History[edit]

OXYGEN CYLINDER 240 CFTThe world’s first natural gas cylinders were invented in China during the Tang dynasty where the Chinese drilled deep boreholes to retrieve natural gas and used bamboo tubes to collect and transport it.^{[1][2][dubious – discuss]}

Materials[edit]

For a detailed discussion about the materials for gas cylinders see pressure vessel.

Design codes and application standards along with the cost of materials dictated the choice of steel with no welds for most gas cylinders, treated to be anti corrosive. There have been some newly developed lightweight gas cylinders from stainless steel and composite materials. Due to the very high tensile strength of carbon fiber, these vessels can be very light, but are much more difficult to manufacture.^[3]

Regulations and cylinder testing[edit]

The transportation of high-pressure cylinders is regulated by many governments throughout the world. Various levels of testing are generally required by the governing authority for the country in which it is to be transported. In the United States, this authority is the United States Department of Transportation (DOT). Similarly in the UK, the European transport regulations (ADR) are implemented by the Department for Transport (DfT). For Canada, this authority is Transport Canada (TC). Cylinders may have additional requirements placed on design and or performance from independent testing agencies such as Underwriter’s Laboratory (UL). Each manufacturer of high-pressure cylinders is required to have an independent quality agent that will inspect the product for quality and safety.

Within the UK the “competent authority“ — the DfT — implements the regulations and appointment of authorised cylinder testers is conducted by UKAS, who make recommendations to the VCA for approval of individual bodies.

There are a variety of tests that may be performed on various cylinders. Some of the most common types of tests are hydrostatic test, burst test, tensile strength, Charpy impact test and pressure cycling.

During the manufacturing process, vital information is usually stamped or permanently marked on the cylinder. This information usually includes the type of cylinder, the working or service pressure, the serial number, date of manufacture, the manufacture’s registered code and sometimes the test pressure. Other information may also be stamped depending on the regulation requirements.

High-pressure cylinders that are used multiple times — as most are — can be hydrostatically or ultrasonically tested and visually examined every few years.^[4] In the United States, hydrostatic/ultrasonic testing is required either every five years or every ten years, depending on cylinder and its service. Helium gas cylinders have the highest pressures possible when full, around 1000 atmospheres