GE H301 Series Operating Manual page 118

108 | Chapter 8: Maintenance
Adjust the VVCP
1. Inspect the cylinder's HE for any special spacers, between the VVCP and the
cylinder. Clearance spacers may have also been installed under some or all
of the suction and discharge valves. In certain high clearance applications
a special HE compression clearance spacer may have been added to the
cylinder's "base" clearance.
2. Determine the desired VVCP stem extension dimension "as-is" on the cylinder
and "as-required" from VVCP charts or performance runs.
3. Prior to adjustment, loosen the VVCP stem jam nut.
4. To set the VVCP at the desired percentage (%) open position, fully close the
VVCP, and then fully open it, counting the number of turns to the full open
position. Fully close the VVCP. Multiply the total number of turns by the desired
percentage open, and open the VVCP the resulting number of turns.
5. During VVCP adjustment, exercise all necessary safety precautions.
6. Apply stem thread lubricating grease compatible with the process gas through
the VVCP flange lubrication fitting
Some chattering and/or light knocking of the VVCP stem/
7. Adjust the VVCP to the desired clearance position determined in step 2.
Turn the piston stem clockwise (CW) to move the piston in and
reduce clearance. Turn the piston stem counter-clockwise
(CCW) to move the piston out and increase clearance.
8. After adjustment, securely tighten the VVCP jam nut against the VVCP thread
seal washer, using torque values shown in GES089.
Failure to maintain proper VVCP jam nut torque can result in
vibration of the VVCP piston in its housing, and possibly lead
to a fatigue failure of the piston/stem connection. Check the
9. Reapply grease to the VVCP stem threads through the flange lubrication
fitting.
10. After final VVCP adjustment and Jam Nut tightening, verify there is no gas
leakage from the VVCP stem seal washer area. If leaks are detected, replace
stem seal washer, or provide other repairs as required. See CN 10-003.
11. Reset high/low process gas shut down points (pressure and discharge
temperature) to proper set points.
See CN 10-002 for more information on seal washer installation.
("Figure 22").
piston may indicate that the jam nut is loose.
Complies with ANSI Z535, ISO 3864, OSHA 1910.145 (f) (9)
Complies with ANSI Z535, ISO 3864, OSHA 1910.145 (f) (9)
piston jam nut torque as required.
Complies with ANSI Z535, ISO 3864, OSHA 1910.145 (f) (9)