Portable metal cylinders have been used to store and transport compressed and liquefied gases from as far back as 1810.
The advent of high pressure compressed gas cylinders of the type used today did not occur until about 1890, when the Mannesmann Company in Germany introduced the first seamless steel high-pressure cylinders
Pressure testing of cylinder valves at full cylinder test pressure has historically presented challenges due to technology limitations involving the cost-effective availability of high pressure compressed air to be used as the test gas.
Till the early 1990s, high-pressure compressors were not readily available, which could rapidly produce an adequate flow of compressed air at 200 bar, let alone 300 or 400 bar required for mass testing of cylinder valves.
Cylinder valves for Industrial gases in those days were rated for working pressure 140 -150 bar. Even this presented problems as compressors were not reliable and were prone to overheating and broke down if made to run on a high duty cycle.
As India did not produce any suitable high-pressure reciprocating compressors, we used second-hand compressors sold in the market by dealers specializing in stocking and selling machines dismantled from old ships.
It was considered a good day if the high-pressure testing room received an uninterrupted supply of compressed air throughout the day without any breakdown.
We bought our first 300 bar three-stage reciprocating high-pressure compressor from Hamworthy (UK) through their local partners, Indian Compressors, based in Noida. I remember visiting their factory for an inspection of the compressor because, at that time, I was doing my MBA in New Delhi.
The technology leap in high-pressure testing experienced by the introduction of Hamworthy can be compared to improved communication by smartphones' advent.
ISO 14246 – Cylinder valves — Manufacturing tests and examinations - require each cylinder valve at the production stage to be tested in both open and closed condition at 1.2 times the working pressure of the valve for compressed gases, at the test pressure of the valve for liquifiable gases and at 0.8 x times the rated pressure of the Burst disc for valves fitted with a burst disc safety.
100% pressure testing of cylinder valves was not always required or carried out in the earlier days, and several manufacturers carried out high-pressure testing on a sampling basis. (Sometimes not even at the working pressure for the which is rated).
Cylinder valves are increasingly being designed for higher pressures and coupled with the increased demand for cylinder valves, the need for compressed air for pressure testing of cylinder valves continues to rise.
Thankfully equipment technology has kept pace with the increased demand. We are now proud to own and operate a series of heavy-duty, energy-efficient and noise-less high-pressure compressors (thanks to German technology) allowing fast-filling of the tank reservoirs used for high-pressure testing at 450 bar in minutes
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