12
Instruction Manual
3.2 RELIEF VALVE ADJUSTMENT
All MILROYAL
®
G liquid ends have a built in relief
valve which allows hydraulic fluid to return to the
pump casing if excessive pressure builds up in the
discharge line. This effectively stops the pump from
pumping, since the forward stroke of the piston
will not displace the hydraulic fluid and force the
diaphragm to flex. During operation of the pump, a
relief condition caused by over pressurization can
easily be seen by looking through the sight glass
(630,
Figure 7
) for excessive oil flow from the drain
tube (640,
Figure 8
).
Note:
Under normal operation, a few drops of oil
should escape from the drain tube during each
pump stroke due to normal oil flow through the
air bleed ball (970, figure 8). If a stream of oil
from the drain tube is evident on each pump
stroke, the system pressure has exceeded the
pump relief valve setting and the pump is in a
relief condition.
The MILROYAL
®
G liquid end relief valve may be
adjusted to operating conditions by the following
procedure. Adjust the relief valve after first installing
the pump and after any maintenance procedures.
THE PRESSURE RELIEF VALVE IS
FACTORY SET TO OPEN AT A
PRESSURE 15% OVER THE CUSTOMER SPECIFIED OPERATING
PRESSURE OR AT 15% ABOVE THE MAXIMUM PRESSURE
RATING OF THE PUMP IF NO OPERATING PRESSURE IS
SPECIFIED BY THE CUSTOMER. WHEN ADJUSTING THE VALVE
SETTING, NEVER SET THE VALVE AT A PRESSURE GREATER
THAN 15% OVER THE PUMP MAXIMUM PRESSURE RATING.
3.2.1 Relief Valve Adjustment (With an
Adjustable System Back pressure Valve).
Refer to Figures 7 & 8
.
The following procedure assumes that a back
pressure valve and pressure gauge are installed
in the discharge line. If these components are not
installed, refer to next section.
1. Make sure all system shut- OFF valves are
open and that the back pressure valve is backed
out to allow for flow against zero discharge
pressure.
SECTION 3 - OPERATION
2. Start pump and set capacity at 100%. If a drain
valve is present in the discharge line, pump
process liquid to drain or other safe point to
establish proper pumping action. Close drain.
3. Slowly increase system pressure until:
a. Significant flow is observed from the drain
tube (640,
figure 8
) as viewed through the
sight glass (630,
figure 7
) or
b. The system pressure reaches 15% over the
desired system pressure.
4. For condition (a) in step 4, if relief condition
occurs at less than 15% above desired pump
operating pressure, the relief valve setting
must be increased. Remove valve cover
(850) and increase relief valve setting by
turning the adjustment screw (890) clockwise
until only a few drops of oil escape on each
pump stroke (normal leakage past air bleed
ball-980). Increase system pressure to 15%
above desired operating pressure to verify that
pump is now in relief condition. If it is not, reduce
relief valve setting by turning adjustment screw
(890) counterclockwise until relief is observed
in sight glass drain tube at a pressure equal to
15% greater than desired operating pressure.
Lock-in relief valve setting by tightening locking
nut (900) while holding adjustment screw (890)
stationary. The relief valve is now properly
adjusted. Reinstall valve cover (850).
5. For condition (b) in step 4, the setting of the
relief valve should be reduced. Remove valve
cover (850) and turn adjustment screw (890)
counterclockwise until relief is observed in
sight glass drain tube at a pressure equal to
15% greater than desired operating pressure.
Lock-in relief valve setting by tightening locking
nut (900) while holding adjustment screw (890)
stationary. The relief valve is now properly
adjusted. Reinstall valve cover (850).
