxiliary unit out of pressure can result in a pressure increase in the CO

3. If the switching on conditions for the CO2 compressor drive motor are fulfilled the motor starts up.

2 cycle and can cause the discharge safety valve in the CO circuit to trigger. 2

Leaking refrigerant in the machine room can be detected with the help of a gas detector and alarm (not included in scope of supply) and can be integrated in the automatic safety chain.

— Oil heater is switched off

— "EHB" (starting frequency limiter) timer starts up

4. The control variable for automatic operation of the cascade is the suction pressure of the CO Hint!

2 circuit. The difference between this actual value and the specified setpoint causes the automatic switching on and off of the CO

The safety information for the NH3 and CO refrigerants must be observed! 2

2 and NH3 compressor output levels.

5. At minimum output and if the pressure continues to drop below the set "setpoint pressure" the cascade switches off.

At minimum output and if the pressure continues to drop below the set "setpoint pressure" the CO unit switches off. 2

— CO compressor drive motor is switched off 2

— Oil heater is switched on



22 _551511_om_kas_gbr_1_.doc

1.8.3.1 Monthly 1.8 Switching off • Check that a gauge pressure is constantly

applied in the cascade. Use a leak detector to check the cascade for leaks once a month. 1.8.1 Normal shutdown

Shutting down for short stoppages (< 48 h) • Start up the oil pump for approx 5 minutes. • Staged output reduction of NH and CO2 3

compressors down to minimum load • Manually rotate the compressor shaft (min 10

revolutions). compressor first, then NHCO2 3 compressor

1.8.3.2 Four weeks before putting back into service • Shut down coolant, heat transfer medium and

cooling water system as necessary • Check the moisture content and ageing condition of the refrigerator oil. Analyse the oil and compare the values with the fresh oil data. Grasso advises an oil change after 1 year (ammonia, see Maintenance Instructions).

• If necessary, shut down ancillary drives

• Leave the valves in the operating position

1.8.2 Shutting down for a lengthy period • Check the insulation resistance of the drive motors (see electric motor's User Manual). Shutting down for lengthy stoppages (> 48 h)

• Switch on the oil pump. — Staged output reduction of CO2 and NH3 compressors down to minimum load • Check the cascade for leaks.

compressor first, then NHCO2 3 compressor 1.8.4 Putting back into service after approx 1

year — Close the shut-off valves on the intake side and outlet side (or shuttable check valves).

• Change the oil filter inserts (see Maintenance Instructions). — Switch off CO refrigerant pump 2

— Remove the heat transfer medium from service • Switch the oil heater on at least one hour before starting the cascade. — Close the shut-off valves (or shuttable check

valves) in economizer suction line. • Open the shut-off valves on the intake side and the discharge side (or shuttable check valves). — Cut-off the refrigerant supply to the

thermosyphon oil cooler. • Open the shut-off valves (shuttable check valves) in the economizer suction line. — Close the manual cut-off valve of the refrigerant

injection. • Open the refrigerant supply to the thermosyphon - oil cooler. — Switch off the oil heater.

• Open the manual shut-off valve of the refrigerant injection.

— Switch off the main switch of the power supply system for the cascade

• Remove all non-condensable gases are removed by venting. To this end, check the condensing pressure and temperature (see parameter list).

Caution!

The main switch for the auxiliary refrigeration unit remains switched on!

• Check the oil collection sump and empty if

necessary. — Ensure you cover the venting slots of the

electric motors! • Switch on the compressor and observe the

operating instructions of the electrical switchgear. Functional run of the cascade to check the sensor technology and actuators (function and display accuracy).

1.8.3 Measures during stoppages

In the event of lengthy stoppages, which last longer than half a year, despite the gauge pressure in the cascade, the moisture contant of refrigerant and the refrigerator oil must be checked. The moisture contant must not differ substantially from the initial values.



_551511_om_kas_gbr_1_.doc 23

2 START-UP / OPERATION OF GSC

2.1 General Information

Warning!

Before switching on the CO 2/NH cascade, carefully read through the operating instructions. 3

The operating instruction are an extract from the GSC User Manual, containing important information for the operator about operating the CO /NH cascade. 2 3

The listed items and annotation is not identical with those of the GSC Manual. The note [X.X.X.] under the headings of these operating instructions refers to the corresponding chapter in the User Manual.

For more specific information see GSC Manual or press the key to obtain more information about the relevant display text.

The GSC is supplied in the national language.

and the COA GSC is assigned both to the NH3 2 circuit.

2.2 Description of the Grasso System Control

2.2.1 View

[Chapter 1.1.1. in user manual]

fig. 21: Exterior view GSC



24 _551511_om_kas_gbr_1_.doc

2.2.2 Lamps/ Push buttons


White indicator light (Running)

This indicator lamp flashes slowly when the compressor unit is in the “Ready“ state.

Yellow indicator light (Warning)

This lamp flashes if an operating condition reaches a preset value (Warning /Pre-alarm).

Red indicator light (Alarm)

This lamp flashes if an operating condition exceeds its permitted value, the machine shuts down on alarm.

Emergency Stop button

This red button can be used to switch the compressor unit off at any time in case of an emergency. The operator terminal controls remain functional.

2.2.3 Operator terminal

[Chapter 1.2. in user manual]

The operator terminal is the interface between the operator and the control unit.

All switching, operating and control actions are carried out via this operator terminal.

fig. 22: GSC operator terminal

System LED’s A

B Function keys

C soft keys

D CPU operating mode setting

E digital keybord

F cursor keys

G System keys

System keys LED‘s H



_551511_om_kas_gbr_1_.doc 25

2.2.3.1 Key assignment


Key Function

Go to the menu item described +

Back to previous display

Move to next display +

Switch on the compressor unit, start enabled

Start 1st compressor (Press key for 5 sec. in operation mode ”Manual”) Increase capacity of 1st compressor (in case of manual capacity control only)

Start 2nd compressor (Press key for 5 sec. in operation mode ”Manual”) Increase capacity of 2nd compressor (in case of manual capacity control only)

without function +

Call up display of actual values

Call up alarm signals

Lamp test

Switch off the compressor unit, start disabled

Stop 1st compressor (Press key for 5 sec. in operation mode ”Manual”) Reduce capacity of 1st compressor (in case of manual capacity control only)

Stop 2nd compressor (Press key for 5 sec. in operation mode ”Manual”) Reduce capacity of 2nd compressor (in case of manual capacity control only)

without function +

Call up controls – settings

Call up operating mode setting



26 _551511_om_kas_gbr_1_.doc

Key Function

Call up the menu overview

Return or cancel input

Acknowledge, reset failure and warning

Confirm input

Press the button once for display of a help text.

Switch over to the 2nd keyboard level

Cursor keys

Special function of the shift key

Change to the ”Status display” +

Change to the “Language selection” or “Contrast menu” +

Change to the ”Digital inputs / outputs display” +

Change to the “Date, Time“ menu +



_551511_om_kas_gbr_1_.doc 27

2.2.3.2 Open table of contents


key. A list of the available menus is then displayed. To open the table of contents, please press the

Number Heading Help text

05 Actual values All the cascade's actual values are displayed here

10 Control All control parameters can be changed here

15 Operating modes Selection of all possible operating modes

20 Limit values Enter the limit value parameters

25 Fault messages Fault messages + histogram

30 Time settings All time parameters can be changed here

35 Options All optional windows are selected from here

50 Configuration Enter:

— Refrigerant

— SC type

— Code

— with/ without economiser

— sensor scaling

90 Main system menu

To open these views, position the cursor on this view (using the or key) and confirm with the key.

