Removal Of Breaking Pin Assembly From Safety Valve Proper; Reconditioning And Testing Of Metallic Seat Valves; Disassembly Of Safety Valve For Initial Inspection; Disassembly Of Safety Valve Proper - Emerson CROSBY STYLE JQ Installation And Maintenance Instructions Manual

CROSBY STYLE JQ 4 IN. PRESSURE RELIEF VALVE
INSTALLATION AND MAINTENANCE INSTRUCTIONS
7.5 Removal of Breaking Pin Assembly from
Safety Valve Proper
CAUTION
Failure to follow these instructions may result in
improper function of the valve.
Always wear proper PPE.
Being careful not to damage the gasket surface
of the Breaking Pin Housing (35), fasten the
flat sides in a vise and remove the wire seal.
With a strap wrench, remove the safety valve
proper from the breaking pin assembly. Note the
presence of corrosion or residue on the upper
portion of the breaking pin assembly or the
chamber of the Base (17). This indicates possible
Lower Diaphragm (37) failure.
8 RECONDITIONING AND TESTING OF
METALLIC SEAT VALVES
8.1 Disassembly of Safety Valve for
Initial Inspection
CAUTION
Failure to follow these instructions may result in
improper function of the valve.
Always wear proper PPE.
The valve should be carefully dismantled in
accordance with instructions in this manual.
Valve parts should be thoroughly cleaned after
disassembly per Section 12.1.
8.1.1 Removal of Cap (1) and Casing (8)
Unscrew the Cap (1) and the Casing (8) from the
Base (17). Do not support the valve upside down
on the Spindle (6).
8.1.2 Initial Inspection
If the visual examination of the safety valve
does not show any evidence of dirt, corrosion,
or moisture, proceed to test as outlined in
Sections 8.6 and 8.7.

8.2 DISASSEMBLY OF SAFETY VALVE PROPER

CAUTION
Failure to follow these instructions may result in
improper function of the valve.
Always wear proper PPE.
If the valve is contaminated or does not pass
the vaportight requirements, it must be
disassembled as follows.
8.2.1 Remove Adjusting Bolt (3)
Loosen the Lock Nut (4) on the Adjusting Bolt (3).
The Lock Nut (4) may be left on the Adjusting
Bolt (3) to approximate the spring setting after
reassembly if so desired. Remove the Adjusting
Bolt (3) with a strap wrench or special tool. If the
Disc Guide (7) is loose on the Base (17), it should
be held in place during this operation to avoid
distorting the small lock screws. A strap wrench
has proven effective if this is necessary.
8.2.2 Remove Spring (5) and Disc (1OA)
Lift out the Spring (5), the top Spring
Washer (9), the Spindle (6) and the Bottom
Spring Washer (19). Remove the Disc (10A) by
lifting it out carefully with fingers. Be very careful
not to mar the seating surfaces; minute damage
will cause the valve to leak.
8.2.3 Remove Disc Guide (7)
First, loosen the two Lock Screws (18) with
a hex wrench. Next, turn the Disc Guide (7)
counterclockwise until it is free from the
Base (17).

8.3 Disassembly/Inspection of Seating Surfaces

CAUTION
Failure to follow these instructions may result in
improper function of the valve.
Always wear proper PPE.
Remove the Lock Pin (12) and then the Adjusting
Ring (11) from the Nozzle (13). Next, unscrew
the Nozzle (13) from the Base (17). Be careful
not to mar either seating surface. Even the most
minute scratch will cause the valve to leak.

8.4 Lapping Seating Surfaces

CAUTION
Failure of the valve to pass the test for
vaportightness indicates that lapping of one or both
of the seating surfaces is required.
The instructions below are based on manual
methods of lapping seats. A competent
machinist or trained specialist should carry out
the procedure.
8.4.1 Lapping Equipment and Compounds
Seating surfaces on the Nozzle (13)
and Disc (10A) are very important when
reconditioning safety valves. The seats should be
perfectly flat and free from surface scratches.
FIGURE 1
Use of reconditioner
Lapping motion
shown by this line
Bottom
rough surface
DO NOT USE
8.4.2 Lapping Block
Lapping blocks for Style JQ 4 in. valves are
2 ⅝ in. in diameter and made of a special grade
of annealed cast iron, perfectly flat on both sides.
It is essential that the lapping block remain
flat to produce a truly flat seating surface. In
checking the lapping block and for restoring
flatness after use, a lapping block reconditioner
should be used.
8.4.3 Lapping procedures Unless the seats have
been damaged badly by dirt or scale, lapping the
seating surfaces should restore them to their
original condition. Never lap the disc insert against
the nozzle. Lap each part separately against a
cast-iron lapping block of the proper size. These
blocks hold the lapping compound in their surface
pores and must be recharged frequently. Lap the
block against the seat. Never rotate the block
continuously, but use an oscillating motion.
Extreme care should be taken throughout to
make certain that the seats are kept perfectly
flat. If considerable lapping is required, spread
a thin coat of medium coarse lapping compound
on the block. After lapping with the medium
coarse compound, lap again with a medium grade
compound. Unless much lapping is called for, the
first step can be omitted. Next, lap again using a
fine grade compound. When all nicks and marks
have disappeared, remove all the compound from
the block and seat. Apply polish compound to
another block and lap the seat.
Top lapping
surface
Lapping
block to be
squared up
7