Pressure Gauges; Safety Valve; Isolating Valves - Spirax Sarco DLV7 Installation And Maintenance Instructions Manual

3.4 Removal of condensate
For steam installations a separator should be
installed on the upstream side of the valve
fitted with a suitable steam trap.

3.5 Pressure gauges

To assist in commissioning the valve and
monitoring operating conditions it is essential
to fit pressure gauges on both upstream and
downstream sides of the valve.

3.6 Safety valve

It is recommended that a suitable safety valve
is installed on the downstream side of the
valve to protect downstream equipment from
excessive pressure. The valve should be set
to lift at a pressure below the safe working
pressure of the downstream equipment and
sized to pass the full capacity of the DLV
should it fail in the fully open position. The
safety valve outlet pipework should discharge
to a safe place.

3.7 Isolating valves

It is recommended that manually operated
isolating valves are installed upstream and
downstream of the pressure reducing valve
station to provide means of isolation for
cleaning and maintenance.
3.8 Water seal pot
If fitted, the water seal pot must be charged with water prior to the valve being put into service.
Remove the water seal pot filling plug and fully charge the vessel with soft water. Replace
the filling plug.
For applications where there are rapid fluctuations in load or pressure the larger volume
WS4-3 is recommended.
To commission the valve, slowly open the upstream manual isolating valve to avoid
waterhammer. The pressure reducing valve is now ready for operation.
3.9 Setting the desired downstream pressure
The valve is supplied 'unset' with the spring adjuster at its lowest adjustment position. The
downstream pressure may be set against either a dead end condition or flowing condition,
depending on the requirements of the application, taking into account the effect of proportional
offset.
The desired downstream pressure is obtained by rotating the adjustment nut whilst monitoring
the downstream pressure gauge.
Adjustment can be made using a standard open ended spanner size 30 mm A/F for all valves.
Compressing the control spring increases downstream set pressure and conversely relaxing
the spring tension reduces the downstream set pressure (see Figure 6).
Note: Prior to any re-adjusting of the set pressure, ensure the valve stem is coated with a
suitable high temperature lubricant.
IM-P204-03 CH Issue 8
Flow
direction
Adjustment
nut
Fig. 6
Increase
set
pressure
Reduce
set
pressure
11