Danger!

Parameter changes made in the menu items 20, 30, 35 and 50 can cause serious errors in the operation of the CO 2/NH cascade! 3



28 _551511_om_kas_gbr_1_.doc

2.2.4 Status messages

[Chapter 1.3. in User Manual]

key several times, or press the key and then . Open the "status messages" display, press the

This view not only shows the most informative actual values but also the status of the unit / the cascade.

fig. 23: "Status messages" display

PV: Actual value (pressure or temperature) display always in °C

SP: Set Point display in °C

Pos: Current control slide position in %

Imot: Motor current in A

Tc: Condensation temperature in °C

dPoil: Differential oil pressure in bar

Hint!

See menu 05 actual values

The status provides information about the current operating status of the aggregate / cascade.

The following status messages are possible:

Initialisation of the control after switching on the power supply or after saving the settings (RAM → ROM)

Initialisation

A starting frequency limiter of the compressor drive motor is still active. EHB 01

A start lock-out is active, the oil pump has run too long by itself. (Minimum position not reached during switching on or off procedure)

Oil drain 01

Unit/ cascade ready to start but one or several starting conditions are still not fulfilled, e.g. cut-in temperature in automatic mode not yet reached

Standby 01

The control is waiting for an external starting release signal. Release start 01

Starting command issued, control slide moves into the minimum position. Forced slide to min 01

Compressor motor has been started but the switchover in "delta! has not yet taken place of the startup has not yet been completed.

Startup 01

Compressor running in "delta" or startup has finished, the unit / cascade is in operation.

Running 01

An output limiter is active (suction pressure too low), "reduce output" solenoid valve is opened.

Limit suct press 01



_551511_om_kas_gbr_1_.doc 29

An output limiter is active (final pressure too high), "reduce output" solenoid valve is opened.

Limit disch press 01

An output limiter is active (motor current too high), "reduce output" solenoid valve is opened.

Limit Imot 01

An output limiter is active (external temperature too low), "reduce output" solenoid valve is opened.

Limit ext temp 01

Oil temperature too high, "refrigerant injection" is released (optional). Limit oil temp 01

The unit / cascade has received a switch-off command, the control slide is moved into the minimum position

Stopping 01

The compressor has switched off Compressor off 01

Start delay after each switching off process Forced stoppage 01

A fault, which is still active, has occurred at the unit / cascade. Fault 01

Text display flashes italic lettering

Text appears as static text Normal lettering

The status of the whole cascade is displayed with the LEDs in and .

Key Colour Status Explanation

Green Flashing The unit / cascade is switched on. The compressor

could start any moment now.

Green Continuous light The unit / cascade is switched on. The compressor is

running.

The unit / cascade is malfunctioning. The compressor is not running. The (red) indicator light ‘Collective fault’ flashes or is permanently lit.

None OFF +

red Continuous light The unit / cascade is switched off. The compressor is

not running.



30 _551511_om_kas_gbr_1_.doc

2.3 System description GSC

[Chapter 4. in user manual]

The system LEDs are located on the front of the GSC. These system LEDs provide information about the status of the controller.

2.3.1 Explanation of the system LED

[Chapter 4.1. in User Manual]

The position of the system LED is given in Chapter Figure 22, page 24.

Meaning of the status and error displays

Display Meaning Explanation

SF (red) C7-CPU-centralised fault Lights up for: — Hardware errors,

— Firmware errors,

— Programming errors,

— Parameterising errors,

— Computational errors,

— Time errors,

— Faulty internal memory storage,

— Battery failure or the standby supply is missing while MAINS ON,

— Peripheral error in the internal peripheral functions.

Further information about the malfunction that has occured can be read out of the diagnosis memory using the PG.

BATF (red) Battery error Lights up, if battery

— does not have enough voltage,

— is defective,

— is missing.

DC5V (green) Voltage supply for C7 lights up, if the internal DC 5V supply is OK.

FRCE (yellow) Force-order lights up, if a Force-order is active.

RUN (green) Operating state RUN of the C7-CPU

lights up, if the C7 CPU application program is running.

flashes (2Hz) during the C7 CPU start up (the STOP lamps also lights up; after the STOP lights go off, the outputs are released).

STOP (yellow) Operating state STOP of the C7 CPU

lights up, if the C7 is not processing a CPU-application program.

flashes at 1-second intervals, if C7 CPU general reset (MRES) is required.

SF-IM (red) Switching module - centralised fault

lights up, if the connection between C7 and the extension rack is interrupted.



_551511_om_kas_gbr_1_.doc 31

Display Meaning Explanation

Alarm active lights up, if a malfunction has been confirmed, but is still active. (red) flashes, if a further malfunction has been activated.

Help (green) Help text available lights up, if a help text is available.

Shift (green) Switch over function active lights up, if the SWITCHOVER function is active.

2.4 Alarms

[Chapter 6. in user manual]

2.4.1 View active alarms and warnings


The ´Status mode´ is displayed by pressing the key several times. The most important actual values are shown in the first three rows and in the 4th row the status message is shown.

By scrolling with the cursor keys and all active alarms and warnings are displayed.

2.4.2 No alarm signal and the compressor will not start


Compressor will not start, although there is no active alarm.

Key “ON” has been pressed and the LED K1 ”ON” is flashing.

Cause Remedy

No ‘start release’ signal The input ´start release´ is not closed.

Close input or install a link.

‘Auto Start dly’ active The time setting ‘Auto start dly’ in ‘control settings menu’ has not yet expired.

Wait until the delay time has expired.

‘Start to start’ delay active The time setting ‘Start to start’ in ‘Timer settings’ menu has not yet expired.

Wait until the delay time has expired.

actual value < (set point + ½ NZ) Check set point and neutral zone settings in ´Control settings´menu. NZ = neutral zone In case of suction pressure control the set point value is entered in degrees Celsius.



32 _551511_om_kas_gbr_1_.doc

2.4.3 Restart following Alarms


fig. 24: Restart following Alarms

Caution!

It is not possible to restart the compressor as long as the cause of the alarm still exists!



_551511_om_kas_gbr_1_.doc 33

Display of the cause(s) of the alarms after deleting the display on view (press the key) or in the case that several alarms have occurred simultaneously:

Step Procedure

1

Call up the "Alarms" menu by pressing the key.

2

Select the "View" menu item for the alarms by pressing the key.

The errors that have occurred can be viewed here with the date and time at which they occur.

Caution!

For more detailed explanations for reading the error messages, see Chapter 1.2.2.2. (GSC User Manual).



34 _551511_om_kas_gbr_1_.doc

3 DESCRIPTION OF DESIGN AND FUNCTION

3.1 Brief Description

3.1.1 Use

These 2-stage CO2 / NH3 cascade units are highly efficient industrial refrigerating plant and as such are suitable for use within the low temperature range with evaporating temperatures between -40 and -54°C, e.g.. for freezing apparatus in the food indutry or for drying processes.

and NH are used. The natural and environmentally friendly refrigerants CO2 3

3.1.2 Design

low temperature and an NHThe cascade unit consists of a CO2 3 high-temperature level with the following main components:

(A) CO screw compressor unit 2

(B) CO liquid separator 2

(C) CO pump unit with 1 or 2 parallel refrigerant pumps 2

(D) CO expansion device (not illustrated) 2

(E) CO2-NH cascade heat exchanger module 3

(F) automatic oil return system of the CO side (not illustrated) 2

(G) automatic oil return system of the NH side (not illustrated) 3

(H) NH screw compressor unit 3

(I) NH injection system 3

(J) CO condenser 2

(K) auxiliary refrigeration unit for CO separator 2

(L) low voltage system with control (M) joint stable baseframe

fig. 25: Diagram of the main components of the CO2/NH cascade, Part 1 3



_551511_om_kas_gbr_1_.doc 35

fig. 26: Diagram of the main components of the CO2/NH cascade, Part 2 3

These cascade units are delivered completely assembled, so that on site only the following have to be integrated:

— the CO liquid line to the CO evaporators / freezing apparatus (not included in scope of supply) 2 2

— the return line to the CO2 liquid separator

— the heat transfer medium lines of the NH compressor 3

— Compressor discharge gas (hot gas) and liquid lines to the NH3 condenser on site

— the vent pipes of the CO and NH safety valves, 2 3

In the case of cascades, which due to their size cannot be transported as a complete unit, the liquid separator is dismantled in the factory. This has to be re-installed on site and connected to the relevant refrigerant lines.

