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|  MIL-C-53057(ME)
of the reservoir. When furnished, the auxiliary steering pump inlet
line suction opening shall be located a minimum of 1/2 inches above
the bottom of the reservoir. Except for sealed reservoir, a
pressurized breather with a 30 psi maximum relief valve and 1 inch Hg
vacuum breaker shall be furnished. The breather shall have a nominal
rating of 40 microns. The breather shall preclude the entrance of
water. The reservoir shall provide a tortuous flow path from the
reservoir inlet to the reservoir outlet in order to prevent a direct
current between the two ports. All return line flow except the vent
line shall discharge into the reservoir at a level which is below the
oil level in the reservoir. When filters are located within the
reservoir, a removable 50 mesh, in tank suction strainer with bypass
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valve shall be installed in the suction line of the reservoir. The
reservoir shall have suction flanges and one or more access holes
with covers for inspection, cleaning and maintenance of the entire
inside.
3.12.5 Relief valve. A relief valve shall be provided to limit the
pump pressure to the maximum required to perform the necessary system
functions.
3.12.6 Hydraulic control valves. The control valve spools shall be
spring centered with sufficient force to return and retain the levers
at the center position throughout all crane operations. The spool
connection eye end shall conform to SAE J748 and shall not bind while
operating as specified herein. The exposed control valve spool
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surfaces shall show no evidence of corrosion or pitting when tested
as specified herein. The contractor shall present information during
first article test that the control valves were tested in accordance
with procedures specified in SAE J747 and J1117. The inlet to outlet
port pressure differential shall not exceed 3 percent of the maximum
operating pressure at rated flow.
3.12.7 Cylinders. All hydraulic system and steering cylinders shall
be fabricated from either seamless steel tubing or welded and redrawn
tubing. All welding and brazing to the cylinder within the zone of
piston operation shall be done prior to final machine honing or
rolling of the cylinder. Cylinders shall be so located as to provide
for ease of maintenance and replacement. All internal cylinder ports
shall be located beyond the area of piston travel. Each cylinder
shall have an exclusion device to prevent foreign material and fluids
from entering around the piston rod and damaging the seal and other
cylinder component. All hydraulic system and steering cylinders shall
perform as specified herein without buckling or bending. Each piston
shall have a bearing surface concentric with the piston to carry the
piston side loads against thc cylinder walls. The bearing surface
shall be of a material that will not scar, score, or gall the inside
surface of the cylinder. All cylinder rods shall be hard chrome
plated. All cylinders shall withstand a pressure that is equal to 1.5
times the system relief valve setting without evidence of rupture,
permanent deformation, damage, internal or external leakage.
3.12.8 Contamination levels for hydraulic system The particulate
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matter in hydraulic fluid removed from the system directly upstream
of the filter, shall not exceed the ISO code level of 19/16 in
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