IM-P157-38
CMGT Issue 4
12
Steam/Water Mixing Stations (MkII valves - 2002 onwards) Safety and Operation
Note: Before actioning any installation observe the 'Safety information' in Section 1.
4.1 General
The steam/water mixing valve should be carefully unpacked and the contents checked against the packing
list. (See Figure 4). The steam/water mixing valve has two hot water outlets which means that hot water can
always flow downwards from the valve regardless of the orientation of the steam and cold water supply lines.
Plug the hot water outlet that is not being used.
4.2 Installation without hoses
4.2.1 Selection and installation of high pressure fixed loading spring
The steam/water mixing valve is supplied with the medium pressure fixed loading spring fitted for steam
pressures between 3.5 to 7.0 bar g (50 to 100 psi g). For steam pressures between 7.0 to 10.3 bar g (100 to
150 psi g) the high pressure fixed loading spring must be fitted and the relevant spring name-plate attached
to the valve body. The following instructions, in conjunction with Figure 3, must be followed when a high
pressure fixed loading spring needs to be fitted:-
IMPORTANT NOTE:
A high pressure fixed loading spring can only be installed if the following site conditions prevail:
-
If the valve is running to an open outlet (i.e. no restriction on the downstream side of the valve),
the steam to water pressure ratio, must not exceed, 3:1. It is advisable that the cold water
pressure does not exceed the steam pressure as this will inhibit the ability of the valve to
produce hot water.
-
If there is a restriction on the outlet (e.g. hosedown gun, pipework or hose, control or isolation
valve, etc.) the steam pressure and water pressure must be nominally equal.
1.
Turn the ball valves to isolate steam and cold water supplies. Remove any residual pressure from the
mixing valve station by opening the outlet from the valve, e.g. hose gun.
Do not assume that the
system is depressurised even when a pressure gauge indicates zero.
2.
Turn the temperature adjustment knob (
12
), clockwise to the fully open (hot) position.
3.
Remove the temperature adjustment knob (
12
) by loosening the temperature adjustment knob retaining
screw (
10
).
4.
Remove the upper head (
1
) (R/H thread) using a 30 mm A/F spanner.
5.
Remove the medium pressure fixed loading spring (
11
) and replace with the high pressure fixed loading
spring.
6.
Before reassembly ensure that the gasket faces of upper body (
3
) and upper head (
1
) are clean ready
to receive the new gasket. Replace the top gasket (
15
).
7.
Before reassembling the top cap ensure that the steam valve spring (
2
) is upright in the spindle
recess. Screw the upper head (
1
) into the upper body (
3
) and tighten to a torque setting of 120 to
130 N m (88 - 95 lbf ft) for
½
" and
¾
" valves. A torque setting of 180 to 200 N m (132 - 147 lbf ft)
for 1" and 1
½
" valves.
8.
Remove the medium steam pressure range label and replace with the high pressure label.
4. Installation
