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Re: Material Suitability
"I think that in Air Products' case, it is probably best left up to them to
provide an answer defining their statement."
Gosh Bruno, you take the fun out of things..... I was hoping to hear from a
few rocket scientists.....
I sent Air Products a query on this caution regarding the use of Neoprene
and Buna-N with CO2, and received the following response:
"The recommended regulator for CP grade CO2 is the general purpose with
neoprene diaphragms. This is an acceptable application. The problem with
rubbers and CO2 comes at high pressure. The CO2 permeates into the rubber
and when the pressure is released the CO2 inside the rubber expands faster
than it can permeate back out and will blow chunks right out of the rubber.
In the case of the diaphragm, it is on the low pressure side of the
regulator and should not be effected by this problem."
Since the pressure on a metering valve is usually limited by the regulator,
I doubt that there would be any problem with seals being made from
rubberized materials - the pressure wouldn't be enough to force CO2 into the
material in the first place. It might however, preclude the use of a high
pressure needle valve directly onto a cylinder, as was described by one
message archived on the KRIB.
James Purchase
Toronto