CO2 Compressor

11/21 K-01 Type : 2MCL527 + GB + 2BCL306a Capacity : 20700 NM3/hr

Suction Conditions Pressure : 1.6 kg/cm2 abs

Temp : 40°C Molecular wt (dry) : 43.58

Discharge Conditions Pressure : 160 kg/cm2 abs Temp : 108°C

Normal Speed (MCL / BCL) 7976 / 11565 RPMRated Speed 8100 / 11745First Critical Speed 3200 / 6090

At normal operating conditions

Stage 1 2 3 4Suction Temp °C 40 45 45 50Suction pr kg/cm2 1.6 6.22 24.16 87.79Discharge pr kg/cm2 6.1 25 88 160Discharge Temp °C 178 174 165 100

The centrifugal compressors are designated by a series of capital letters and numbers. The capital letters describe the casing features. MCL indicates a compressor with the casing in two halves horizontally split. BCL indicates a compressor with the casing vertically split at end cover locations. The numbers after the letters, describe the impeller nominal diameter in millimeters and the impeller number.

FUNCTIONAL DESCRIPTION

The gas is compressed from 0.66 kg/cm2 to a final pressure of 160kg/cm2 in four compression stages by two centrifugal compressors driven by a single steam turbine driver (EHNK 32/36/64-3)The saturated wet gas from BL, before entering the compressor passes through suction knockout drum MV 09.The condensate from the gas is separated and drained through LV 61. The KO drum is provided with a very high level switch LSXH 62 A/B/C that will trip the machine if actuated.Three pressure switches PSXL 601A/B/C are provided down stream of the KO drum on CO2 line, which will actuate if the suction pressure drops below the specified limit. A voting logic two out of three will set the trip memory to trip the machine. Also near the first stage suction inlet on suction pipe a liquid trap is provided.

Interstage coolers are provided for 1st, 2nd and 3rd stages to maintain the gas at proper suction temperatures. After each cooler the gas flows through interstage condensate separators.

The condensate formed during cooling in the interstage coolers is separated and drained through level control valves (LIC-605, LIC-608 LIC- 611) All the three separators are fitted with high level switches (LSXH 606 / 609 / 612) to trip the machine on very high separators levels.

To avoid over cooling, the cooling water flow from the third stage intercooler is controlled by a temperature controller TIC-619 that controls the temp of 4th

stage suction. 4th stage suction temp is maintained at 50°C (The critical properties of CO2 are Tc = 31.1°C; Pc 73.2 kg/cm2) An antisurge line with surge control valve FV602 bypasses the 4th stage discharge gas to first stage suction. Antisurge line u/s and d/s are steam jacketed.

Another bypass line with HV603 bypasses the third stage suction gas to the first stage suction ( Interstage spill back)

A vent line with interstage vent valve HV601 vents out gas from 3 rd stage suction to atmosphere. On the final discharge a vent valve PV03 maintains the discharge pressure by venting the gas to atm.

Solenoid valves causes the antisurge valve FV602 and interstage vent valve HV601 open rapidly in response to the trip system.

Safety valves are provided in the discharge of each stages to prevent the downstream from overpressurisation.

Safety Valves Set pressures

First stage disch. PSV : 7 kg/cm2

Second stage disch PSV : 28 kg/cm2

Third stage disch PSV : 105 kg/cm2

Final stage disch PSV : 175 kg/cm2

Shaft sealing In order to minimise the gas losses from the compressor, the shaft ends are provided with shaft sealing systems.On MCL, we have labyrinth seals on both 1st and 2nd suction ends. The first leak off gas from the 2nd suction labyrinth is balanced with the 1st suction end and second leak from both ends are connected to vent.

On BCL, we have labyrinth seal with mechanical gas film type seals (dry gas seals) on 3rd and 4th suction ends.

On 3rd suction end one hot gas injection for labyrinth seal and one seal gas injection for dry gas seal are provided. A positive pressure difference across

hot gas injection and 3rd suction pressure, seal gas injection and hot gas injection pressure is to be maintained. The leakage from mechanical seal is vented to atmosphere. In the event of excessive leakage, pressure increases and the pressure switch PSH632 will activate an alarm.

On 4th suction end labyrinths, after the hot gas injection, the leakage through the balance drum is balanced with the 2nd disch gas line. A positive pressure difference across seal gas injection and balance leg is maintained. The leakage from the mech. seal is vented to atm and pressure switch PSH633 will activate an alarm on excessive leakage.

The seal gas is from the 3rd disch and filtered through 5-micron gas filter and its flow is regulated through flow orifices.

TK 01 TURBINE Normal power output 5552 KWMaximum power output 6365 KWSpeed - normal 7976 rpmSpeed Min/ Max 7290 / 8505 rpmFirst critical speed 3300 rpmSteam pressure 110 kg/cm2

Temperature 510°CExhaust pressure 0.1 aExtraction pressure 24.5 kg/cm2

Ext stm temp 326°CTurbine to governor speed 8.5 : 1Ratio

FUNCTIONAL DESCRIPTION

Steam flow through the turbine is in the axial direction. Arranged before the turbine casing is the emergency stop valve, the function of which is to shut off the total steam supply from KS header to the turbine in the shortest possible time. The live steam flows through the body of emergency stop valve to the valve chest of the HP control valves. These control valves are actuated by a lift bar and are so designed that their point of opening is determined by the lift bar, which is raised and lowered by the relay cylinder through a system of levers. The relay cylinder receives its control pulses from the hydraulic governor. The hydraulic governing system is designed to control the speed of turbo compressor. Simultaneously the extraction steam pressure in extraction line is also maintained by the governing system. Additionally,turbine governing system incorporates protective device to protect the turbine during adverse operating conditions,such as overspeed, rotor axial shift, low control oil pressure.

