Special Instructions for Installation of GAS Street Line for CAT Gas Engines

1. Special Instruction
Installation and Maintenance of the Fuel System for Certain Gas Engines{1250}
Media Number -REHS8184-01 Publication Date -18/09/2013 Date Updated -18/09/2013
i05459490
Installation and Maintenance of the Fuel System for Certain
Gas Engines{1250}
SMCS - 1250-GFU
Engine:
G3512E (S/N: GFL1-UP; GFM1-UP; SSR1-UP; NGS1-UP)
G3516H (S/N: GLM1-UP; GLN1-UP)
Introduction
Gas Trains are now available for the above Gas Engine Generator Sets. This Special Instruction
provides the necessary information to install and maintain these gas train systems. All gas trains
discussed in this document are designed to utilize dry pipeline quality natural gas to the below
specifications. Consult the factory for applications using other fuels
Table 1
Component Specification
Maximum Design Inlet Pressure 48 kPa (7 psi)
Minimum Inlet Pressure
19 kPa (2.78 psi)
Minimum Gas LHV 800 BTU/FT3
Maximum H2S Rate 0.1%
These gas trains are designed for installation as shown and are not to be disassembled to the
individual components during assembly. Gas trains are comprised of several main components
that serve a role in providing clean fuel to the engine fuel inlet at the required pressure. The main
gas train components are shown in illustration 1 below.

2. Illustration 1
(A) Weldable flange
(B) Manual Isolation Valve
(C) Pressure Gauge
(D) Gas Filter
(E) Pressure Regulator
(F) Dual Solenoid Shutoff Valve
(G) Flexible Hose
Main Components
Weldable Flanges
Inlet and outlet flanges are provided with each gas train designed to be welded to customer
supplied piping. These flanges can then be bolted directly to the inlet or outlet of the gas train.
The outlet weldable flanges are not required as the outlet connection on the flexible hose can
mate directly to the engine fuel inlet.
Manual Isolation Valves
A manual isolation valve is provided with each gas train on the inlet side prior to the gas filter.
The manual valve allows for isolation of the gas train and engine from the fuel source. The
manual isolation valve will either be a ball valve or a butterfly valve depending on the specific

3. gas train purchased. When leak testing gas supply piping this valve should be closed to prevent a
pressure spike from damaging the gas train components.
Note: Quickly opening the manual isolation valve can permanently damage other gas train
components. The manual isolation valve should be opened slowly to allow for a gradual build of
pressure in the system.
Pressure Gauges
Illustration 2
(A) Manual push button
Three pressure gauges are provided with the typical gas trains. The gauges will either be 0 - 70
kPa (0 - 10 psi)or 0-600 mbar gauges depending on the intended market for installation. The first
two are on the inlet and outlet sides of the gas filter to show differential pressure across the filter.
The third gauge is on the outlet side of the shutoff valves to show inlet fuel pressure feeding into
the engine. Each gauge is equipped with a manually operated shutoff device between the
measuring line and pressure gauge. In the normal state, the push-button cock is closed.
Therefore, the pressure gauge is relieved of pressure. The push button must be pushed to apply
pressure on the pressure gauge (illustration 2).
Gas Filter

4. Filter systems are utilized to increase the service life of gas engines. Gas lines contain varying
amounts of scale and rust which can cause malfunction or damage to the gas train and engine
components. The filters used on the gas trains filter to the following levels: 1 micron at 96%
efficiency, 2 microns at 99.5% efficiency.
Note: Prior to removing the condensation drain plug or the filter element, the manual isolation
valve must be closed. Verify that the system is not pressurized before removing the plug or filter.
Illustration 3
(A) Filter housing cover
(B) Condensation drain plug
The differential pressure gauges should be used when determining if the filter element needs to
be replaced. If, the pressure difference between the filter inlet and outlet gauges is greater than
104 M Bar (1.5 psi)the element should be serviced. In order to change the filter element the filter
housing lid must be removed. All of the bolts on the lid must be removed and the element will be
removed vertically from the filter housing. Do not introduce foreign debris into the filter housing
when replacing the filter element. Replace the two sealing O-rings at the same time the filter
element is replaced. The filter housing is also equipped with a condensation drain and plug on
the bottom of the filter housing. Water vapor in the gas can sometimes build and condensation
can pool on the bottom of the housing. The drain plug should be removed periodically to drain
this water from the system.
Pressure Regulator

