Logo

Duplex 2205 used for United Nations Navy Recompression Chambers


Posted 17 May 1999

When the United States Navy required 35 lightweight transportable recompression chambers in the late 1980s, Cowan Manufacturing took up the challenge of developing the units.

Cowan Manufacturing developed a prototype out of a virtually unknown material. It was duplex 2205 (UNS 31803) stainless steel.

No other manufacturer in the world was producing chambers out of 2205 and, after six years of negotiations, Cowan was sourced as the sole supplier of the chambers.

Cowan chose 2205 for its high strength, light weight and corrosion resistant properties. This enabled them to meet the Navy's requirements without the weight and corrosion problems of other materials.

Traditionally, recompression chambers have been made out of carbon steel and required high maintenance because of the severe marine environment in which they are used (on ships at sea). Chamber walls had to be thick to combat the effects of corrosion and so were very heavy.

The strength and corrosion resistance of 2205 over other materials enabled the chamber shell thickness to be reduced to 3mm. The thinner chamber walls effectively halved the weight of the units and corrosion resistance lengthened their service life.

However, Cowan faced some difficulties with the material because it was new on the market at the time. Staff had to be specially trained in welding techniques for the 2205 which had to be approved by Navy certification teams. (2205 is now a common material that is used for many industrial applications.)

The 2205 material was supplied by Sandvik Australia. The 3mm x 2000mm wide coil material was sized on its cut to length line and plasma arc cut the conical sections and the end cap discs which were then formed by Dome Engineering.

The strict quality requirements specified by the US Navy resulted in all material being ultrasonically examined and charpy tested before processing.

The chambers were produced at the Cowan Manufacturing facility at Warners Bay in New South Wales. Cowan has since become a specialist
in its field, supplying recompression chambers to 12 countries including the United States and Australia.

This article featured in Australian Stainless magazine - Issue 13, May 1999.

Lissel Pilcher