The HP control valves admit the live steam to the nozzle groups of the single row regulating stage.Turbines designed for regulating the steam flow through nozzle groups are provided with regulating stage,which takes the form of impulse blading permitting partial admission. After the part of energy of the

live steam has been utilized in the regulating stage which is of single row impulse type,the steam is passed to drum blading for doing further work and finally to LP blading section. In accordance with available heat drop,work is done and finally the expanded steam is passed out through exhaust hood to condensor.

Steam Extraction

For this type of turbine (partial condensation and extraction type), part of steam is bled from the turbine at the extraction branch behind the wheel blading and fed to the extraction steam. The control member here is the extraction stop valve (QCNRV),which operates and is tripped out in the same manner as the HP emergency stop valve. The purpose of the extraction stop valve is to separate the turbine from the extraction steam on tripout in order to prevent the turbine from overspeeding due to reverse flow of medium pressure steam when the machine is shut down.The pressure at the extraction branch is controlled by the LP control valve. The steam rate through the HP section is matched to the extraction rate in such a way that the pressure at the extraction branch is kept constant within the design data. Governing is by means of extraction pressure controller. The LP section consists of a further length of drum blading.

TURBINE CASING

The turbine casing is split axially. It is mounted on and aligned at the front end bearing pedestal, the front bearing pedestal serves both for supporting the turbine shaft by a journal bearing and a thrust bearing and for strutting the turbine casing by means of the casing side brackets and centering guides. Particular importance is attached to proper alignment, because the turbine shaft and the outer shell are supported independently of each other in the bearing pedestals. Whilst the position of the shaft is fixed by the bearings, the outer support of the casing must be so designed as to allow thermal expansion at the front end-bearing pedestal as well. The vertical position of the casing is governed by the bracket supports, whilst the small clearance under the heads of the bolts (used to bolt down the casing side brackets to the bearing pedestal) permits transverse thermal expansion of the casing relative to the bearing pedestal. The upper and lower casing guides fix the center position of the casing in the horizontal plane through the axis. They are designed to permit the casing to expand freely upwards and downwards. The rear end bearing pedestal is cast integral with the exhaust branch which is fixed in the axial direction relative to the bed plate,but which can freely expand radially in accordance with thermal expansion. Since the front end casing centering guide does not allow any axial displacement of the casing relative to the bearing pedestal,the front end bearing pedestal is moved towards the front end on thermal expansion of the casing. The oil piping is therefore installed with sufficient flexibility. Transverse displacement of the front end-bearing pedestal is precluded by an axial feather key. Likewise, transverse displacement of the exhaust branch relative to the bedplate is prevented by a centering guide.The exhaust branch is flanged to the turbine casing.

The turbine shaft is machined from an alloy steel forging. The journal bearings supporting the turbine shaft are arranged in two bearing pedestals. The front end bearing pedestal also houses the thrust bearing which locates the turbine shaft axially and takes up the axial forces.

The blading consists of an impulse stage, which permits partial admission and consequent efficient governing, and of no. of reaction stages in the LP drum part. The radial and axial clearances are liberally designed with a view to combining high operational safety with an optimum utilization of available heat drop.

The function of balance piston is to compensate the axial thrust to the highest possible degrees. Since the axial thrust varies with the load, the residual thrust is taken up by the thrust bearing mentioned above. At the same time, the balance piston seals of the high pressure in the wheel chamber against the pressure prevailing before the shaft glands.

The shaft glands seal off the casing at the points where the shaft passes through .The sealing elements consists of packing strips in the gland rings and of grooves machined in the shaft.

The packing gland shell (gland ring) carries on the periphery of its inner surface caulked in sealing strips which together with the edges of corresponding sealing strips or comb like projections on the rotor shaft, are forming a seal without mechanical contact between the moving rotor and stationary turbine casing. Such a series connection of consecutive sealing edges constitutes a seal of labyrinth type which acts on the principle of transforming potential energy (pressure) into kinetic energy (velocity of flow) and subsequently dissipating the kinetic energy by the formation of eddies. With sealing devices, which have no mechanical contact with the rotating member, a slight flow of leakage steam has to be accepted.

The governing system of the turbine is of the oil hydraulic type. The pulses are transmitted by governing members, located in the governing system flanged to front end bearing pedestal.

The function of emergency governor is to interrupt the steam supply to the turbine as soon as speed rises to an inadmissible value in the event of a disturbance.

DESCRIPTION OF TURBINE CONTROL SYSTEM

INTRODUCTION

The turbo compressor set is equipped with hydraulic governing system. The governing system is designed to control the speed of turbo compressor set according to the signal issued by compressor capacity controller (HIC). Simultaneously the extraction steam pressure in extraction line is also

maintained by the governing system. Additionally turbine-governing system incorporates protective devices to protect the turbine during adverse operating conditions such as overspeed, rotor axial shift.

