Up from the Deep

Molenaar’s submarine rescue system uses stainless steel to save lives by Dean Jobb

Nickel Magazine, March 2007 -- A South African supplier of food-processing and canning equipment might seem an unlikely choice to build hyperbaric chambers to rescue submariners from the ocean floor. But H.G. Molenaar & Co.’s expertise in building pressure vessels was exactly what was needed for NATO’s new submarine rescue system.

“In a way, it’s a natural progression for us,” says Martin Molteno, technical manager of the engineering and equipment firm based in Paarl, in the heart of South Africa’s fruit-growing region. Molenaar has designed and built massive pressure vessels and some of the largest rotary cookers in the world. “And now we’ve drifted into more high-technology applications,” says Molteno, “including small decompression chambers for divers.”

The rescue system consists of three stainless steel tubular chambers providing 100 cubic metres of interior space that can accommodate and treat up to 72 people rescued from a stricken submarine. The system is installed on the deck of a rescue ship. A submersible
craft ferries submariners to the surface in groups of eight for treatment and decompression.

A Scottish firm, Divex Ltd., designed the system to be airlifted anywhere in the world, for deployment on the nearest compatible surface ship within 48 hours of a submarine emergency. S32205, a duplex stainless containing 5.5% nickel, was specified to reduce the weight of the pressurized chambers without compromising their strength. “It’s tough and it’s strong, and therefore you can go thinner [in this case to as thin as 5 mm],” Molteno says of the alloy.

Molenaar’s expertise in manual tungsten inert gas welding was vital, especially in regards to avoiding distortion of the S32205 plates. One of the chambers measures 5 metres (m) long with a diameter of 2.1 m; the others are 12 m long and 1.8 m in diameter.

“The weld has to be carefully prepared,” Molteno says, noting that the shape of the pieces must correspond exactly and the distance between them must be precise. “If you have a slight variation in the distance apart, then point A will pull in more than point B and the whole thing will twist.
“All our welds are checked for quality by a third party,” he adds. “They're X-rayed and tested
so we can certify that they're completely acceptable.”

In recognition of Molenaar’s fine work, the Southern Africa Stainless Steel Development Association (SASSDA) named the firm overall winner in the 2006 Stainless Steel Awards.
It also won in the project category.

“The strict specifications placed considerable demands on the manufacturing process, which showcases South Africa’s ability to meet global standards,” says Dr. Oliver Damm, managing director of the SASSDA.

The awards are gratifying, says Molteno, whose latest project is a bid to supply two components of a pebble-bed nuclear reactor being built in South Africa. “We're a small fabricator in a small [and distant country], but we are building pressure vessels for the world;
it’s reassuring that someone has recognized that we worked [extremely] hard.”

Dean Jobb is a Halifax, N.S.-based freelance writer.

PHOTOS: H.G. Molenaar and iStock

H.G. Molenaar P.O. Box 5 Paarl 7622 South Africa Phone 27 21 868 2210 Fax: 27 21 868 2209 E-mail: info@molenaar.co.za Web site: www.hgmolenaar.co.za

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