IM-P157-38
CMGT Issue 4
36
Steam/Water Mixing Stations (MkII valves - 2002 onwards) Safety and Operation
5.10 Stripping down for service and fitting of maintenance kit 1"
and 1½" mixing valves only
To renew the PTFE seat, steam valve assembly and bypass valve. (Figure 27 item nos.
6, 7
and
8
). It is
necessary to remove the mixing valve from the pipework (this will enable the work to be carried out much
more easily and will save time in the long run).
Please read in conjunction with Figure 12:
1.
Remove the temperature adjustment knob (
12
) by loosening the screw (
10
).
2.
Remove the upper head (
1
)
(R/H thread).
3.
Remove the fixed loading spring (
11
) (and spring top guide, 1
½
" size only).
4.
Remove the steam valve spring (
2
).
Note 1½" size does not have this spring.
5.
Remove the spigoted spring guide (
21
).
6.
Remove the upper body (
3
) and replace the top gasket (
15
), the body 'O' ring (
13
) and bypass valve
'O' ring (
20
).
7.
Remove the bypass screw (
9
), remove the bypass valve (
8
) and refit with replacement parts. Replace
the bypass valve washer (
16
).
8.
Remove the steam valve plug assembly (
6
) from the piston (
4
) by removing the holding screws.
9.
Remove the steam valve housing by means of a
5
/
16
" diameter Tommy bar (for 1" valve and
¼
" diameter for
1
½
" valve) passed through the holes in the piston (
4
) and through the holes in the steam valve housing.
Note:
the piston (
4
) will have to be raised slightly to align this.
10.
Remove the crinkle and pressure washers and PTFE seat.
11.
To reassemble do the reverse of the break down procedure.
Before reassembly please ensure that all sealing surfaces are clean ready to receive the new gaskets and
'O' rings. Reassemble the mixing valve and test for correct operation.
IMPORTANT PLEASE ENSURE THAT:
a.
The PTFE seat and pressure plates must be assembled as follows:
-
First install the PTFE seat in contact with the steam inlet valve.
-
Place the plain pressure washer on top of the PTFE seat.
-
Finally install the Beryllium copper crinkle washer on top of the pressure washer; the crinkle washer
must be in contact with the steam valve housing.
b.
Ensure the piston
(
4
) moves freely up and down, before fitting the springs and final assembly. The
securing screws should be tightened progressively.
c.
When renewing the steam valve plug assembly (
6
), to prevent the securing nut becoming loose during
working conditions, stake the steam valve plug to the nut with three dots using a centre punch.
d.
When refitting the upper body (
3
), the 8 x cap screws (
18
) should be tightened progressively, to a torque
setting of 13-15 N m (10 - 11 lbf ft).
It is essential that for all sizes a certain amount of 'float' on
steam valve assembly is provided, to allow for self-centering.
