This report describes an evaluation procedure for determining the presence in a liquid of silting particles in the 0.5 to 5.0 μ size range. The procedure is fast, highly specific, and involves simple apparatus and simple calculations. Essentially, the procedure consists of filtration of a contaminated liquid through an 0.8-μ filter. Filtration is done at constant head, and the passage time is noted for three specific volumes. An arithmetic calculation using these three times gives a silting index, expressed by the formula: ?? where t represents the times for specified volumes of filtrate and K is a constant determined by the apparatus and sample size.

This index is used (1) to determine the quality of process waters, (2) to evaluate clogging and the abrasion properties of a liquid in a high-performance hydraulic system, (3) to determine the quality of oil-well injection waters, and other similar applications. The data gathered show that the accuracy of the test is such that the average of three determinations on a given sample will give a number within 15 per cent of the true value at 90 per cent confidence limits.

A portable device to effect measurement of liquid contamination has been developed and extensively tested and is now commercially available.