202 manual hydra step
TRANSCRIPT
LevelstateLevelstateSystems Ltd.
7. Bentley Ind. Ctr., Bentley,
Farnham, Surrey. GU10 5NJ.
England. UK.
Tel : 01420 22818
Fax : 01420 22824
Boiler Water Level Monitor
202 System
INSTALLATION MANUAL
ISSUE: E March 2003
© 1992 Levelstate Systems Ltd. With technical progress the Company
All rights reserved reserves the right to change specifications
without notice.
Contents
Section Page
Boiler Codes or Standards - Summary of requirements 3
1 . Operating Principle 4
2. General Configuration 6
2.1 Trip Circuits 11
2.1.1 Low Level Trip 12
2.1.2 High Level Trip 13
3. Installation & Cabling
3.0 General 14
3.1 Water Column 15
3.2 System Cabling 18
3.3 Electronic Unit 21
3.4 Remote Display 25
4. Commissioning
4.1 Probes 27
4.2 Electronic Unit 29
4.3 Water Column 30
5. Maintenance & Fault Identification
5.1 Pressure Parts 32
5.2 Electronic Units 34
5.3 Fault Identification Procedure 35
6. Electronic Unit Descriptions
6.0 Electronic Enclosure 37
6.1 Discriminator & Display - PCB1 39
6.2 Supply & Relay - PCB2 41
6.3 Remote Display Unit 43
6.4 202 EDLI Parts List 45
7. System Specification 46
8. PED DIRECTIVE DOCUMENTATION 48
2
Figs Page
1.1 Sensing Element 4
1.2 Water Level Monitoring 4
1.3 Typical Water Conductivities 5
1.4 Switching Hysteresis 5
2.0 System Configuration 8
2.1 Side Arm Water Column 9
2.2 Probe Type 801 and 803 10
3.1.1 Water Column Installation Detail 16
3.1.2 Water Column Support Structure 17
3.2.1 System Cabling 19
3.2.2 Water Column Probe Cable Routing 20
3.2.3 Cable Gland Allocation 20
3.3 Electronic Enclosure Outline Dimensions 22
3.4 Remote Display Outline Dimensions 26
5.3.3 Fault Identification Procedure 36
6.0 Electronic Enclosure Layout 38
6.1 PCB1. Layout 40
6.2 PCB2. Layout 42
6.3 PCB3. Layout 44
3
Boiler Codes or Standards - Summary of requirements
ASME Boiler Code
Boilers must have one gauge glass. Above 400psi operation two gauge glasses shall be provided. For
boilers with safety valves set at or above 900psi two independent remote level indicators may replace one
of the two gauge glasses. If both remote indicators are in reliable operation the remaining gauge glass
may be valved off but must be maintained in serviceable condition. If gauge glasses are not visible to
the operator two dependable Indirect Indicators shall be provided. The lowest visible level of the
gauge shall be at least 2” above the lowest permissible water level where there is no danger of
overheating any part of the boiler. Each water gauge glass shall be equipped with a top and bottom shutoff
valve of through flow construction to prevent stoppage by deposits of sediment. Straight run globe valves
shall not be used. Connections from the boiler to the remote level indicator shall be at least 0.75" pipe size
including isolation valves. For gage glasses connected to the boiler the steam and water connections shall
not be less than I" pipe size. There shall be no sag or offset in the steam pipe and no part of the water
connection shall be above the point of connection to the gauge.
It is recommended that each boiler have two independent low water cut-offs. The permanent installation of
cutout devices for low water cut-offs should not be provided; temporary devices can be installed for
testing.
British Standard BS759. Part 1. 1984
Boilers shall have two independent gauge glasses each capable of being isolated from the boiler. One
water level gauge is permitted for boilers of less than 145kg/h evaporative capacity. For boilers with safety
valves set at or above 60bar in two independent manometric remote level indicators may replace one of
the gauge glasses. One gauge glass with its isolating valves shall be connected directly to the boiler.
Remote level Indicators which have been approved by an “Inspection Authority” may replace
gauge glasses. The lowest visible level of the gauge shall be at least 50mm above the lowest permissible water level
where there is no danger of overheating any part of the boiler. Steam and water isolating valves if straight
pattern globe type shall be mounted with the spindle horizontal.
The bore of steam and water connections shall be not less than 25mm, local to fittings not less than
20mm. The level gauges shall be mounted as close as is practical to the boiler shell or drum.
Automatic controls shall effectively shut off the fuel supply in the event of low water level.
There is a reasonable degree of commonality between the above requirements and this is generally
reflected in other National Regulations. Accepted or recognised standards must be used for the design,
material selection, welding and inspection of pressure containing components.
4
1. Operating Principle
The Levelstate 202 System is an ‘approved’ electronic alternative to the gauge glass providing a
significant improvement in accuracy, visibility, reliability and safety, enabling transmission of the water
level condition to a remote display and the application of alarm and control functions. It includes
connections for two separate Mains Supply inputs to achieve the ultimate security and reliability for the
indication and control functions.
The discrimination between water and steam is based on the significant difference in resistivity between
the two states over the saturation range. The sensing element is a Probe with an insulated tip inserted in
a side-arm water column FIG 1.1. If a voltage is applied to the tip, conduction occurs between the tip and
the inside wall of the column. The dimensions are selected to provide a resistance typically less than 0.1
Mega-ohms when the Probe is immersed in water, which results in a resistance greater than 5.0 Mega-
ohms for the steam condition. An electronic discrimination circuit is arranged to sense whether the Probe
resistance is less than 0.1 Mega-ohms representing water or greater than 0.1 Mega-ohms representing
steam. The detection level is dependent on water purity and boiler operating conditions.
With 14 Probes spaced vertically in a side-arm vessel attached to the boiler FIG 1.2 and with each Probe
connected to its own sensing and water/steam indication circuit a vertical display of 14 Green/Red
indicators provides sufficient resolution for the water level indication. The spacing between Probes is
chosen to cover the required Sight-Range.
Fig 1.1 Fig 1.2
5
Fig 1.3
Fig 1.4 below shows the relationship between boiler water resistivity (the inverse of conductivity) and boiler drum
pressure. The side-arm column purposely stimulates condensate flow and this flushing effect results in the column
water being purer than the water in the drum. As the pressure increases the water resistivity increases and it is
essential that the water/steam switching threshold lies above the side-arm water resistivity for the maximum boiler
pressure encountered. On the other hand it is advisable to use as low a resistivity switching threshold as possible to
render the system less susceptible to switching over due to moisture and water droplets.
6
2 General Configuration
The 14 probes are installed in a side-arm water column in two staggered vertical rows, numbered from the
bottom; the ODD numbered probes are located on one side of the column and the EVEN numbered
probes on the opposite side. A typical Water Column is shown in Figs 2.1 and two versions of Probe
shown in Fig 2.2.
Two printed circuit boards contained in an IP65 (NEMA 4X) wall mounted enclosure provide 14 discrete
water/steam discrimination circuits, LED display, relay alarm outputs, 4-2OmA output and terminals for the
connection of a Remote Display Unit. A Probe channel comparison or validation circuit is included
whereby any channel indicating a "water above steam" or "steam below water" condition illuminates a
yellow system fault indicator and initiates a relay contact output.
Generally the water column is aligned for Normal Water Level (NWL) located between Probes 7 and 8,
with the lower probes normally sensing water and the upper probes normally sensing steam. As the steam condition presents a high resistance to the sensing circuit which is indistinguishable from an
open circuit connection, two wires are used on the probe channels normally sensing steam; if either wire is
disconnected the sensing circuit indicates the water state thus declaring the fault. For the single wire
connection to the lower probe channels an open-circuit connection obviously indicates the steam state at
the channel output again declaring the fault.
For this standard arrangement a 22 core PTFE cable is provided for probe connections with the lower 8
Probes having a single wire connection and the upper 6 Probes having a two wire connection.
To avoid galvanic action at the probe and variations in sensing voltage due to changing electrolytic
potentials, an alternating voltage source is applied to the probe and the sensing circuit responds only to an
alternating waveform. Two low frequency oscillators are provided for the source voltage, one driving the
odd numbered channels and the other the even numbered channels. The voltage applied to the probe is
less than 6 volts, current limited to 50 microamps and presents no risk to personnel.
Collectively the discrimination or sensing channels may be set to one of three sensitivity selections for
water conductivity.
Each channel output drives a Green LED for Water detected or a Red LED for Steam detected and also
increments the 4-2OmA Transmission circuit.
Two alarm relays RL2, RL3 with integral delays, may be programmed to any channel except 1, 7 and 14. If
more than one channel is linked to the RL2 or RL3 delay circuit either channel will initiate the delay relay
action.
If a channel from 2 to 6 is linked and a channel from 8 to 13 linked to the same delay circuit the low
channel will initiate delay relay action when steam is indicated (Lo Alarm) and the high channel will
7
initiate action when water is indicated (Hi Alarm). This can provide a single alarm contact for a combined
Lo or Hi Level Alarm.