GENERAL CONTROL PHILOSOPHY For control purpose single casing condensing turbine with one controlled extraction has been divided internally with steam glands in two parts , namely HP Part and LP Part.

In each part of the turbine steam flow is regulated by a set of steam control valves. The amount of opening of each valve is controlled by the hydraulic signal(secondary oil pressure) generated by speed governor and extraction pressure controller.

Speed governor generates the secondary oil pressure for control valve actuator (servomotors) in such a way that the change in amount of steam flow through HP &LP parts of turbine is same. This does not affect the steam flow through extraction.

Extraction pressure controller acts in such a way that upon decrease in extraction pressure, HP control valves open more and LP control valves move in close direction. Valve movements through changes in secondary oil pressures are designed such that the increase in power in HP part of the turbine is equal to the decrease in power in LP part of turbine. This arrangement does not affect the total power developed by the turbine. Similarly, upon increase in extraction pressure,HP control valves move in close direction and LP control valves move in open direction.

Output of speed governor and extraction pressure controller is coordinated in a hydraulic amplifier through simple lever system.

SPEED CONTROL :-

A woodward PG-PL speed governor is employed to control the speed of turbo compressor set. An automanual station (HIC-604) provides air signal of 0.2 to 1.0 kg/cm2 to pneumatic speed setting mechanism for adjusting the governor speed. Actual speed is acquired from turbine shaft through gear drive by a centrifugal flyweight head pilot valve assembly. Depending upon speed setting and actual speed, pilot valve controls the flow of oil to and from the governor power cylinder assembly. The power cylinder assembly in turn positions a lever of hydraulic amplifier.

HYDRAULIC AMPLIFIER

Hydraulic amplifier consists mainly of 3 sets of control sleeve, hollow follow-up piston,tension spring and a set of lever system for extraction pressure

control. Control sleeves and hollow follow-up pistons are provided with control ports. The hollow follow-up pistons are held in their respective control sleeves with the help of tension springs. The overlap of ports between control sleeve and follow-up piston depends upon output from Woodward speed governor power cylinder and tension in the tension springs.

Oil from trip oil circuit is admitted into the follow-up piston through an orifice. The pressure inside follow-up piston depends on overlap of control ports. This pressure is called as secondary oil pressure.

Any variation in the position of power cylinder output due to speed change, or change in pneumatic speed setting signal causes the overlaps of port between control sleeve and follow-up piston to readjust. These results in either increase or decrease of HP secondary oil pressure and LP secondary oil pressure. These pressures are transmitted to the HP and LP control valve actuators respectively.

EXTRACTION PRESSURE CONTROL

Extraction pressure is sensed by a pressure transmitter and provides actual value to a pressure controller PIC647. Pressure controller depending on the set pressure and actual pressure, produces 0.2~1.0kg/cm2 pneumatic signal. This signal is transmitted to a pneumatic actuator (positioning device) which in turn position the tension springs in follow-up pistons through levers. Upon decrease in extraction pressure HP follow-up piston spring is pulled up and LP follow-up piston spring is released. These results in increase in HP secondary oil pressure and decrease in LP secondary oil pressure. Upon increase in extrn pr, control action is reversed. These pressures are transmitted to the HP and LP control valve actuators respectively.

Thus the HP & LP secondary oil pressures are generated in hydraulic amplifier through combined action of speed governor and extraction pressure controller.

CONTROL VALVE ACTUATORS

Control valve actuators position the control valve corresponding to the secondary oil pressure generated by hydraulic amplifier.Control valve actuator (servomotor) mainly consists of a pilot valve; a power cylinder and a feed back system. Upon change in secondary oil pressure, pilot valve provides oil passages to and from power cylinder. The movement of power piston is transmitted to the control valves through levers. The feed back lever resets the pilot valve to its neutral position once the power piston occupies new position corresponding to changed secondary oil pressure. The system is such that the increase in sec oil pr causes the control valves to open. Hence interruption of sec oil pr causes the control valves to close.

EMERGENCY STOP VALVE AND STARTING DEVICE

The emergency stop valve provided in KS line is of quick closing type. The valves are actuated by means of a starting device. Emergency stop valve consists of spring-loaded piston and piston disc, which is connected to the valve cone through a spindle. For opening the ESV, startup oil from starting device is admitted to the space above the spring-loaded piston, by operating the starting device. Due to start up oil pressure the piston moves towards the piston disc and they form a tight seal against each other. Oil from trip oil circuit is then admitted to the space under the piston disc, and the space above the piston is connected to oil drain. The trip oil now forces both the piston disc, and piston to the outer position thereby opening the ESV. As long as the trip oil pressure is maintained, the piston and piston disc cannot be separated by spring force. The stop valve is closed only when trip oil pressure drops substantially. On the loss of trip oil pressure, the pressure of secondary oil tapped from trip oil circuit drops to zero, thus causing the control valves to close. This arrangement provides a two-fold protection against steam entering the turbine.

