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6.2.1. Accessing the Balanced Main Valve Assembly (MVA)
*Note: Figure 2 should be used as a reference for the following set of instructions
To access the Main Valve Assembly:
i.
Firmly clamp the flats at the bottom of the regulator in the vice, with the bottom
nut (18) facing up. Remove the bottom nut (18) from the body (22).
ii.
The main valve spring (17), seat cartridge (27), main valve (36), washer (20), PTFE
spacer (21), and 'O' rings (14,15,16) can then be removed from the assembly.
Note: It may be necessary to remove the regulator from the vice to do so.
iii.
The connector pin (19) may also be withdrawn at this point using needle nosed
pliers or by up righting the regulator with the main valve assembly removed.
Note: Care should be taken when reassembling not to damage the sealing face of
the connector pin (19).
iv.
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 (34).
v.
Place the soft seat (40) into the seat cartridge (37) with the 'O' ring groove on the
seat facing outwards and place the BS806 'O' ring (15) into the groove.
vi.
Holding the regulator upright, position the assembly (15,37,40) into the regulator
body (22) ensuring that it finds the locating bore, then turn the regulator body (22)
upside down whilst supporting the assembly (15,37,40) to ensure it does not fall
out of place.
vii.
Replace all of the seals (14 & 16) on the bottom nut **(18).
viii.
Place the washer (20) into the small recess, on the top of the bottom nut (18).
ix.
Place/push the PTFE spacer (21), into the upper bore of the bottom nut (18)
x.
Note: Add a small amount of Krytox lubricant to the underside of the PTFE spacer
(21), before placing into the bottom nut (18). This is to help the PTFE spacer from
coming away from the bottom nut, during assembly into the regulator body (22).
xi.
Guide the main valve spring (17), over the stem of the main valve (36).
xii.
Guide/place the main valve (36) and the main valve spring (17), into the central
bore of the bottom nut (18) and seated onto the washer (20). (which acts as a
lower spring rest).
xiii.
With the regulator remaining upside down, guide the full bottom nut assembly
(4,10,13-18,20,21,36,37,40), with the main valve (36), leading into the central bore
of the seat cartridge (37) and screw the bottom nut (18) into the regulator body
(22)
**The small back up ring (13) should be placed into the bottom nut (18) first, followed by the
3.6mm 'O' ring (4)
10
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