When choosing an "O"-ring there are several factors to consider in determining proper selection including: the application for which the "O"-ring is to be used; the media to be sealed; the size of the fastener to be sealed; and the temperature and pressure to which the "O" ring will be subjected. Once each of these factors has been considered and an "O" ring has been chosen, engineering calculations should either be checked manually or by using "O" ring selection software.
