Pipeline Forces and Pressures


1) Determine the inside diameter of the pipeline in inches.
2) Determine the maximum back pressure.
3) Calculate the pipe area in square inches. (Pipe area =p r2)
4) Calculate the force the plug must withstand.
(pounds of force = PSI X pepe area)

* Calculating pounds of force aids in building blocking systems. It also illustrates the tremendous force generated by a sewer air test.

Formula: pr2 X PSI = POUNDS OF FORCE
Example: 36" diameter pipe

Radius = 18"
p = 3.14
PSI = 5
18" x 18" X 3.14 x 5 PSI = 5087 POUNDS OF FORCE

Special Notes:
• Pressures being exerted on a plug—regardless of the medium (liquid, water, or air)—are the same. Ten (10) PSI of water is the same as ten (10) PSI of air. However, air is a compressible media. Therefore when a plug dislodges under air back-pressure, it is much more dangerous than water pressure as the air will expand to its original atmospheric volume. Use extreme caution when conducting air tests!• Air back-pressure ratings reflect absolute back-pressure capabilities. Common engineering standards have been used to convert head pressure to PSI. It is imperative to block pipe plugs when performing air pressure tests and to ensure no one is in the danger zone when a plug is in use. Please see the Cherne Safety and Instruction Manual for complete details  General Safety and Usage Instructions:

1) Death, bodily injury, and/or property damage may result if plug fails for any reason.
2) Read and understand safety instruction sheet before using plug.
3) Must wear safety glasses and a hard hat.
4) Do not enter danger zone when plug is in use.
5) Measure pipe diameter before selecting plug.
6) Inspect plug for damage before and after use.
7) Never use a plug in a pipe size different from recommended usage range.
8) Always attach an inflation hose so plug can be inflated and deflated from outside the danger zone
 9) Never remove the inflation hose until all back pressure is released and the plug is deflated.
10) Must inflate plug to the pressure shown on plug.
11) Always use properly-calibrated pressure gauges.
12) Do not exceed recommended maximum allowable back pressure (refer to safety instruction sheet).
13) Always release back pressure from the pipe first, before deflating plug.
14) Check pneumatic plug inflation pressure at least every four hours.

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