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 plugs and their hot tap insertion systems, it's important to know what the 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

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