Seals

6. Choose a seal

The choice of seal size and the dimensions of the sealing surfaces are inter-related and affected by the function size and performance of the machine. Normally commercial constraints demand that an off-the-shelf seal is specified so its dimensions will dominate and the component detail design must take account of them. These dimensions are normally shown in the catalogues produced by the seal manufacturers. Custom seals are more common in gaskets where the shape of the sealing face varies widely between machines.

Optimising the choice is now process of finding the best compromise (in the opinion of the designer) between the priorities of the system and the availability of the hardware. As far as the factors involving numerical data are concerned, some yield a 'go/no-go' situation which will eliminate those seals which are too costly, too heavy, too big etc.

Other requirements involving more subjective data should be compared on the basis of their ability to meet the criteria as laid down in the Product Design Specification.

This may be an iterative process, which converges on the best compromise. The evaluation technique used here will be similar to that used elsewhere in the design activity.