3.2 Refrigerant circuit

3.2.1 CO2 low temperature stage

The compressors of the low temperature stage are state of the art screw compressors, specially developed for the CO2 refrigerant from the Grasso series C (see compressor manual, drawings and parts list).

The CO2 screw compressor sucks in the refrigerant vapour from the CO2 liquid separator via the suction filter.

After the CO2 refrigerant has been compressed to condensing pressure the condensing takes place in the plate pack of the cascade heat exchanger by

extracting the heat generated by the evaporation of NH3 in the shell-side.

The liquid CO2 in the liquid separator is expanded (relaxed) with the help of an electronic injection valve in conjunction with an electronic high-pressure level controller

In the liquid separator, the refrigerant vapour and liquid are separated. The CO2 liquid is passed through the system's evaporator (not included in the scope of supply) by means of hermetic refrigerant pumps (pump circulation principle).

Here heat is absorbed in order to cool the medium to be cooled.



36 _551511_om_kas_gbr_1_.doc

The refrigerant pumps can be individually shut off and are protected against dirt by generously dimensioned filters in the inlet.

The oil carried through the pressure line and the condenser into the liquid separator while the compressor is running is directly injected back into the compressor with the help of partial flow deoiling.

3.2.2 NH3 high temperature stage

The NH3 circuit includes a complete chiller unit and its design corresponds to the FX VP type series, whereby the evaporator is installed as a cascade evaporator condenser. The condenser already exists on site.

The NH3 compressors of the high temperature stage are modern, highly efficient screw compressors of the LT series (see compressor's manual, drawings and parts list).

The NH3 screw compressor sucks in the refrigerant vapour from the NH3 liquid separator of the cascade evaporator via the suction filter.

After the NH3 refrigerant has been compressed to condensing pressure it is condensed in the condenser (Grasso scope of supply or installed on site).

The liquid NH3 in the liquid separator of the cascade evaporator is expanded (relaxed) with the help of an electronic injection valve in conjunction with an electronic high-pressure level controller.

In the liquid separator, the refrigerant vapour and liquid are separated. From there the liquid refrigerant is passed via an outer circulation pipe into the shell-side of the cascade evaporator.

The quantity of heat absorbed during evaporation of the NH3 coolant is drawn from the CO2 refrigerant gas flowing in the heat exchanger plates.

The NH3 coolant therefore evaporates in the shell-side, while CO2 condenses in the plates.

The oil carried via the pressure line and the condenser into the liquid separator while the compressor is running is separated from the refrigerant again with the help of cyclically operated automatic oil return and is passed back to the compressor.

This is a basic precondition for a fault-free operation of the evaporator system.

3.3 Oil return system

The refrigerant cycles have an automatic oil return system with which the oil accumulated in the compressor's oil sump is cyclically returned to the intake side of the compressor.

3.3.1 CO2 circuit oil return system

Despite the very low oil carry over of the screw compressor, over a longer period soluble refrigerator oil accumulates in the liquid CO2 on the low pressure side.

The result of this is the oil level in the oil separator falls during the startup period and oil has to be added accordingly.

A slight accumulation of oil in the refrigerant does not have any negative effects on the system side and is completely normal.

To limit this accumulation of oil, the oil is returned with the help of partial flow deoiling on the discharge side of the CO2 pumps.

The partial flow is directly injected into compressor.

3.3.2 NH3 circuit oil return system

The NH3 side oil return system already tried and tested in the Grasso chiller series is cyclically carried out in the following steps:

1. Filling the Draining Tank (2300)

The oil carried from the compressor in the refrigerant circuit is fed into the deoiling vessel at the evaporator's "oil dome".

At the same time, the solenoid valve (2305) is opened. The solenoid valve (2310) is closed.

The oil accumulating in the evaporator's oil dome continuously runs into the deoiling vessel.

2. Evaporation of refrigerant

Any liquid refrigerant in the deoiling vessel can evaporate by adding ambient heat. At the same time, oil runs in and the oil level in the vessel rises.

After a fixed unit of time the oil is then pushed out of the deoiling vessel.

After the evaporation process a solenoid valve (2310) is briefly opened and hot gas presses the oil out of the deoiling vessel back into the compressor's intake side.

The control timed for the solenoid valve can be parameterised at the control.

3.4 Auxiliary refrigeration unit for CO2 separator

The maximum operating pressure of the low pressure side of the CO2 circuit is 25 bar g.p. The section of the circuit is equipped with a discharging safety valve.



_551511_om_kas_gbr_1_.doc 37

In order to avoid a pressure rise in this area up to 25 bar g.p, while the system is at a standstill and thus to avoid the refrigerant from being blown out, the refrigerant is cooled in the CO2 liquid separator with the help of an external chiller.

The auxiliary refrigeration unit is part of the cascade and is completely installed. It is delivered like the complete CO2/ NH3 cascade without a refrigerant charge.

It is a small standard refrigeration condenser unit, which is connected to a pipe coil acting as an evaporator in the CO2 liquid separator.

The auxiliary unit is switched on and off depending on the pressure in the CO2 liquid separator.

3.5 Safety devices

The cascade is equipped with the necessary safety devices in accordance with the relevant regulations, in particular EN 378.

The following safety devices are installed in every cascade.

3.5.1 CO2 circuit

• Safety devices to prevent exceeding of the maximum allowable final discharge pressure

— Pressure transducer (5105)

If the limit value is exceeded, the compressor control switches off the CO2 unit.

Limit value final pressure alarm (max) = see parameter list

However, before the limit value is reached the compressor's output level is lowered to prevent exceeding of the limit value.

— Safety pressure switch (5350)

The CO2 compressor is switched off if the limit value is exceeded.

Limit value p = 0.9 x pmax bar

(pmax = maximum allowable operating pressure on the high-pressure side)

— Pressure relief device (5340)

The back-pressure independent overflow valve discharges on the compressor's intake side when pmax is reached.

• Pressure relief device of the pressure vessel on the high-pressure side (6420) (overflow valve to the low pressure side)

The counter-pressure overflow valve discharges on the low-pressure side of the plant (liquid separator) if pmax = 48 bar g.p. is reached.

• Pressure relief device of the pressure vessel on the high-pressure side (6230) (discharging safety valve)

The safety valve discharging into the outside opens the low-pressure side of the plant if pNDmax = 25 bar g.p is reached.

• Safety device to prevent the suction pressure falling below the allowable limit (pressure transducer 5100)

If the pressure falls below the limit value the compressor control switches off the CO2 unit.

However, before the limit value is reached the output level of the CO2 compressor is lowered to prevent the value falling below the limit value.