Once ESV is opened, further operation of starting device builds up sec oil pressure. At a preset value of sec oil pressure, control valve actuator shall open the control valves, thereby admitting the steam into turbine. Maximum value of sec oil pressure can be limited at any point of operation by starting device. At certain speed governor takes over the speed control. At this point starting device can be released fully.

TESTER FOR ESV

Testing device is provided to check the proper functioning of ESV during normal operation of turbine. If the testing device is operated, it will admit the pr oil to the space behind the test piston of ESV, which will then be pushed against the piston and move the piston and valve spindle towards the closed position ( partial closing)

TRIPPING DEVICE

Whenever the turbine is to be tripped, the governing oil pr (trip oil line after tripping device) is drained by tripping device. Thus pr in front of ESV piston disc and sec oil pr falls, resulting in closure of ESV and control valves.

The tripping device is operated on the occurrence of any of the following - Manual operation - Actuation of overspeed governor- Rotor axial movement- Drop in trip oil pressure.

OVERSPEED GOVERNOR

Overspeed governor protects the turbine against speeds higher than the safe value for turbine operation. Overspeed governor consists of an eccentric pin located inside the turbine shaft and held in position with a spring. At a preset

speed (trip speed) centrifugal forces of eccentric pin will overcome the spring force and the pin will move out of shaft. The outward movement of the pin actuates a lever of tripping device and thereby tripping the turbine.

AXIAL SHIFT PROTECTION

Whenever the turbine rotor movement in axial direction is excessive, then a projection on the rotor comes underneath the lever of tripping device and actuates the lever and thereby tripping the turbine.

OVERSPEED GOVERNOR TESTER

Overspeed governor tester facilitates the testing of overspeed governor pin when turbine is operating at maximum continuous speed. When overspeed governor tester is operated it will hydraulically bypass the tripping device ensuring uninterrupted oil supply to governing system irrespective of the position of tripping device. On further operation of overspeed governor tester, pressurised oil is injected below the overspeed governor pin. The pressurised oil causes the pin to move out of shaft and actuates the tripping device lever, this ascertains the free movement of overspeed governor pin.

NON RETURN EXTRACTION STEAM VALVE In the extraction steam line, non-return quick closing flap valve has been provided, which prevents reverse flow of steam into turbine. Also at turbine trip, non-return valve is closed by its actuator, which in turn acts at the loss of trip oil pr. Drain speeder helps in quick draining of oil from QCNRV actuator.

TRIP SOLENOID VALVE (SSSV 2222)

Trip solenoid valve facilitates the tripping of turbine from remote place such as control room through push button. Whenever the solenoid valve is de energized, it interrupts the oil supply to trip oil circuit and simultaneously depressurizes the trip oil circuit.

SURFACE CONDENSOR

The surface condensor is a shell and tube nest arrangement with water boxes at either end. The steam side of the condensor is connected to the exhaust hood of the turbine. The main functions of the condensor are,

- To condense the steam exhausted from the turbine.- To maintain a vacuum such that the heat drops to be utilised in the

turbine is maximum.- To maintain the temperature of the condensate always at the saturation

temp so that all dissolved gases are liberated .- To facilitate the extraction of air and other gases.

To operate the condensor at the optimum efficiency, the condensor is designed such that the temp of the exhaust steam and that of the condensate are nearly equal. In other words, the cooling water will carry no heat other than the latent heat of condensation.High level switch LSXH 641 A/B/C are provided on hot well and will trip the machine in case of high level.

EXTRACTION SYSTEM OF NON-CONDENSIBLES

Each system consists of two steam jet ejectors, one intercondensor and one after condensor. There are two such systems along with a hogging ejector.The primary ejectors by means of motive steam (LS) eject the gases and vapors from the turbine condensor and condense them in the inter condensor. The secondary ejectors further ejects the uncondensed gases from inter condensor and condenses in the after condensor. The cooling medium in these ejector condensors is cooling water. The after condensor operates at atmospheric pressure and the uncondensed vapors are vent into atmosphere. The condensate from intercondensors flow to hot well by means of loop line and the condensate from after condensor by means of condensate traps.The hogging ejector is a single stage ejector which by means of motive steam ejects the air of turbine condensor to atmosphere. The hogging ejector reduces the startup time and is also called as startup ejector.The normal operating pr of the condensor is -0.95 ataPr switch PXH 648 A/B/C, if activated on turbine exhaust pr very high will trip the machine.

LUBE OIL SYSTEM

The lubrication system for turbine and compressor is common one.The main reservoir has a capacity of 18.8 m3 and a electrical heater for heating purpose so that the right viscosity for start up is obtained.

The overhead tank has a capacity of 5.0 m3 .The overhead run down tank is placed about 7.5 m over the compressor center line. This tank shall cater required oil quantity to the bearings during the time taken for the turbine to reach zero speed after it is tripped in the event of all the lube oil pumps fail. This tank caters compressor side lubrication for 5 min and turbine side for 10 min .Two identical centrifugal oil pumps P 24 A/B provide the oil circulation, both pumps are motor driven. Each pump is capable of supplying the capacity required by the whole system; therefore each pump can operate as stand by pump for continuous service. The stand by starts automatically by pr switch PXL 677.

On the lube discharge header a hydropneumatic accumulator (holdup tank) direct contact type (V13) with a retention time of 5 sec is installed, it is fitted with level control valve for discharging into the system and level switches to maintain proper level into the vessel. Nitrogen from pressurized cylinders is used for maintaining the hold up tank pressure.

