Pipe Plugs are mainly for blocking and stopping the flow in the pipes temporarily. These flows can be water, sewage water, gas or petroleum. Thus, proper application of pipe plugs requires a special emphasis on pipe plug inflation and back pressure.
Pipe plugs are called many different names in the market such as inflatable pipe plugs, pipe balloons, pipe stoppers, pneumatic plugs and rubber plugs. They can be used for pipeline leakage testing, blocking or stopping, or repairing.
Pipe Plugs are suitable for testing as per requirements of European Standard EN 1610. Also, they are produced with a size up to 144” (DN3600) and a back pressure up to 6 Bar. Pipe Plugs can work with 1-6 bar inflation pressure. Also, they can hold 0,5-6 bar back pressure. So, back pressure is the level difference between the upstream and the downstream ends of the test line; or, in other terms, the height of the water column behind the plug.
Inflation pressure and back pressure are related to each other. So, when we examine the below formulization, we can understand clearly. When pipe plug inflates with air, it effectuates pressure on the contact surface. Then friction force occurs between pipe surface and pipe plug. As a result, this friction force can prevent sliding of the pipe plug. Hence, if we inflate the pipe plug less pressure, the plug can slip inside the pipe. Therefore, that can be so dangerous. This is the back-pressure calculation formula for pipe plugs. So then, this formula will help you to design plugging operation to answer the “what is the back pressure of this pipe plug?”
Formulization of Pipe Plug Inflation Pressure and Back Pressure
- F_g= πr^2*P_b
- F_s=(k*P_i*2 πr*L)+(k*W)
- P_b=F_g/(πr^2 )
- P_b=(k*P_i*2 πr*L)/(πr^2 )+(W*k)/(πr^2 )
- P_b=(k*P_i*L)/r+(W*k)/(2 πr^2 )
- P_b: Back pressure
- W: Weight of plug
- L: Contact surface
- r: radius of pipe
- P_i: Inflation pressure
- k: friction coefficient
- F_s: Friction force
- F_g: Back force
Lastly, in order to see how Pipe Plug Inflation Pressure and Back Pressure works please see our video here.