• Safety device to prevent the final discharge temperature from being exceeded (resistance thermometer 5120)


Limit value t = 80 °C

• Safety device to prevent the oil temperature from being exceeded (resistance thermometer 5125)


Limit value t = 60°C

• Safety devices of the compressor drive motor

— Rated current limiting control (5016) realised by the respective compressor control.

If the rated motor current is exceeded, the output level of the CO2 compressor is lowered until the motor current is back within the allowable range.

The normal output control then comes back into force.

— Thermistor (5017) which shuts down the compressor drive motor if its winding temperature exceeds the allowable value.

• Level monitoring of the CO2 liquid separator, level transmitter (6900)

The CO2 compressor switches off if the maximum level is exceeded.

• Differential pressure CO2 pumps differential pressure switch (6910)

The control switches off the refrigerant pump if the differential pressure falls below the minimum limit value.



38 _551511_om_kas_gbr_1_.doc

• Safety device to prevent exceeding of the maximum shutdown pressure in the CO2liquid separator, pressure switch (5900)

The auxiliary refrigeration unit (6800) is switched on if the maximum allowable shutdown pressure is exceeded.

3.5.2 NH3 circuit

• Security devices against exceeding of the final discharge pressure

— Pressure transducer (105)

The compressor control switches off the cascade if the limit pressure is exceeded.

Limit value final pressure alarm (max) = see parameter list

However, before the limit value is reached the output level of the NH3 compressor is lowered to prevent the limit value from being exceeded.

— Safety pressure switch (350)

The NH3 compressor is switched off if the limit value is exceeded.

Limit value p = 0.9 x pmax bar

(pmax = maximum allowable operating pressure on the high-pressure side)

— Pressure relief device (overflow valve 340)

The back-pressure independent overflow valve fitted to the oil separator discharges on the compressor's intake side when pmax is reached.

• Pressure relief device of the pressure vessel on the low-pressure side (discharging safety valve 2230)

The safety valve discharging into the outside opens the low-pressure side of the plant if pNDmax = 16 bar g.p. is reached.

• Safety device to prevent the suction pressure falling below the allowable limit (pressure transducer 100)

The compressor control switches off the cascade if the pressure falls below the limit value.

Limit value p = p f(to-10 K)

However, before the limit value is reached the output level of the NH3 compressor is lowered and the hot gas bypass is opened on the ND (low-pressure) side to prevent the pressure falling below the limit value.

• Safety device to prevent the final discharge temperature from being exceeded (resistance thermometer 120)



• Safety device to prevent the oil temperature from being exceeded (resistance thermometer 125)



• Safety devices of the compressor drive motor

— Rated current limitation (016) which is realised by the respective compressor control.

If the rated motor current is exceeded, the output level of the NH3 compressor is lowered until the motor current is back within the allowable range.

The normal output control then comes back into force.

— Thermistor (017) which shuts down the compressor drive motor if its winding temperature limit has been exceeded.



_551511_om_kas_gbr_1_.doc 39

3.6 Monitoring devices circuit 3.6.2 NH3

The following ACTUAL values are continuously shown on the compressor control's display.

3.6.1 CO circuit 2

The following ACTUAL values are continuously shown on the compressor control's display. Output level

Compressor1 PS pos Comp1

Control slide position compressor 1

PS pos Comp1 Current consumption of the motor

I (motor) Comp1

Current consumption of the motor

I (motor) Comp1 Differential oil pressure - oil circuit monitoring

D (p[oil cir]) Comp1

Differential oil pressure - oil circuit monitoring D (p[oil cir]) Comp1

Suction pressure (controlled variable)

p (0) Comp1

Suction pressure (controlled variable)

p (0) Comp1 p (k) Comp1 Final discharge pressure

p (k) Comp1 Final discharge pressure p (oil) Comp1 Oil pressure

p (oil) Comp1 Oil pressure T (Final disch press) Comp1

Final discharge temperature

T (Final disch press) Comp1

Final discharge temperature T (Oil)Comp1 Oil temperature

T (Oil)Comp1 Oil temperature T (suct gas)Comp1 Suction gas temperature

T (suct gas)Comp1 Suction gas temperature Suction pressure's saturation temperature

T [p(0)]

Suction pressure's saturation temperature

T [p(0)] Final discharge pressure's saturation temperature

T [p(k)]

Final discharge pressure's saturation temperature T [p(k)]

Operating hours of the compressor motor

Operation Comp1

Operating hours of the compressor motor

Operation Comp1

Hint!

See manual for compressor control Hint!

See manual for compressor control



40 _551511_om_kas_gbr_1_.doc

If repairs are necessary, contact the service department of Grasso GmbH Refrigeration Technology.

4 MAINTENANCE INSTRUCTION

4.1 General Information Warning! The CO /NH2 3 cascade may only be serviced /

maintained by qualified operating personnel. These maintenance instructions shall be adhered to during all maintenance work. Moreover, all health & safety and fire prevention regulations and the safety regulations for refrigeration systems must also be observed.

All service and maintenance work must be carried out with care to ensure the CO /NH2 3 cascade maintains its efficiency and functional reliability. Any guarantee claims will be rejected if the customer failed to follow the Maintenance Instructions. This maintenance manual contains the service

regulations and records (certificates) for the CO2/ NH

3 cascade's first 10 years of service. The maintenance certificates are completed and signed as part of the inspection and service / maintenance by authorized fitters as evidence of the work done. During the guarantee period these confirmed maintenance certificates are also a precondition for possible claims under the guarantee provided by Grasso GmbH.

Caution!

Pay attention to maintenance manual!

every 24 Check weekly monthly Remarks to 72hrs

Final discharge temperature X

Minimum superheat must not be lower than 25 K.

Maximum final discharge temperature 100°C.

See parameter list! X Oil temperature The viscosity may not be less than 7 cSt at max.

speed.

Oil pressure X The oil pressure must be at least 0.5 bar above the final discharge pressure, an oil pressure fault may be caused by a clogged oil filter.

Final discharge pressure X See project value (parameter list). Determine the superheat on the discharge side by comparison with the final discharge temperature.

Oil level in oil separator X An oil level must be visible in the sight glass at all times. If the oil level is below the bottom third of the sight glass, recharge oil.

While compressor is stopped, the heater must automatically start up. If the thermostatic cutout (limiter) switches off the heater, this may be an indication of an oil shortage.

X Oil heater

Adjusting the safety devices X See set values in the parameter list.



_551511_om_kas_gbr_1_.doc 41

every 24 Check weekly monthly Remarks to 72hrs

Solenoid valves must switch audibly when the output is adjusted. Check in operating mode "1 (manual + manual)“.

X Output control

Number of operating hours

Cf. maintenance schedule for necessary maintenance/servicing work. X

Oil pump collection sump X Empty oil pump collection sump.

Oil collection sump �shaft seal X Empty oil collection sump shaft seal.

Visual inspections for leaks and replace ring gaskets if necessary. See heat exchanger documentation.

Heat exchanger X

(for chillers only))

Before starting work on the CO4.2 Servicing/maintenance and safety 2 circuit the refrigerant must be completely removed by suction.

Caution! When working on the CO2 circuit ensure good ventilation in the room, including in the area of the floor.

The safety data sheets of the refrigerant used and the refrigeration oils and in particular the Grasso safety information for the refrigerants NH

Contact with the refrigerant can cause cold burns or frostbite.

(R717) and CO3 2 (R744) are to be observed when working on the CO /NH2 3 cascade. Released gas can have a suffocating effect.

