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Annual Maintenance Checklist
The VRP-SB-PID pilot is built to exact specifications and high
precision. However, like any pneumatic device it is necessary
to periodically test and maintain the pilot to ensure optimum
performance. For the VRP-SB-PID we recommend the following
procedure once a year.
1. Internal Friction Test
Friction may occur to any one, or a combination of the
following reasons:
A. Diaphragms are not centered properly
B. Control spring is not seated properly over the spring nut,
or is defective
C. Dirt or ice build up inside pilot
Follow these steps to perform and internal friction test on the
VRP-SB-PID:
A. Keep pilot at setpoint and close output block valve.
B. Adjust the pilot using INITIAL ADJUSTMENT procedure found
on page 12.
C. Observe the output pressure. The output pressure must
be stationary at setpoint. If output pressure changes
continuously, note the direction of the change. Change
may occur due to a leak in the sensing chamber or due to
internal friction.
If needle moves, note
direction of change
Needle is
stationary
Figure 8 - Internal Friction Test Step C
D. Verify that no leak exists in the sensing chamber area. If
output pressure still changes after all leaks are eliminated,
the controller has internal friction present. In this situation,
the controller must be taken apart and rebuilt.
2. Derivative Orifice Cleaning
A. Close the output block valve in order to prevent the controller
from moving.
B. Close the valve on the measured variable line.
C. Shut of the supply pressure and bleed the system down
at the pilot.
D. Take careful note of derivative orifice settings and all
connections of tubes and fittings.
21 | GE Oil & Gas
Block valve is closed
E. Remove derivative orifice. Take apart and clean inside
thoroughly.
F.
Remove old O-rings and reinstall new O-rings before
reassembling derivative orifice.
G. Reinstall derivative orifice to original location. Be sure
to connect all tubing and fittings to their original
configurations. Adjust orifice to original setting before
disassembly procedure.
3. Balance Valve / Seat Inspection
A. Close output block valve. Change the control pressure
at least 5% above and below the setpoint using the
"false signal" valves found at the top of the pilot. In each
case soap test the exhaust port.
Direct Acting VRP-SB-PID Controller
B1. For the direct acting case the exhaust port is labeled
P2. When the control pressure is above the setpoint, the
supply balance valve (top block) is open and the exhaust
balance valve (bottom block) is closed. Gas exhausting from
port P2 indicates wear and contaminates in the exhaust
balance valve assembly (located in bottom block).
C1. When the control pressure is below the setpoint the
supply balance valve is closed and the exhaust balance
valve is open. Gas exhausting from port P2 indicates
wear or contaminants in the supply balance valve
assembly.
Reverse Acting VRP-SB-PID Controller
B2. For the reverse acting case the exhaust port is labeled
P4. When the control pressure is above the setpoint, the
exhaust balanced valve (top block) is open and the supply
balanced valve (bottom block) is closed. Gas exhausting
from port P4 indicates wear and contaminates in the supply
balanced valve assembly (located in bottom block).
C2. When the control pressure is below the setpoint the supply
balanced valve is open and the exhaust balanced valve
is closed. Gas exhausting from port P4 indicates wear or
contaminants in the supply balanced valve assembly.
4. Soap Test / Gauge Inspection
A. Soap Test around all diaphragms, vents, and orifice
assembly. Unless a leak is found it is not necessary to take
the pilot apart. If any leak is found around the diaphragms,
all rubber goods must be replaced. Take pilot apart, replace
all rubber goods, then reassemble pilot.
B. Apply a "false signal" pressure in the sensing chamber
using the "false signal" valves. Closely observe operation of
gauges. If any gauge is defective then replace immediately.
The above test procedure precisely indicates the mechanical
and pneumatic condition of the VRP-SB- PID pilot. Should any
additional information or assistance be required, please
contact GE.
© 2016 General Electric Company. All rights reserved.
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