FIGURE A5-B:
RETURN-TO-TANK PRESSURE RELIEF VALVE
Discharge
Suction
Pump Head
Valve Always Mounts
on Discharge Side of
Pump
⚠
CAUTION !
Internal type relief valves mounted on Viking pumps
should always have the cap or bonnet pointed toward
the suction side of the pump. Return-to-tank type relief
valves should always be mounted on the discharge side
of the pump. If pump rotation is reversed, change the
relief valve. Turn the internal type end for end; move the
return-to-tank type to the other port. If on a particular
installation rotation is reversed, e.g., using one pump
to fill a tank, and then by use of a reversing switch or
other means of changing the rotation to permit the same
pump to circulate the liquid through a heater or to load
out, then pressure protection must be provided on both
sides of the pump for both rotations. This may be a
combination of relief valves, torque limiting devices or
rupture disks.
⚠
CAUTION !
Pumps or systems without relief valves should have
some form of pressure protection, e.g. torque limiting
devices or rupture disks.
5. Pressure Protection
- Viking pumps are positive
displacement pumps. This means that when the pump is
rotated, liquid will be delivered to the discharge side of
the pump. If there is no place for this liquid to go, i.e. the
discharge line is blocked or closed, pressure can build up
until the motor stalls, the drive equipment fails, a pump
part breaks or ruptures, or the piping bursts. Because of
this, some form of pressure protection must be used with
a positive displacement pump. This may be a relief valve
mounted directly on the pump, an inline relief valve, a
torque limiting device or a rupture disk.
The pressure relief valve mounted on most Viking pumps
and most in-line valves are of the spring-loaded poppet
design. See
Figure A4
. The spring (a) holds poppet
(b) against the seat in the valve body (c) with a given
force determined by the spring size and by how tightly
it is compressed by the adjusting screw (d). The pump
discharge pressure pushes against the underside of the
poppet at point (e). When the force exerted by the liquid
under the poppet exceeds that exerted by the spring, the
poppet lifts and liquid starts to flow through the valve.
As the discharge pressure builds up, more and more of the
liquid flows through until a pressure is reached at which all
of the liquid being pumped is going through the valve. This
pressure is the relief valve setting.
Viking pumps can be furnished with either an internal
pressure relief valve - one which directs the flow from the
valve back to the suction side of the pump - or a return-
to-tank valve - which directs the flow through piping back
to the supply tank. See
Figure A5-A
and
Figure A5-B
.
An inline relief valve mounted in the discharge piping also
directs the flow back to the supply tank. This type of valve
should be mounted close to the pump so that the pressure
drop through the piping between the pump and the valve
is at a minimum. Be sure there are no shutoff valves
between the pump and relief valve. Piping from a return-
to-tank or an in-line valve to the supply tank should also
be as short and as large as possible.
NOTE:
On some models, the relief valve is mounted on
the pump casing instead of the pump head.
The spring-loaded poppet-type valve is strictly a differential
valve, sensing only those pressures on each side of the
poppet. It should not be used as a pressure or flow control
device. It is intended strictly as a relief valve.
The pressure at which either the return-to-tank or internal
relief valve bypasses can be changed by turning the
adjusting screw. Do not back the adjusting screw all the
way out. Stop when spring tension is off the screw (the
screw starts to turn easily). For details on maintenance
of the relief valve, refer to the Technical Service Manual
covering your model series.
6. Motor
- follow local electrical codes when hooking up
motors.
FOUNDATION
Every pump should have a solid foundation. It may be any
structure sufficiently strong to hold the pump rigid and to
absorb any strain or shock that may be encountered.
A certified print of the pumping unit should be used in
preparing the foundation. If a separate foundation is provided,
make it at least four inches wider and longer than the base of
the unit.
When the unit is placed on the foundation, it should be leveled
and checked for position against the piping layout and then
fastened down.
COMPONENT & UNIT LIFTING
FEATURES
Removable lifting features, such as threaded eye bolts and
hoist rings, installed in components (pumps, reducers, motors,
etc.) and baseplates should be left on the components.
These features are used to safely lift and move the individual
components. Following are general guidelines for lifting Viking
Pump
®
units.
TSM 1741 | Issue B | Page 12 of 20
© 2019 Viking Pump, Inc. • Cedar Falls, IA
© Viking Pump, Inc.
© Viking Pump, Inc.
© Viking Pump, Inc.
© Viking Pump, Inc.
© Viking Pump, Inc.
© Viking Pump, Inc.
© Viking Pump, Inc.
© Viking Pump, Inc.
© Viking Pump, Inc.
© Viking Pump, Inc.
© Viking Pump, Inc.
© Viking Pump, Inc.
© Viking Pump, Inc.
© Viking Pump, Inc.
© Viking Pump, Inc.
© Viking Pump, Inc.
© Viking Pump, Inc.
© Viking Pump, Inc.
© Viking Pump, Inc.
© Viking Pump, Inc.
© Viking Pump, Inc.
© Viking Pump, Inc.
© Viking Pump, Inc.
© Viking Pump, Inc.