An additional two relays RL1, RL4 are included for instantaneous or delayed Trip action whereby an
extended 2 out of 3 Probe Channel voting logic is applied. RL1 is allocated to Low Water Level Trip and
RL4 to a High Level Trip.
Relay action can be selected for normally energised or normally de-energised depending on the
alarm/trip policy required.
A link-programming feature allows selected display LED’s to flash on initiation of Alarm relays RL2 and
RL3. Any illuminated Red LED (Lo Water Level) on channels 2 to 6 and any illuminated Green LED (Hi
Water Level) on channels 8 to 13 may be selected to flash when either RL2 or RL3 bus line is activated.
An identical linking facility is also provided to flash LEDs on the Remote Display Unit.
To achieve the highest operational integrity, provision is made for Two Separate Mains Supply inputs to be
applied. The DC output voltages from separate transformers are interconnected to 12V regulators so that
in the event of one Mains Supply failing the 202 instrument remains fully operational. Either Mains
failure is signalled through the system fault alarm. One regulator is allocated to supply the Odd numbered
Probe channels and the second supplies the Even numbered Probe channels. A third regulator
separately supplies the logic board and alarm circuits. All regulators are current limited to prevent
rupturing of the Mains fuses in the event of a short on the associated circuitry.
PROBE END CONNECTION ELECTRONIC END CONNECTION
Pure Nickel PTFE coated
5 or 10 METRE
22 core
NICKEL ring crimps for probe connection
Ferrule crimps for electronic connection
Type 202 22 core probe cable
9
FIG 2.1 Side Arm Water Column
The 202 System employs multiple Probes installed in a vertical Column, usually in two
diametrically opposite rows. Two types of Probes are available; one rated at 120bar which is
directly screwed into the Type 501 Water Column or, for ratings to 207bar a flanged type is
inserted into the Type 503 Water Column and retained by a clamp plate which is secured by
four studs and nuts.
Fig. 2.2 PROBES
Spiral wound Metaflex Gaskets
St. Steel / Supagraf
Thread M16 x 1.5
PROBE TYPE 801 Rating 150 Bar @ 343 C
PROBE TYPE 803Rating 207 Bar @ 370 C
PROBE TYPE 802Rating 207 Bar @ 580 C
Compression nut fitting
11
2.1 Boiler shut-down or trip circuits
Two low water level shutdown devices are a stipulated requirement in the Regulations for the protection of
steam raising boilers, Two remote level indicators may replace one gauge-glass; if a trip circuit is derived
from each remote level indicator system the requirements are satisfied.
For the practical application of shut-down systems the consequences of malfunction of the protection
circuit must be considered when deciding which method of implementation is the most appropriate. If a
relay is normally energised in the healthy state of the plant, supply failure or relay coil open circuit will
obviously induce a spurious trip; if the relay is normally not energised, supply failure or relay coil open
circuit prevents initiation of a required trip action. Similarly if a normally closed relay contact is used and a
wire disconnection occurs a spurious trip is initiated. If a normally open contact is used a wire
disconnection is not apparent and a trip requirement cannot be initiated.
The economics of Power Plant boiler operation dictates that spurious trips due to protection system faults
must be minimised and the required degree of shut-down system "availability" must be achieved by
duplication of protection devices. For other boilers perhaps the consequent hazards created impose the
policy that a trip requirement must always be actioned and the possibility of spurious tripping has to be
accepted.
The protection system policy must first be established and the duplication and interconnection of the trip
circuits organised to suit the requirements in terms of Reliability and Availability. When discussing
industrial equipment performance the mere mention of 'failures' evokes Murphy's Law. It must be
accepted that even with an extremely small failure rate of one in a million hours (probability of failing once
in 114 years) it could happen tomorrow, so however remote the probability the consequential effects of
failures should be considered.
For the 202 System the prime failures which affect reliability are the following:-
1. Mains supply source. It a highly secure instrumentation supply is available this should be used. If
two Water Level Indicators are fitted they should be supplied from separate mains supply sources.
The 202 Electronic Unit has provision for two separate Mains Supply inputs. In the event of one
Mains Supply failure the Unit remains fully operational.
2. Steam leaks from valves can cause level indication errors.
3. The prime failure of the Probe is to the 'water’ state due to the possibility of insulator
contamination caused perhaps by poor control of boiler water quality. The water column
intentionally stimulates condensate flow through the system to reduce density errors but this also
improves the water purity in the column preventing contamination. Failure of the pressure seal at
the ceramic insulator generally causes the water state to be indicated. For probes normally
immersed in water at the lower levels this failure is not apparent and is only discovered when a
low level occurs where a trip may be required. It is recommended that a test for this type of failure
is performed at least every 6 months.
12
2.1.1 Low Level Trip
For boilers many ‘Operating Guidelines’ or ‘Codes of Practice' recommend that for low level tripping
devices any equipment fault should initiate a boiler trip. This presumably applies to single element
devices and does not reflect the fault tolerant approach of multi channel devices or the duplication of
equipment.
With the prime failure mode of the Probe to the water state and, for the lower Probes, a wire
disconnection inducing the steam state, there is some confliction in conforming to the above 'Guidelines'.
For the 202 system a secure fault tolerant approach has been implemented whereby the basic 2 out of 3
arrangement has been modified to produce 4 Pairs from 4 Probe channels. Any one pair where both
channels indicate the Steam condition will initiate trip relay action . The pairings are chosen to counter the
possibility of a 12V supply regulator failing which would eliminate the respective odd or even numbered
channels from the circuit. A delay on relay action is also available with time period of 1, 5, 10 or 15
seconds. To satisfy the ‘Guidelines’ a normally energised relay with normally closed contacts should be
used.
Spurious trips will be initiated for the following remotely possible failures:-
(a) 12V Supply failure or relay coil open circuit.
(b) A disconnection in the wiring to the shutdown device.
To avoid these spurious trips the following circuit should be implemented where the relay is not energised
and a normally open circuit connection to the shutdown device is used:
The problem here is the possibility of missing a necessary trip action if faults (a) and (b) ever occur. If a
second water level indicator is fitted and supplied from separate Mains Sources and its relay contacts
separately connected to the shutdown device, the possibility of both systems failing simultaneously is so
remote that it can be discounted. Ideally two separate shutdown devices should be installed.
E
D
NO
NC
+12v
0v
Shutdown Device
RL1 Delay
1 , 5, 10, 15 Seconds
Logic 4 pairs form 4 channels
Select Trip @ Probe 2
or 3 1
2
3
4
Relay Energised – De-energise to Trip
E
D
NO
NC
+12v
0v
RL1Delay
1 , 5, 10, 15 Seconds
Logic 4 pairs form 4 channels
Select Trip @ Probe 2
or 3 1
2
3
4
Relay Energised – De-energise to Trip
13
2.1.2 High Level Trip
There are no 'Guidelines’ for high level trips as the risks involved are not as disastrous - except for
associated plant. However the 202 Unit also provides the security of a modified 2 out of 3 arrangement
for the high level trip. Here the channel output logic level is reversed compared with LLT; a 12V regulator
failing would induce a spurious trip so the pairings are chosen to avoid this problem. A delay action is also
available.
2.1.3 Alarm Circuits
Two relays RL2 and RL3 provide Alarm signalling and have integral delay action which can be set to 1, 5,
10 or 15 seconds. RL2 and RL3 may be connected for two separate Lo or Hi alarms or one Lo and one
Hi. More than one channel may be connected to each relay; this feature allows a configuration whereby a
Lo and a Hi Probe channel connected to one relay provides a single output contact for a combined Lo/Hi
Alarm.
NOTE: Internal Test Switches SW1,SW2 are provided to check operation of the electronic
circuits, if these are operated the Alarms and Trips would be Initiated. An internal Link
(RL) Is available to prevent relay action if SW1 or SW2 is operated, otherwise the Trip
Circuits should be disarmed externally before opening the 202 Enclosure.
If required the switches SW1 and SW2 may be disconnected by unclipping and removing the spring and
shorting contact. The plastic caps may then be replaced to prevent any possibility of shorting the fixed
contacts.
E
D
NO
NC
+12v
0v
RL1Delay
1 , 5, 10, 15 Seconds
Logic 4 pairs form 4 channels
Select Trip @ Probe 2
or 3 1
2
3
4
Relay Energised – De-energise to Trip
14
3.0 Installation - General For Boiler applications the installation must conform to the accepted Regional or National Standards.
Pipework connections must be welded, tested and inspected to the relevant procedures. Ensure that the
appropriate Regulations are adhered to and procedures documented.