5. Illustration 4
(A) Vent/breather connection
(B) External feedback pressure connection
(C) Upstream pressure connection
The pressure regulator is designed to reduce the inlet pressure into the gas train down to an
acceptable level for use by the engine. Refer to Illustration 4 for pressure tap locations of the
pressure regulator.
Illustration 5
(A) Breather plug
(D) Breather hole

6. The pressure regulator has a breather plug (A) that threads into the regulators vent connection.
When, installing the gas train this plug should not be removed unless venting outdoors is
required. This plug is not the vent limiter, and the plug prevents debris from entering the upper
chamber of the regulator. Debris in the upper chamber of the regulator could adversely affect
regulator performance. The pressure regulator must also be able to exchange air through breather
hole (D) in order to operate. Do not plug the breather hole and clean out the hole if necessary.
If external venting of the regulator is required, follow the local code for vent sizing and
termination requirements. The vent line should be terminated at an approved location based on
local code requirements. Install an insect screen and terminate the pipe with the exit facing
downward. If venting the regulator, the vent line is to be connected to the upper dome of the
regulator to the breather plug location. In general, the piping run should be as short and direct as
possible.
Illustration 6
An external pressure feedback is not required with this regulator type. If, an external impulse
feedback is desired then the internal impulse must be plugged. Seal the internal impulse
connection with a silicone or RTV sealant suitable for exposure to natural gas, propane, or
butane.

7. Illustration 7
If, inlet pressure to the gas train is between 19 to 48 kPa (2.78 to 7 psi)the outlet pressure to the
engine will be between 10 to 34 kPa (1.5 to 5 psi). The spring installed in the regulator from the
factory is designed to operate in the pressure range and does not require adjustment. Refer to the
steps listed below and Illustration 7 in order to adjust the outlet pressure.
1. Remove the black cover on top of the regulator
2. To increase the outlet pressure, turn the adjustment spindle clockwise
3. To decrease the outlet pressure, turn the adjustment spindle counterclockwise
4. Utilize the downstream pressure gauge to verify that the outlet pressure is in the desired
range.
5. Reinstall the black adjustment cover.

8. Illustration 8
6. To prevent unauthorized adjustment, holes in the black cover and the side of the regulator
can be used to secure a lead seal.
Personal injury can result from parts and/or covers under spring
pressure.
Spring force will be releasedwhen covers are removed.
Be prepared to hold spring loaded covers as the bolts are loosened.

9. Illustration 9
1. Remove the adjustment cover
2. Release the spring tension by turning the adjustment spindle counterclockwise.
3. Remove the aluminum cap.
4. Remove the spring.
5. Install one new spring.
6. Reinstall the aluminum cap with the adjustment spindle.
7. Reinstall the adjustment cover.
8. Adjust as necessary
Dual Solenoid Shutoff Valve
The gas shutoff valve (GSOV) is one of the most important safety devices in the gas train. The
valve allows gas to the engine only when the engine is ready to use the gas. The GSOV
positively blocks the gas supply line to stop gas flow when the engine is shut down. The GSOV
utilizes two safety shutoff valves in series in one compact housing. Both of these valves must
open for gas to flow to the engine. Both solenoids operate in a default shutdown condition,
requiring actuation to allow gas to flow. The valves are commonly referred to as an "energize to
run" system. The two valves can be wired independently or in parallel. Refer to local code
requirements to determine if independent valve wiring is required. Electrical connections are on
the top of the valve

10. Table 2
Gas Shutoff Valve Specifications
Maximum Body Pressure
103 kPa (15 psi)
Maximum Operating Pressure
48 kPa (7 psi)
Supply Voltage
24 VDC
110-120 VAC / 50-60 Hz
Approximate Operating Current
5.6 A at 24 VDC
1.12 A at 120 VAC
Electrical Connection DIN connector with 1/2 inch NPT conduit adapter
Opening Time (to maximum flow) less than one second
Closing Time less than one second
Illustration 10
g03401766

