! WARNING !
For the protection of persons and property the discharge system from each Reciprocating Pump must be
equipped with a device which relieves the system of all pressures which exceed the pressure rating applied
by the manufacturer to each particular piston or plunger diameter. Allowances will be made for pressure
surges which are inherent with the reciprocating action of piston and plunger pumps. The percentage of
pressure allowance appears later in this publication and in the “Standards of the Hydraulic Institute” (13
th
edition).
The relieving device must provide for instantaneous pressure relief, it may be a valve designed for automatic
or manual resetting; however, if preferred, rupture discs or burst discs may be installed.
FAILURE to comply with the procedures outlined in the Warning may result in damage to the pump and
related equipment and more importantly may cause serious bodily injury or death!
THE PRESSURE RELIEF VALVE:
1. This valve must be a full opening type.
2. It must have a working pressure rating, equal
to or greater than, the maximum working
pressure of the pump.
3. The through capacity of the valve, when fully
opened, must be sufficient to relieve the full
capacity of the pump without excessive
overpressure.
RUPTURE DISC OR BURST DISC:
1. These discs must have a diameter which is
not less than the pipe size of the pressure
relief flange.
2. These discs must have a rupture or burst
pressure rating consistent with the
specifications tabulated later in this
publication.
LOCATION OF THE RELIEF VALVE:
1. The relief valve must be placed in the
discharge line as close as possible to the
pump fluid end or it may be mounted on the
pump discharge manifold.
2. The relief valve must be on the pump side of
any discharge strainer.
3. The relief valve must be between the pump
fluid end and any valve in the discharge
system.
4. There must be no restricting device(s)
between the relief valve and the pump fluid
end.
THE RELIEF VALVE DISCHARGE LINE:
1. The relief valve discharge line should not
terminate in the pump suction line.
2. The line should terminate in the supply tank,
if possible.
3. The line must be securely anchored.
4. The line must be the same pipe size as, or
may be larger than, the discharge connection
on the relief valve.
5. If the line is of great length, this must be
taken into consideration in sizing the relief
valve.
6. There must be no restrictions or valves in the
relief valve discharge line.
NOTE: Follow the foregoing instructions if
rupture discs or burst discs are installed.
SUGGESTED SET PRESSURES FOR THE PUMP RELIEF VALVES:
PUMP TYPE: OPERATING PUMP PRESSURE:
Double Acting – Duplex Piston Pressure Rating – Plus 25%
Double Acting – Triplex Piston Pressure Rating – Plus 10%
Double Acting – Quintuplex Piston Pressure Rating – Plus 10%
Single Acting – Triplex Piston Pressure Rating – Plus 10%
Single Acting – Simplex Plunger Pressure Rating – Plus 25%
Single Acting – Duplex Plunger Pressure Rating – Plus 20%
Single Acting – Triplex Plunger Pressure Rating – Plus 10%
Single Acting – Quintuplex Plunger Pressure Rating – Plus 10%
Single Acting – Septuplex Plunger Pressure Rating – Plus 10%
Note: The above set pressures are to be observed when installing rupture discs or burst discs.
