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6.3. Servicing the LF-691 regulator
*Note: Fig 4 should be used as a reference for the following set of instructions
6.3.1. Accessing the Main Valve Assembly
To access the Main Valve Assembly:
i.
Firmly clamp the flats at the bottom of the regulator in the vice, with the bottom nut (7) facing
up.
ii.
Remove the bottom nut (7) from the body (1).
iii.
The valve spring (6), shuttle (4), seat cartridge (5), ceramic plug (9) and ceramic seat (2) can now
be removed from the assembly. It may be necessary to remove the regulator from the vice to
do so.
iv.
The connector pin (8) may also be withdrawn at this point by up righting the regulator with the
main valve assembly removed.
v.
Care should be taken when reassembling not to damage the sealing face of the connector pin
(8). Needle nose pliers should be used 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 (3).
vi.
The new ceramic seat (2) should be placed in the seat cartridge (5) with the BS 806 'O' ring (26).
vii.
These can then be placed into the regulator body, being careful to ensure that the 'O' ring (26)
remains in place and that the seat cartridge (5) locates in the correct place within the body (1).
viii.
The ceramic plug (9) and shuttle (4) can then be placed into their location within the seat
cartridge (5).
ix.
The main valve spring (6) can now be placed on the stem of the shuttle (4).
x.
Replace the BS019 'O' ring (25) and back up ring (28) on the bottom nut (7), then assemble into
the regulator body.
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.
13
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