Swagelok Fast Loop Module User manual

A Swagelok®Pre-Engineered
Subsystem
• Pre-engineered subsystems
available in weeks, not months.
• Field-tested design ensures
optimum system performance.
A Swagelok®Pre-Engineered
Subsystem
User’s Manual
Fast Loop
Module

A Swagelok Pre-Engineered Subsystem Fast Loop Module
2
Contents
Fast Loop Module System Manual . . . . . . . . . . . . . . . . . 3
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Congurations . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Mounting . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12
System Startup . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . 20
System Component User Instructions . . . . . . . . . . . . . . .24
Swagelok Instructions
Swagelok Tube Fitting Instructions for 1 in. (25 mm)
and smaller ttings, MS-12-01 . . . . . . . . . . . . . . . . . 24
Swagelok VCO Fittings Installation Instructions,
MS-CRD-VCO . . . . . . . . . . . . . . . . . . . . . . . . . 25
Packing Adjustment for 40 Series Ball Valves,
MS-INS-40 . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Packing Adjustment for 40G Series Ball Valves,
MS-INS-40G . . . . . . . . . . . . . . . . . . . . . . . . . . 28
R3A Series Externally Adjustable Relief Valve
Maintenance Instructions, MS-CRD-0013 . . . . . . . . . . .29
R4 Series Relief Valve Maintenance Instructions,
MS-CRD-0048 . . . . . . . . . . . . . . . . . . . . . . . . . 36
Plug Valve Subassembly Replacement and O-Ring
Rebuild Instructions, MS-CRD-0012. . . . . . . . . . . . . .38
Repacking Instructions for N and HN Series Valves,
MS-INS-N. . . . . . . . . . . . . . . . . . . . . . . . . . . .39
CH Series Check Valve Service Instructions,
MS-CRD-0025 . . . . . . . . . . . . . . . . . . . . . . . . . 41
Tornado™ Instructions
Tornado Model 601 Element Replacement Kit Instructions
Element Kit Part #601-5TX . . . . . . . . . . . . . . . . . . .47
Tornado Model 601 Flow Screen Replacement Instructions
Flow Screen Kit Part #601-6XX . . . . . . . . . . . . . . . . 49
Tornado Model 602 Maintenance Instructions . . . . . . . . . . 51

Fast Loop Module
(FLM)
System Manual
Conguration 4
1/2 in. Liquid System
with Optional Grab Sample and Relief Outlets Shown
A Swagelok Pre-Engineered Subsystem Fast Loop Module
3

Introduction
Fast Loop Systems are designed to handle high
ows in sample transport lines to reduce time
delays for online analyzer systems. Located
at the analyzer and offering a bypass, the
Swagelok® Fast Loop Module (FLM) can isolate
the sample system and introduce a purge gas
for system cleaning. The FLM extracts a sample
through a lter while using the high ow rate of
the fast loop to keep the lter element clean.
All FLM subsystems feature dual interlocked
ball valves which enable the fast loop to be
bypassed when the analyzer is not in service.
This feature maintains ow through the fast
loop system and improves overall system
performance once the analyzer is back online.
A Swagelok Pre-Engineered Subsystem Fast Loop Module
4

