Gaskets Explained

Posted: 28th February 2014

Gasket or seal

When liaising with our customers, we have noticed, there is some confusion as to the difference between gaskets and seals. Very often clients call asking for a seal, when in fact a gasket is needed. The comments below should help you decide on what type you need.

Gasket

A gasket is placed in between two objects/faces and compressed in order to prevent leakage of any kind of the pressurised or not pressurised media.

Seal

The O-ring may be used in static applications or in dynamic applications where there is relative motion between the parts and the O-ring.

Gasket material

Whether for a gasket, valve gasket, or seal, the choice of elastomer might seem like a minor decision, but it can have a major impact.  If a seal material is a poor fit for the application, you could run into any number of problems, from swelling, to peeling or cracking.  Needless to say, these could be a big deal in the pharmaceutical industry sanitary process. But how do you decide what elastomer to use?

Your best bet is always to look at what is already being used in the same or a similar application.  With variables like chemical compatibility, temperature, pressure, and mechanical wear, it’s almost impossible to predict with certainty what the best material will be.  In most cases, several materials will work, but you might see a longer life in some.  At that point, it’s a judgment call where the life can be weighed against the cost. See our material compatibility chart for a guild as to what grade material suites your application.

Standards

First, consider the standards you must meet.  It’s easy to think that EPDM is EPDM, but there’s more to the story.  An EPDM O-ring could be perfectly safe for sanitary processing, or it could contain any number of potentially harmful components, depending on how the O-ring is made.  It’s possible for these components to leech into your finished goods.  That’s why it’s important to be specific about your standards.  Are the components considered food grade?  Do they meet FDA standards?

Temperature

A final consideration is the temperature that your elastomer will experience.  As with the other success factors for an elastomer, we can only speak in general terms until we try an elastomer in the specific application.  Time at temperature, variations in temperature, and the combination of temperature with other chemical and mechanical stresses can all affect elastomer life.

Gasket Material Chemical Compatibility

In order to simplify the selection of suitable gasket materials for aggressive fluids, we have produced a Gasket Material Compatibility Guide which provides useful information on the optimal choice of gasket materials.

Gasket Material Chemical Compatibility Guide