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6.2. Servicing the MF-414H
*Note: fig 2 should be used as a reference for the following set of instructions
6.2.1. Accessing the Main Valve Assembly
*The top works and sensor assembly must first be removed to access the main valve
assembly. Before
continuing follow the steps ‘i. –
iv.’ shown in
-
‘6.2.2. Accessing the Sensor
Assembly’.
To access the Main Valve Assembly:
i.
Unscrew the body nut (2) from the body (1) of the regulator to access the lower
section of the main valve assembly.
ii.
Remove the Valve Spring (3).
iii.
Secure the upper section of the main valve (10) with a 10mm socket and use a
screwdriver to turn the seat nut (4) anti-clockwise.
iv.
Remove the seat nut
, ‘O’ rings
and ceramic seat (4, 6, 9 and 8) from the lower main
valve assembly.
v.
The main valve pin (10) should be removed through the top of the regulator to
avoid damaging the ‘O’ ring (11) located on it.
vi.
Remove the hard seat (7) from the body of the regulator (1) by turning it anti-
clockwise with a 19mm socket.
vii.
Insert a new hard seat (7) into the regulator body after carefully positioning the
12mm x 1mm ‘O’ ring (9) into the body.
viii.
Place two drops of Loctite thread lock 638 (or equivalent) on the M6 thread on the
main valve pin (10)
ix.
Replace the ‘O’ ring (11) and back
-up ring (12) on the main valve (10) and place
the main valve into position through the top of the regulator body with the hex
section facing upwards.
x.
Turn the regulator body upside down so that the lower section of the main valve
is visible and place a new ceramic seat (8) onto the main valve stem.
xi.
Replace the BS-
610 ‘O’ ring (6) and place into the seat nut (4).
xii.
Screw the seat nut (4) on to the main valve (10) and tighten both parts together
using a 10mm socket and a screwdriver.
xiii.
Place the valve spring (3) into the bottom nut (2) and screw into the regulator body
(1). Tighten the bottom nut to 30Nm.
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.