Configurations
The FLM is available in four main congurations. See the Fast Loop Module Application
Guide, MS-02-361, for additional information.
Configuration 1: Base Module, Bypass Only
PI
BV2
BV1
NV
NV
FFL
SN
FI
C
C
Fast
Loop
Out
Fast
Loop
In
To
Analyzer
(Liquid)
(Gas)
(Liquid)
PR
FP
BV
BV
PI
RV
FM
FP
FM
FC
MV NV1
NV
FI
PSV
C
CV SHV
SSV
FFL
SN
PV
NV
FI
BV Ball valve
PR
FP
BV
BV
PI
RV
FM
FP
FM
FC
MV NV1
NV
FI
PSV
C
CV
SHV
SSV
FFL
SN
PV
NV
FI
CV Check valve
PR
FP
BV
BV
PI
RV
FM
FP
FM
FC
MV NV1
NV
FI
PSV
C
CV SHV
SSV
FFL
SN
PV
NV
FI FI Flow indicator
PR
FP
BV
BV
PI
RV
FM
FP
FM
FC
MV NV1
NV
FI
PSV
C
CV SHV
SSV
FFL
SN
PV
NV
FI
FFL Filter - fast loop
PR
FP
BV
BV
PI
RV
FM
FP
FM
FC
MV NV1
NV
FI
PSV
C
CV SHV
SSV
FFL
SN
PV
NV
FI
NV Needle valve - grab sample or
purge outlet
PR
FP
BV
BV
PI
RV
FM
FP
FM
FC
MV NV1
NV
FI
PSV
C
CV SHV
SSV
FFL
SN
PV
NV
FI
NV Needle valve - ow indicator
PR
FP
BV
BV
PI
RV
FM
FP
FM
FC
MV NV1
NV
FI
PSV
C
CV SHV
SSV
FFL
SN
PV
NV
FI
PI Pressure indicator
PR
FP
BV
BV
PI
RV
FM
FP
FM
FC
MV NV1
NV
FI
PSV
C
CV SHV
SSV
FFL
SN
PV
NV
FI
PV Plug valve
PR
FP
BV
BV
PI
RV
FM
FP
FM
FC
MV NV1
NV
FI
PSV
C
CV SHV
SSV
FFL
SN
PV
NV
FI
RV Relief valve, (optional)
PR
FP
BV
BV
PI
RV
FM
FP
FM
FC
MV NV1
NV
FI
PSV
C
CV SHV
SSV
FFL
SN
PV
NV
FI
SN Snubber tting-gauge protector
(standard for liquid service)
Configuration Symbols
Needle valve
(NV)
Ball valve
(BV1/BV2)
Pressure
indicator
(PI)
Flow
indicator
(FI)
Filter
(FFL)
A Swagelok Pre-Engineered Subsystem Fast Loop Module
5

Configuration 1: Base Module, Bypass Only
with Grab Sample and Relief Outlets Shown
Configurations
PI
BV2
BV1
NV1
NV1
NV2
FFL
SN
RV
FI
C
C
Fast
Loop
Out
Fast
Loop
In
To
Analyzer
(Liquid)
(Gas)
(Liquid)
Grab
Sample
Outlet
Relief
Outlet
Needle valve
(NV1)
Ball valve
(BV1/BV2)
Relief valve
(RV)
Pressure
indicator
(PI)
Grab sample
needle valve
(NV2)
Flow
indicator
(FI)
Filter
(FFL)
A Swagelok Pre-Engineered Subsystem Fast Loop Module
6

Configuration 2: Return from Analyzer To Process
PI
BV2
BV1
CV
NV1
NV1
NV2
FFL
SN
RV
C
C
FI
Fast
Loop
Out
Fast
Loop
In
To
Analyzer
From
Analyzer
(Liquid)
(Liquid)
(Gas)
Needle valve
(NV1)
Ball valve
(BV1/BV2)
Pressure
indicator
(PI)
Grab sample
needle valve
(NV2)
Flow
indicator
(FI)
Filter
(FFL)
Relief valve
(RV)
Configurations
A Swagelok Pre-Engineered Subsystem Fast Loop Module
7

Configuration 3: Return from Analyzer Switch Drain
Configurations
PI
BV2
BV1
BV3
CV1
CV2 PV
NV1
NV1
NV2
FFL
SN
RV
C
C
C
FI
Fast
Loop
Out
Fast
Loop
In
To
Analyzer
Oily
Drain
(Vent)
Oily
Drain
(Vent)
From
Analyzer
(Liquid)
(Liquid)
(Gas)
Needle valve
(NV1)
Ball valve
(BV1/BV2)
Ball valve
(BV3/BV4)
Plug valve
(PV)
Pressure
indicator
(PI)
Grab sample
needle valve
(NV2)
Flow
indicator
(FI)
Filter
(FFL)
Relief valve
(RV)
A Swagelok Pre-Engineered Subsystem Fast Loop Module
8