4.3 Searching for leaks on refrigerant side / leak test circuit NH3

Danger! Prerequisite for perfect functioning of the cascade is an absence of leaks in it. All work on the NH3 refrigerant circuit,

primarily opening, are significantly more dangerous than the familiar safety refrigerants!

Leaking parts or connection elements lead to refrigerant and oil losses. The leaking point must therefore be localized and repaired in the event of:

— Loss of inert gas charge (delivered condition)

Before starting work on the NH3 circuit the refrigerant must be completely removed by suction and evacuation.

— Loss of the entire refrigerant charge or

— resulting undercharge 5

The most striking feature when leaks occur in the filled NH

The pressure must then be equalized with the environment by way of dry nitrogen. Only then can the circuit be carefully opened or work performed that could lead to unintentional opening of the circuit.

3 refrigerant circuit is the pungent odour of the refrigerant.

The odour threshold of ammonia concentrations in air are far below the allowable maximum workplace values (MAK values) and is very far removed from Personnel protective equipment must be used if the

escape of even small amounts of ammonia cannot be ruled out with certainty.

circuit CO 5 see "charging characteristics" chapter 2



42 _551511_om_kas_gbr_1_.doc

the hazard limit, which ensures a very good early warning effect.

The purpose of the evacuation is to remove any air or moisture that may have penetrated the refrigerant circuit.

Leak detection methods: Evacuate the cascade by means of a vacuum pump. The cascade's compressors are not to be used for the evacuation.

— Regular visual inspections:

Smudges/dirt stains indicate leaking refrigerant/oil mixture. During evacuation, all affected parts of the circuit

should be at least at room temperature because cold parts hinder the removal of moisture.

— Leak test with nitrogen or dry air with a dwell time > 3 h:

If there is still any moisture in the cascade it will lead to a rise in pressure. Evacuation is to continue until the pressure no longer increases. Pressure comparison requires a constant ambient temperature.

Brush all connection points with foaming agent.

Oil-filled compressors or circuit section are to be charged with nitrogen only, not with air, to generate pressure.

— with NH or CO leak detector 3 24.4.2 Charging with refrigerant (see also initial

startup; initial charge with refrigerant) — Leak test with other aids:

Ammonia dyed red litmus paper blue Liquids are charged blotting paper dipped in phenolphthalein turns red (moisten)

1. after the leak test and evacuation of the respective circuit

For the leak test to determine leaks on the refrigerant side, e.g. in case of escaped inert gas or refrigerant charge, a test pressure must be generated in the refrigerant circuit which does not exceed 16 bar.

2. for recharging/topping up.

The refrigerant circuits are only charged via the charging valves of the respective circuit.

circuit Item (6865) COIf equipment is tested individually, the maximum operating pressure given on the respective piece of �equipment for the corresponding pressure chamber must not be exceeded.

2

NH

Danger!

Oxygen must never be used to build up the pressure because of the risk of explosion!

If leaks are found, relieve the test pressure before starting the repairs!

Evacuate the system after repairs and after rechecking for leaks.

4.4 Vacuating, charging and draining refrigerant and oil

4.4.1 Evacuating the refrigerant (see also initial start-up)

Evacuation is necessary:

1. after intervention in the refrigerant circuit and elimination of leaks

2. before the initial start-up / after restarting

3 circuit Item (2865)

The location of these charging valves is given in the P+I flow diagram.

Caution!

Mixing even the smallest quantities of CO and NH2 3 in the refrigerant circuits must be avoided under all circumstances.

Liquid refrigerant is added via the refrigerant feed valve of the respective circuit.

The refrigerant cylinder must be securely connected to the filling valve (drawing in valve) via a lockable filling hose. Ensure the filling hose does not contain any air (e.g. by including the line in the evacuation process).

The refrigerant is drawn in after slowly opening the refrigerant feed valve and the cylinder valve.

The charge volume capacity of the cascade is given on the manufacturer's name place and in the "Technical Specifications".



_551511_om_kas_gbr_1_.doc 43

To this end there is a level measurement probe (item 6900) on the separator, whose signal is detected by the GSC control and indicates the charge level.

Place the refrigerant cylinder on weighing scales during the charging process to check the charged volume.

Avoid overcharging the refrigerant circuit to prevent wet steam from being sucked into the compressor. 4.4.4 Draining the refrigerant

After the pressure has equalized between the cascade and refrigerant cylinder, a pressure difference for further charging can be generated by:

4.4.4.1 General notes on draining refrigerant

This action is required:

— if the system is overfilled — the compressor of the cascade (for initial startup) or — if the refrigerant or oil circuit is dismantled and

repaired — a connected auxiliary compressor. — for maintenance work on the oil circuit Once the circuit has been charged, the cylinder and

refrigerant charging valves should be closed tight. The refrigerant charging line and the refrigerant cylinder are to be removed.

— if foreign gases are detected in the system

Whenever work is carried out on the parts of the refrigerating system carrying refrigerant or oil, extreme caution is required as leaking refrigerant can cause hazards.

The system is in normal operation.

4.4.3 Charging characteristics For health and safety reasons, safety goggles and protective gloves must be worn. Comply with the charge quantities of the respective

refrigerant circuits given on the manufacturer's name plate or in the technical documentation of the CO

When work is carried out on the cascade, the refrigerant and oil must be moved to storage locations or disposed in accordance with the regulations and with the least possible loss.

/NH cascade. 2 3

The cascade's performance is reduced when it is under or over-charged.

If any liquid refrigerant is still left in the section to be opened, continue drawing it off until it evaporates. The cascade charge can only be correctly assessed

during operation (steady state, full load). Caution!

circuit NH3

Watch out for possible risk due to residual refrigerant! If the cascade is correctly filled, a liquid level can be

seen in the upper sight glass of the external circulation line (not separator) of the cascade heat exchanger during operation.

4.4.4.2 Charging refrigerant Undercharging characteristics:

The liquid refrigerant can be removed from the system and transferred into refrigerant cylinders or suctioned off as refrigerant vapour using an extraction device.

— During operation the liquid level can only be seen in the lower sight glass or not at all

— Excessive intake superheating The cylinders into which the refrigerant is transferred must be evacuated and cooled beforehand. — Evaporation temperature too low

— No refrigeration A sufficient number of cleaned, dry and subcooled cylinders must be made available ready for use before starting to empty the refrigerant. The refrigerant cylinder must be placed on the weighing scales.

— Cascade is switched off because of negative pressure/partial vacuum

— Unallowably high compressed gas temperature

Overcharging characteristics: The charging hose is securely screwed to the service valve of the respective refrigerant cycle at one end and to the valve of the refrigerant cylinder or extraction device at the other end. Then the service valve and then the flange valve are opened slowly.

— level can be seen in the liquid separator's sight glass.

circuit CO2

The CO2 circuit's charge is detected by the level of the liquid CO

The refrigerant cylinder charge is measured using weighing scales whereby it must be taken into account that the cylinder may only be filled up to

in the liquid separator (item 6000). 2



44 _551511_om_kas_gbr_1_.doc

80% of its capacity. If this charge volume has not yet been reached, although there is still refrigerant in the system, the cylinder pressure can be reduced by discharging gas from the cylinder.

For example, the cylinder's gas side can be relieved via a hose connection with the service valve into the suction line. If the cylinder is 80% full, the refrigerant feed valve and the cylinder valve are closed and the next cylinder is connected.

Repeat this procedure until all the refrigerant has been bottled. The transferred refrigerant volume must be documented.

After transferring the refrigerant into the cylinders, reclose the feed (drawing in) valve.

