INSOLUBLES IN HYDRAULIC FLUIDS: ASTM D4898
EXPLANATION
This test method indicates and measures the amount of insoluble contamination of hydraulic fluids. Minimizing the levels of insoluble contamination of hydraulic fluids is essential for the satisfactory performance and long life of the equipment. Insoluble contamination can not only plug the filters but can damage functional system components resulting in wear and eventual system failure. This method measures the insoluble contamination using a gravimetric method. The contamination determined includes both particulate and gel like matter, organic and inorganic, which is retained on a membrane filter disk of pore diameter as required by applicable specifications (usually 0.45 m or 0.80 m).
To indicate the nature and distribution of the particulate contamination, the gravimetric method should be supplemented by occasional particle counts of typical samples in accordance with Test Method F 312.
TEST SUMMARY
A given quantity of a fluid sample is passed through a membrane filter disk and the resultant weight increase of the filter is measured. The fluid sample is drawn through the filter by a vacuum and the insoluble contamination is collected on the surface of the filter. Additionally, the filter disk is microscopically scanned for excessively large particles, fibers, or other unusual conditions.
TEST PRECISION
Repeatability: 3.6 % of the weight of contamination per 100 mL of sample.
Reproducibility: Not known
Bias: Cannot be determined.