Configuration 4: Gas or Liquid Purge, Manual Drain
PI
BV2
BV1
BV3
BV4
CV1
CV3
CV2 PV
NV1
NV1
NV2
FFL
SN
RV
NV3
FI
C
C
C
Fast
Loop
Out
Fast
Loop
In
To
Analyzer
Oily
Drain
(Vent)
Purge
Oily
Drain
(Vent)
From
Analyzer
(Liquid)
(Liquid)
(Gas)
Needle valve
(NV1)
Ball valve
(BV1/BV2)
Ball valve
(BV3/BV4)
Plug valve
(PV)
Pressure
indicator
(PI)
Grab sample
needle valve
(NV2)
Purge needle
valve (NV3)
Flow
indicator
(FI)
Filter
(FFL)
Relief valve
(RV)
Configurations
A Swagelok Pre-Engineered Subsystem Fast Loop Module
9

Mounting
The FLM must be mounted to a vertical
face or wall for function of the owmeter
and to allow for gravity to assist in draining
the system. Mount the FLM as close to
the analyzer inlet system or analyzer as
possible.
The mounting holes are designed to t
over the bolt heads and assist in mounting.
Attach with 1/4 in. fasteners with a
maximum head size of 1/2 in. (not provided)
in the four mounting holes on the plate.
The FLM is designed to ow with fast loop
(process) connections on the left and the
outputs to the analyzer on the right. System
operation is not recommended in any other
orientation.
Dimensions, in inches (centimeters), are for
reference only and are subject to change.
Top
7.50
(19.0)
1.50
(3.81)
13.0
(33.0)
13.5
(34.3)
4 mounting holes for
1/4in./6 mm socket
head cap screw or
hex head bolt
0.35 (0.89)
0.40 (1.02)
1/4 in. Fast Loop Module
Left Side Right Side
Fast loop inlet
Fast loop outlet
Relief outlet
(option)
7.15
(182)
1.71 (43.4)
11. 9
(302)
9.90
(251)
0.69
(1.75)
0.92 (23.4)
4.56
(116 ) 5.24
(133) 7. 97
(202)
11. 0
(279) 12.8
(325)
Return from
analyzer
Out to
analyzer
Grab sample
outlet (option)
Purge in
Drain/vent
Drain/vent
Weight
22 to 27 lb (10.0 to 12.2 kg)
A Swagelok Pre-Engineered Subsystem Fast Loop Module
10

1/2 in. Fast Loop Module
Top
0.50 (1.27)
2.66
(6.76)
26.2
(66.5)
15.0
(38.1)
20.2
(51.3)
0.75 (1.90) 4 mounting holes for 1/4 in./6 mm
socket head cap screw or hex head bolt
Left Side Right Side
Fast loop inlet
Fast loop outlet
Relief outlet
(option)
5.94
(15.1)
1.81 (4.60)
16.2
(41.1)
13.8
(35.1)
1.09
(2.77) 6.70
(17.0)
18.7
(47.5)
8.10
(20.6) 9.39
(23.9) 10.7
( 27. 2 )
0.88 (2.24)
Return from
analyzer
Out to analyzer
Grab sample
outlet (option)
Purge in
Drain/vent
Drain/vent
Weight
65 to 75 lb (29.5 to 34.0 kg)
Mounting
A Swagelok Pre-Engineered Subsystem Fast Loop Module
11

Installation
1/4 inch and 1/2 inch systems have
fractional Swagelok tube ttings or metric
Swagelok tube ttings for the system
connections.
Note: For 1/4 in. systems, all inlet and
outlet connections are 1/4 in. or 6 mm
with the exception of the sample to
analyzer connection, which is 1/8 in.
or 3 mm.
Note: For 1/2 in. systems, the fast loop out,
fast loop in, relief outlet, oily drain
(bottom right), and grab sample outlet
connections are 1/2 in. or 12 mm;
return from analyzer, purge in, and
oily drain (center right) connections
are 1/4 in. or 6 mm; sample to
analyzer connection is 1/8 in. or
3mm.
Note: All internal ttings (non-system
connections) are fractional ttings.
Install Swagelok tube tting according to
the Swagelok Tube Fitting Instructions for
1in. (25 mm) and smaller fittings, page 24.
Inlet Connections
1. Fast Loop In - connect to the sample
transport line to be analyzed.
2. Sample to Analyzer - connect to the
remainder of the sample conditioning
system prior to the analyzer.
3. Return from Analyzer (option) - connect
to the outlet line from the analyzer.
There must be sufcient pressure to
create ow back into the FLM return.
4. Purge In (option) - connect to a purge
line. It will be used to purge the sample
side of the system prior to servicing.
Conguration 4 - The purge media may
be either a liquid or a gas.
Outlet Connections
5. Fast Loop Out - connect to the return
transport line. This line must be at lower
pressure than the process supply line
and is typically downstream from the
sample point.
6. Relief Outlet (option) - connect to a
sample disposal. This line will open if an
overpressure event activates the relief
valve.
7. Grab Sample Outlet (option) - connect
to a grab sample unit to collect samples
for analysis.
8. Oily Drain × 2 (Vent) (option) - connect
to an oily drain or sample disposal
suitable for the system media.
Fast loop
out
Fast loop
in
Relief outlet
Return from
analyzer
Purge in
Sample to
analyzer
Grab sample
outlet
Oily drain
(vent)
1/2 in. Fast Loop Module, Gas System, Conguration 4
Oily drain
(vent)
A Swagelok Pre-Engineered Subsystem Fast Loop Module
12