The system is evacuated until it is completely drained. After the extraction equipment has been switched off no further pressure rise may occur.

4.4.4.3 Connections for draining refrigerant

NH3 circuit

The NH3 refrigerant circuit or circuit sections can be drained via the following service valves:

— at the low-pressure level probe item (2875)

— the charging and draining valve in the liquid line item (2865)

— the service valves in the suction line (gas side)

— the service valves in the oil return line

CO2 circuit

The CO2 circuit can be drained via the following service valves:

Service valve in the pump discharge line item (6925)

Service valve in the injection line item (6865)

4.4.5 Venting the refrigerant circuits

Air which has penetrated the refrigerant circuit or remains there due to incomplete evacuation, will accumulate at the coldest point in the condenser during operation, because it cannot be condensed.

The result is a pressure rise in the condenser by the partial pressure of the air fraction. This leads to increased energy consumption through to cut-off off due to overpressure.

NH3 circuit

Venting takes place during operation by means of the service valve (installed on site) at the condenser outlet.

Conduct the air into a water tank while the valve slightly open so that residual ammonia is absorbed. If necessary, change the water in the tank to ensure

the ammonia concentration does not lead to nuisance/skin irritation, etc.

If the gas bubbles fully dissolve in the water there is no air.

Eliminate the causes of air penetration.

CO2 circuit

Venting of the CO2 circuit can only take place via the service valve item (6865) in certain circumstances.

The CO2 air mixture when the system is at a standstill should be drained to the outside in a controlled way using the hose connected at the service valve.

Note and comply with the safety regulations for handling the coolant.

4.5 Charging and draining oil (see also putting into service)

4.5.1 General notes on handling refrigerator oil

Oil drained from the compressor may not be reused. Always use fresh oil from sealed containers!

Make sure the oil cannot mix with other oil grades or types.

4.5.2 Check oil level

The liquid level in the oil sight glass of the oil separator should be between 1/2 and 3/4 of the sight glass height.

4.5.3 Oil filling

Follow the compressor start-up and operating instructions for refilling oil.

4.5.4 Draining, changing, checking oil

It may be necessary to drain the oil:

— to inspect or repair the compressor and

— if there is too much oil in the circuit

The oil in the cascade has to be changed:

— if the operating hours of the oil charge has reached the oil changing interval based on technical reasons

— if the oil was impermissibly contaminated due to a breakdown or accident (e.g. intrusion of water into the refrigerant circuit).

The serviceability and performance condition of the refrigeration machine oil is assessed by a rough visual inspection (contaminations) or laboratory analysis:

— after 5000 hours or

— at the end of one year's operation or



_551511_om_kas_gbr_1_.doc 45

— after remedying major damage.

— if the oil is dark coloured or highly turbid

Depending on the results of the analysis, the owner must decide whether to release the oil charge until the next assessment date or whether to have the oil changed.

Impermissibly damp oil must be removed from the unit immediately.

oil change sequence(see also the maintenance instructions for the compressor)

The cascade must be run for at least half an hour to reach its operating temperature before the oil can be changed.

— In mode 1 "manual + manual" with the compressor running and intake cut-off valve closed, transfer refrigerant from the compressor into the condenser.

If necessary, to this end change the set value of the minimum suction pressure limit on the NH3 side to 0.5 bar (a) and reset to the original value after evacuation

— Use an extraction device to remove the residual refrigerant (from the compressor).

— Use nitrogen to generate a slight overpressure.

— Drain oil through the filling line into a container provided for waste oil.

4.5.5 Used oil

Refrigeration machine oil drained from the circuit is no longer suitable for use in refrigeration plants. It has to be stored or transported in appropriately labelled containers. The operator is responsible for its proper disposal.

4.6 Maintenance Work

4.6.1 General notes

Work involving intervention in the refrigerant circuit is only to be undertaken by trained fitters in compliance with the terms of the guarantee.

The CO2/NH3 cascade must always be taken out of service before dismantling. All live parts must be disconnected from the power supply and the refrigerant must be removed from the apparatus concerned. This work must be performed extremely carefully in compliance with the safety regulations so that the operating personnel is not harmed by the refrigerant or refrigerating machine oil contained in the system.

Equipment under pressure must not be opened until it has been completely drained.

The CO2/NH3 cascade and parts of the cascade must not be left open as penetrating moisture endangers its function.

The main principle must be to allow as little air and moisture as possible to enter the cascade. As far as possible, all foreign substances must be kept away or eliminated as well, e.g.

• welding residues

• sealant residues

• auxiliary materials such as greases, oils or solvents

Welding and soldering work may only be performed with written permission. The necessary safety measures must be set out in the permit. These include:

• complete emptying of the respective equipment

• personal protective measures when opening equipment

• cleaning with suitable substances

• concentration measurements

• ensuring adequate ventilation

Renewed acceptance is necessary after any repair work or changes are made to pressure vessels requiring official acceptance. The welding may only be carried out by approved welders with valid welder’s qualifications.

4.6.2 Opening the compressor (see also compressor maintenance instructions)

If the compressor has to be opened to clean the suction casing or to replace components, it must be depressurised.

Sequence

Transfer the refrigerant into the condenser while the cascade is in operating mode 1 "manual + manual" by closing the suction cut-off valve and the oil return shut-off valve.

If the intake pressure has dropped to p = 0 bars g.p., switch off the compressor and close both manual shut-off valves on the compressor.

Attach hose to pressure chamber service valve and use extraction equipment to remove residual refrigerant.

The compressor may now be opened. Comply with the relevant health and safety regulations.

The work on the compressor must be carried out in accordance with the compressor operating instructions.



46 _551511_om_kas_gbr_1_.doc

Each time the compressor is opened, remove all air that may have entered by means of evacuation before putting it back into service.

Warning!

In addition to the usual cleanliness, work on the suction filter requires special care because the compressor is completely unprotected against coarse dirt particles during this work.

4.6.3 Dismantling the compressor suction filter (see the compressor maintenance instructions)

The intake filter is a dirt trap on the intake side of the compressor. To clean it, proceed in the same way as for dismantling the compressor. Remove the intake filter after the ambient pressure is reached. After cleaning or filter change and reassembly, you should evacuate.

4.6.5 Changing the suction filter before refrigerant pump - CO circuit 2

1. Switch off the unit/ cascade.

2. If the suction filter is very dirty it may be necessary to replace it outside the normal maintenance schedule. 4.6.4 Replacing the suction filter

1. Close the discharge-side shut-off valve on the unit/ cascade.

3. To change the suction filter insert before regrigerant pump, close the following valves in accordance with the P+I diagram: 2. Open suction-side shut-off valve and shut-off

valve bypass check valve - suction side - and thus equalise pressure with the low pressure side.

— (6005) Stop valve before suction filter

— (6085) Stop valve behind suction filter 3. Close suction-side shut-off valve and bypass valve

- check valve. 4. Equalise pressure with the atmospheric pressure.

5. Drain refrigerant (6925). 4. Draw off residual overpressure via vent valve of suction filter or drain taking into account the safety regulations.

6. Dismantle cover of suction filter (6010).

7. Remove the filter element and properly dispose of manner if it is highly soiled. 5. Unscrew housing cover of compressor.

6. Remove suction filter element. 8. Carefully insert a new filter element. 7. Clean suction filter element, wash out with

suitable grease-dissolving cleaning agent then blowing out with compressed air.

