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|  MIL-B-45390A(AT)
3.4.1 Hydraulic operating system. The hydraulic system shall be powered by a hydraulic
pump driven through a right angle drive speed reducer attachable to the transmission power
take-off shaft. A four-position control valve shall direct the oil flow to the double-acting
hydraulic cylinders for control of the blade. The pump when operating at 2800 revolutions per
minute (rpm) shall deliver a minimum flow of 60 gallons per minute at a pressure of
1000 pounds per square inch (psi) (see 4.6.3.1).
3.4.2 Controls and linkage. Prior to initial bulldozing operation, all controls and linkage
shall be operated through all ranges of operation (see 4.6.3.2).
3.4.3 Safety relief valve. Hydraulic system shall be protected from high shock pressures by
a relief valve set to operate at 5000 psi (see 4.6.3.3).
3.4.4 Digging depth. Full downward pressure applied to piston shall hold the cutting edge of
the blade down to not less than 9 inches below ground level. The hydraulic system shall hold the
moldboard at any height within operating range, or allow moldboard to float at ground level
(see 4.6.3.4).
3.4.5 Rate of lift. The hydraulic system shall lift and lower the moldboard at rates of speed
listed in table I. The specified rates of speed shall be accomplished when using oil specified in
3.3.1 with an applied pressure of 1000 psi (see 4.6.3.5).
TABLE I. Rate of lift.
Engine speed
Minimum rate of lift or lower
(rpm)
(inches per second)
minimum
Up
Down
1000
2.5
6.5
1500
4
6.5
2000
5
6.5
2400
5.5
6.5
2800
6
6.5
3.4.6 Environmental.
3.4.6.1 High temperature. The bulldozer shall meet the requirements of 3.4.1 through 3.4.5
during and after exposure to temperatures up to 115oF (see 4.6.1.6.1).
3.4.6.2 Low temperature. The bulldozer shall meet the requirements of 3.4.1 through 3.4.5
during and after exposure to temperatures down to -40F (see 4.6.3.6.2).
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