Why Do Pipe Gaskets Fail?

Why Do Pipe Gaskets Fail?

The inclusion of a gasket in a joint to prevent leakage is only effective as long as there is sufficient force generated and maintained to allow effective mating of the gasket to the joint surface to ensure sealing.

Joints fail, not just gaskets. Low bolting torques, over-tight bolt loads, weak bolt materials, inadequate bolt / washer / nut lubrication, poor flange design or materials, poor gasket cutting or storage, improper installation practices, all contribute to seal failure, even though the gasket material itself may be correctly specified.

Forces acting on a gasket joint that could lead to failure if not addressed are:

Internal Pressure: The force acting in two places working against the seal. Pressure against the gasket is known as blowout pressure and the force acting against the flanges holding the gasket is known as hydrostatic end force.

Pipe_failure

Over torquing of the above joint would lead to an uneven flange load and weaken the effectiveness of the flange/bolt load. This weakening leads to an increase in blow-out pressure and hydrostatic force leading to an eventual joint failure even though the gasket material is suited to the application.

Temperature: Temperature causes the metals in the joint to expand or contract, causing the gasket to be over compressed or too relaxed.

 Medium: The possible corrosive affect that the gases or liquids the gasket is sealing against may have on its material make up.

Flange Load: The pressure compressing the gasket to create a seal as a result of bolt loading.

Bolted flanges have a recommended tightening sequence along with the correct torque measurement.

Failure to follow the sequence or correctly tighten the bolts can lead to an uneven loading of the flange faces creating weak areas where the above mentioned blow-out and hydrostatic pressures will have greatest effect on the gasket.

gasket leakage

 

bolt tightening sequence

Example of Bolt Tightening Sequence