The lube oil from the pumps discharge is cooled in the oil cooler E38 A/B. The twin oil coolers are designed for one in service at a time and the oil can be diverted to one of the coolers by means of two three way valves which are simultaneously operated by a hand lever, and leaving the other cooler as standby.

From the lube oil pump's discharge header, hot oil at the discharge pr is fed to control / governing oil system. In the governing oil circuit there is a duplex filter assembly whose filtration range is 5 micron.

The cooled lube oil then passes through a duplex filter system with one in service at a time. The filtration range is 10 microns.

The filtered clean cool oil then flows to the lube oil header whose pr is maintained by PCV 670. The lube oil header is split into two separate headers catering the requirements of compressor train and turbine separately.

The overhead lube oil tank is fed from this L.O. header and during normal running a constant amount of oil is fed through a flow orifice and overflow of the O.H. tank is diverted to mail oil reservoir. The O.H. tank is fitted with LSXL 653, which is connected to compressor start up interlock.

On lube oil header the pr switch PSXL 677 shall alert low oil header pr and also give command to - Start up interlock permissive - Standby pump start interlockThe emergency lube oil pump P25 is motor driven with emergency power supply. In case of shut down of both oil pumps, the lube oil header pr switch will trip the machine and as well as gives command for starting EOP. During such shut down event , the lubrication requirement of turbine are met by this pump for cooling down period.

THE LUBRICATING POINTS ON COMPRESSOR / TURBINE

- Turbine MCL coupling- MCL thrust bearing- MCL front journal bearings- MCL rear journal bearings- MCL gear box coupling- Gear Box- Gear box BCL coupling- BCL front journal bearings- BCL rear journal bearings- BCL thrust bearings- Turbine rear journal bearings- Turbine front journal bearings- Turbine thrust bearings- Governor drive gears- Barring device

The oil to individual bearings and other points is controlled with regulating valves. The individual oil pressure, are in the following range:Thrust bearings 0.3 ~ 1.3 kg/cm2 (adjust 0.7 kg/cm2)Journal bearings 0.5 ~ 1.5 (adjust 1.5 kg/cm2)Couplings 1.5 ~ 2.0Gear box 1.8 ~ 2.0

The oil outlet from these points is collected to individual return headers and flows to the main oil reservoir. All the return headers are provided with flow glasses, and local temperature gauges.The lube oil reservoir is also fitted with a oil clarifier which will separate moisture and any foreign material from the oil. This unit operated in closed circulation and its operation is intermittent or need based.

START UP PREPARATION

The compressor start up is divided into following activities:- Lube oil system preparation- Steam network preparation- Turbine condensor preparation - Compressor gas circuit preparation- Rolling the machine- Loading the machine

Lube oil system preparation

1. Be sure that main oil tank is filled with recommended grade of oil (T 46)2. Check the oil level in main oil tank, if necessary make up.3. Confirm that the suction strainers of P24 and P25 are clean and are in

position.4. Check that the suction and discharge valves of all the pumps are open.5. Lube oil header pr control valve u/s & d/s i/v are open and bypass is

closed6. Hold up tank level control valve is in line7. All oil drain valves of coolers, filters and pipes are closed8. Check that the isolation valves of pr switches, pr gauges, pr transmitters,

level gauges, switches and valve actuators are open.9. Oil coolers CW inlet i/v are open and CW outlet i/v are crack open.10.Start the lube oil pump P24 and check its discharge pr.11.Open the vent of the cooler in line to bleed off all the air. Once oil starts

coming through flow glass, close the vent. Open the bypass of the stand by cooler and bleed off all the air. Thus the stand by cooler is also full of oil and is at working pr.

12.Bleed off all the air from the filter in line and isolate the vent. Open the bypass of stand by filter and also bleed off all the air, thus the stand by is full of oil and is at working pr.

13.Fill the overhead tank by slightly opening the bypass of filling orifice. Close once the overflow starts. During this operation care must be taken not to overload the lube oil pump. Once overflow starts, there will be a constant overflow from this tank.

14.Check L.O. temperature and if necessary adjust the cooler CW outlet i/v.15.Check the oil pr at various points and confirm they are OK

- Lube oil pump disch pr : 10.0 kg/cm2

- Lube oil header pr : 2.5 kg/cm2

- Lube oil pr to journal bearings : 0.5 to 1.5 kg/cm2

- Lube oil pr to thrust bearings : 0.3 to 1.3 kg/cm2

- Lube oil pr to coupling or gear box : 1.5 to 2.0 kg/cm2

- Control oil pr : 8 kg/cm2

16.Check the normal flow of oil coming from all the return headers. The temp of all the outlets shall be same.

17.Check the L.O. filter diff pressure It should be normal.

Steam network preparation

Once the K.S. network is charged up to compressor battery limits, the K.S. header upto turbine stop valve should be brought to the operating temp and pr. The line heating should be carried out gradually in order to maintain the stresses on turbine flanges uniform and to achieve an uniform heating of turbine body and rotor, proceed as follows:1. Start turbing the rotor by engaging barring device.2. Open the drains (2 nos) and 2 " start up vent on K.S. header.3. Crack open the K.S. isolation valves bypass. Slowly the K.S. line temp

starts increasing. Up to 300°C follow an approx. temp gradient of 50 to 60°C/hr, beyond 300°C open the bypass fully and start throttling the start up vent. Once a temp of 400°C is obtained, close the drains and the header can be pressurized and i/v be opened as and when required.