4. Place the FLM in sample mode by
moving the black handle to the right.
Pressure will be shown on the pressure
gauge (PI).
5. Adjust the ow to the desired rate.
1/4 in. systems - use the metering valve
that is integral to the owmeter.
1/2 in. systems -
■Gas systems: use the needle
valve (NV1) that is upstream of the
owmeter.
■Liquid systems: use the needle valve
(NV1) downstream of the owmeter.
System Startup
1. Place the FLM in bypass mode by
moving the black handle (BV1/BV2) to
the left.
2. Congurations 3 and 4 - Close the
sample return valve by moving the red
handle (BV3/BV4) to the up position.
3. Open ow to the FLM by opening all
fast loop in, fast loop out, and process
return lines. Since the FLM is in bypass
mode, allow your system to run for a
minimum of ve minutes in order to ush
the sample return lines.
Congurations 3 and 4 - verify the plug
valve (PV) is closed.
1/2 in. Fast Loop Module, Liquid System, Conguration 4
Black handle
(BV1/BV2)
Red handle
(BV3/BV4)
Needle valve
(NV1)
Plug valve
(PV)
Pressure
indicator
(PI)
A Swagelok Pre-Engineered Subsystem Fast Loop Module
13

6. Verify that ow is reaching the sample
conditioning system downstream of the
FLM.
7. Adjust the relief valve set pressure, if
desired, according to the appropriate
instructions.
Note: The relief valve is pre-set at
the factory as specied in the
ordering information.
1/4 in. - R3A Series Externally
Adjustable Relief Valve
Maintenance Instructions,
page29.
1/2 in. - R4 Series Relief Valve
Maintenance Instructions,
page36.
Note: 1/2 in. systems with
peruorcarbon FFKM seals
will contain R3A series
relief valves.
Needle valve
(NV1)
1/2 in. Fast Loop Module, Gas System, Conguration 4
Black handle
(BV1/BV2)
Red handle
(BV3/BV4)
Plug valve
(PV)
Pressure
indicator
(PI)
Relief valve
(RV)
System Startup
A Swagelok Pre-Engineered Subsystem Fast Loop Module
14

Operation
1. To place the FLM in sample mode, move
the black handle (BV1/BV2) to the right.
This will switch the ow to the sample
side of the FLM.
2. To place the FLM in bypass mode, move
the black handle to the left. This allows
all FLM ow to bypass the sample side
of the loop.
3. Congurations 3 and 4: To drain the
system while in bypass, open the plug
valve (PV). Conguration 3 systems may
not drain completely. If more effective
draining is required, Conguration 4
would be more appropriate.
4. Congurations 3 and 4: To place the
system in drain/purge mode, move the
black handle to the left to put the FLM
in bypass mode. Then move the red
handle to the down position to switch
the analyzer return line to drain mode
and opens the purge lines. (Purge lines
are in Conguration 4 only.)
5. Conguration 4: To adjust purge ow,
turn the handle of the purge needle
valve (NV3), clockwise for less ow or
counterclockwise for more ow.
6. To collect a sample from the grab
sample outlet, open the needle valve
(NV2) .
7. To return the FLM to sample mode,
reverse steps 1 through 3.
 Failure to periodically inspect and
maintain valve packing may result
in leakage.
 Swagelok ball valves are
designed to be used in the fully
open or fully closed position.
Needle valve
(NV1)
1/2 in. Fast Loop Module, Gas System, Conguration 4
Black handle
(BV1/BV2)
Red handle
(BV3/BV4)
Plug valve
(PV)
Pressure
indicator
(P1)
Grab sample
needle valve
(NV2)
Purge needle
valve (NV3)
A Swagelok Pre-Engineered Subsystem Fast Loop Module
15

