Gasket Function

A gasket is a material or combination of materials clamped between 2 surfaces to create a seal between the flanges and maintain this seal for an extended period of time. The gasket must be capable of sealing the mating surfaces as well as being impervious and resistant to the medium being sealed at the same time it must be able to withstand the applications temperatures and pressures.Gaskets for an internal combustion engine may appear simple but in reality are a highly engineered product and its function is much more dynamic than most people think. The requirements of these gaskets include:

  • Heat and media resistance
  • Zero leakage through the gasket
  • Zero leakage across the gasket
  • Be affordable
  • Be environmentally safe
  • Accommodate surface finish conditions of flanges
  • Reduce and/or control port and flange distortion
  • Accommodate thermal expansion and contraction
  • Possess adequate recovery properties
  • No re-torque and minimise torque loss
  • Transfer heat as desired
  • Meter fluid
  • Have anti-stick properties
  • Accommodate service assembly requirements

One of the main consideration in gasket design is the choice of materials. It has to be soft enough to conform to irregularities in flanges and solid enough to resist the motions of castings while at the same time maintaining adequate bolt torque. In theory if the flanges were perfectly smooth and parallel and infinitely rigid, you should be able to bolt them together without a gasket. But in reality flanges have a rough surface finish and the flange loading is often inconsistant. Gaskets are introduced to the joint to maintain sealing by compensating for non-uniform flange loading or conforming to flange surface irregularities. Gasket designers also must consider whether the application is for OE or aftermarket uses as OE gaskets are designed to fit between new castings with close to perfect surface finishes, flatness and precise bolt torque. Where as aftermarket gaskets have to seal used, warped, bent, pitted flanges with imprecise bolt torque.

Is a thicker gasket material the best for the application??
Thicker, softer gasket materials are subject to relaxation and torque loss but have superior conformability. They are generally used in applications where:

  • Bolt load is low
  • Bolts are spaced far apart
  • Flanges are uneven
  • Flanges are relatively thin or weak
  • Surfaces are rough or irregular

Thinner, harder gasket materials generally relax less over time and resist torque loss but may not conform to irregular surfaces. They are generally used in applications where:

  • Bolt load is high
  • Bolts are spaced close together
  • Flanges are flat
  • Flanges are relatively strong (machined castings)
  • Surfaces are relatively smooth
Posted in Technical.