Duff-Norton RAM-PAC - Relief Valve

relief
valve
The HP -150
Pump has two relief
valves; one
for high
pressure, and one for low
pressure.
The high pressure
relief valve is a protective
device used
to prevent excessively high hy-
draulic pressure from
being developed by the
pump.
This valve is set to open at 10,000
p.s.i.
thereby by-passing the
oil flow back to the
reservoir. The spring load on
the 5/32" dia-
meter relief ball can be adjusted
by means of
the adjusting set
screw to change the pressure
at which the relief valve will
open. The design
of the low pressure relief valve, except for the
size and pressure setting of the spring, is
quite similar to the overload relief valve.
Each relief valve
consists of a connecting
port
which connects
with its respective pressure
chamber (small
cylinder for high pressure
and
large
cylinder for low pressure) and
leads to a
valve chamber which contains a relief ball, a
( DI .)
SUCTION BALL.
compression
spring, an adjusting
screw, a cap
screw and a
rubber washer to seal
against
leakage. The valve
chamber is connected by
a small port which
permits the oil to return
to the
reservoir. When the force
developed by
the oil pressure acting on
the overload relief
ball is greater
than the force exerted by the
spring, it will
create an unbalanced
condition
and thus
will lift the relief ball from its
seat
and
allow
the oil
to
return to
the
reservoir.
Both
the high pressure and the low pressure
relief valves are carefully preset at the fac-
tory and
should not be
tampered with.
If, for
some reason,
it is
desired to
change the
setting
of the relief valve, particularly the high pres-
sure
relief valve, a hydraulic gage should be
used to check the pressure at which
the valve
opens. It should never be
set for a pressure
greater than 10,000
p.s.i.
SECTION
THRU OVERLOAD
RELIEF
VALVE
FOR
NP -150
HYDRAULIC PUMP ONLY
ADJUSTING
SET
SCREW
VALVE
C AMBE R
COM PRE
SSI ON
SPRING
OVERLOAD RELIEF
BALL
CONNECTI NG
PORT
DISCHARGE
BALL
( DIA.)