4. During heating, 25-30°C more than the saturation temperature (320°C+30°C=350°C) must be achieved to avoid possible condensation during rolling the machine.

5. Keep the extraction line steam trap by pass crack open to drain out the condensate. Also crack open the extraction line isolation valve bypass.

6. Now the auto changeover of P 24 A to B and vice versa may be checked and the pr dip should be minimum, so that it does not activate the trip switches. A smooth change over indicates effective hydropnuematic hold up system.

Turbine condensor Preparation

1. Ensure condensor CW inlet and outlet valves are open. Bleed off the air from vents.

2. Ensure the air valves between condensor and ejectors are open.3. Close the hot well drain4. Ensure the i/v of level gauges, level switches, pr switches are open5. Ensure all the individual drain valves coming to drain collecting header

are open. These drains are:- Turbine HP casing drain- Extraction header drain- Turbine LP casing drain- Balance leg drains

6. Ensure that the condensate inlet and outlet valves of one of the ejector condensor are open

7. Open the isolation valve of LV640 A/B. Ensure that the condensate inlet and outlet valves of one of the ejector are open.

8. Crack open PW make up and once the level is made up, open the suction, discharge and vent valves of both the condensate pump

9. Keep LC640 on manual and start P27. This is to avoid overloading of the pump during startup. Now maintain the hot well level with LC 640 and take it on auto mode. If necessary, now build up the hot well level till the high level alarm appears. At this point the stand by condensate pump should take a start automatically. If satisfactory, stop one of the pumps, and normalize hot well level and leave the control on auto mode. Thus the condensate circulation is established and vacuum can be pulled as and when required.

10.Take clearance from shift engineer and proceed to pull the vacuum.11.Open the motive steam LS i/v.12.Ensure that the i/v of sealing condensate header is open and check that

for all the sealing points condensate injection is on.13.Open the turbine gland steam condensor cooling water inlet and outlet i/v.

Open the gland steam vent line isolation to the gland steam condensor.14.Keeping the gland steam header drains open, charge gland steam header

by opening PV653. Maintain the gland steam header at a positive pr (approx. 0.2 kg/cm2)

15.Open the motive steam to the gland steam condensor ejector and maintain the gland steam vent header pr slightly positive.

16.Now line up the hogging ejector. Lineup first motive steam followed by opening of the air valve. Once the air from the system is evacuated, line up secondary and primary ejectors system. Open the air valve for this system. Now we can cut the hogging ejector, first by cutting air valve followed next cutting by motive steam. Now the vacuum level at no load must be constant about 0.12 to 0.15 ata.

Compressor gas circuit preparation

1. Obtain clearance from the shift engineer to charge the gas.2. Open the casing drain valves of MCL (5 drains) and BCL (1 drain)3. Check that interstage separators MV16, MV17, MV18 and KO drum MV09

's LCV bypass valves are in close position and LIC's are in auto mode set at 40%.

4. Ensure that interstage coolers E25, E26, E27 's CW inlet and outlet valves are open and E27 CW outlet control valve is on auto with bypass crack open.

5. Compressor discharge vent PV03 is on manual and is open approximately by 30%. All the steam tracing and jackets are live.

6. Open CO2 valve on the inlet of KO drum7. Now check in field and confirm that

- Antisurge valve FV602 is fully open- 2-1 kick back valve HV 602 is fully open- Interstage vent HV 601 is fully open (because the turbine is yet

reset)

- Manual vent on 2nd suction is kept open.

ROLLING THE MACHINE

1. By this time KS header temperature has reached a minimum of 400°C. close the start up vent and drains and pressurise KS header,open KS motorized valve.

2. Open the extraction line i/v. close the trap bypass and line up trap.3. Obtain clearance from shift engineer for rolling.

*** CONFIRM FOLLOWING ***- Speed signal is zero HIC 604- Extraction signal is zero PIC 647 - Antisurge control is on manual and valve is fully open- 2 - 1 spill back valve is fully open

4. Reset the turbine. Turbine reset is possible only when - All the trip conditions are in reset condition- Overhead tank level is normal- Antisurge valve is open- 2 - 1 spill back valve is open- Barring device disengaged- L.O. header pr normal

5. On reset: - The control oil solenoid valve (SSSV 2222) energizes and control oil

circuit shall be pressurized. However engage automatic trip gear for permitting trip oil pressure to build up

- Interstage vent valve closes.

