There are two sets of UK standards for O rings, with metric BS 4518 and Imperial BS 1806 these define cord size and ring diameter, in terms of fitting standard slots . There is an ISO series of sizes used in Aerospace that the Germans like to use as well, that are not compatible with the UK series, so we need two sets of boxes.
The choice of cord material is not defined in these standards, but nitrile rubbers are the workhorse for general use, silicone has better corrosion resistance, PTFE for some really nasty chemicals, but it is not so elastic, and viton if it is a moving seal .
There are two sets of UK standards for O rings, with metric BS 4518 and Imperial BS 1806 these define cord size and ring diameter, in terms of fitting standard slots . There is an ISO series of sizes used in Aerospace that the Germans like to use as well, that are not compatible with the UK series, so we need two sets of boxes.
The choice of cord material is not defined in these standards, but nitrile rubbers are the workhorse for general use, silicone has better corrosion resistance, PTFE for some really nasty chemicals, but it is not so elastic, and viton if it is a moving seal .
