Pressure Tech THE LW-351 Series Service manual

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THE LW-351 SERIES
Operating and Service Manual
Series includes LW351-06-A-XX-X-K-XX-XXXX
Issue 001
March 2020

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TABLE OF CONTENTS
1. Description.............................................................................................................................3
2. Installation .............................................................................................................................3
3. Operation...............................................................................................................................4
4. Special Conditions for Safe Use .............................................................................................4
5. Hazardous Location Usage.....................................................................................................4
6. Servicing and Maintenance....................................................................................................4
6.1. Servicing the LW-351..............................................................................................5
6.1.1. Accessing the Main Valve Assembly ...................................................................5
6.1.2. Adjusting the Set Point .......................................................................................6
6.1.3. Figure 1 –Sectional View of the LW-351............................................................7
7. Technical Data........................................................................................................................8
8. Warranty Statement ..............................................................................................................8

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1. Description
The LW-351 is a piston-sensed pressure regulator, designed specifically to provide constant
pressure supply to the hydrogen fuel cell for lightweight applications. With a low 0.15%
decaying pressure effect, it offers accurate control in a single-stage pressure reduction.
Pressure Equipment Directive (PED) 2014/68/EC Declaration
This equipment is designed and manufactured in accordance with Sound Engineering
Practice (SEP) Article 4, Paragraph 3 of the directive 2014/68/EC. As such, CE marking must
not be applied. The equipment is marked under section 3.3 of Essential Safety Requirements
of the directive.
2. Installation
Before system start-up, it is recommended that all systems be pressure tested, leak tested
and purged with an inert gas such as nitrogen.
Prior to placing into service ensure that the regulator is in the fully closed position, with the
adjusting mechanism turned completely anti-clockwise.
Check the model number reference to ensure that the pressure range complies with the
installation requirements.
Visually inspect the regulator for any signs of damage or contamination. If any foreign
materials are present and cannot be removed from the regulator, or if the threads on the
regulator appear to be damaged, please contact the office immediately to arrange for the
regulator to be returned for service.
Select the correct size and type of connection fittings for each relevant port, as indicated in
the regulators part number and also in-line with the product data sheet. Both British
Standard Pipe (BSPP) ‘B’ and National Pipe Thread (NPT) ‘N’ options are available on this
regulator. Use the correct dowty or bonded seal for BSPP connections, self-centering seals
are recommended. For NPT threads, ensure that PTFE tape is applied correctly to the
fittings, applying two overlapping layers in the direction of the thread, taking care that the
tape does not come into contact with the first thread. Any gauge ports on the regulator will
be 1/4” NPT unless otherwise stated. If any gauge port is not required, ensure that the port
is plugged prior to installation.
The media supplied to the regulator must be clean. Contamination can damage the seat
which may cause the regulator to fail. Filtration suited to the application is recommended
upstream of the regulator. Should further assistance or information be required in relation
to installation of any Pressure Tech regulator please contact the office, giving reference to
the regulators part number and/or serial number.

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3. Operation
Turning the adjusting mechanism clockwise compresses the spring, which in turn opens the
main valve and allows the inlet pressure to pass through the seat orifice until the outlet
pressure is equivalent to the loading forces set by the compressed spring. Increase the
outlet pressure in this way until the desired pressure is achieved.
To reduce the outlet pressure, the adjusting mechanism should be turned anti-clockwise
whilst the media is flowing, or whist venting downstream of the regulator.
The desired outlet pressure should be set whilst increasing the pressure. Do not exceed the
maximum inlet and outlet pressures of the regulator which are indicated on the regulator
label.
4. Special Conditions for Safe Use
The LW-351 series are non-venting type regulators; therefore, the outlet pressure shall be
reduced by venting downstream of the regulator whilst simultaneously turning the adjusting
mechanism anti-clockwise.
5. Hazardous Location Usage
This equipment has not been manufactured specifically for use in potentially explosive
atmospheres and as such an ignition hazard assessment has not been carried out on this
product. If the user should wish to use this product in such an environment where there
may be a potentially explosive atmosphere then it is the responsibility of the user to
conduct an ignition hazard assessment against 99/92/EC.
6. Servicing and Maintenance
Servicing and maintenance work on the LW-351 regulators should only be performed after
fully reading and understanding the Operating and Servicing Manual. Due to the
compressibility of gases, the operator should not endanger themselves or others by working
on this regulator without prior knowledge of the Health and Safety risks relating to handling
of technical gases. Any uncertainty should be clarified with Pressure Tech before working on
the regulator.
Pressure Tech Ltd recommends the use of Krytox GPL 205 as a lubricant for O-rings and the
Adjusting Screw during servicing.
Prior to commencing service, please ensure that:
-The equipment has been de-pressurised
-The load spring has been de-compressed by turning the adjusting mechanism fully
anti-clockwise
-Applications involving toxic, flammable or corrosive media have been fully purged
To ensure the best possible results from servicing, when re-assembling the regulator and
any assemblies within it, ensure that all areas of the components and the regulator body are
cleaned and free from contaminants which may result in failure of the regulator.