Now the machine is ready for rolling

Rolling

To roll the machine turn the starting device in the opening direction slowly. Gradually the trip oil pressure above the piston disc of ESV will start building up. As soon as the oil pr above the piston disc exceeds the pr of the oil below the piston, the emergency stop valve begins to open. Stop turning startup device until the ESV is fully open.Once the ESV is fully open and the oil pr below the piston has collapsed to ZERO, proceed further by gradually turning the startup device in opening direction. The secondary oil pr will start building up. At the secondary oil pr value shown in governor adjustment report, (1.5 kg/cm2) the control valves are going to open. Very cautiously allow the control valves to open and admit KS to turbine. The rotor will start rotating and allow it to accelerate to the lowest speed shown on the starting and loading chart.Following the start up chart, increase the turbine speed through further turning of the startup device in the opening direction and while paying special attention to the prohibited speed ranges and to the smooth running behavior of the entire machine set. Speed up and achieve the minimum

governing speed, from where the speed governor takes over. Now the starting device can be further turned in the opening direction into its ultimate position and lock it.

NB:The first critical speed of MCL is 3200 rpm,Turbine- 3600 rpm , BCL -7000 rpm (equivalent compressor train speed is 3925 rpm) are all falling in the range of 3000 - 4000 rpm. So the prohibited speed range for the entire machine is 3200 ~ 4500 rpm should be crossed stepless and as fast as possible i.e. care should be taken not to hold the machine in prohibited speed range.

During starting, before and after the prohibited speed range limits check the following:

- Machine vibrations- Bearing oil pr and temp- Bearing metal temp

All these parameters must be normal and well within the acceptable limits.6. Close the casing drains.7. Cut off PW water make up to the condensor.8. Slowly start closing vent valve in the 2nd suction, watching 1st /2nd suction,

watching 1st disch/ 2nd suction pr. If the machine surges, do not close further, increase the speed by 30 ~ 50 rpm and then close.

9. Confirm the seal leak vent valves are open.10.Confirm the hot seal gas injection to 4th suction side end seal is fully open

and crack open the same to 3rd suction side end seal and maintain a positive pr difference, i.e. the hot seal gas pr must be 0.8 ~ 1.0 kg/cm 2

above the third suction pr.11.Check the pr differential of clean seal gas to dry seals of both BCL ends is

positive.12.Line up the extraction (MS header is already charged)

- Line up extraction at MGS - If there is an isolation valve closed on trip oil supply to extraction

NRV, release the NRV flap by operating the oil relay by opening the isolation valve slowly. While operating the oil relay ensure that the trip oil pr to ESV does not fall.

- Now start giving the extraction control signal PIC647 watching the extraction pr. The extraction steam starts flowing into the MS header, maintain normal header pressure, so that normal extraction pr is maintained. Maintain a minimum extraction flow of about 25 t/hr. Depending on the requirement increase the extraction flow

Machine expansion should be achieved before loading the machine. As a result of thermal expansion of turbine casing an absolute displacement of bearing pedestal can result. By knowing the rotor position and casing position safe conclusion can be drawn with regard to the axial clearances inside turbine.

13.Now close the turbine casing drains and extraction header drain.

14.Do not run the machine with low vacuum of turbine condensor as this will increase the turbine exhaust temp.

Loading the machine

1. Using the speed controller HIC 604, increase the speed in increments and simultaneously start closing HV 603. Watch out not to increase first and 2nd discharge pr beyond normal values. Closing HV603 will increase the flow to 3rd suction.

2. Check the 3rd suction flow and 4th suction temperature maintain TIC 619 at 50°C.

3. By closing HV 603, MCL is loaded fully and any increase in speed shall increase the capacity. Now start closing closing the main antisurge valve FV 602 slowly. On closing FV 602, the 3rd suction gas flow shall decrease and final discharge pr shall start building up. In order to maintain the required suction flow, simultaneously raise the speed of the machine. At any given speed, maintain a safe suction gas flow so as to operate the machine away from surge limits.

4. Maintain the disch pr by either slowly closing PV 03 or by closing FV 602. But the 3rd suction flows to be maintained above the surge limit.

5. During loading maintain the individual suction temp at near normal values, and observe the thrust bearing temp and pr differential across each stages of MCL and BCL. If the thrust loading is high, immediately pr differential to be adjusted accordingly to maintain / minimize thrust load and bring down the bearing temp. Imbalance in pr ratios will cause an increase in thrust and so maintain the compressor ratios while loading.

6. Do not keep the machine running at low pr (100 ~ 120 kg/cm2) and at low speeds for longer time. This causes an increase in thrust.

7. Now the machine is in fully loaded condition and CO2 is being discharged to atm through PV 03

8. Once the CO2 feed to reactor is started, slowly the vent PV 03 will close and the CO2 flow to the reactor can be increased/ decreased by either varying the speed of the machine or by varying the antisurge flow. However the safe limit is not to be crossed, as the machine may reach a surge point.

Monitor the following while the machine is running:

a. Radial and axial vibrations of the turbine and compressor.b. Bearing metal temp.c. Oil overflow in overhead tankd. Behavior of hot well level controllere. Interstage separators and KO drum level controllerf. Liquid trap functioning in first stage suction drip legg. Check whether HV 601,HV 602, PV 03 are passing in full close conditionh. Seal gas injection pr for BCL and gland steam header pr for turbinei. Lube oil pr to each individual pointj. DP across LO and GO filtersk. The intercoolers CW outlet temp.l. The compressor interstage temp and pr

m. Woodward governor oil leveln. Lube oil temp of reservoir, after cooler and temp of LO from discharging

pointso. Pressure and level in L.O. hold up tankp. Secondary oil pressure of governing system and corresponding valve lift

vs. speedq. Expansion of turbine casingr. Periodically sample the main reservoir oil for moisture, sediments and

other quality checkss. Regularly (every shift) run the oil clarifier for a period of 2 hrs. when the

oil clarifier is running precaution should be taken not to drain out the reservoir.