A typical Water Columns installation is shown in Fig. 3.1.1 and 3.1.2 but special versions may be required
for particular applications. In all cases it is essential to achieve the minimum length of connecting
pipework to the water column to minimise density errors. This is caused by heat loss which produces a
temperature difference and therefore a density difference between the water in the column and the water
in the boiler or heat exchanger. In particular the lower water connection should be as straight as possible
with a slight downward slope from the column to achieve good water circulation, preventing the
accumulation of dissolved solids and avoiding the possibility of level indication errors. The top equalising
connection should project inside the boiler shell to prevent surface condensate cascading down the
pipework to the column, excessive water flow in the column causes a pressure drop resulting in level
indication errors. Both steam and water shell tappings should terminate internally away from localised
turbulence, which causes pressure differences, and therefore level indication errors.
The inclusion of isolation valves requires the assembly to be supported by the top suspension lug of the
column ensuring there is no differential expansion between the support structure and the boiler drum. Fig
3.1.2.
If a boiler low or high water level trip circuit is connected to the 202 Electronic Unit it is recommended that
all isolation valves are lockable in the open position and the drain valve lockable in the closed position to
prevent spurious tripping by inadvertent valve operation.
The 202 Electronic Unit enclosure is usually sited adjacent to the Water Column within a distance suitable
for the 4m (12') length of special high temperature PTFE cable supplied. If longer cable lengths are
required, terminate the PTFE cable in a suitable watertight junction box and extend with standard 22 core
stranded conductor instrumentation cable; ensure extension cable is protected from heat sources.
Siting of the 202 enclosure must consider adequate visibility of the display, the routing of other cables
away from heat sources and the minimum risk of damage from surrounding plant or activities.
15
3.1 Water Column - Installation - General Requirements
3.1.1 For boiler side-arm columns Figs. 3.1.1, 3.1.2 the support structure should be installed, the column
attached by the top suspension lug and, in most cases, aligned with the drum NWL between Probes 7 and
8, Fig. 3.1.1. The support structure should be sufficient to take the weight of the column plus steam and
water isolation valves, drain valves and pipework.
Parallel slide or gate valves should be used particularly for water side isolation as they allow full bore
opening without restricting water flow. Straight run globe stop valves shall not be used (ASME) but if
permitted by other codes they must be mounted horizontally as shown. If the 202 System low and/or high
water boiler trip circuit is used it is recommended that all isolation valves are lockable in the open position
and the drain valves lockable in the closed position to prevent spurious tripping by inadvertent valve
operation.
It is essential to ensure there is a continuous downward slope of at least 1:50 from the Water Column to
the Boiler Drum to enhance water circulation. (ASME Code: No part of this water connection shall be
above the point of connection at the Water Column. For the steam connection to the boiler there shall be
no sag or offset in the piping which shall permit the accumulation of water)
The column connections are profiled for butt weld fitting to pipework; if socket weld fittings are to be used
the 40º profile should be removed and the fittings supported to allow 2mm (0.08") spacing to the fully
seated position. After welding to documented procedures any temporary supports should be removed and
alignment to NWL checked prior to weld inspection.
Fit Guards to protect Probe seatings.
Lag steam and water pipework and valves.
Before commissioning install Probe Cable as shown in Fig. 3.2.2.
As a precaution ensure steam and water isolation valves are closed and drain valve open.
16
3.1.2 Water Column Installation Detail
Fig 3.1.1 Water Column Installation 1. The Water Column should be suspended such that there is no differential vertical movement
between the Boiler Drum and the Column. Generally a spring suspension should be provided where the spring rate includes column, isolation valves, drain valves and associated pipework.
2. The lower water connection to the Column must be above the level of the connection to the Drum to
prevent air locks. For the same reason the steam connection to the Column must be below the connection to the Drum. Preference should be given to the continuous slope of the water connection with no restrictions, to aid water circulation.
3. The water connection inside the Boiler Drum should avoid turbulence from down-comers, feedwater
inlets etc. The steam connection should protrude sufficiently (X) to avoid drum surface condensate flowing to the Column.
4. Procedures for site welding of pipework and valves must conform to the National or Accepted
Standards for boiler applications.
Sight Range
NORMAL WATER LEVEL
ISOLATION VALVES
ISOLATION VALVES
DRAIN VALVES
Maximum slope possible
Suspension Lug Hole Dia. 25mm
X
MINIMUM DISTANCE POSSIBLE TO SUIT SITE CONDITIONS. Distances greater than 2 metres cause indication errors due to reduced water temperatures
in water column
17
5. Connection pipework and valves should be lagged to prevent heat loss. 6. Guards should be provided to prevent accidental contact with the Water Column; these should not
restrict convection cooling of the Column. 7. Probes should not be fitted to the Column until mechanical installation and Drum cleaning
processes are completed.
Fig 3.1.2 Water Column Support Structure
18
3.2 System Cabling
Fig 3.2.1 shows the System Cabling requirements. Fig 3.2.2 shows Probe Cable Fixings on the water
column and Fig 3.2.3 Cable Gland allocation on 202 Unit.
A 4 metre (12') sheathed length of special 22 core high temperature PTFE cable is provided for Probe to
202 Unit connections. This cable is pre-formed for the standard vessel arrangement where NWL is
between Probes 7 and 8. For longer cable lengths a junction box and standard PVC multi-strand
instrument cable should be interposed in the run to the 202 Electronic Unit. The Water Column looming
has been arranged for the cable to be clamped on the right hand side with the ODD numbered Probes on
the left hand side and the EVEN numbered Probes on the right hand side. It is recommended that the
cables are taped to the 6mm (1/4") vertical Tie Rods using 12mm PTFE Thread Seal Tape (as used in
pipe sealing RS 512-238).
Cable for the Mains Supply, 20 Core Remote Display, Alarm and 4-2OmA circuits are fitted as required
using standard instrumentation cable through the 202 Unit Cable Glands as shown.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
Gy/Bk
R
O
V
W
R/Bk
O/R
O/W
Gy/R
Gy/W
W/Bk
Bk
Br
P
Be
Gy
R/Be
R/W
O/Be
O/Bk
GyBe
W/Be
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
14
13
12
11
10
9
8
7
6
5
4
3
2
1
4
3
2
1
20
19
18
17
16
15
E N L L N E
TB2
TB1
TB6
TB7
TB4
TB5
NC
NO
RL1 C
NC
NO
RL2 C
NC
NO
RL3 C
NC
NO
RL4 C
NC
NO
RL5 C
4/20mA +
Output -
14
13
12
11
10
9
8
7
6
5
4
3
2
1
20
19
18
17
16
15
TB1
TB2
20251 - 20252
REMOTE
DISPLAY
UNIT
REMOTE
DISPLAY
CONNECTOR
TYPE 202 ELECTRONIC UNIT
MAINS INPUT
110240V 15VA
MAINS INPUT
110240V 15VA
ALARM / TRIP Relay & 4/20mA outputs
Br
P
Be
Gy
R/Be
R/W
O/Be
O/Bk
Gy/Be
W/Be
Bk
R
O
V
W
R/Bk
O/R
O/W
Gy/R
Gy/W
W/Bk
Gy/Bk
WATER COLUMN
& PROBES
22 Core Instrument cable
1 sqmm cores. Lmax 500m
1.5sqmm cores Lmax 750m
22 Core PTFE cable Assembly
Part Number: 2022818/Length
Mains 1 | Probe Cable | Relay Outputs | Remote Display | Mains 2
PG 13.5 PG 9 PG 16 PG 21 PG 13.5
Top Guard
Block
Lower Guard
Block
Fig 3.2.2 Probe cable routing on water column
Fig 3.2.3 Cable Gland allocation
Using cable clamps run odd and even cables either side of the column
Tie cables along cable tie rod
21
3.3 Installation of 202 Electronic Unit
3.3.1 Before installation remove the front cover assembly and PCB 2 with chassis plate from the
enclosure and store in a safe place. Refer to Figs 3.3 and proceed as follows:
1 . Open front cover by loosening the two top captive plastic screws.
2. Disconnect ribbon cable from PCB 1 by pressing the two ejection levers on PL3 in an
outward direction and ease out the plug/cable assembly. Press the two bottom cover hinge
pins inwards and remove the complete cover assembly.
3. Unscrew the four M6 Cap Head (5mm Key) fixings at the corners of the base unit and
remove PCB 2 and chassis assembly. Refit M6 chassis plate screws into corner inserts to
avoid loss.
SPRING HINGE COVER REMOVAL
3.3.2 Mount the base of the enclosure with cable glands downwards at the site chosen using 4 corner
fixing screws, M6 or 0.25".
Strip cable sheaths so that they do not project beyond the inside of the cable gland; PTFE Probe cable is
preformed for correct length. Insert cables through glands, trim ends to template supplied and fit crimped
ferrules where required.
Test cable continuity as required.
202FAULT
2
4
14
10
12
8
6
1
3
13
9
11
7
5
Levelstate
200 mm
Mains 1 | Probe Cable | Relay Outputs | Remote Display | Mains 2
PG 13.5 PG 9 PG 16 PG 21 PG 13.5
120 mm320 m
m178 mm
298 mm
Type 202 Electronic Unit
23
3.3.3 At a convenient time before Commissioning, programme the required mode of operation of the
PCBs as follows :-
PCB1 - Refer to Section 6.1.1.
