6
6.1. Servicing the LF-690 regulator
*Note: Fig 1 should be used as a reference for the following set of instructions
6.1.1. Accessing the Unbalanced Main Valve Assembly (MVA)
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 ball (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The connector pin (8) may also be withdrawn at this point by up righting the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 ball (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.
