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Inflatable Pipe Plug

Important Inflatable Terminology

Petersen® inflatable hot tap pipe plug insertion systems greatly reduce the time and costs associated with stopping the flow in pressurized pipelines. They allow you to insert inflatable plugs quickly into live pipelines without flow interruption. In order to understand inflatable pipe plugs and their hot tap insertion systems, it's important to know what the pipe terminology means.


  • Back Pressure is the amount of air or water in the pipeline that has built up behind or in front of a pipe plug.
  • Feet of Head or Head Pressure is the depth of the water from the pipe invert (lowest point) to the water's surface .
  • Grade or Slope is the percentage that the pipe is slanted downward to allow the effluent to flow. For example, if the pipe is on a 1% grade that means the pipe gradually slants downward at a rate of 1 foot every 100 feet of pipe.
  • Pounds of Force is the amount of force being exerted on the plug from the pipeline back pressure. It is important to know the pounds of force that a plug is holding back to understand the force the plug and its anchoring system must block and the amount of damage that can be caused if a pipe plug fails or deflates.

Important calculations for inflatable plugs


Pounds of Force Formula
3.14 x (radius of pipe²) = square inches or area of the pipe. Multiply this figure by PSI (back pressure) to calculate the pounds of force.


Calculating Feet of Head Using the Slope or Grade of the Pipe:
To calculate the feet of head or head pressure that is backing up behind a pipe plug, you must know the grade or slope of the pipe and the distance the water is backing up behind the plug.

If a pipe is laid on a 1% grade, and the water inside the pipe has backed up 500 feet behind the plug, then the plug will be holding back 5 feet of head. You calculate the feet of head by multiplying the number of feet of water backed up in the pipe behind the plug (500') by the slope or grade (1% or .01).

Important Conversions for inflatable Plugs


Conversion Table

Convert from Unit

Multiply by

Convert to Unit

PSI (Pounds per Square Inch)

2.307

Feet of Head

Feet of Head

0.4335

PSI (Pounds per Square Inch)

Inches of Mercury

0.4912

PSI (Pounds per Square Inch)

PSI (Pounds per Square Inch)

2.036

Inches of Mercury

Bars

14.5

PSI (Pounds per Square Inch)

PSI (Pounds per Square Inch

0.0689

Bar

Inches

0.03937

Millimeters

Millimeters

25.4

Inches

Feet

0.3048

Meters

Meters

3.281

Feet


Contact Petersen to discuss whether inflatable hot tap insertion systems are right for your job.

The information may be used but with no warranty or liability. This information is believed to be correct but should always be double checked with alternative sources. Strictly adhere to and follow all applicable national and local regulations and practices.