1 . Remove thin glass fibre cover.
2. Solder split pad link (centre of PCB) for the selected channel outputs
corresponding to the required alarm levels (middle pad to LH pad for
operation of RL2 or middle pad to RH pad for operation RL3).
3. Solder the appropriate split pad link "F" for the selected LED to flash
indicating the alarm level.
4. Solder split pad links for the required Trip Levels on the 2 out of 4
Logic circuits applied to RL1 and RL4.
LLT, split pads either side of IC18: LLT
Middle pads to upper for trip level at Probe 3. ( 3 ( 3
Middle pads to lower for trip level at Probe 2. 2 2
HLT, split pads either side of IC19: HLT
Split pad not linked for trip at level 13.
Split pad linked for trip at level 12.
5. Solder split pad links for the time delay required on LLT (RL1), HLT
(RL4) and Alarms RL2 and RL3.
6. If Trip Circuits are applied and it is required to inhibit relay action when
Test Switches SW1, SW2 are operated, solder link split pad (RL) ∩∩∩∩
located at the bottom of the PCB. To inhibit Trips only, link RL and (R L)
remove D26, D28.
7. Solder split pad links S or W to the middle pad (top centre of PCB1) W
to define whether the "all steam" or "all water' state is to represent 4mA
the 4mA current output for the 4 to 20 mA transmission signal. S
8. The two sets of split pad links above PL1 and below PL2, Sa, Sb Odd No.Chs.
determine probe channel sensitivity and should only be made after
evaluation of system performance. With no linking the setting is for Sa Sb
conductivity greater than 2µS/cm, middle pad linked to Sb for greater
than 1µS/cm and middle pad to Sa for greater than 0.5µS\cm. Both Even No.Chs.
sets must be linked identically.
Sa Sb
(
Ch.O/P
RL2 RL3
F.Bus
Ch.O/P→
12
) 15 10 5 1
24
PCB2 - Refer to Section 6.2.1.
1 . Set the correct mains source voltage using jumpers provided. (fit two jumpers for 115V; one
for 240V as indicated).
2. Solder the split pad links D or E for the selected mode of operation of RL1 to RL4.
D = Normally De-energised - Energise to Alarm or Trip.
E = Normally Energised - De-energise to Alarm or Trip.
RELAY
D
E
25
3.4 Installation of Remote Display Unit 20251
This unit is intended for panel mounting with cut-out size 174mm x 67mm (6.85"x2.64") and panel
thickness to 6mm (0.25")
Before fitting, solder link the appropriate split pads ‘F’ as on the 202 unit, PCB1.
Method of fitting :-
1. Remove the rear cover by unplugging the terminal block and removing the four corner
hexagonal nuts.
2. Insert the bezel assemble from the front of the panel, fit the cover at the rear and tighten the
four hexagonal nuts.
3. Terminate the cable ends on the free terminal blocks and insert into Display Unit plugs. Clamp the
cable as shown in Fig 3.3 (a) or (b).
CABLE CLAMP
TB2
UNIT AND REMOTE DISPLAY LAYOUT
REAR ELEVATION
UNIT AND REMOTE DISPLAY LAYOUT
SIDE ELEVATIONREMOTE DISPLAY CUT-OUT
PANEL CUT-OUT
Max panel thickness 6 mm
174
mm
67 mm16
3 m
m
56 mm
24 mm8 mm 60 mm MIN FOR ACCESS
USES 1 x 22 CORE 1mm COPPER
Max 400 m
202
UNIT AND REMOTE DISPLAY LAYOUT
FRONT ELEVATION
72 mm
180
mm
FAULT
2
4
14
10
12
8
6
1
3
13
9
11
7
5
Levelstate
TB1
Stainless Steal rear cover with 4 x M3
fixings.
One 14 way and one 6 way cable connectors
TYPE 202 REMOTE DISPLAY
4.0 Commissioning
It is essential that Probes are not installed until acid or steam purging of the plant has been completed. The
water column may be valved off during this procedure or special Probe position blanking plugs can be
inserted (Part No. 80151 for 501 Water Column, or 80351 for 503,or 80251 for 502).
4.1 Probe Installation.
Caution : Handle Probes with care. Do not remove from packing until required for insertion. The
Probe insulators are high quality ceramic material which is liable to crack if subjected to impact - Do
not use if dropped!
Type 801 :
1. First clean the vessel seating recess ensuring it is dry and free from radial score marks. Do not
use any form of release coating or jointing compound on the seating face; the spiral wound
gasket has exfoliated graphite filler which does not stick to seating faces.
2. Use a Moly Disulphide anti-scuffing paste on threads avoiding contact with seating face and
Probe insulators.
3. Screw in each Probe and tighten. Do not exceed 7ONm (52 lb.ft).
4. Connect wires to Probe terminals, tighten knurled nuts using finger pressure only. Refit Guards
for Probe protection.
Type 803 :
1. Inspect the vessel seating recess ensuring it is clean dry and free of radial score marks. Clean
butting faces of Clamp Plate and Vessel.
2. Insert Gasket and Probe to Vessel and carefully fit Clamp Plate over Probe and Studs.
3. Apply a thin film of Copper or Molybdenum based grease to exposed ends of studs.
4. Fit nuts finger tight; adjust nuts to obtain clamp plate parallel to vessel face (approx.
1mm gap).
5. Set Torque Wrench fitted with 17mm A/F long socket to 2ONm.
Initially tighten each nut equally through
45º or subsequently where wrench
‘clicks' at torque setting, in the sequence
1, 2, 3, 4 until clamp plate is flush with
vessel face. If the torque wrench ‘clicks'
without nut rotation this indicates that the
Clamp Plate is not parallel to Vessel
Face; before proceeding adjust nuts for
parallel faces.
1
4 2
3
6. Set Torque Wrench to 25Nm and tweak each nut until the Wrench clicks at the torque
Limit.
DO NOT ROTATE WRENCH BEYOND THE POINT WHERE IT BREAKS (CLICKS)
DO NOT EXCEED 25Nm TORQUE SETTING
7. Connect wires to Probe terminals, tighten knurled nuts using finger pressure only. Refit Guards
for Probe protection.
Type 802 :
Inspect the Insert seating taper ensuring it is clean, dry and free of radial score marks. Use a
Moly Disulphide anti-scuffing paste on threads. Fit Probe and tighten retaining nut until Probe
body is just nipped, i.e. where it just cannot be rotated. Apply 27mm A/F long socket and
tighten by 1/6 of a turn.
29
4.2 Electronic Unit.
4.2:1 Fit chassis plate + PCB2 to base of enclosure
4.2:2 Fit cover + PCB1 to enclosure by springing hinges inwards before locating on base hinge
holes.
4-2:3 Connect ribbon cable to PCB1 via PL3 ensuring hinged retainers on PCB1/PL3 are first
hinged outwards.
4.2:4 Ensure mains cable is not live and connect separate mains supply to PCB2 / TBl and TB2
checking that mains jumper links are correctly installed for mains voltages (115v or 230v)
4.2:5 Do not fit other terminal blocks to PCBs at this stage.
4.2:6 Switch on Mains Supply. Depress SW1 Green Button and check that all Green LEDs
become illuminated. Release SW1 and depress SW2 Red Button and check that all Red
LEDs become illuminated.
4.2:7 Connect Probe wires to PCB1 by inserting TB2 and TB3. If the column is empty all Probe
channels should have Red LEDs illuminated. Short out each Probe in turn by touching a
wire between the knurled nuts and probe body and check that the corresponding Green
LED becomes illuminated.
In some instances condensation in the column or Probe assembly may cause the Green LEDs to be
illuminated which cannot be cleared until steam heating is applied to the column. In this case a check can
be made by disconnecting the wire on the Probe; when open circuit the Red LED should be illuminated,
when shorted to Probe body the Green LED should be illuminated. If two wires are connected to the Probe
these must be held together for the above test.
4.2:8 If a Remote Display is fitted, insert PCB2/TB4 and 5 and check correct illumination of LEDs
by operation of SW1 & SW2.
4.2:9 Insert PCB2/TB6/TB7 and check the various operation states of external alarm circuits etc.
by open-circuiting or shorting the relevant Probe wires as above.
4.2:10 If any problems arise during the above procedures check above connections and refer to
Fault Identification and Maintenance, Section 5.2.
4.2:11 It is advisable to keep the 202 Enclosure Cover closed at all times except for test and
maintenance. Generally plant locations have sulphurous atmospheres which in the
presence of moisture can cause serious corrosion problems with electronic equipment
particularly terminals and contact connections.
30
4.3 Water Column Bringing on-line.
4.3:1 Notify personnel of the intention to commission the Water Level Monitoring System.
4.3:2 Ensure Probe Guards are in place.
4.3:3 Close Drain Valves.
4.3:4 Slightly crack open the Steam Isolating Valve and observe by the Display that the column fills
slowly due to condensation (15 minutes +).
