A CENTURY OF CYLINDERS:
AN OPEN LETTER TO THE COMPRESSED GAS INDUSTRY

JUNE 2002

This year marks our 100th anniversary of manufacturing steel seamless high-pressure cylinders for the compressed gas industry. It is a fitting occasion to reflect on the history of that endeavor and examine issues that affect it’s future. As our industry advances into the 21st century, it is incumbent on manufacturers, regulators, gas producers, and end-users of high-pressure gas cylinders to contemplate the implications of indefinite use of gas cylinders. We believe that the current industry practice of using cylinders indefinitely needs to change.

From the beginning, safety has been the guiding principle in the design, material selection, manufacturing and inspection of high-pressure cylinders. As technical advances were made, the safety of high-pressure cylinders improved.

Essentially, there have been four generations of cylinder technology over the past 100 years.

The first generation ran from 1902 to approximately 1930. Cylinders were made from carbon steel, the principle material for use at that time.

By 1930 the second generation of cylinders, manufactured from intermediate manganese steel, was in use.

The development of the third generation of cylinders was driven by U.S. military demands for cylinders that would not fragment when ruptured like earlier cylinders. The result was the development of quenched and tempered chrome molybdenum alloy steel cylinders designated as 3AA.

The fourth generation of cylinders are high strength cylinders manufactured from enhanced alloy steels. These cylinders are currently manufactured under DOT exemptions; such as E9421 and E9909.

Concurrent with cylinder material and technology developments, innovations in the machinery and process employed by the steelmaking industry have further contributed to the enviable safety record of today’s cylinders.
The progression from Bessemer converters to open-hearth furnaces to present day electric furnaces and BOF’s (basic oxygen furnaces) all factored into current, enhanced cylinder composition and design.

Each advance from carbon steel to intermediate manganese steel to the modern chrome moly alloy steel has resulted in the enhanced toughness of seamless steel cylinder products. In addition to allowing thinner walls, the increased toughness equates to cylinders that exhibit improved flaw tolerance and fracture performance. For example, an antiquated carbon steel cylinder may fragment on failure as opposed to the predictable, "leak before break" attribute of a modern chrome moly cylinder. Decades of advancements in cylinder design, manufacturing technology and inspection expertise have also contributed to a modern cylinder population with improved fracture performance.

Taylor Wharton recommends that in the interest of public safety, only seamless steel high-pressure cylinders employing state-of-the-art technology (third and fourth generations) be used.

As a result, Taylor-Wharton believes that users of the first generation cylinders should be warned of the potential fragmentation hazard associated with those cylinders.

                          

Ronald W. Kaplan                                            Clark K. Hall
President, Harsco Corporation                           Director – Cylinder Technology
Gas & Fluid Control Group                                Taylor-Wharton