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MIL-T-46797B(AT)
fittings or adaptions to flared type fittings, or tapered pipe thread with dry seal fits shall be
furnished. Hydraulic lines and fittings shall be air and liquid tight and shall be installed to
preclude vibration and chafing. High pressure hoses which are located in areas where chafing
may occur shall be covered with spiral type hose guards. The system shall be designed to
preclude hydraulic transients. Provisions shall be made for bleeding air from the hydraulic
system and completely draining all hydraulic lines, when necessary. A manual type bleeder shall
also be provided as on-vehicle equipment on closed-centered systems. Hose assemblies and all
seamless steel hydraulic lines shall be adequate to provide the rate of flow, temperature, and
pressures required to operate the system smoothly and efficiently. Galvanized pipe and copper
tubing shall not be acceptable. A pressure gage shall be provided on the discharge side of the
hydraulic pump. Accumulators shall not be furnished. The system shall be designed to a safety
factor of 3 for normal operating conditions.
*
3.5.5.5.1 Hydraulic valving. An in-line relief valve shall be provided, fully adjustable,
and compatible with the working loads and test loads specified herein. The valve shall have
provisions for a safety lock wire on the adjustment portion of the valve to permit sealing and
locking at the proper working pressure after test. A normally closed, 12-volt dc, solenoid
operated check valve or valves shall be provided to lock the cylinder(s) in the event of a failure
in any other portion of the hydraulic system. If the check valve is not integral with the cylinder,
a minimum number of fittings shall be used between the check valve and the cylinder, with a
burst strength of at least three times the maximum operating pressure. A normally open, 12-volt
dc, solenoid operated, two position, two way valve with pilot assist, shall be provided to raise
and lower the body. The high pressure hydraulic system shall be provided with a gage port to
accommodate a 2-1/2 inch face, 0-3000 psi, glycerin filled, stem-mounted gage. The gage shall
be easily visible with the body in the down position. The gage need not be furnished.
3.5.5.6 Hydraulic cylinders. The lift mechanism shall be actuated by single or dual
cylinders. When dual cylinders are used, they shall be so connected to a hydraulic manifold to
assure equal pressure and simultaneous operation of both cylinders. Cylinders may be single,
multiple telescoping, or other special design. All seals, rings, gaskets, and other related
components shall be designed for easy removal and replacement. Metal nonflexing hydraulic
lines shall be used where flexing is not required during operation. An armored or otherwise
protected flexible hose shall be used where flexing is required. Provisions shall be made for
bleeding the system at all necessary points without removing or loosening any component of the
system. The cylinder(s) shall be positioned to preclude the cylinder(s) extending above the body
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