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6.2. Servicing the LF-690 Balanced Regulator
*Note: Fig 2 and 3 should be used as a reference for the following set of instructions
6.2.1. Accessing the Balanced Main Valve Assembly (MVA)
To access the Main Valve Assembly:
Disassembly
i.
Firmly clamp the flats at the bottom of the regulator Body (1) in a vice, with the bottom nut (3)
facing up.
ii.
Remove the bottom nut (3) from the body (1).
iii.
The main valve spring (2), seat cartridge (9), main valve (8), washer (5), PTFE spacer (6), 'O' rings
and Backups (31,34,38,39,40) can then be removed Bottom Nut (3).
Note: It may be necessary to remove the regulator from the vice to do so.
iv.
The connector pin (4) may also be withdrawn at this point by up righting the regulator with the
main valve assembly removed.
Reassembly
v.
Use needle nose pliers to replace the connector pin chamfer down into the body, while the
body is up-side down. The pin should locate within the baffle plate (7).
Note: Care should be taken when reassembling not to damage the sealing face of the connector
pin (4).
vi.
Place the soft seat (10) into the seat cartridge (9) with the 'O' ring groove on the seat facing
outwards and place the BS806 'O' ring (32) into the groove.
vii.
Holding the regulator upright, position the assembly (9,10,32) into the regulator body (1)
ensuring that it finds the locating bore, then turn the regulator body (1) upside down whilst
supporting the assembly (9,10,32) to ensure it does not fall out of place.
viii.
Replace all of the 'O' rings and Backups (31,34,38,39,40) within and around Bottom Nut (3).
Note: The small back up ring (38) should be placed into the bottom nut (3) first, followed by the
3.6mm 'O' ring (34).
ix.
Place the washer (5) into the small recess, on the top of the bottom nut (3).
x.
Place/push the PTFE spacer (6), into the upper bore of the bottom nut (3)
Note: Add a small amount of Krytox lubricant to the underside of the PTFE spacer (6), before
placing into the bottom nut (3). This is to help the PTFE spacer from coming away from the
bottom nut, during assembly into the regulator body (1).
xi.
Guide the main valve spring (2), over the stem of the main valve (8).
xii.
Guide/place the main valve (8) and the main valve spring (2), into the central bore of the
bottom nut (3) and seated onto the washer (5). (which acts as a lower spring rest).
xiii.
With the regulator remaining upside down, guide the full bottom nut assembly
(2,,5,6,10,31,32,34,38,40), with the domed sealing edge of the main valve (8), leading into the
central bore of the seat cartridge (9) and screw the bottom nut (3) into the regulator body (1)
xiv.
Firmly clamp the flats at the bottom of the regulator Body (1) in a vice, with the bottom nut (3)
facing up.
xv.
Use a torque wrench, tighten the bottom nut (3) against the body (1) to 40Nm
It is recommended that all parts in the repair kits are used. Any defect parts removed during the service
should be disposed of.
To ensure that the main valve assembly has been correctly and effectively installed it may be required to
perform the appropriate seat leak test as per ANSI/FCI 70-2
9
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