Case Study: Optimizing Inflatable Pipe Plug Design with FEA
Pipe plugs are inflatable, reinforced rubber products used to seal off piping systems by blocking fluid flow. When positioned inside a pipe, an inflated plug creates sufficient friction against the pipe wall to withstand back-pressure from a water column on the other side. If the friction force is exceeded, the plug can be pushed out, potentially causing dangerous situations. In this case study, we explain how TANIQ leveraged finite-element analysis (FEA) to optimize the design of a 600/1500 pipe plug, improving both performance and cost-efficiency.
TANIQ’s FEA for reinforced rubber products
TANIQ specializes in FEA for reinforced rubber products, including pipeplugs, rubber expansion joints, and hoses. Our TaniqWind software precisely designs the elastomer and reinforcement layers, feeding directly into an integrated FEA Toolbox. This toolbox defines meshing parameters, geometries, and element types to create a high-fidelity model, which can then be exported to commercial FEA packages like Abaqus. By using the same design data for both simulation and robotic manufacturing, TANIQ ensures consistency between the virtual model and the final product.
Visual of pipe plug simulation made with TANIQ’s FEA Toolbox
Simulation of a 600/1500 Pipe plug
The 600/1500 designation indicates a minimum internal diameter of 600 mm and a maximum of 1500 mm. After inflating the pipe plug to a working pressure of 2 bar inside a 1500 mm pipe, we gradually increase the back-pressure on the other side of the plug until the plug is being pushed out. Key parameters tracked in the FEA include:
Internal Pressure: The inflation pressure of the plug (up to 2 bar).
Attaching Pressure: pressure in the pipe plug at which sealing is obtained between pipe plug and pipe wall
Friction Force: The contact force between the plug and the pipe wall, dependent on internal pressure, contact surface, and the friction coefficient (0.7 for rubber on metal).
Back Pressure: The external pressure exerted by water on the downstream side of the plug.
Back-Pressure Force: The product of back-pressure and the cross-sectional area of the pipe.
The orange line in the graph visualizes an increasing Back-Pressure Force. The increase of Back-Pressure on the backside of the plug deforms the plug and reduces the contact area with the pipe wall, which results in a decreasing the Friction Force (blue line). At the point where the Friction Force becomes lower than the Back-Pressure Force, the pipe plug will be pushed out.
Graph showing the pipe plug performance during inflation in a pipe with increasing Back Pressure.
Graph definitions:
Internal Pressure: pressure in the pipe plug with a maximum working pressure of 2 bars.
P_attach: pressure in the pipe plug at which sealing is obtained between the pipe plug and pipe wall
Friction Force: The contact force between the pipe plug and the pipe wall. The Friction Force is determined by the Internal Pressure in the pipe plug, the contact surface area between the pipe plug and pipe wall + friction between rubber plug and pipe material. For this case study we used a friction coefficient of 0.7, representing friction between rubber and metal.
Back Pressure: pressure on the backside of the pipe plug caused by the build-up of water flow
Back-Pressure Force: The force exerted by the Back Pressure on the pipe plug. The Back-Pressure Force is determined by the Back-Pressure multiplied by the cross-sectional area of the pipe.
Key Findings and Optimizations
Simulation revealed the plug could withstand more back-pressure than originally required. Therefore, we reduced its length without compromising safety margins. This optimization cuts both material usage and manufacturing cost. Real-life testing confirmed that the simulation accurately predicted the plug’s performance, validating our FEA model.