Pressure Reducing Valve Installation
A pressure reducing valve (PRV) should be installed in the motive pressure line to regulate how fast the
Liqui-Mover pump discharges the condensate out of the pump tank. Normally the motive pressure setting
will be approximately 20 psig higher than the back pressure to achieve a proper discharge time. The dis-
charge time should be a little less than the time it takes to fill the pump tank under maximum condensing
load.
Here are some guidelines to be followed when installing a PRV in conjunction with a Liqui-Mover pump:
1. Never install a PRV immediately adjacent to the Liqui-Mover pump. The shock caused by the
sudden opening and closing of the motive valve will ultimately damage the PRV. We recom-
mend a distance of 20-25 feet between the PRV and the Liqui-Mover pump, where the pipe
size is the same as the motive inlet connection. A larger diameter pipe of a shorter length that
has an equivalent volume is acceptable. The PRV should be sized by a pressure reducing
valve manufacturer or representative.
2. A safety relief valve should be installed downstream of the PRV to prevent over-pressurization
of the motive medium. The safety relief valve should be sized by a safety relief valve manu-
facturer or representative.
3. When steam is the motive pressure, a drip trap, dirt leg, and strainer should be installed ahead
of the PRV. The drip trap should not be piped to the Liqui-Mover pump. When compressed
air is the motive pressure, a liquid drainer, dirt leg, and strainer should be installed ahead of
the PRV. The liquid drainer should not be piped to the Liqui-Mover pump.
4. The piping from the PRV outlet to the Liqui-Mover pump should be sized to minimize the pres-
sure drop under ‘flow conditions’.
5. A throttling valve should be installed immediately ahead of the Liqui-Mover pump so it can be
used in conjunction with the PRV to adjust the Liqui-Mover pump discharge time. Typically the
throttling valve is a globe valve.
The above sketch is for reference only. Always consult with the PRV and safety relief valve manufacturer
or representative for proper sizing and application of their products.
Motive Inlet
of Liqui-Mover
Pump
Throttle Valve
(Globe)
PRV
Drip Trap(Steam) or
Liquid Drainer(Air)
Y Strainer
20' to 25'
Motive Supply Header - Steam or Compressed Air
Safety Relief Valve
(Piped to safe location)
Dirt Leg
