SYMPOSIA PAPER Published: 01 January 1963

The Silting Index: An Evaluation of Micron and Submicron Contamination in Liquids


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.

Author Information

Dwyer, J., L.
New Products Development, Millipore Filter Corp., Bedford, Mass.
Price: $25.00
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Developed by Committee: F01
Pages: 69–78
DOI: 10.1520/STP44481S
ISBN-EB: 978-0-8031-6211-2
ISBN-13: 978-0-8031-6139-9