Maintenance
 Warning
Before servicing any installed
system component you must
■depressurize the system
■purge the system (when
possible).
Follow these steps to depressurize your
FLM:
1. Place the FLM in bypass mode by
moving the black handle (BV1/BV2) to
the left. Fig. 1.
2. Congurations 1 and 2 - There is
no direct method within the FLM to
fully depressurize the system. Use
external means to depressurize these
congurations.
3. Congurations 3 and 4 - Place the
system in drain/purge mode by moving
the red handle (BV3/BV4) to the down
position.
4. Congurations 3 and 4 - Open the purge
valve (PV).
5. Congurations 4 - After a suggested
minimum of ve minutes, close the
purge line by moving the red handle to
the up position.
6. Verify that the FLM is depressurized by
checking the pressure on the pressure
gauge (PI).
Ball Valve Packing Adjustment
If a packing adjustment is needed on the 40
series ball valves (BV1/BV2 and BV3/BV4)
it is not necessary to shut down or remove
the system from service.
Fig. 1
System shown in Bypass mode.
Shown without tubing or system
connections for clarity.
Upper
coupling
Lower
coupling
Interlock
ange
Black
handle
Fig. 2
System shown in Sample mode.
Shown without tubing or system
connections for clarity.
Upper
coupling
Lower
coupling
Interlock
ange
Black
handle
A Swagelok Pre-Engineered Subsystem Fast Loop Module
16

To access the valve packing, you must
remove the black handle subassembly:
1. Turn the black handle to the left to place
the system in bypass mode. Fig. 1.
2. Congurations 3 and 4: Remove the
interlock ange. Fig. 2.
3. Remove the black handle shaft by
turning it counterclockwise. Fig. 2.
4. Loosen the two set screws on the upper
coupling. Fig. 2.
5. Loosen the set screw on the lower
coupling. Fig. 2.
6. Slide the couplings toward the center.
Fig. 3.
7. Lift out the black handle subassembly.
Fig. 4.

8. Adjust the valve packing according to:
1/4 in. - Packing Adjustment Card
for 40G Series Ball Valves,
page28.
1/2 in. - Packing Adjustment Card for
40 Series Ball Valves, page 27.
9. Congurations 3 and 4, To adjust the
valve packing on the 40G valves:
■Loosen the interlock set screws.
Fig.5.
■ Remove the interlock gears.
Note: Conguration 3, only the lower
gear must be removed.
■ Adjust the valve packing according
to Packing Adjustment Card for 40G
Series Ball Valves, page 28. Fig.6.
Reverse steps 1 to 8 to replace the handle
subassemblies.
Access
to valve
packing
Interlock
set screws
Access
to valve
packing
Fig. 3
Fig. 4
Fig. 5
Fig. 6
Maintenance
A Swagelok Pre-Engineered Subsystem Fast Loop Module
17

Conguration 4
1/2 in. Liquid System
with Optional Grab Sample and Relief Outlets Shown
VCO®Fitting Maintenance
When required, maintain the VCO ttings
within the system according to VCO Fittings
Installation Instructions, page 25. Verify that
the O-ring is in place when reassembling
the tting.
The locations of the VCO ttings within a
Conguration 4 FLM are indicated in the
drawing below.
Note: The VCO tting locations may vary
slightly between congurations.
Maintenance
A Swagelok Pre-Engineered Subsystem Fast Loop Module
18

