8
Key
Shaft
Pilot
Figure 5
2. Indirect Drive – Chain, spur gear or v-belt pulley
drives may also be used with these pumps. Flat belt drives
are not recommended because of the possibility of slipping.
To prevent excessive side loads on pump bearings, it is
important to check for correct alightment and guard against
excessive belt or chain tension.
C. Shaft Rotation
Pumps are normally assembled for right-hand (clockwise)
rotation as viewed from the shaft end. A pump made for
left-hand rotation is identified by an “L” in the model code
(see Table 2).
NOTE
These pumps must be driven in the direction of the
arrows cast on the pump ring. If it is desired to
change the direction of drive rotation, it is necessary
to reverse the ring (see Section VI, B–D and Figure
9).
CAUTION
Never drive a pump in the wrong direction of
rotation. Seizure may result, necessitating
expensive repairs.
D. Piping and Tubing
1. All pipes and tubing must be thoroughly cleaned
before installation. Recommended methods of cleaning are
sand blasting, wire brushing and pickling.
NOTE
For instructions on pickling refer to instruction sheet
M-9600.
2. To minimize flow resistance and the possibility of
leakage, only as many fittings and connections as are
necessary for proper installation should be used.
3. The number of bends in tubing should be kept to a
minimum to prevent excessive turbulence and friction of oil flow.
Tubing must not be bent too sharply. Recommended radius for
bends is three times the inside diameter of the tube.
E. Hydraulic Fluid Recommendations
Fluid in a hydraulic system performs the dual function of
lubrication and transmission of power. It constitutes a vital
factor in a hydraulic system, and careful selection of it should
be made with the assistance of a reputable supplier. Proper
selection of fluid assures satisfactory life and operation of
system components with particular emphasis on hydraulic
pumps. Any fluid selected for use with pumps is acceptable
for use with valves or motors.
Three important factors in selecting an oil are:
1. Viscosity – Viscosity is the measure of fluidity. In
addition to dynamic lubricating properties, oil must have
sufficient body to provide adequate sealing effect between
working parts of pumps, valves, cylinders and motors, but
not enough to cause pump cavitation or sluggish valve
action.
Optimum operating viscosity of the oil should be between 80
SSU and 180 SSU. During sustained high temperature
operation viscosity should not fall below 60 SSU.
2. Viscosity Index – Viscosity index reflects the way
viscosity changes with temperature. The smaller the
viscosity change, the higher the viscosity index. The
viscosity index of hydraulic system oil should not be less
than 90. Multiple viscosity oils, such as SAE 10W-30,
incorporate additives to improve viscosity index (polymer
thickened). Oils of this type generally exhibit both temporary
and permanent decrease in viscosity due to the oil shear
encountered in the operating hydraulic system. Accordingly,
when such oils are selected, it is desirable to use those with
high shear stability to insure that viscosity remains within
recommended limits.
3. Additives – Research has developed a number of
additive agents which materially improve various
characteristics of oil for hydraulic systems. These additives
are selected to reduce wear, increase chemical stability,
inhibit corrosion and depress the pour point. The most
desirable oils for hydraulic service contain higher amounts of
antiwear compounding.
Suitable types of oil are:
1. Crankcase Oil meeting API service classification MS
(most severe). The MS classification is the key to proper
selection of crankcase oils for Mobile hydraulic systems.
2. Antiwear Type Hydraulic Oil – There is no common
designation for oils of this type. However, they are produced
by all major oil suppliers and provide the antiwear qualities of
MS crankcase oils.
