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|  MIL-T-62110G
with pilot check or holding valves to prevent descent of the derrick assembly and retraction of
the outriggers because of loss of hydraulic pressure. Means shall be provided to install pressure
gages for testing the hydraulic system pressure and relief settings. Hydraulic ram piston rods
shall be chrome-plated full length with sufficient thickness to withstand a 30-hour salt spray test
in accordance with ASTM B117.
3.12.2 Hydraulic lines and fittings. Hydraulic lines shall be located to facilitate
maximum ease of removal and installation, visual inspection for failures, and maximum
protection from damage during operation of the derrick assembly. Flexible hydraulic hoses or
collector rings shall be used where flexing of hydraulic lines is encountered and where
installation of components requires a flexible coupling. Standard straight-thread, flared type
fittings or adaptions to flared type fittings or tapered pipe thread with dry seal fits shall be
furnished. The hydraulic lines to the digger shall be of the telescopic or cat-track type to prevent
damage that is encountered during operation of the equipment. The hydraulic lines and fittings
shall be air- and liquid-tight and shall be installed to prevent vibration and chafing. The system
shall be designed to prevent hydraulic transients. Provisions shall be made for bleeding air from
the hydraulic system and for completely draining all hydraulic fluid lines. A manual type
bleeder shall also be provided as on-vehicle equipment on closed-center systems. The 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 furnished. A pressure gage shall be provided on the
discharge side of the hydraulic pump.
3.12.3 Hydraulic pump system. A hydraulic pump with necessary pressure and flow
capacities to operate all hydraulic powered components shall be provided. The hydraulic pump
shall be driven by a full torque, heavy duty power takeoff unit attached to the truck chassis
transmission. Chain drives shall not be used. The pumping system shall include an adjustable
pressure relief valve or unloading valve with a range of adjustment which allows raising or
lowering of the derrick assembly with any working or test loads specified herein.
3.12.4 Hydraulic fluid reservoir. A hydraulic fluid reservoir shall be provided and shall
have sufficient capacity to hold the required volume of hydraulic fluid, with not less than
10 percent for expansion space. The reservoir shall be fully baffled. The reservoir shall be
provided with a filler opening and removable oil strainer and a vented filler cap accessibly
located to facilitate filling the tank from a one-gallon container using a funnel. The vented filler
cap shall have means to prevent fluid from splashing out of the tank during movement of the
vehicle. The filler cap shall be attached to the tank by a corrosion-resistant chain to prevent
loss. Provision shall be made for inspection and cleaning of the interior and draining of the
reservoir. The reservoir drain shall be located to prevent fluid from draining on other
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