9. Close the suction filter cover (6010).

10. Reopen valves in accordance with item 3.

11. After the pressure has been equalised, vent suction filter via the vent valve (6920).

8. Renew round ring on suction filter element and reinsert suction filter element.

9. Renew round ring on cover, firmly close cover. 4.6.6 Oil change

10. Use a vacuum pump to evacuate the unit/ cascade. 4.6.6.1 Meaning

Aged oil features an increasing loss of lubricity. So all rotating components of the compressors are endangered. The filter elements become prematurely clogged and must be cleaned and replaced at shorter intervals.

Warning!

Shut off oil pump!

If evacuation is not possible, the unit/ cascade is vented in the next step via the vent valve on the suction filter. Collect escaping refrigerant and dispose in accordance with the legal regulations.

The degree to which oil in refrigeration plants has aged must be checked by analysis and comparison of the data with those of fresh oil. Oil ageing can also be judged from the darkening of the oil colour and the deposits found in the oil filters. If the degree of ageing cannot be assessed reliably by laboratory analysis and the results of visual examination, it is advisable to change the oil at the following intervals (see Maintenance schedule).

11. The unit/ cascade is pressurized with a slight overpressure via the shut-off valve bypass check valve discharge side.

12. Then check all components for leaks. If this has been done, completely equalise pressure with the pressure line and then check the unit/cascade again for leaks.



_551511_om_kas_gbr_1_.doc 47

8. Use a vacuum pump to evacuate the unit / cascade.

Warning!

Oil change intervals Warning! Change oil in SCUs using ammonia as

refrigerant after every 5,000 operating hours or after 1 year at the latest.

Shut off oil pump!

Change oil in SCUs using ammonia as refrigerant after every 10,000 operating hours or after 2 year at the latest.

If evacuation is not possible, the unit / cascade is vented in the next step via the vent valve on the suction filter. Collect any escaping refrigerant and dispose of in accordance with the legal regulations. 4.6.6.2 Maintenance Work

Take oil samples for analysis and comparison of the data with those of fresh oil at regular intervals. Examine the colouration of the oil visually and evaluate the degree of contamination.

9. The unit / cascade is pressurized with a slight overpressure via the shut-off valve bypass check valve discharge side.

10. Then check all components for leaks. If this has been done, completely equalise pressure with the pressure line and then check the unit/cascade again for leaks. Charge oil and startup the unit / cascade in accordance with the Operating Instructions.

4.6.6.3 Changing the oil

1. The unit/ cascade must be run for at least half an hour to reach the operating temperature before the oil can be changed.

2. First shut down the unit/ cascade as described in the Operating Instructions. 4.6.7 Replace oil filter

1. Switch off the unit / cascade. 3. Open the shut-off valve in the bypass line around the check valve - suction side and the suction-side shut-off valve to equalise the pressure between unit / cascade and suction line. If several units are operated in parallel, if possible the refrigerant should be drawn off to attain a pressure approx. 1 to 3 bar above atmospheric pressure. Then reclose the shut-off valves bypass and suction-side shut-off valve. Otherwise the pressure can be reduced by opening the vent valve on the suction filter and then disposing of the refrigerant as specified by law.

2. If the oil filter is very dirty it may be necessary to replace it outside the normal maintenance schedule.

3. To change the oil filter insert, close the following valves in accordance with the P+I diagram and the oil filter with multi-function block documentation):

— (065) shut-off valves upstream of oil filter

— (070) shut-off valve function oil

— (080) Control valve - injection oil with integrated check valve function 4. Then drain the waste oil via the oil draining/oil

charging valves and dispose of (Important! hazardous waste!). Once this has been done, reclose the valve and if possible continue to draw off the refrigerant with a compressor connected in parallel until atmospheric pressure is virtually reached.

When closing the valve (080) note the number of revolutions actuated. When opening the valve it must be returned to its initial position (see item 10). This is necessary to ensure the final temperature remains unchanged and therefore to avoid possible vibrations in the oil line. 5. Otherwise depressurize the unit / cascade by

opening the vent valve - suction filter, taking into account the safety regulations for refrigeration systems.

— Shut-off valve bypass oil cooler (optional)

4. Equalise pressure with the atmospheric pressure.

5. Drain oil. 6. Open the drain plugs and valves on the oil cooler, oil separator and oil filter with multi-function block to drain any residual oil. Then reclose the drain plugs and valves.

6. Dismantle oil filter cover of the multi-function block.

7. Remove the oil filter element and properly dispose of manner if it is highly soiled. 7. Replace the filter element of the oil filter and

clean or replace the filter insert of the suction filter. 8. Carefully insert a new oil filter element.



48 _551511_om_kas_gbr_1_.doc

9. Close the oil filter cover of the multi-function block.

The axial grooved ball bearing ist not adjustable. The axial play is predetermined by the manufacturer and cannot be changed.

10. Reopen valves in accordance with item 3. The valve (080) must be returned to its initial position.

The axial grooved ball bearing should be subjected to a visual examination and replaced according to the oil pump documentation, if required.

11. After the pressure has been equalised, vent oil filter via the vent valve.

4.6.11 Checking the pull-in torques at fastener of fixing base

circuit 4.6.8 Changing the filter driers - CO2

1. Switch off the unit/ cascade. the pull-in torques at the top 25 Nm

2. Filter driers (6055) should be inspected according to the normal maintenance schedule. Replace the filter drier if indicated at sight glass.

the pull-in torques underneath 100 Nm

3. To change the filter drier (6055) close the following valves in accordance with the P+I diagram:

4.6.12 Changing the oil fine separation cartridges

The oil fine separation cartridges generally have a service life of approximately three years. — (6050) Stop valve before filter drier

If the oil carry over of the unit / cascade increases severely (oil recharging at unusually short intervals) the cartridges must be changed:

— (6090) Stop valve behind filter drier

4. Equalise pressure with the atmospheric pressure.

5. Remove the filter drier (6055) and properly dispose of manner if it is highly soiled.

1. Close the discharge and suction side shut-off fittings.

6. Carefully mount a new filter drier. 2. Draw off refrigerant and depressurize the unit / cascade. 7. Reopen valves in accordance with item 3.

3. Check the pressure on the display of the control or connect a test pressure gauge.

8. After the pressure has been equalised, vent filter drier via the vent valve (6065).

4. Dismantle the pipe bend on the oil separator. 4.6.9 Clutch maintenance

5. Dismantle the check valve installed in the oil separator, this step is omitted if a shuttable check valve is used on the discharge side.

1. Switch off the unit/ cascade.

2. Secure the electric motor against accidentally being switched on. 6. Remove the securing wire [3].

3. Visually inspect the plate packages. 7. Undo the hexagon screws [2] used to fix the oil fine separation cartridges. 4. Check the tightening torques of the fitting

screws. 8. Remove the cartridge [1].

5. Check the alignment of the electric motor and if necessary correct it according to the steel multi-plate clutch documentation.

9. Install the new cartridge in the reverse order.

Warning!

6. Regrease the clutch (if provided for in the maintenance instructions for the clutch).

Securing wire [3] must be re-attached !

4.6.10 Oil pump maintenance� (for external oil pump)

An amount of leakage oil of up to one drop/minute is required for lubrication of the slide ring seal and thus permissible.

The slide ring seal is free of maintenance. If the amount of leakage oil is too large, replace it according to the Oil Pump Documentation.



_551511_om_kas_gbr_1_.doc 49

• the type of heat carrier or cooling agent circuit (open or closed),

• the quality of the heat carrier or cooling agent,

• the materials in the circuit,

• the flow rate.

Deposits on the tubing of the heating exchangers increase the difference in temperature between the condenser temperature (tC) and heat-carrier outlet (t ) or between evaporating temperature (tW2 0) and cooling agent outlet (tK2) lead to greater �pressure drops. This reduces the chiller’s performance, output, flow rates, etc. The pump power input is increased.

