Fast Air Pump Advice
Fast Air Pump Advice
(OP)
I'm in need of a way to seal a pneumatic piston. The piston needs a bore ID over 7.5 inches with a stroke between 2 to 3 inches. The piston will stroke an entire cycle in 400ms. The pressure within the cylinder will not exceed 6psi. The volume of air which the piston will move is enclosed so I can allow no leakage otherwise the system will fail. I am trying to find a way to seal the piston to the bore which will not leak yet be able to survive the speeds over millions of cycles. I would love to use U-cup or other mechanical seal however with the speeds concern me. I've also looked at alternatives such as diaphragms however finding them in bore IDs over 4 inches becomes hit or miss and I would like off the shelf components.
Any ideas or inputs?
Any ideas or inputs?





RE: Fast Air Pump Advice
RE: Fast Air Pump Advice
Hope that helps.
RE: Fast Air Pump Advice
At 6 psi peak pressure, you could darn near mold your own diaphragm from urethane casting resins. Or buy sheet butyl rubber (low permeability) and make a flat diaphragm, but it would have to be a fairly large diameter to allow for the stroke you want.
Another alternative would be to dis-assemble a small hot water expansion tank, bladder-type, and extract the bladder, then adapt it for your use. Or just buy a replacement bladder from the tank mfgr.