11. Top View of the GSOV and Electrical Connections
Illustration 11
The valve can be wired to operate on either AC or DC power supplies. Refer to Illustration 11for
AC and DC wiring.
Due to the current draw exceeding or being near the maximum capability of most engine ECMs,
a relay is to be used.
During normal operation of the generator set, the GSOV solenoids will open and close as
signaled by the engine. During normal stop conditions the engine will close the GSOV while the
ignition system is left active while the engine runs down. Closing the valve helps to burn the fuel
in the fuel lines between the GSOV and the combustion cylinders. Closing the valve also
prevents fuel from being pumped into the exhaust system.
In an emergency shutdown, the GSOV is closed and the ignition system is grounded
immediately. The ignition system is grounded to stop the engine as quickly as possible but can
leave unburned fuel in the engine and exhaust system. The unburned gas poses a hazard and can
result in exhaust stack explosions. Thus an emergency shutdown should only be utilized in case
of emergencies and not used for normal shutdowns.
Note: Ensure that the engine and exhaust lines are purged following an emergency shutdown.
Purging the engine and exhaust will help avoid exhaust stack explosions due to unburned fuel in
the system. Purging the fuel can be accomplished by cranking the engine while keeping the
GSOV closed and the ignition system inactive.
Flexible Hose
The connection between the gas train and the engine fuel inlet is an important junction. Because
the engine is subject to vibration during operation, the fuel inlet can move relative to the fixed
piping of the gas train installation. If, a rigid connection was used, vibration transmitted to the
gas supply piping could lead to fatigue and failure resulting in a dangerous gas leak. Flexible
lines help to isolate the engine vibration from the gas supply lines.

12. Each flexible line consists of a stainless steel annular corrugated flexible metal hose with a single
braided stainless steel outer cover. The inlet side of the hose consists of a mating flange designed
to mate directly to the outlet side of the GSOV. The outlet side of the flexible hose consists of a
mating flange which should mate directly to the engine fuel inlet.
Other Components
Table 3
Guidelines/Regulations
Component AS5601/3814
CSA
B149.1
EN 746-
2
NFPA
37
Switch with visual position indicator X X X X
High Pressure Switch 100 to 500 mbar
- Auto Reset
X X
High Pressure Switch
10 to 50 kPa (40 to 200 inch of H2O) -
Manual Reset
X X
Low Pressure Switch 5 to 150 mbar -
Auto Reset
X X
Low Pressure Switch
3 to 15 kPa (12 to 60 inch of H2O) -
Auto Reset
X X
Valve Proving System - Tightness
Controller
X X X
Normally Open Vent Valve X
The gas train may contain other components based on the region and specific requirements it was
intended to be compliant with. Table 3 specifies which components are provided for each of the
regional gas train designs.
Switch with Visual Position Indicator
The position indicator signifies both physically and electrically when a valve is either in the
closed or open position. The indicator switches mount directly to the GSOV. The switch
indicator indicates orange when the valve is open and green when the valve is closed.
Table 4

13. Switch Type SPDT
Contact Rating
10A res, 8 FLA, 48 LRA at 120 VAC
1 A maximum at 24 VDC
Valve Open Green Light
Valve Closed Orange Light
Indicator light consumes 20 mA when energized
Illustration 12
(A) Indicator Switches

14. Illustration 13
g03402040
Follow local regulations as required when wiring the indicator switches. Do not exceed the
electrical rating of the switches and use at least 14 or 16 AWG wire rated for at least 75C (167F).
For NEMA 4 applications, NEMA 4 conduit or wiring methods must be used. Refer to
Illustration 13 for referenced wiring locations.
1. Connect one wire to the L1 terminal (common).
2. Connect one wire to the ground terminal.
3. Connect one wire from Terminal 2 (proof terminal) to proof of closure terminal of the
flame Safeguard.
Note: If the neutral is not wired to Terminal L2 on the switch, the lights will not indicate
the valve position.
4. Connect one wire from the neutral to Terminal L2.
Note: Do not wire the switch to close a circuit that will directly power another safety shutoff
valve. Doing so could result in a safety valve being energized and opened rather than remaining
closed.

15. If the switch is not operating properly and is in need of calibration, refer to the steps listed below.
1. The switch must be mounted to the GSOV and the GSOV must be closed.
2. Disconnect all power to the switch to prevent electrical shock and equipment damage.
3. Remove the clear cover.
4. Turn the adjustment dial counterclockwise until the dial stops.
5. Turn the adjustment dial clockwise until the switch trips. The switch should make an
audible noise.
6. Note the position of the set point in reference to the white lines on the scale.
7. Turn the adjustment dial two additional increments clockwise to the same relative
position.
8. Install the clear cover.
The valve should be checked for continuity annually. Refer to the steps listed below.
1. Turn the manual shutoff valve to the off position.
2. Check the continuity between Terminal T3 (common) and Terminal T2 (proof
terminal).The continuity between Terminals T3 and T1 should not exceed 0.2 Ohms.
Note: Terminal T3 and T1 should not have continuity.
3. Energize the GSOV solenoids and verify the continuity for each switch between
Terminals T3 and T1. The continuity between Terminals T3 and T1 should not exceed
0.2 Ohms.
Note: Terminal T3 and T2 should not have continuity.
4. Replace the switch if the continuity is not correct.
5. Verify that the repair eliminated the problem.
NFPA 37 and CSA B149.1 High and Low Pressure Switches

