Symptom
Cause
Remedy
Fast-loop pressure
and flow are
acceptable, but
there is little or
no flow to the
analyzer.
The filter element is obstructed.
Replace the filter element.
Filter element is becoming
frequently obstructed (e.g. daily
replacement needed).
If possible, increase the fast-loop flow and check
for improvement.
If the additional time delay is acceptable, decrease
the filtered sample flow (consider reducing analyzer
bypass flow).
Change the element to one with a larger pore
size – if analyzer can accept the additional particle
load.
If the analyzed sample returns
to the FLM, there may not be
enough pressure drop in the
FLM to drive the sample flow
through the analyzer.
Restrict the fast-loop flow to increase sample
pressure by turning needle valve (NV1) handle
clockwise – being careful not to reduce flow too
much.
Check that the sample return valve (BV3) is fully
open – release set screws, reposition handle, and
retighten set screws if necessary
Consider changing the method of disposing of the
analyzed sample.
The check valve (CV1) is not
cracking.
Maintain or replace the check valve.
Pressure at sample return point
is too high.
If the sample is returned via fast-loop return to
process, reduce the return line pressure drop by
installing a larger size tube or pipe for sample
return line to process.
Consider changing the method of disposing of the
analyzed sample.
There is high flow resistance in
the sample path to the analyzer
external to the FLM.
Check all sample conditioning equipment, analyzer
flow path, and analyzer vent for a closed valve or
obstruction.
There is no flow in
the grab sample
outlet.
The needle valve (NV2) is
closed.
Open the needle valve by turning the handle
counter clockwise.
Pressure indicator (PI) shows
zero or low pressure.
See cause and remedy for
Pressure indicator (PI)
shows no or low pressure
.
There is no purge
flow.
The needle valve (NV3) is
closed.
Open the needle valve by turning the handle
counter clockwise.
There is insufficient purge fluid
pressure.
Check that the purge fluid is supplied to the FLM
at a sufficient pressure.
Drain valve is not open
Configuration 4, open the plug valve (PV).
The drain is blocked.
Check that there is no closed valve in the drain line
external to the FLM.
Remove any blockage from the drain.
The process
sample is leaking
into system during
purge.
The FLM is not fully in bypass.
Move the black handle to the left.
One of the ball valves (BV1/BV2)
is not fully in bypass.
Release set screws, reposition handle, and
retighten set screws.
Ball valves BV1 or BV2 need
packing adjusted.
Tighten the packing according to
Maintenance
,
page 16.
Troubleshooting
A Swagelok Pre-Engineered Subsystem Fast Loop Module
22
