The U.S. Army Mobility Equipment Command is responsible for specification requirements for a number of kinds of construction equipment. In studying a newly acquired warehouse forklift truck, it was noted that the hydraulic fluid was quite clean even though the system filter was not an exceptionally good one. The vehicle manufacturer stated that a study had indicated that the air breather on the reservoir was a major ingression point for contamination. As a result, this company had equipped the vehicle with a much more efficient breather than required by the Government specification.
No reasonable breather test standard appeared to exist. Engine air cleaner tests were judged unsuitable and extremely complicated. A test was derived to simulate the oil volume change normally found in warehouse forklifts (Fig 1).
Breathers tested included sintered bronze, phenolic ribbon, and pleated paper elements. The test showed dramatic differences in efficiency and dirt capacity of breathers, not always related to size, cost, or “nominal” rating.