UNLOADING THE MACHINE

Whenever there is a planned shut down, machine has to be gradually unloaded and then stopped. Unnecessarily do not resort to Emergency Trip for normal shutdowns. Follow the steps below: Obtain clearance from the shift engineer; inform steam generation plant and ammonia plant positively.

1. Assume that CO2 is being discharged through PV03 and PV03 is on auto control mode.

2. Slowly start reducing the speed and simultaneously maintain 3rd suction flow by opening antisurge valve.

3. Once the pr drops to 100~110 kg/cm2, start opening 2-1 spill back HV 601. Keeping a watch on the thrust-bearing temp, further open FV602 and HV 601.

4. Now reduce the speed to minimum governing speed.5. Now stop the machine by activating any of the stop devices.

Shut Down Operation

a. Keep the machine turning on barring device for about 24 hrs (till the casing expansion of turbine comes less than 1 mm) from the time of shut down.

b. Ensure that the oil pump is running and emergency power availability for barring device motor and emergency L.O. pump.

c. Keep the condensate pump running for about eight hours after shut down. Keep PW make slightly open.

d. Cutoff vacuum cut off gland steam and gland steam ejector.e. Isolate KS, MS.f. Isolate the compressor suction valve. Open the interstage manual vent on

2nd suction.g. Open the compressor casing drains on MCL & BCL.h. Open the turbine casing drains and extraction header drains.i. After approx., six hours, when the turbine exhaust temp comes to normal,

isolate PW make up to hot well and stop the condensate pump.

TURBINE DRAINS IDENTIFICATION

1. HP Wheel chamber drain2. Extraction NRV u/s drain3. Extraction PSV u/s drain4. Extraction line (just outlet) drain5. HP wheel chamber to LP side balancing line drain6. LP casing first drain7. LP casing second drain8. Turbine front end leakage to rear end line drain9. PV653A d/s line drain10.PV653B d/s line drain

DRY GAS SEAL DESCRIPTION

UREA PLANT SIDE

AMMONIA PLANT SIDE

E- 28 SIDE

P- 27 SIDE

DRAINS COLLECTING HEADER

1 2 3 8

1097654

To E 28

As explained earlier that in order to minimise the losses from BCL, dry gas seal is used at both the ends. Seal gas tapping is taken from 3rd discharge line after filtering it. Its detailed description is as follows:

SERVICE CONDITIONSMake John CraneSeal temp 45°C/175°C (normal)Seal pressure 88-bar g max

25 bar g normalSpeed of rotation 12332 rpm (max continuous)Process gas CO2

SEAL CAPABILITIESAxial movement +/- 2.5 mmRadial movement +/- 0.6 mm

LEAKAGE RATESEstimated leakage at 11745 rpm (equal to 8100 turbine rpm) at 25 bar g Process side seal 39 standard liter per minute

Simply explained, the typically comprises of an 'O' ring sealed carbon FACE, located in a stainless steal retainer, spring loaded against a rotating carbide SEAT, fixed to the shaft.

Sealing of the fluid is achieved at the radial interface of rotating and stationary rings by a unique and ingenious method. The sealing surfaces are lapped to a high degree of flatness, but the rotating carbide ring has a series of logarithmic spiral grooves machined into its running face. The profile of these grooves is shown below:

SPIRAL GROOVE

RIDGE

SEALING DAM

ROTATIONAL DIRECTION

ROTATING SHAFT

ROTATING TUNGSTENRING

STATICCARBONRING

With rotation, fluid is drawn inwards towards the root of the groove, called the sealing dam. The sealing dam provides resistance to flow, increasing the pr. The generated pr lifts the carbon ring surface out of contact with the tungsten carbide ring by a precise amount, typically 3 microns. The gap between the radial faces is set when the closing forces of hydrostatic pr and spring load equate to the opening forces generated within the fluid film. Under dynamic equilibrium conditions, the force acting upon the seals can be graphically shown below

The closing force, Fc , is a result of the system pr plus a very small spring force. The opening force, Fo , is a result of the system pr breakdown between the face and seat, plus the pr generated by the spiral grooves. At equilibrium, i.e., when Fc equals Fo , the operating clearance is, as previously mentioned, approx. 3 microns for most commonly encountered fluids.

If a disturbance occurs which results in a reduced sealing gap, the pr generated by the spiral grooves considerably increases as shown below

Similarly, if an upset causes the gap to increase there is reduction in the pr generated and the seal regains its equilibrium very quickly

The result of this mechanism is highly stable yet very thin fluid interface between the static face and the rotating seat. This results in the two surfaces

CLOSING FORCE

REDUCED GAP

INCREASING OPENING FORCE

F PFC=FO

GAP=0.003MM

NORMALRUNNING

COMPRESSION

EXPANTION

FOOPENING FORCE

SPRING LOAD+HYDROSTATIC

being kept apart and not touching under normal dynamic operating condition. Inturn this leads to a long life, reliable seal with no wear at the interface.