Emerson Fisher 4194HA Instruction Manual page 39

Instruction Manual
D200156X012
Table 5‐1. Troubleshooting Chart
Fault Possible Cause
1. Process wanders or 1.1 Proportional band and
cycles about set point. reset settings.
1.2 Supply pressure
varying.
1.3 Process pointer
rubbing on cover or scale.
1.4 Failure of differential
pressure unit.
1.5 Linkage failure.
1.6 Relay malfunction.
1.7 Differential relief valve
set too low.
2. Controlling off set 2.1 Supply pressure not
point as reflected by set correctly.
process and set point
indicators. 2.2 Flapper not aligned.
Note: Some offset is 2.3 Linkage not aligned
inherent with correctly.
proportional‐only 2.4 Leak in differential
controllers (4194HA pressure unit or tubing.
controllers). The
amount of offset is a 2.5 Indicators out of
function of the calibration.
proportional band
setting. 2.6 Linkage not connected
correctly.
2.7 Leak in feedback
system.
2.8 Reset valve leaks.
2.9 Leak in remote set
point system.
Check
1.1 Refer to the Start‐up section for
controller settings.
1.2 Monitor the supply pressure with an
external gauge. Ensure that it is set correctly
and does not fluctuate. Note the number of
instruments being supplied by the regulator.
1.3 Note if the pointer is bent.
1.4 Inspect the differential pressure unit.
Using a soap solution, check for leaks. Refer
to the differential pressure unit instruction
manual.
1.5 Check for links bent or not connected
properly, or pivots broken.
1.6 By changing the process differential
pressure in the sensor and observing the
output, verify that the output will move at
about the same speed in both directions.
1.7 The minimum relief valve setting is
dependent on the loop dynamics and the
controller settings. If, under normal load
changes, the relief valve opens, instability
can occur. Check by observing the controller
reaction to a set point or load change under
closed loop conditions.
2.1 Check with an external source.
2.2 Refer to the Flapper alignment
procedure.
2.3 Refer to the Maintenance Calibration
section.
2.4 Using soap solution, check for leaks.
Refer to the differential pressure unit
instruction manual.
2.5 Refer to the process (and remote set if
applicable) zero and span adjustment
procedure.
2.6 Inspect for loose screws, links or pivots.
2.7 Open the reset valve to .01 minute/
repeat. Adjust output pressure to 1.4 bar (20
psig). Using soap solution, check for leaks in
the proportional and reset bellows in the
tubing that connects these bellows.
2.8 Adjust output to 1.0 bar (15 psig) for a
0.2 to 1.0 bar (3 to 15 psig) output or 2.0 bar
(30 psig) for a 0.4 to 2.0 bar (6 to 30 psig)
output. Close the reset valve. If the controller
output varies as reset valve is closed and no
leaks were found in the rest of the feedback
system (Step 2.7), the reset valve is leaking.
2.9 Adjust remote set point pressure to 1.0
bar (15 psig). Using soap solution, check for
leaks in the remote set point and tubing
assembly.
4194HA, HB, HC Controllers
Correction
1.1 If stable control cannot be attained, and all
other elements of the loop are functionally
correct, examine other possible causes related to
the controller.
1.2 Correct as necessary. One regulator per
instrument is recommended.
1.3 Bend pointer to provide clearance.
1.4 Replace the differential unit as necessary.
1.5 Replace or repair as necessary.
1.6 If the output moves fast in one direction and
sluggishly in the other, replace the relay.
1.7 If the differential relief valve appears to be set
too low, refer to the section of this instruction
manual that covers the anti‐reset windup option.
2.1 Reset the supply pressure if necessary. If the
condition occurs again, the regulator should be
rebuilt or replaced.
2.2 Align the flapper as necessary.
2.3 Adjust as necessary.
2.4 Repair or replace parts as necessary.
2.5 Adjust as necessary.
2.6 Repair or replace parts as necessary.
2.7 Repair as necessary.
2.8 Replace the reset valve.
2.9 Repair or replace parts as necessary.
July 2018
39