4.3:5 After 15 minutes crack open the Water Isolating Valve and check with Display that the water
level falls to the expected NWL in approximately 2 minutes.
4.3:6 Check valves and probes for steam leaks. Tighten probes if necessary. If steam issues
from the probe top insulator replace probe using Fault Repair Procedure Section 5.1
4.3:7 Open Water Isolation Valves fully.
4.3:8 Open Steam Isolation Valves fully.
4.3:9 The System is now operational. Where valve locks are fitted these should be locked if the
system is to remain in service:
Isolation valves locked in the OPEN position.
Drain valves locked in the CLOSED position.
The above method allows the Column to fill slowly and to be heated at a controlled rate and avoids
subjecting the Probes to any significant thermal shock which could adversely affect the pressure sealing
interfaces within the Probe assembly.
CAUTION: DO NOT BLOW-DOWN THE WATER COLUMN WITH PROBES INSERTED.
31
5.0 Maintenance and Fault Identifications
The following sections outline fault identification and rectification procedures. No routine maintenance is
required apart from periodic dusting of Probe external insulators using a small paintbrush to remove the
possible accumulation of flyash.
It is recommended in the interests of preventative maintenance that all Probes are replaced every 4 years,
or at least replace the lower Probes which are continuously immersed in water within 4 years as some
dissolution of the ceramic insulator does occur.
A check on the condition of the lower Probes normally immersed in water is recommended every six
months to ensure they correctly switch to the steam condition when the Water Column is drained. With
the system at operational temperature isolate Column, Procedure 5.1.3. When fully drained check that all
Probe channels indicate the steam condition (Red). If any channel indicates water (Green) check that the
Electronic Unit and Probe connections are functioning correctly by removing the Probe connection and
verify that the indication changes from Green to Red, in which case the Probe is faulty and must be
replaced. If a fault has occurred on the Electronic Unit rectify this first then replace the Probe connection
before determining whether Probe is faulty.
32
5.1 Pressure Parts
The large bore thin wall Water Column permits heat loss which stimulates condensate flow preventing the
build-up of sediment which obviates the need for vessel blow-down. As periodic blow-down is not
necessary the system reliability is enhanced due to reduced valve operation. The high purity condensate
keeps the Probes clean and the flow maintains the Water Column temperature near the Drum water
temperature which minimises density errors. Any flow restriction or pressure loss due to Valve or Probe
leaks can cause errors in water level indication.
If a serious Probe leak occurs the Water Column should be isolated immediately otherwise gasket seat
erosion may entail re-machining of the Column seating faces.
For damaged seat faces on the Type 501 and Type 503 Water Columns
For the 501and 503 Water Columns, re-cut seating face to an N8C finish which must be accurately
machined at 90' to the centre line of the opening.
5.1.1 Valve steam leaks - requires replacement of steam gland packing. Drain valves not sealing
properly requires seat replacement or re-grinding. Rectification should follow the normal
practices for the particular valve types.
5.1.2 Probe leaks - It is difficult to distinguish between Probe internal seal failure or Probe to
Column seal failure unless the leak is small. Steam emanating from the Probe top ceramic
insulator indicates internal seal failure and requires Probe replacement. Steam emanating
from the Column/Probe seating area may be rectified by further tightening of the Probe but
DO NOT EXCEED specified Probe tightening torque - otherwise replace Probe or gasket
using the following procedures.
5.1.3 Column Isolation Procedure
(i) Ensure Operators are informed that erroneous indications and alarms are to be expected.
(ii) If shutdown or trip circuits are connected to the system ensure they are disarmed.
(iii) Close the Steam and Water Isolation Valves.
(iv) Slowly open the Drain Valve(s) and leave open.
(v) Check at Drain outlet that the Isolation Valves are sealing properly.
33
5.1.4 Probe Replacement Procedure
(i) Isolate Column as 5.1.3 above, ensuring Drain Valve is open, with Steam and Water Isolation
Valves closed and sealing properly.
(ii) Remove Probe Guard and disconnect Probe wire(s).
(iii) Replace Probe as procedure Section 4.1 for Type 801 or 803.
5.1.5 Column Recommissioning Procedure
(i) Close Drain Valve(s).
(ii) Crack open the Steam Isolation Valve(s) and check with the display that the Column fills
slowly due to condensate (15 to 20 minutes).
(iii) Crack open the Water Isolation Valve(s) and check that the water level falls to the expected
level.
(iv) Check Probes for steam leaks using procedure of 5.1.2.
(v) After approximately 10 minutes fully open Water then Steam Valves.
(vi) Ensure all Valves are correctly set (and locked).
(vii) Inform Operators that the Indication System is now in service.
(viii) Check that approximately normal water level is displayed before rearming any shutdown or
trip circuits connected to the System.
The above procedure allows the Column and Probes to be heated at a controlled rate to prevent the
Probes being subjected to excessive thermal shock which could damage the ceramic insulators.
5.1.6 Column or Pipework Blockage
If the Column and pipework installation complies with recommendations of Section 4 and with the
intentional stimulation of condensate flow through the Column pipework blockage should not occur. This is
providing the boiler water treatment conforms to recommended practices such as ASME "Consensus on
Operating Practices for the Control of Feedwater and Boiler Water Quality in Modern Industrial Boilers" or
BS 2486 "Recommendations for treatment of water for land boilers".
If a partial blockage is suspected by the slow response times of the level indicator isolate the Water
Column as procedure 5.1.3. With the Drain Valve open slowly open the Steam Isolating Valve until there is
free flow of steam at the Drain outlet then close the Steam Valve. Slowly open the Water Isolating Valve
until there is free flow at the Drain outlet then close the Water Valve. Close the Drain Valve(s) and open
Steam and Water Valves. Ensure all valves are correctly set (and locked) and rearm trip circuits if fitted.
If the response time is still sluggish suspect problems with Isolation Valves not opening fully.
34
5.2 Electronic Unit Faults
Electronic faults can be diagnosed using the procedures for Fault Identification Section 5.3
If a circuit board is defective it is preferable to replace with a spare. For a local board repair ensure
precautions are taken to avoid STATIC as some components are MOS devices.
5.2.1 Check 202 Electronic Unit. Open enclosure cover by releasing the two top captive plastic
screws.
Depress Green Push Button SW1 at top of Display PCB (10 Seconds) - all Green LEDs
should be illuminated - no Reds.
Release SW1 and depress Red Push Button SW2 - all Red LEDs should be illuminated - No
Green.
If O.K. check for loose Probe connections to TB2, TB3 on PCB1.
Close enclosure cover.
5.2.2 Check Probe Connections. Remove Probe Guards. If channels indicating water oscillate
between Red/Green check Black & Grey/Black connections to bottom guard blocks or vessel
body.
Check Probe connections. (HOT? - wear gloves)
Channels indicating Steam (Red) - Apply a short circuit across the Probe top ceramic
insulator - Probe channel should change to Green.
Channels indicating Water (Green) - Disconnect wire from Probe, if two wires are fitted short
them together but isolated from column - Probe channel should change to Red. If this check
is O.K. but when wires reconnected to the Probe the Channel indicates Water when it is
judged to be in "Steam" by comparison with lower channels in Steam, suspect a faulty Probe.
Water cannot exist above Steam, unless the Probe is contaminated!
Refit Probe Guards.
35
5.3 Fault Identification Procedure
5.3.1 Fault on all Channels
5.3.1.1 Display Blank - Mains supply failure on both inputs
Fault signalled by external alarm - Fuse Fl and F2 ruptured
- PCB2 LED's illuminated - PL3 not
connected between PCB1 and 2 or
fault on cable or connector.
Switch off the Mains Supply before replacing fuse. If fuse has ruptured disconnect PL1 from PCB1 before fitting a replacement.
5.3.1.2 False all steam indication - O.V not connected to Water Column
- Column valved off and drained
5.3.1.3 Water indicated on upper channels - Probe connections open circuit
(2 wire connection) with steam - TB1, TB2 not inserted in PCB1
indicated on lower channels
(1 wire connection)
5.3.2 Fault on Alternate Channel Display Blank on Odd Channels - Regulator IC1 on PCB2 faulty.
Display Blank on Even Channels - Regulator IC2on PCB2 faulty.
Green LEDs illuminated - Oscillator fault IC1a for Odds, IC8b for
Evens
5.3.3 Fault on Single Channel 5.3.3.1 Neither LED illuminated - LED failure. TR2, TR3 faulty. R11,
R12 open circuit. Test as section
5.2.1 a (SW1 & SW2)
5.3.3.2 Water above steam indication (Fault indicated)
(i) The water indication is probably false if more than one channel immediately
below it indicates steam
(ii) The steam indication is probably false if more than one channel immediately
above it indicates water
(iii) If only one channel indicates water with only the one channel below it
indicating steam, either channel could be faulty.
CHECK:PCB1 by operation of SW1 and SW2 using procedure of Fig 5.3.3.
