- P Quickly Spots Leakage

by Joe Gordon, Chief Engineer

When fluid-power assemblies must be tested for leakage, the traditional low-tech approaches have been:

• Fill the assembly with compressed air, then slop soapy water on it to see if bubbles will reveal leaks,
• Immerse the whole assembly in a water bath, then pressurize it with air- again watching for bubbles, and
• Pressurize the sealed assembly and watch a gage for pressure decay.

At best, these methods are cumbersome and time-consuming. At worst, they add drying and corrosion problems. All interrupt production flow. A simple, high-speed leakage test, suitable for production work, can be assembled from a differential-pressure gage, a pair of 2-way valves, and a vessel that is know to be leak-free—in the circuit shown in the diagram below.

With the test assembly in place, valve A is opened to pressurize both volumes. The gage will read zero. Then valves A and B are closed. Because the reference volume holds pressure, and leakage from the test assembly immediately results in a measurable differential that registers on the gage. The leakage rate can be calculated from the formula:

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