How to Make a Gasket Seal
The Science of Sealing
A gasket is just one part of an assembly. The quality of a gasket seal is a function of the quality of the assembly. Gasket failure is often attributable to defects in flanges or mating surfaces. The quality of a seal depends upon the quality of not only the gasket, but also of the surfaces of the joint to be sealed.
Creating a seal with a gasket is a mechanical process.
A seal is created when the material of the gasket is compressed between the two surfaces of a joint, or faces of a flange, thus preventing the leak or ingress of fluids or gases through the joint.
To seal, the pressure of the flanges on the gasket must exceed the pressure exerted by the contents of the vessel. Once the gasket has been seated properly, there must be sufficient forces continuously operating on the gasket to maintain intimate contact between the gasket and the seating surface, to prevent leakage or blow outs.
As the flange bolts are tightened the gasket typically changes in a way that causes it to compensate for any imperfections on the faces of the joint by flowing into, around, and over the imperfection.
In sealing a flange with a gasket the following are important to prevent the joint leaking:
- Are the flanges, or mating surfaces, flat and free from imperfections?
- Is the gasket made from a material with the required chemical resistance?
- Does the gasket have sufficient resistance to operating temperature for the application?
- Is the gasket strong enough to resist the internal pressure of the pipe?
The correct selection of the gasket is important because the material must:
- Withstand the pressures exerted against it.
- Withstand any corrosive medium that may attack its structural integrity.
- Withstand the entire temperature range of the process it is a part of.