5.3.4 'Fault' Indicated - No S-W display fault.
Mains 1 or Mains 2 failure. Fl or F2 ruptured.
36
Fig 5.3.3 Fault Identification Procedure
37
6.0. Type 202 Electronic Enclosure, Fig. 6.0
The polyester glass-fibre reinforced enclosure with overall dimensions of 320 x 200 x 120mm is intended
for wall mounting using four M6 or 0.25" fixing screws through the corner apertures of the base external to
the cover sealing gasket. The cover has quick release hinge pins at the bottom and two
polyester/glassfibre screws at the top. Four cable glands are provided on the bottom face of the base
unit. Protection Rating for this enclosure is IP65.
The discriminator/display PCB is retained in the cover by the 6 screws, which secure the display bezel,
and by slot insertion along one edge. A thin glassfibre board provides protection for PCB1 components.
The clear laminated glass display window is sealed between the bezel and enclosure cover.
A metal chassis plate is secured to the base unit by four M6 screws. The supply/relay PCB2 is mounted
on the chassis plate and retained by eleven M3 screws and three M3 screws through the PTFE heatsink
supports. Terminals are provided for two separate 115/240V Mains Supply Inputs.
A 34 core flat ribbon cable which plugs into PCB1 interconnects the two PCBs.
The PCBs have been designed for long term reliability using the minimum number of components which
are significantly under-stressed.
Replacements for PCB Components is a delicate operation requiring special equipment to avoid
damage to static sensitive devices. To maintain operational reliability and security it is
recommended that spare boards are available and the faulty board returned to the manufacturer
for repair and test.
202
FAULT
2
4
14
10
12
8
6
1
3
13
9
11
7
5
Levelstate
Display Bezel & Window
PCB12022501
PCB12022501
Ribbon Cable connection
Fig 6.0 Electronic Enclosure Layout
39
6.1 Discriminator & Display. PCB1 Assembly No 2022501
This board contains the sensing circuits and display for 14 probe channels. Circuits are included for
channel validation, alarm and trip levels with delay action, 4 to 20 mA Transmission, display flashing and
push-button circuit test facility.
Channels 1 to 8 are "normally' servicing water and the source and sense are linked and a single wire
connection is made to the Probe. For Channels 9 to 14 'normally servicing the 'steam' condition, separate
source and sense connections are linked at the Probe to retain the lead monitoring feature. Any wire
disconnection induces the abnormal state at the associated channel sensing circuit so that the fault can
be detected and alarmed by the validation circuits.
Bu comparison with adjacent channels the invalid condition of 'Water above Steam' or ‘Steam below
Water’ can be detected. Additionally a supply failure from PCB2 is also applied to the validation circuits to
ensure detection of an equipment fault, this is annunciated by flashing of the display yellow LED and the
de-energisation of RL5.
The Odd Numbered Probe Channels are connected to PL1 and the Evens to PL2.
Solder split-pad linking is provided for the following functions:
1 Sensitivity selection for Water Conductivity. (Sa, Sb - odd and even channels)
2 Probe channel linking to Alarm Relays RL2, RL3
3 Trip Level selection
4 Alarm and Trip Delay Periods
5 Selection of Display LED Flashing at Alarm Levels (F)
6 The 4mA output of the 4/2OmA signal to represent ‘all water’ or ‘all steam’ condition
7 Inhibiting Alarm and Trip Relay action when Test Switches are operated (RL)
Two push-buttons SW1, SW2 provide a Test Water (Green Cap) and Test Steam (Red Cap) facility for
checking the electronic circuits.
Operation of SW1 or SW2 does not inhibit operation of relays RL1 to 4 unless split pad (RL) is linked.
F2
F3
F4
F5
F6
F8
F9
F10
F11
F12
F13
3
5
9
11
13
2
4
6
8
10
12
RL
Sa Sb
Connection to PCB 2||
Water Conductivity selection to be setAt site to suit operating conditions
Sa = Min. uS/cmNo Link = Max uS/cm
PL1 / TB 1
Odd Numbered Channels
Sa Sb
PL2 / TB 2
Even Numbered Channels
2022501 4/20mA
4mA=
All W
All S||
Lo & Hi AlarmsCh. Selection for
RL2 & RL3
TESTW SRL4RL1RL2
RL3
10 5 1
10 5 1 10 5 1 10 5 1
Delays: No linking = 15 Seconds approx
LL Trip / Alarm(validated)RL1
||
3
2
LL Trip / Alarm(validated)No Link=ch 13Link=ch 12RL4
||
3
2
| 12
Level AlarmsRelay: RL2 RL3
When 12 channel board then channels 11 & 10
Link for requiredRed LED to Flash(low water level)
Link for requiredRed LED to Flash(low water level)
Fig. 6.1 PCB 1 Layout
41
6.2 Supply & Relay. PCB2 Assembly No. 2022502
Each mains supply input is connected via a delay fuse to the primary windings of the transformer which
are either connected in series for 240v Mains input using a single jumper plug, or parallel for 115V Mains
input using two jumper plugs.
Each Secondary windings of the transformer is individually rectified by a bridge rectifier and the DC
outputs smoothed by a 2000µF electrolytic capacitor. Mains transient protection is provided and each of
the 4 DC outputs has an LED indicator L1 - L4.
Three 12V Regulators are provided to separately supply the following:
12VX Odd numbered Probe Channels
12VY Even numbered Probe Channels
12VZ Validation/Relay/4-20mA circuits. L5 LED.
Each regulator is supplied via transformers from Mains Supply 1 and Mains Supply 2 so that in the event
of a single Mains Supply failure the Unit remains fully operational.
PL3 provides connections between PCB1 and PCB2 via a ribbon cable.
TB4 and TB5 provides terminal connections for the Remote Display.
RL2 and RL3 are driven by associated time delay circuits on PCB1 and are intended for delay alarm
signalling.
R1 is allocated to a Low Level Trip and RL4 to a High Level Trip. RL5 provides output contacts for a
System Fault Alarm.
Relay circuits for RL1 to RL4 are identical, the input is normally at +12V; for Alarm or Trip conditions input
switches to 0.V. Linking solder pads D or E serve to define the state of the relay for normal or safe water
level conditions.
If a System Fault occurs RL5 de-energises signalling the Fault condition at the contact output, RL5 is
normally energised to enable initiation of System Fault if faults occur in the circuitry of RL5.
TB7 provides output terminal connection for the single pole changeover contacts of RL1 to RL5
TB6 provides output terminals for the 4-20mA signal.
RL1
RL2
RL3
RL4
E
D
E
D
E
D
E
D
D Link = Relay De-eng in normal state ( Energise to Trip)E Link = Relay Eng in normal state ( De-energise to Trip)
TB6 TB4
TB5
TB7 PL3
TB7/1
TB7/2
TB7/3
L N E E N LTB2 TB51
115V230V
MAINS VOLTAGE SELECTION250Ma ‘T’ 20 x 5 Fuses
F2 F1115
115
230
2022502
43
6.3 Remote Display Unit. 20251. PCB3 Assembly No 2022503
This separate DIN Size 180mm x 72mm display unit duplicates the 14 probe indications on the 202 unit.
Plugs 14 way and 6 way and associated cable terminal block sockets are provided at the rear with a cable
clamp facility.
The LEDs for the odd numbered channels are supplied from the 12V. X line TB2/20, and the even
numbered channels from the 12V. Y supply line TB2/18.
Solder split-pad linking is provided for the selection of Alarm Level Flashing of LEDs.
NB The row of green LEDs and the row of Red LEDs are each categorised for brightness to avoid
excessive differences in illumination. If replaced ensure correct category is selected.
F13
F12
F11
F10
F9
F8
F5
F4
F3
F2
F1
LY
LG LRD1
R3
R2 R1
R4 R5
Fig 6.3 PCB 3 Layout – Rear view
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
F6
45
6.4 202-EDLI Parts List
Description Part No
Detector PCB1 2022501
Supply Relay PCB2 2022502
PCB1 Fibreglass Cover 2023015B
Enclosure Base 2023011
Enclosure Cover Assembly 2022005
Chassis Plate PCB2 2023006C
Heatsink Support Bracket PTFE 2023016
Terminal Sockets TB1, TB2 BL11
Terminal Sockets TB4 BL14
Terminal Sockets TB5 BL6
Terminal Sockets TB6 BL4
Terminal Sockets TB7 BL15
Cable Gland PG9
Cable Gland PG 1 3.5x2
Cable Gland PG16
Cable Gland PG21
Mains selector Link MJO5
Mains Terminal Cover 2023009
Mains Fuses 20/250T
Probe Cable 4 metres 20228-04
Probe Cable 10 metres 20228-10
Installation Manual 2026900
46
202 Electronic Unit Specification
1 Electronic Level Indicator Unit. Type 202A
Enclosure:
Wall mounted glass-fibre reinforced polyester, IP65/NEMA4X protection for location in harsh
environments. Dims: 320mmH x 200mmW x 120mmD (12.6'x 7.8'x 4.7')
Inputs:
Discrimination between water and steam for 14 channels numbered in ascending order.
