
19
J125B: Maintenance Instructions
Diaphragm Case
Drawing Reference: Figs. 17
NOTE: Numbers in brackets identify items on drawings
Diaphragm Case Dismantling Procedure
.
1.
Unscrew top cap (1) and remove "O" ring (2).
2.
Unscrew and remove adjusting screw (3) and loading spring (7).
3.
Remove top cover (30) by unscrewing the 12 nuts (21) and screws (22).
NOTE: It is not recommended to strip down the Vent Valve Assembly items: (25), (26), (29) & (31).
For Relief Versions go to instruction (6).
4.
Remove diaphragm assembly (35), from the diaphragm case (17).
5.
Unscrew the hexagon cap screw (33) from the diaphragm assembly (35) to allow assembly to be
dismantled.
For No Relief Version go to instruction (9).
6.
Prior to dismantling the relief valve assembly, measure the height "h" of the relief valve spring (8). The spring
will have to be compressed to the same dimension on reassembly.
7.
Remove diaphragm assembly (Full Relief) (23) or (Limited Relief) (35), and relief assembly from the diaphragm
case (17).
8.
Unscrew spring adjusting nut (6) from diaphragm assembly (23) or (35) to allow dismantling.
9.
Lift lever assembly (19) to disengage with BVO piston (13).
10.
Withdraw BVO valve assembly (10, 12, 13, 14, 15, 45, 96 & 97) from the diaphragm case (17).
11.
Take BVO piston (13) and BVO loading spring (96) from BVO piston holder (14) and remove “O” rings (10, 45 &
97).
12.
Unscrew BVO sensing screw (12) and check hole for dirt.
13.
Remove lever assembly (19) from the diaphragm case (17).
Diaphragm Case Rebuilding Procedure
.
NOTE: Inspect all sealing "O" rings, diaphragms and gaskets and replace where necessary (a soft spares kit is
available for this purpose see page 17).
1.
Check main diaphragm (23) or (36) for signs of damage, if necessary replace with a new diaphragm
assembly (23) + (24) or (35) + (36).
2.
Check that the sealing surfaces on the diaphragm (23) + (36) and diaphragm stem (20) are clean.
For Relief versions go to instruction 7.
3.
Push cap screw (33) through centre hole of spring guide (34) with lip facing screw head.
4.
Now push cap screw (33) through centre hole of diaphragm assembly (35) + (36), with diaphragm plate lip
facing spring guide (34).
‘h’