Page 420 - Practical Machinery Management for Process Plants Major Process Equipment Maintenance and Repair

398 Major Process Equipment Maintenance and Repair

Warning: If spring (10) does not compress, readjustment is re-
quired. If backseating occurs with fife edge more than
.12 inches below latch, the "play" in connection (5)
will be exceeded. This may cause the lever (2) to bend
and result in excessive forces holding the knife edges,
so that the trip system is rendered inoperative or dam-
age to the trip valve stem pin occurs.

10. Reconnect closing spring and check trip valve operation.

Rip System Linkage
Note: The backseating adjustment has a direct effect on steam leak-
age along the trip valve stem. Check trip valve operation af-
ter every adjustment.
1. Frequently inspect the trip system linkage for cleanliness and free-
dom of movement.
2. Replace pin (6, Figure 84, bushing (7), blocks (45) or shoulder stud
(33) if the linkage develops excessive play.
3. Lubricate the linkage pins, shoulder stud and auxiliary resetting
lever (10) with a high temperature water resistant silicone grease.

Trip System Clearances (Refer To Figure 9-4)

1. With the resetting lever latched, maintain %6 in. (1.6 mm) clearance
between the weighted end of the trip pin (1, Figure 8-12) and plunger
assembly (7, Figure 8-12).
2. The diametral clearance between the valve cover bushings (16) and
the trip valve stem should be .008 to .010 in. (0.20 to 0.25 mm).
3. To ensure positive backseating, adjust the trip valve to provide .12
in. (3 mm) overlap between the resetting lever knife edge (12) and
the hand trip lever latch (3 1).
4. The resetting lever knife edge (12) and latch knife edge (31) must
overlap approximately 1/8 in. (3 mm) when the resetting lever (1 1)
is latched.

Note: Latch knife edge (31) can be rotated in 90" increments to
provide a new latching surface for the resetting lever
knife edge (12). The resetting lever knife edge (12) can be
rotated 180" to provide a new mating surface for the latch
knife edge (31). Replace the knife edge and latch when
adjustment can no longer be made to compensate for
worn latching surfaces.