16. Illustration 14
g03402434
(A) Low Pressure Switch
(B) High Pressure Switch
The high and low-pressure switches for NFPA and CSA-compliant gas trains are mounted to the
side of the GSOV body as shown in Illustration 14. The switches can be utilized to ensure that
the proper gas pressure range is provided to the engine.
Table 5
Switch Specifications
Switch Type SPDT
Contact Rating
10A resistive at 120 VAC
3A inductive at 120 VAC
1A at 12-48 VDC
Maximum Operating Pressure 7 psi (500 mbar)
Electrical Connection Screw terminals via 1/2 inch NPT conduit connection
Incorporates a vent limiter per UL353 and limits escape of gas less than 1.0 cfh at
48 kPa (7 psi) if internal switch diaphragm ruptures. No vent line is required when accepted by

17. the authority having jurisdiction.
Wiring the Low and High Pressure Switches
1. Remove the clear cover from the switch.
2. Use 14 or 16 AWG wire rated for at least 75° C (167° F).
3. Route the wires through the conduit connector
4. Install a conduit plug between the switch and the closest panel that contains switching
contacts to prevent possible gas leaks into the conduit.
Illustration 15
5. Connect the wires to the appropriate terminals. Refer to Illustration 15.
Adjusting the Set Point of the Switches

18. Illustration 16
(C) Set Point Dial
(D) Reset Button
(E) Clear Cover
Follow the steps listed below to adjust the set point The High Pressure set point should be set to
35 kPa (140 inch of H2O). The low-pressure set point should be set to 10 kPa (42 inch of H2O).
1. Remove the clear cover

19. Illustration 17
g03402781
2. Turn the dial until the desired trip pressure is opposite of the white arrow of the dial face.
3. After readjusting the set point for normal operation, verify that the gas pressure switch
operates as adjusted.
Note: Use the upstream pressure gauge to verify proper operation of the pressure switch.
4. Reinstall the clear cover.
Illustration 18
g03402495
For the high-pressure switch with manual reset, as pressure rises above the set point 2 NO closes,
1 NC opens, and a Neon light will turn on signifying a fault as the switch trips and locks out. The
same process will happen for the low-pressure switch but as the pressure falls below the set point
2 NO will close, 1 NC opens, and a neon light will turn on. For the low-pressure switch with
automatic reset the switch will trip but will not lock out.
The low-pressure switch will reset automatically when the gas pressure returns to a level above
the set point. To reset the high-pressure switch manually, wait until the gas pressure returns to a

20. normal operating level. Then press and release the clear cover over the red reset button in the
center of the yellow dial face shown in Illustration 16. Removing the cover is not necessary.
EN746-2 and AS 5601/3814 High and Low Pressure Switches
Illustration 19
g03402434
(A) Low Pressure Switch
(B) High Pressure Switch
The high and low-pressure switches for EN746-2 and AS5601/3814 compliant gas trains are
mounted to the side of the GSOV body as shown in Illustration 19. The pressure switches can be
utilized to ensure that the proper gas pressure range is provided to the engine.
Table 6
Pressure Switch Specifications
Voltage Rating
24-250 VAC
24-48 VDC
Current Rating
20 mA AC minimum
20 mA DC minimum

21. 1A DC maximum
Maximum Operating Pressure
500 mbar (7 psi)
Wiring the Low and High Pressure Switches
1. Remove the clear cover from the switch.
2. Use 14 or 16 AWG wire rated for at least 75° C (167° F).
3. Route the wires through the conduit connector
4. Install a conduit plug between the switch and the closest panel that contains switching
contacts or other sparking devices to prevent possible gas leaks into the conduit.
Illustration 20
g03402516
5. Connect the wires to the appropriate terminals. Refer to Illustration 21.

