Page 416 - Practical Machinery Management for Process Plants Major Process Equipment Maintenance and Repair

394 Major Process Equipment Maintenance and Repair

nip Body Clearance

1. The trip body to the shaft diametral interference fit is .001-.002 in.
(.025-.051 mm).

Caution: Consult the manufacturer if interference is less than .001
in. (.025 mm).

Rip Body Replacement

1. Heat the trip body in hot oil or an oven. Do not exceed 500°F
(260°C).
2. Place the heated trip body on the rotor shaft and align the set screw
holes in the trip body and shaft.
3. Tighten the set screw to ensure proper positioning on the shaft, then
back the set screw out of the body one or two turns.
4. Tighten the set screw when the trip body has cooled to ambient tem-
perature.
5. Check the trip body runout. Runout should not exceed .003 in.
(0.07 mm) on the outboard end of the trip body.
6. Gradually overspeed the turbine by overcoming the governor (See
Governor Operation, Chapter 10).
7. Check that the plunger assembly (7) is properly positioned in the
bearing housing, and return the rotor to the turbine casing.

Assembly, Overspeed nip Mechanism

1. If furnished, place the auxiliary weight (6, Figure 8-12) on the trip
pin (1).
2. Insert trip pin (1) into the trip body. Position the weighted end of the
pin on the opposite side of the trip body set screw.
3. Press the “U” lock staple (3) into the trip body to secure the
weighted end of the trip pin. Be sure the staple is fully seated in the
circular groove in the trip body.
4. Place the trip spring (2) in the trip body. (Install washers (9, if fur-
nished.)
5. Return the adjusting nut (4) to its original setting, by tightening the
nut the same number of turns recorded during disassembly.
6. Press the “U” lock staple (3) into the trip body to lock the adjusting
nut (4). Be sure the staple is fully seated in the circular groove in the
trip body.

Note: The overspeed trip should be tested after performing any
maintenance on the trip system.