7
3. When pump delivery is more than the flow rate
determined by the orifice plug, pressure builds up across the
orifice and forces the spool open against the light spring.
Excess fluid is throttled past the spool to the tank port as
shown in Figure 4B.
4. If pressure in the system builds up to the relief valve
setting (Figure 4C), the pilot poppet is forced off its seat.
Fluid in the large spring chamber flows through the spool and
out to tank. This flow causes a pressure differential on the
spool, shifting it against the light spring. All pump delivery is
thus permitted to flow to tank.
Light spring
holds relief
valve closed
when pressure
is equal on
both ends
Pilot poppet
To
tank
Spool blocks
tank port off
Relief valve
spring
System
pressure
sensed in
spring
chamber
through
orifice
Pressure
port
Orifice
determines
flow rate
Delivery
from
pumping
cartridge
To
tank
Pressure
port
To
tank
Pressure
port
Excess fluid
throttled past
valve to tank
Pressure in spring
chamber lower
than system due
to pressure drop
across sensing
orifice
Poppet
forced
off seat as
relief valve
setting is
reached
Spring
orifice
Figure 4A
Low Drive Speed – All Pump
Delivery to System
Figure 4B
Normal Operation
Figure 4C
Excessive Pressure
Build-Up in System
Section IV – Installation and Operating Instructions
A. Installation Drawings
The Installation Drawings listed in Table 1 show the correct
installation dimensions and port locations.
B. Drive Connections
CAUTION
Pump shafts are designed to be installed in couplings,
pulley, etc., with a slip fit or very tight tap. Pounding
can injure the bearings. Shaft tolerances are shown
on pump installation drawings. (See Table 1.)
1. Direct Mounting – A pilot on the pump mounting
flange (Figure 5) assures correct mounting and shaft
alignment. Make sure the pilot is firmly seated in the
accessory pad of the power source. Care should be
exercised in tightening the mounting screws to prevent
misalignment.
If gaskets are used, they should be installed carefully and
should lay flat. Shaft keys and couplings must be properly
seated to avoid slipping and possible shearing.