22. Illustration 21
g03402518
The high and low-pressure switches for these applications are automatic reset and will not lock
out if the pressure falls above or below the set point. For the high-pressure switch, as pressure
rises above the set point 2 NO closes, 1 NC opens signifying a fault as the switch trips. The same
process will happen for the low-pressure switch but as the pressure falls below the set point 2
NO will close, 1 NC opens signifying the fault as the switch trips.
Adjusting the Set Point of the Switches
Follow the steps listed below to adjust the set point The High Pressure set point should be set to
35 kPa (140 inch of H2O). The low-pressure set point should be set to 10 kPa (42 inch of H2O).
1. Remove the clear cover

23. Illustration 22
g03402781
2. Turn the dial until the desired trip pressure is opposite of the white arrow of the dial face.
3. After readjusting the set point for normal operation, verify that the gas pressure switch
operates as adjusted.
Note: Use the upstream pressure gauge to verify proper operation of the pressure switch.
4. Reinstall the clear cover.
Valve Proving System Tightness Controller
Illustration 23
g03402789
(F) Valve Proving System
The valve proving system (VPS) mounts to the side of the GSOV and is used to verify that both
safety shutoff valves in the gas train are fully closed before a system start-up or after a shutdown.
Table 7

24. Valve Proving System Specifications
Maximum Operating
Pressure 500 mbar (7 psi)
Maximum Body Pressure
1000 mbar (15 psi)
Electrical Ratings
110-120 VAC at 60 Hz
24 VDC
Switch Output Rating
4 A at 24 VDC at Run
1 A at 24 VDC at Alarm
Power Ratings
(Consumption)
Test Period: 60 V A
In operation: 17 V A
Electrical Connection Screw terminals with 1/2 inch NPT conduit connection
Operating Time 100% duty cycle, mas 20 test cycles per hour
Test Volume Maximum .(0004)m3
( 0.14 ft3
)/min
Release Signal Timing
Roughly 10 seconds for test volume less than (.014m3
)(0.5
ft3
)
More than 10 seconds (26 seconds maximum) for test
volume great than (.01 4m3
)(0.5 ft3
)
Detectable leakage rate
through both valves
(0.006 cubic meter)(0.2 cubic feet) to (0.03 cubic meter)(1
cubic feet)/hour at (500 mbar)(7 psi) inlet pressure

25. Illustration 24
g03402830
Programming the VPS
Illustration 25
g03403882
1. During an idle state the GSOV valves one and two are closed.
2. During valve proving the internal pump in the VPS pumps gas pressure from the P1
safety valve to the volume between the two safety valves.
3. The P2 pressure between the two valves increases 2 kPa (8 inch of H2O) above P1.
4. If P2 pressure increases 2 kPa (8 inch of H2O) above P1, the motor pump is switched off
and no leak is detected.
5. The contact RUN T5 is energized after 26 seconds maximum and the yellow signal lamp
illuminates continuously. For 24 VDC system, terminal B is energized.
6. If, P2 does not increase 2 kPa (8 inch of H2O) above P1 the motor pump is switched as a
leak is detected.
7. The Alarm contact T3 is energized after about 26 seconds and the red signal lights
continuously. For 24 VDC system, terminal S is energized.
8. During operation the VPS remains off. The RUN contact remains energized and both
safety valves are open.

26. Normally Open Vent Valve
Illustration 26
g03403883
(G) Normally open valve
(H) Vent line connection
The normally open vent valve is provided on gas trains intended for NFPA37 compliant
installations. The valve allows for venting of gas trapped between the two valves. The vent line
connected to this vent valve should be installed and vented to appropriate location according to
local regulations and code. The normally open valve is mounted on a line on the side of the
GSOV.
Note: Energize the normally open vent valve during operation. If both safety shutoff valves are
open but the vent valve is not energized, gas will vent through the vent valve. Energize the valve
to close shortly before or at the same time the safety shutoff valves are energized and allowed to
open.

27. Illustration 27
g03403888
Electrical connections for the vent valve
Maintenance Intervals
Table 8
Maintenance Schedule
Interval Procedure
Daily
Check filter Differential Pressure
Check fuel inlet pressure to gas train, adjust knock down
regulator if greater than
48 kPa (7 psi).
Check fuel inlet pressure to engine, adjust with gas train
regulator if greater than
34 kPa (5 psi).
Every 2000 Service Hours
Shut manual valve, remove condensation drain plugs from
regulator and filter bodies, drain, and replace plugs
Annually Replace the filter element
In Frame Overhaul : 40,000 Rebuild Regulator with regulator kit, replacing diaphragms and

28. Service Hours seals
Major Overhaul : 80,000
Service Hours
Replace all valve position switches, high and low-pressure
switches, and valve coils