scope:

This specification defines the requirements for toroidal sealing rings ('O' rings) manufactured from materials which have been approved to DTD 5543 - "Fluorocarbon Rubbers".

They may be used in reciprocating mechanisms or for static purposes in contact with air, silicone liquids and petroleum based fuels, lubricants and hydraulic fluids where temperatures up to 225°C are encountered. In certain applications the materials may be suitable for use outside this temperature range, but where such use is contemplated the designer should satisfy himself of the suitability.

The materials are not suitable for use in contact with certain phosphate ester based liquids.

There are generally suitable for use in contact with other ester based liquids, but there may be temperature limitations in service.

NOTE: At ordinary temperatures and in the absence of hostile environments e.g. when properly stored, these rubbers deteriorate only very slowly. For most practical purpöses the effect is insignificant and storage life of fluorocarbon rubbers may be considered indefinite. However, the rate of deterioration increases markedly with increased temperature and the service life of the rubber therefore depends upon the operational temperature. Conversely, the maximum temperature at which the rubber may be used depends upon the useful life required.