System Component Reference for Replacement Ordering
Information
Proportional relief valve
(1/4 in. FLM - R3A series,
1/2 in. FLM - R4 series)
Proportional Relief Valves — R Series,
MS-01-141
Plug valve
(1/4 in. FLM - P4T series,
1/2 in. FLM - P6T series)
Plug Valves — P4T and P6T Series,
MS-01-59
VCOfitting VCOO-Ring Face Seal Fittings,
MS-01-28
Needle valve —
flow indicator
(1/4 in. systems - M1 series)
Variable Area Flowmeters — G Series and
M Series,
MS-02-346
Needle valve —
flow indicator
(1/2 in. systems - 12N series)
Severe-Service Union Bonnet Needle
Valves—N Series and HN Series,
MS-01-164
Needle valve —
optional grab sample outlet
(1/4 in. systems - 3N series,
1/2 in. systems - 12N series)
Needle valve —
optional purge outlet
(3N series)
Flow indicator
(1/4 in. FLM - M1 series,
1/2 in. FLM - M3 series)
Variable Area Flowmeters — G Series and
M Series,
MS-02-346
Ball valve
(40G or 40 series)
One-Piece Instrumentation Ball Valves —
40G Series and 40 Series,
MS-02-331
Pressure indicator
(PGI series, B model)
Pressure Gauges, Industrial and Process—
PGI Series,
MS-02-170
Check valve
(CH series)
Check Valves — C, CA, CH, CP, and
CPASeries,
MS-01-176
Snubber fitting Pressure Gauges, Industrial and Process —
PGI Series,
MS-02-170
Filter Kit Information
Module
Size Filter Type Kit Type
Element Size
2 micron 10 micron 25 micron
Ordering Number
1/4 in. FLM 601 Filter
Gasket / Element Kit 601-5T2 601-5T10 601-5T25
Flow Screen Kit 601-62SS 601-610SS 601-625SS
1/2 in. FLM 602 Filter Element Kit 602-5T2-1 602-5T10-1 602-5T25-1
5 Piece Element Kit 602-5T2 602-5T10 602-5T25
Maintenance
A Swagelok Pre-Engineered Subsystem Fast Loop Module
19

Troubleshooting
Symptom Cause Remedy
Pressure indicator
(PI) shows no
pressure.
FLM is in bypass mode.
Place the FLM into sample mode by moving the
black handle to the right.
Check that both ball valves are turning when black
handle is moved – if not, tighten set screws with
valve in correct orientation.
Fast loop is shut off. Open all valves in fast loop line external to the
FLM.
The sample supply line is
obstructed.
Check that there is pressure in sample supply line.
There is an obstruction
upstream of the FLM.
Check that sample fluid is passing through the
probe and isolation valves.
There is no process pressure. Check that the process line is pressurized.
Pressure indicator
(PI) shows low
pressure.
Configuration 3 and 4, the plug
valve (PV) may be open.
Close the plug valve (PV).
The needle valve (NV1) is fully
open.
Turn the needle valve handle clockwise to restrict
flow and increase pressure.
The relief valve (RV) is relieving
pressure and flowing to the vent.
Check the set pressure on the relief valve and
increase if necessary.
Pressure indicator (PI) is
damaged.
Check the pressure indicator (PI) and replace if
necessary.
There is low process pressure. Check the pressure in the process pipe near the
sampling nozzle.
If flow rate is acceptable, there
may be a partial blockage in
probe or sample transport lines
to the FLM.
Partially close the needle valve (NV1) and check for
pressure increase on the pressure indicator (PI) – if
pressure increases there may be an upstream flow
restriction.
There is a flow restriction
external to the FLM (ex. process
probe or regulator not properly
sized for the system).
Check the pressure at the probe or regulator outlet
– if the system is losing pressure replace with a
wider-bore probe or different regulator.
During initial startup the flow is
too low, the fast-loop supply line
may be too narrow or too long.
Replace the fast-loop supply and return lines with
larger tubing.
Pressure indicator
(PI) shows high
pressure.
There is high process pressure. Reduce the pressure in the process pipe near the
sampling nozzle.
The needle valve (NV1) is
restricting flow.
Turn the needle valve handle counter clockwise to
increase flow and release pressure.
Pressure indicator (PI) is
damaged.
Check the pressure indicator (PI) and replace if
necessary.
If using a liquid fast-loop pump,
the return line or process
isolation valve may be blocked.
Check that the process isolation valve and all
valves in the return line are fully open. Then check
for possible blockage.
A Swagelok Pre-Engineered Subsystem Fast Loop Module
20