DA Form 2440, Suggestion Title: Truck, 20 Ton Dump, Relocation of Hoist Filter Assembly, 222-C-77
b. The suggested relocation of Hoist Filter Assembly has been installed by an IHC truck dealer in the state of, while
the dump trucks were under warranty. It is reported that 16 trucks have had their hoist hydraulic filters relocated, following
the suggestion's procedure.
c. The suggestion, as presented, cannot be fully approved for the following reasons:
(1) The new hydraulic oil filter bracket creates a safety hazard by impeding the relatively cool air flow past the
brake system air drier. The bracket would be installed in front of the air dryer and cause stagnant air or vortex type air
flow. The air drier must have unrestricted air flow past the housing to permit the desiccant crystals to absorb airborne
water vapor from the compressed air of the brake system. Overflow of water vapor into the airbrake system is a serious
safety hazard for an airbrake truck of this 71,000 GVWR weight class. Compressed air from the air compressor is
approximately 175 through 400F in temperature and the relative coolness of the air drier in ambient air stream, allows the
drier to absorb the water vapor from the compressed air. Commercial users report the major cause of inoperative air
dryers and of resulting increases in brake maintenance are attributed to blocked air flow pas t the air drier. At slow
speeds, the engine fan blast also contributes to keeping the air drier relatively cooler than the compressed air from the air
(2) The weight of the hydraulic filter, including oil, and the hydraulic oil dynamic force through the curved hose
lines dictate that any hoist filter bracketing must be designed with the minimum possible, cantilevered distance from the
bracket mounting points. The 12 inch, cantilevered mounting distance of the 16 inch long hoist filter support bracket is far
too great for maintenance free bracket life. In addition, the cab rear mount cross member bolts must not be used to
mount accessories of this nature, since these rear of cab cross member bolts are intended for the cab dynamic forces and
not for user added accessories. Any added loading, especially heavy cantilevered loading imposed by the hoist filter,
could result in damage to the mounts and the cab. The only acceptable user accessory attachment practice is mounting
of components onto the frame members of the chassis and as close to the frame as configuration permits.
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