Discrimination threshold may be selected for minimum conductivity of 0.5 micro Siemens/cm, 1
micro Siemen/cm or 2 micro Siemens/cm.
The lower 8 Probe Channels have a single wire connection the Probe and the upper 6 channels
have two connections to each Probe. Any wire disconnection on the Probes reverts the channel to
steam indication if the Probe is immersed in water and any disconnection on the upper Probes
reverts the channel indication to water it immersed in steam. This facility enhances fault declaration.
A 4 metre (12') length of special high temperature PTFE cable is supplied for Probe connections.
For longer cable lengths connection to standard PVC cable advised, max. cable length 30 metres
(100’).
Display:
Two vertical columns of 10mm (0.4") square LED's provided on the front of the enclosure. One row
of Green LED's represents water and the second row of Red represents steam. Particular LED's
may be selected to flash on initiation of Alarm Relays. On channels 2 - 6, the Red LED (Lo Water
Level) and on channels 8 - 13, appropriate Green LED (Hi Water Level) may be programme to
flash. The flashing is initiated by alarm relay action.
A Yellow flashing LED signals a System Fault Condition
Supply Requirements: - Two independent AC sources
92 to 127Volts ) AC @ 15VA, 48 - 63Hz
or 184 to 254Volts )
The 202 Instrument provides improved operational integrity in the event of one Mains supply failure
by the method of implementing dc supplies to the electronic circuitry.
Temperature Rating:-
Ambient:- -10ºC to +65ºC, Storage : -50ºC to 100ºC
47
Outputs:
(1). Alarm Trip Relays. Four sealed relays, each having single pole changeover contacts provide Alarm
and Trip signalling.
Two relays provide low and high level alarms and each may be linked to Probe channels in the
range 2 to 6 and 8 to 13. A low and high channel may be linked to the relay for a combined Lo/Hi
alarm output.
The two Trip relays provide low level and high level trip initiation. For the trip circuits a 2 out of 3
Probe channel voting circuit is applied with a 4th channel backup to counter internal supply failure.
The normal LoTrip level may be selected for channel 2 or 3 and the Hi Trip level for channel 12 or
13.
Each relay may be programmed for the normally energised or normally de-energised state with a
delayed action period of 1, 5, 1 0 or 15 secs.
Contact Rating: Max. Current : 5 Amps.
Max. Voltage : 350 Volts
Max. Switching Power: AC - 600VA
DC - 3OW @ 110V
12OW @ 30V
(ii) Remote Display. Twenty terminals are provided for direct connection to a Remote Display Unit.
4/2OmA Signal: An integral circuit provides a 4 to 2OmA transmission signal whereby each
probe channel contributes a step change of 1.14mA. Selection of 4mA to represent the all water or
all steam state is included.
Output Current: 4 - 2OmA in 14 incremental steps
Load Impedance: 300ohms Max.
(iv) System Fault Alarm. A single pole changeover contact is available for signalling:-
(a) Supply failure.
(b) Probe channel malfunction by validation between adjacent Probe channels.
2. Remote Display Unit Option. Type 20251A
Panel mounted 180mm x 72mm x 30mm ( 7.1” x 2.83" x 1.2” )
Housing: IP20
This unit duplicates the display on the front of the main unit and is intended for control room
location.
Panel Cut-out Dimensions : 174mm x 67mm (6.85' x 2.64')
Panel Thickness: 1.5mm to 6.4mm (0.06'to 0.25’)
Page 1 of 1
Conformity Assessment for Manufacture of Water Columns to the PED (97/23/EC)
1. Pressure Equipment Classification Water Columns designed & manufactured in accordance with ASME B31.1 Power Piping and ASME B&PV Code Section 1 Power Boilers. (Not Code Stamped) Type 501E: Max Allowable Operating Pressure 150 bar Type 502: Max Allowable Operating Pressure 207 bar Type 503 Max Allowable Operating Pressure 207 bar Type Definition: - Pressure Accessories where the nominal size DN is more appropriate than volume. All DN sizes >32 but <100 Length of column where the volume becomes more appropriate:- For type 501E: 734mm For type 502: 634mm For type 503 582mm 2. Product Classification a). The state of the intended fluid contents: Gas b). The classification of the intended fluid contents: Group 2 c) Fluid type: Steam Therefore using Chart 7 in the Guidance Notes to give Category Assessment when DN is more appropriate: - Equipment Category 1 Using Chart 2 when the lengths of the columns are greater than shown above and volume becomes more appropriate:- Equipment Category II 3. Conformity Assessment Procedure From Equipment Category 1, the Conformity Assessment Procedure used will be: -
Module A: Internal Production Control
From Equipment category II, the Conformity Assessment Procedure used will be:-
Module A1: Internal Production Control with monitoring of final assessment
Justification of compliance with Essential Safety Requirements Levelstate Systems Limited Item of equipment : Water Columns Type 501E, 502 & 503 PED Category: II PED Module: A1 ESR N°
Subject
Justification
Justification of compliance with Essential Safety Requirements Page 1 of 2
0 – 3 Hazard analysis See Technical File & separate Hazard Analysis
1 Responsibilities to be clear for • Design • Manufacture • Checking • Installation (if applicable)
See Levelstate Specification 180031 issue A
1.1 Manufacturer’s instructions See Installation Manuals 1.1 Service conditions to be covered as reasonably
foreseeable
See Installation Manual for recommended practice and guidance
1.2 Approach taken to design Refer to Hazard Analysis
1.3 The potential for misuse See Installation Manual for recommended practice and guidance
2.2.1 Design for adequate strength - load factors
In accordance with ASME B31.1 Chapter II Part 1
2.2.3a Calculation method for pressure containment and loading
In accordance with ASME B31.1, ASME B&PV Code Sections 1 & VIII, Levelstate Design Spec 180031 Issue A
2.2.3b Calculation method for resistance In accordance with ASME B31.1 Chapter II Part 1
2.2.4 Experimental Design Method Not Applicable
2.3 Provisions to ensure safe handling and operation See Installation Manual for recommended practice and guidance
2.4 Means of examination ASME Code Section 1 PG 60 2.2 2.5 Means of draining and ventilating See Installation Manuals 2.6 Corrosion or other chemical attack See Installation Manuals. ASME B31.1 Calcs 2.7 Wear Not Applicable
2.8 Assemblies Not Applicable
2.9 Provisions for filling and discharge Not Applicable
2.10 Protection against exceeding allowable limits of pressure equipment
See Installation Manual for recommended practice and guidance. Water Columns to be fitted to pressurized steam systems protected by suitable devices.
2.11 Safety accessories In accordance with ASME B31.1 Chapter II Part 1 2.12 External Fire Not Applicable 3.1.1 Preparation of Component Parts ASME B31.1 Chapter V 3.1.2 Permanent Joining ASME B31.1 Chapter V ASME Section IX
3.1.3 Non-destructive testing Not Applicable
3.1.4 Heat treatment Not Applicable
3.1.5 Traceability ASME Section 1 & Levelstate Spec. 180031 issue A 3.2.1 Final inspection
In accordance with ASME B31.1 Chapter VI & Levelstate Specification 180031 Issue A
3.2.2 Proof test In accordance with ASME B31.1 Chapter VI &
ESR N°
Subject
Justification
Justification of compliance with Essential Safety Requirements Page 2 of 2
Levelstate Specification 180031 Issue A 3.2.3 Safety Devices In accordance with juridstriction Regulations by end-
user. 3.3 Marking and labelling
Nameplate detailed drawings
3.4 Operating Instructions Refer to Installation Manual 4.1 Materials suitable for duty Refer to Assessment of Suitability 4.2 a Material design Refer to Particular Material Appraisal
4.2b Which of the following options do materials comply with: • compliance with harmonised standards • European approval of materials • by a particular material appraisal
Refer to Particular Material Appraisal
4.2c For Categories III and IV, has material appraisal been done by the Notified Body
Not Applicable
4.3 Material documentation Refer to material Certification in accordance with EN10204 Type 3.1b or 3.1c
5a Appropriate protection of steam raising plant Not Applicable
5b Fluid sampling points Not Applicable
5c damage from deposits Not Applicable 5d Safe means of removal of residual heat after
shutdown Not Applicable
5e Avoiding dangerous accumulation of ignitable mixtures or flame blowback
Not Applicable
6a Pipework design (overstressing)
Installed by end-user
6b Pipework drainage Installed by end-user 6c Pipework turbulence and vortices Not applicable 6d Fatigue from pipe vibration
Installed by end-user
6e Group 1 fluids - take-offs
Not Applicable
6f Pipework - inadvertent discharge
Installed by end-user
6g Records of routing of underground piping for maintenance and repair
Not applicable
7.1 Allowable stresses In accordance with ASME B31.1 Chapter II Part 1 7.2 Joint coefficients In accordance with ASME B31.1 Chapter II Part 1 7.3 Pressure limiting devices. Not Applicable 7.4 Hydrostatic test pressure In accordance with ASME B31.1 Chapter VI &
Levelstate Specification 180031 Issue A 7.5 Material properties. Refer to Material Test Certification
Levelstate Hazard Analysis for the PED Equipment : Water Columns 501E, 502 & 5031) Determine which hazards are applicable for the pressure equipment.2) Determine if this hazard is reasonably foreeable for this equipment, for the use and design parameters specified.3) Determine how the hazard can be reduced / eliminated or what protective measures or notices will be given concerning the hazard.4) State whether if the hazard and the control measure used are acceptable and provide a high degree of health and safety protection.Ref. Hazard Reasonably Solution / Control Measure Acceptable ?No. Foreeable ?1 Explosion / Leakage of probes seats & Yes Use only on properly operated boiler with end users Yes
over heating - Hazard of stored energy correct operating procedures2 Brittle Fracture No Use only on steam raising plant. Yes
3 Damage instrument probes, freedom of Yes Use only on properly designed plant in accordance Yesvessel to expand, examination problems ? with juridstictions regulations and Inst. Manual
