SYMPOSIA PAPER Published: 01 January 2001

Analysis of Failure Modes of a Military Hydraulic Fluid: MIL-H-46170


The Army replaces the hydraulic fluids in its vehicles annually. A feasibility investigation to determine if used military hydraulic fluid could be reused was conducted.

Samples of used fluid from military vehicles were collected, analyzed to determine the physical and chemical properties, and compared against specification requirements for new fluid. These fluids were then purified and retested to determine the failure modes. Results showed that the ability to control foaming was the only property that significantly suffered. Restoring the foaming resistance, and removing water and particulate contamination returns the fluid to full specification performance. Adding anti-foaming additive in the field is highly impractical because it is needed in such a low concentration.

Virgin fluid is sufficiently robust in anti-foaming agent, that mixing one part of virgin fluid to three parts of purified, used fluid would bring the mixture back to full specification performance.

Author Information

Mowery, RB
Fuels and Lubricants Technology Team, U. S. Army Tank-Automotive Research, Development and Engineering Center, Warren, Michigan
Purdy, EM
Ofc. of the Asst. Secretary of the Army, (Acquisition, Logistics and Technology), Headquarters, Washington, D. C.
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Developed by Committee: D02
Pages: 167–175
DOI: 10.1520/STP38274S
ISBN-EB: 978-0-8031-5567-1
ISBN-13: 978-0-8031-2883-5