Most discussions about "optimum" storage pressures are derived from an old study done by the University of Rhode Island back in the 1970s.
In one phase of the study about six 3AA steel cylinders were baked for 100 days at 104 degrees with about a cup or two of either fresh or salt water dumped inside. After 100 days the researchers analyzed the cylinders for corrosion and tried to draw some conclusions about the effects of positioning, contaminating fluid, etc.
Two steel cylinders were compared, both of which contained salt water and both of which were stored upright (vertically). One of these cylinders was stored with only 100 psi of air and had the least overall internal corrosion. The other matched cylinder (vertical, salt water) was stored at full operating pressure and had much more significant corrosion.
The conclusion was that the increased pO2 in the full cylinder contributed to the increased overall corrosion. Their recommendation was to store steel cylinders at a low pressure, both to keep ambient moisture out and to minimize the pO2 that is available to contribute to corrosion. Exact numbers were not studied per se, but the recommendation was 100 to 500 psi.
A previous phase in the same study had shown that the storage pressure really didn't matter when it came to corrosion in aluminum cylinders.
As Richard said, cylinders are rated to 100,000 fill cycles. From a purely metallurgical standpoint, there is no issue with storing a cylinder long-term at its full, rated operating pressure.
Clearly the Rhode Island study was not randomized, not properly case-controlled and not statistically significant. The test conditions were exaggerated to speed up the corrosion process. But that's the only study that was ever done in this regard. Draw your own conclusions.
Read the full story here about cylinder storage studies.
In one phase of the study about six 3AA steel cylinders were baked for 100 days at 104 degrees with about a cup or two of either fresh or salt water dumped inside. After 100 days the researchers analyzed the cylinders for corrosion and tried to draw some conclusions about the effects of positioning, contaminating fluid, etc.
Two steel cylinders were compared, both of which contained salt water and both of which were stored upright (vertically). One of these cylinders was stored with only 100 psi of air and had the least overall internal corrosion. The other matched cylinder (vertical, salt water) was stored at full operating pressure and had much more significant corrosion.
The conclusion was that the increased pO2 in the full cylinder contributed to the increased overall corrosion. Their recommendation was to store steel cylinders at a low pressure, both to keep ambient moisture out and to minimize the pO2 that is available to contribute to corrosion. Exact numbers were not studied per se, but the recommendation was 100 to 500 psi.
A previous phase in the same study had shown that the storage pressure really didn't matter when it came to corrosion in aluminum cylinders.
As Richard said, cylinders are rated to 100,000 fill cycles. From a purely metallurgical standpoint, there is no issue with storing a cylinder long-term at its full, rated operating pressure.
Clearly the Rhode Island study was not randomized, not properly case-controlled and not statistically significant. The test conditions were exaggerated to speed up the corrosion process. But that's the only study that was ever done in this regard. Draw your own conclusions.
Read the full story here about cylinder storage studies.
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