4 Damage to equipment - transport Yes Comply with Sect 15 of Quality Assurance Manual Yesor installation
5 Escape of PED Group 1 fluid - damage No Not Applicable Yesto persons, buildings, environment etc..
6 Rapid release of high pressure fluid Yes Water columns encased in steel shrouding. Yesprojection of vessel components / blast Refer to Inst.Manual for best positioning
7 Collapse, vacuum implosion - leakage No Due to rigid construction using forged components Yesof vessel / detachment etc..
8 Furnace explosion of fired vessels - No Refer to section 3 of Inst.Manual for best positioning Yesblast, projection of flame tc..
10 Domino or knock on effect - with No Items of inconsiquencial size on large boiler plants Yessubsequent damage to plant / property Refer to Inst.Manual for best positioning
11 Thermal expansion/pipework support Yes Refer to Inst.Manual for best positioning ensure Yes& vibration items fitted to properly designed sytem (i.e.B31.1)
12 Wind / Seismic / Snow / Transport / Cyclic / No Refer to inst. Manual for best practise YesExternal / Nozzle loading, Creep etc.. Items operate outside the creep range
13 Protective Device / Control system failure Yes Use only on propely operated steam systems Yes(response time / safe discharge / lockout) properly protected in accordance with Juridstn.Regs
14 Other - Specify : Yes Use only with properly treated boiler water as per YesCorrosion & Erosion Inst.Manual and allowances built into design calcs.
This document is provided for information purposes only. It is the manufacturer’s responsibility to ensure that they have considered all hazards that exist for their pressure equipment.
Further infor from CEOC guidance
Particular Material Appraisal in accordance with PED (97/23/EC) Part 4.2.b
Assessment of Suitability The materials used in the manufacture of the pressurised parts have appropriate properties for
aloperating conditions; in particular they are ductile and tough.
They are suitable for the steaming conditions of the boiler using feed water which is chemically
controlled and where corrosion is insignificant.
They have welding compatibility, as they are all low carbon alloy steels grouped by P numbers in
accordance with ASME B&PV Code Section IX.
They comply with the specifications of the ASME B&PV Code Section 1 PG 23 and ASME B31.1
Chapter IV Table 126.1
They conform to the requirements of ANNEX D of the PED (97/23/EC) Sections 2.2.3, 4, 4.1, 4.2
and 4.3.
They are supported by Inspection Reports in accordance with EN10204 type 3.1b & 3.1c.
An appraisal of each material used at the max operating limits of
700 degF /371 degC for low Carbon Steel & 1076 degF / 580degC for High Alloy Stainless Steel is
given in the table below.
The materials are purchased from a material manufacturer holding an appropriate Quality
Assurance System.
Material Specification ASTM
Ductile? Tough ? Weldability ? Suitable for High Temp ?
Certs reviewed ?
3.1b or 3.1c ?
A105 22% <0.25 % Carbon
Yes Yes 3.1c
A106 Grd B 22% <0.25% Carbon
Yes Yes 3.1b
A312 Type 316 22% <0.25%
Carbon Yes Yes 3.1b
Materials do not operate in brittle conditions Boiler Plant
Declaration of Conformity to 97/23/EC
Levelstate Systems Limited
7 Bentley Industrial Centre Bentley
Hampshire GU10 5NJ England
Pressure Equipment: Water Column Pressure Accessories used to
monitor steam/water levels in steam generating plant.
Type identification: 501E, 502 & 503 Equipment Category: Category II Conformity Assessment Procedure: Module A1 Notified Body: Royal & SunAlliance 17 York St, Manchester, UK Notified Body No: 0040 Technical Standards Used: ASME B&PV Code Section 1
Power Boilers ASME B31.1 Power Piping Authorized signature: ……………………………… Name: ……………………………… Position: ……………………………… Date of Signature : ………………………………
Absolute Temperature Specific Specific Latent heatPressure °C volume weight kJ/kg
Bar m³/kg kg/m³ of water of steam
20 212.37 0.09954 10.05 908.6 2797.2 1888.622 217.24 0.09065 11.03 931.0 2799.1 1898.124 221.78 0.08320 12.02 951.9 2800.4 1848.526 226.04 0.07686 13.01 971.7 2801.4 1829.628 230.05 0.07139 14.01 990.5 2802.0 1811.530 233.84 0.06663 15.01 1008.4 2802.3 1793.932 237.45 0.06244 16.02 1025.4 2802.3 1776.934 240.88 0.05873 17.03 1041.8 2802.1 1760.336 244.16 0.05541 18.05 1057.6 2801.7 1744.238 247.37 0.05244 19.07 1072.7 2801.1 1728.440 250.33 0.04975 20.10 1087.4 2800.3 1712.942 253.24 0.04731 21.14 1101.6 2799.4 1697.844 256.05 0.04508 22.18 1115.4 2798.3 1682.946 258.75 0.04304 23.24 1128.8 2797.0 1661.148 261.37 0.04116 24.29 1141.8 2795.7 1653.950 263.91 0.03943 25.36 1154.5 2794.2 1639.755 269.93 0.03563 28.07 1184.9 2789.9 1605.060 275.55 0.03244 30.83 1213.7 2785.0 1571.365 280.82 0.02972 33.65 1241.1 2779.5 1538.470 285.79 0.02737 36.53 1267.4 2773.5 1506.075 290.50 0.02533 39.48 1292.7 2766.9 1474.280 294.97 0.02353 42.51 1317.1 2759.9 1442.885 299.23 0.02193 45.61 1340.7 2752.5 1411.790 303.31 0.02050 48.79 1363.7 2744.6 1380.995 307.21 0.01921 52.06 1386.1 2736.4 1350.2100 310.96 0.01804 55.43 1408.0 2727.7 1319.7110 318.05 0.01601 62.48 1450.6 2709.3 1258.7120 324.65 0.01428 70.01 1491.8 2689.2 1197.4140 336.64 0.01150 86.99 1571.6 2642.4 1070.7150 342.13 0.01034 96.71 1611.0 2615.0 1004.0160 347.33 0.009308 107.40 1650.5 2584.9 934.3180 356.96 0.007498 133.40 1734.8 2513.9 779.1200 365.70 0.005877 170.20 1826.5 2418.4 591.9220 373.69 0.003728 268.30 2011.1 2195.6 184.5
221-2 374.15 0.003170 315.50 0.0
1 bar = 1.019716 kg/cm³
1 kg/cm² = 0.980665 bar
1 kcal/kg = 4.1868 kJ/kg
SATURATED STEAM TABLES(From VDI tables of constants of steam / water)
Enthalpy kJ/kg
2107.4
1 kJ/kg = 0.238845 kcal/kg
SpecifiedNominal Product Spec Grade Minumum -20 to 200 300 400 -20 to 500 600 650 700 750 800 850 900 950 1000 1050 1100Composition Form Number Class Tensile 100 400
C-Mn-Si Smls pipe SA-106 B 60.0 15.0 15.0 15.0 15.0 14.4 13.0 10.8 7.8 5.0 3.0 1.5
C-Si Forging SA-105 70.0 17.5 17.5 17.5 17.5 16.6 14.8 12.0 7.8 5.0 3.0 1.5
16Cr-12Ni-2Mo wld pipe SA-312 TP316 75.0 16.0 13.8 12.4 11.4 10.6 10.1 9.8 9.6 9.5 9.4 9.3 9.2 9.1 9.0 8.9 8.8
SA-106 Maximum operating temperature 370°C or 698 °F
SA-105 Maximum operating temperature 370°C or 698 °F
SA-312 Maximum operating temperature 580°C or 1076 °F
For Metal Temperatures Not Exceeding °F
multiply by 1000 to obtain psi
MAXIMUM ALLOWABLE STRESS VALUES FOR WATER COLUMN MATERIALS