MIL-H-46170 Hydraulic Fluid Recycling: Field Demonstration.

This final report documents the results of laboratory and field evaluations of commercially available recycling units for recycling MIL-H-461 70 hydraulic fluid. Previous laboratory efforts demonstrated used hydraulic fluid could be restored to specification performance by removing water and particulate contaminants and mixing with 25 new fluid. The field demonstration confirmed this by demonstrating fluid performance in test vehicles. Used fluid was drained from the vehicles, processed through approved recycling equipment, mixed with 25 new fluid, and returned to vehicle service. The vehicle performance was monitored for six months with satisfactory results. In addition, other batches of used fluid were processed through the recycling equipment and analyzed for performance. Results of these additional analysis confirm that used fluid retains most of its additive performance with the exception of antifoaming ability, but that the addition of the 25 new fluid restored the cleaned up used fluid to specification performance. Lessons learned during the demonstration are identified in the report with the most important lesson being the need for clean processing containers. Hydraulic fluid contaminated by other types of fluids engine oils, brake fluid, gear oil, etc cannot be recycled. Used drums must be free of these types of fluids or they risk contaminating the hydraulic fluid. A total of five units were approved for use with MIL-H-46170 hydraulic fluid. The units vary significantly in the technology employed and cost as well as throughput capability, but all satisfactorily remove water and particulate contaminants. Experience with the approved units reveals that recycling hydraulic fluid would be easier if the units contained on-line fluid condition monitoring which would provide a clear indication of when contaminants have been removed.