Some of the companies that make piston rings should have info on bypass.
I was told many years back that a Rule of Thumb was:
One Cubic Inch/Minute per Inch of bore per 1000 PSI.
There are several designs of piston rings that would appear to have lower bypass but I have had very little experience with Piston Ring cylinders.
Work with a couple of 50" bore hydraulic presses locally that appear to take about 20-25 GPM to keep them in the up position, at 850-900 PSI, between cycles. They were built id 1953 and have never had to be repaired.
Bud Trinkel, Fluid Power Consultant
HYDRA-PNEU CONSULTING, INC.
Thank you Bud for your response.
I think your hydraulic presses leakage is high but within reason.
When applying your rule of thumb to your presses I get a theoretical leakage of about 0.2 gal per min?
Am I missing something?
Bryan
No Bryan, I had never applied that formula to the presses.
I got my figure from knowing there are two 185 GPM Bi-directional Variable Volume Pumps that have a total stroke of approximately 5/8" either side of center and must be offset approximately 1/32" each to keep the Platen from drifting down when the oil is up to operating temperature.
From some old literature on the presses they state there is 5/8-3/4" end gap on the four piston rings when assembled and the presses operate 3 shifts per day 5 days per week about 50 weeks per year for a 60-70 second total cycle time .
You can figure the number of feet of piston travel for a 6' stroke during that length of time.
Bud Trinkel, Fluid Power Consultant
HYDRA-PNEU CONSULTING, INC.