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6.1. Servicing the LW-351
*Note: fig 1 should be used as a reference for the following set of instructions
6.1.1. Accessing the Main Valve Assembly
To access the Main Valve Assembly (MVA):
i. With the flats of the Regulator Body (1) secured in a vice, ensuring that the
Adjusting Screw (7) is fully wound anti-clockwise (*Ref. 6.1.2), loosen and
remove the Bonnet Assembly (7, 9, 12, 15) using a 27mm wrench
ii. Remove the Upper Spring Rest (10) and Load Spring (11)
iii. Using needle nosed pliers, remove the sensor assembly (8,17)
iv. The Solid Disk Seat (3) and Soft Seat (2) can then be removed using a 12mm
socket.
v. Visually inspect the Solid Disk Seat (3) and soft seat (2) for any potential damage
under a microscope
*Note: As the seat is a compression fit, it is likely that the soft seat will be secure
in the Solid Disk Seat. As such it is always recommended to replace both the
parts during service, where necessary.
vi. Remove the Main Valve (4) and Main Valve Spring (6) from the regulator body (1)
vii. Visually inspect the Main Valve (4) for any potential damage under a microscope
viii. Remove and replace the main valve O-Ring (16)
ix. Replace the Main Valve Spring (6) and Main Valve (4) and place into the
Regulator Body (1)
x. Guide the Solid Disk Seat (3) and Soft Seat (2), over the stem of the Main Valve
(4) taking care not to damage its sealing face against the tip of the valve.
xi. Screw the Solid Disk Seat (3) into the regulator body (1) and tighten to 4.5Nm,
using a 12mm socket
xii. Replace the O-ring (17) from around the sensor (8), then place the sensor
assembly (8,17), into the Regulator Body (1)
xiii. Position the Load Spring (11) around the top of sensor (8) and place the Upper
Spring Rest (10) on the to the assembly
xiv. Screw the Bonnet assembly (7, 9, 12, 15) into the Regulator Body (1) and using a
torque wrench with a 27mm open ended attachment, tighten to 15Nm
It is recommended that all parts in the repair kits are used. Any defect parts removed during
the service should be disposed of. Parts should be kept clean in line with media
requirements. Following re-assembly of the regulator, pressure tests should be made to
both the inlet and outlet side of the regulator, to ensure there is no internal or external
leakage across the regulator.
To ensure that the main valve assembly has been correctly and effectively installed it may
be required to perform the appropriate seat leak test as per ANSI/FCI 70-2.

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6.1.2. Adjusting the Set Point
i. Loosen the Lock Nut (12), from the Adjusting Screw (7).
ii. Connect the correct fittings to the Inlet and Outlet ports of the regulator. Ensure
that any gauge ports are plugged or that the correct gauge is fitted.
iii. With the Regulator Body (1) secured (either in a vice or other safe means of
securing the regulator) apply the Maximum Working Pressure (MWP) to the
Inlet (01C = 5/8”-18 UNF or 02C = M18 base stem) of the regulator.
iv. Connect the Outlet port to a calibrated pressure test gauge appropriate to the
required set pressure. As the regulator is non-venting, ensure that a ball/needle
valve is fitted to allow pressure to be relieved downstream of the regulator.
v. Using a slotted screwdriver, turn the Adjusting Screw (7) clockwise until the
desired set point has been reached.
vi. Ensure repeatability by allowing flow through the regulator using the
ball/needle valve.
vii. With the outlet pressure set, screw the Lock Nut (12) to the base of the
Adjusting Screw (7) and tighten against the top of the Bonnet (9)
*Note: Ensure that the Lock Nut (12) is sufficiently tightened, taking care not to
adjust the set point.
viii. If the set point is not correct, repeat steps v. to vii.
ix. Isolate the upstream pressure, then allow pressure to be released by opening
the downstream valve until flow diminishes completely –then the regulator can
be removed from test set up.

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6.1.3. Figure 1 –Sectional View of the LW-351
© Copyright of Pressure Tech Ltd
PARTS LIST
ITEM
PART NUMBER
DESCRIPTION
1
PT-LW-351-Z-01C-A-XXX
BODY - 'C' PORTING
2
PT-C-224-004
PCTFE SOFT SEAT
3
PT-C-007-016
SOLID DISC SEAT
4
PT-MINI-301-UHP-009-001
METAL MAIN VALVE
5
PT-C-185
SS SUPORT RING
6
PT-C-006-002
MV COMPRESSION SPRING
7
PT-LW-351-001
ADJUSTING SCREW
8
PT-LW-351-005
28mm SENSOR
9
PT-LW-351-003
LW351 BONNET
10
PT-LW-351-002
UPPER SPRING REST
11
SPR-YCMS20-H4S17-X
LOAD SPRING
12
PT-C-020
LOCKNUT
13
FILT-SCRM3803040S
8mm DIA SCREEN FILTER
14
FIT-472008-SS-CIRCLIP
CIRCLIP
15
FIT-D1400-0090
CIRCLIP
16
OR-BS004
O' RING STD
17
OR-0251-16
O' RING STD
18
OR-BS1806-112
O' RING STD

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7. Technical Data
Fluid Media: All gases are compatible with materials of construction
Max Inlet Pressure*: 350 bar (5,075 Psi) (with PCTFE Seat)
Outlet Pressure Range: 0-1 bar (other pressure ranges available are 1-3 bar
and 3-5 bar)
Operating Temperature: -20°C to +80°C
Materials: Body and Trim: Aluminum 6082
Seat: PCTFE
Flow Capacity (Cv): 0.06
Leakage: Gas: Bubble tight
*Max Inlet Pressure determined by seat material and Cv of regulator.
8. Warranty Statement
Pressure Tech Ltd guarantee all products correspond with their specification at the time of
delivery and, with exception to wear and tear, wilful damage, negligence, and abnormal
working conditions, will be free from defects for a period of 12 months from date of
delivery.