The cleaning cycle depends on the installation and should be defined in accordance with it.

4.6.14.1 Chemical cleaning

A specialized company has to perform the chemical cleaning of the equipment. The materials used in the components of the package must be taken into account in this respect.

Chemical cleaning requires a separate cleaning circuit for which separate connection possibilities should be provided. To do so, proceed as follows:

fig. 27: Oil fine separation cartridge

• Block the corresponding heat exchanger from the remaining circuit

4.6.13 Finding and fixing leaks

Lower refrigerant levels in the containers are due to loss of refrigerant as a result of leaks. For this reason, all pipes, connections and valve glands should be checked regularly, especially in the initial period after fitting, with a suitable indicator (litmus paper, etc.).

• Drain the heat carrier/cooling agent or cooling water from the heat exchanger

• Connect the cleaning circuit to the heat exchanger (check for leaks into the environment and other parts of the circuit and remedy if necessary).

Leaks are revealed by a change of colour and must be sealed immediately.

The handling and cleaning technology must conform to the manufacturer’s information pertaining to the cleanser (neutralization, flushing, disposal).

The supplier is not liable for losses of refrigerant caused by a lack of or improper maintenance!

New flange gaskets made of It-KVD are subject to fatigue immediately after installation. For this reason the flange screws should be tightened three times at 24-hour intervals. After that, hardly any further fatigue will be observed.

The delivery rate of the pump for the cleaning circuit has to be set in such a way that dislodged contaminants and particles do not cause the heat exchanger to become clogged. The cleaning circuit must be in the form of an open circuit to prevent pressure from building up in the system and to be able to observe the cleaning process.

4.6.14 Cleaning the heat exchangers (heat-carrier / cooling agent sides)

To avoid excessive soiling, the unit has to be equipped with a filter (mesh size 0.3 mm) installed in the refrigerant and heat carrier circuit lines immediately in front of the evaporator and the condenser.

4.6.14.2 Mechanical cleaning

Module welded plate heat exchangers can be removed for manual mechanical cleaning. Proceed according operating instructions of plate heat exchanger. Close all plate modules and check them for leakages after cleaning works.

The soiling and the associated required cleaning cycle are affected by the following:�



50 _551511_om_kas_gbr_1_.doc

4.7 Steps to be followed before starting the system after major repairs

4.7.1 Repair information

When repairing the chiller system, it should be borne in mind that new and advanced refrigeration plant is expected to meet the following standards as regards the technology and manufacturing processes they embody. Requirements:

• Absolute tightness of all devices and pipes.

• Dryness and cleanliness of the entire system.

• Use of welding methods causing only a minimum amount of dirt to collect in the system.

• Pipes bent on a pipe-bending machine only using refrigerating oil.

• If repairing the piping system from your own stocks, you are recommended to use a pipe with NBK sur�face quality (soft-annealed and descaled, mechani�cally or chemically descaled after soft annealing).

• When carrying out repairs to piping systems, care should be taken to maintain the original piping routes.

• Only pipes of sufficient quality should be used which are certified according to DIN 8975.

4.7.2 Pressure test, leak test

See operating manual, start-up instructions

4.7.3 Vacuum Test

After the pressure test has been completed, the system is evacuated and subjected to a vacuum test for 3 hours.

Evacuation is used to remove air and moisture from the refrigerant circuit (see operating instructions).

4.8 Repair work

Modifications and repair work may only be carried out by experts or persons with suitable training with the manufacturer's agreement and must strictly comply with the rules set out in the maintenance instructions for the components concerned.

Particular attention is to be paid to the aforementioned maintenance instruction.

Danger!

Before carrying out any maintenance or repair work the personal protective clothing must be checked.

Only spare parts made by the original equipment manufacturer may be used for repairs and for replacing wearing parts. They are available from the customer service department of Grasso GmbH Refrigeration Technology under the following address:

Grasso GmbH Refrigeration Technology

Holzhauser Straße 165

D - 13509 Berlin

Tel.: +40 (0) 30 435 92 766

Tel.: +40 (0) 30 435 92 759

Please remember to carry out the following steps before starting up the system again following repair or maintenance:

• Check the charge of the unit / CO /NH2 3 cascade with service media/resources (refrigerant, refrigerating machine oil, heat transfer medium) and set specified charge levels (sight glasses, level indicator). Charge using the built-in charging lines and record the charge volumes in the machine's log book.

• Set all fittings according to the operating instructions.

• Check all important technical parameters after switching on the unit /CO /NH2 3 cascade until a stable operating condition is reached.

Non-permissible operating conditions result in the shutdown of the refrigerating system or part thereof by the automatic safety system. If this happens, the causes of the shutdown must be determined and rectified.

The safety devices should be checked at least once a year and the switching values confirmed.



_551511_om_kas_gbr_1_.doc 51

4.9 Guide to disturbances, their causes and remedies

The units/ CO2/NH3-cascade units manufactured by Grasso GmbH Refrigeration Technology are highly advanced, automatic and extremely efficient systems. It is, however, possible that disturbances may occur, making it difficult to maintain continuous operation or causing part or the whole of the system to break down.

Table of disturbances

Failure Cause Remedy

Slow loss of refrigerant through leaks in the refrigerant circuit.

Check the entire system for leaks. Repair where found and top up the refrigerant if necessary.

Pressure gauge defective. Replace manometer.

Defective capacity control devices in the compressors

Check capacity control devices, connections for solenoid valves.

The suction pressure is too low, performance reduced and the system overheats.

The suction filters in the chiller are clogged.

Remove suction filter elements, clean or replace.

The suction pressure increases and the compressors become covered with a thick layer of hair frost or makes noises which indicate the presence of liquid (refrigerant) in the compressors.

The compressors are sucking in wet steam or liquid when it is started up. The safety device to prevent a too high liquid level is not responding.

Check liquid levels, drain some refrigerant if necessary. Repair safety device. Check superheat.

The condensation pressure is too high.

There is air or other non-condensable gases in the refrigerant circuit.

The refrigerant circuit should be vented.

The electrical circuit is interrupted by a pressure switch in the safety chain.

Switch on the power supply, check the pressure switch and replace or set properly as appropriate.

The compressors do not start up after the system is switched on or turns itself off again.

No oil pressure is building up in the unit/ cascade. The oil circuit is disturbed by clogged oil filters or leaks.

Replace or clean the oil filters, seal the leaks and top up with oil.

The compressors do not adjust to the required capacity.

The capacity control device is malfunctioning due to disturbances in the oil circuit or mechanical influences.

Check the oil circuit. The compressors should only be repaired by experts. Check the position detector of the compressor control slide.

The condensation pressure is too high.

See above. The compressors are shut off very often by the maximum pressure governor.

The maximum pressure governor is defective or set wrongly.

Remove the maximum pressure governor, repair it, set it correctly or replace it.



52 _551511_om_kas_gbr_1_.doc

Failure Cause Remedy

The suction pressure is too low. Open all valves on the suction side of the compressors.

The minimum pressure governor is defective or set wrongly.

Remove the minimum pressure governor, repair it, set it correctly or replace it.

The compressors are shut off very often by the minimum pressure governor.

The heat transfer capacity of the evaporator decreases.

Check the evaporator as to elevated oil concentration, possibly drain oil

The unit/ cascade is extremely noisy in operation.

The compressors or the drive motors are defective.

Please, call Grasso Service for more information

co2 and nh3 operation manual

Documents