HG Molenaar and Company, of Paarl, has scored a world-first for the South African fabrication industry with the development of a submarine rescue system for deployment in any ocean under the jurisdiction of the North Atlantic Treaty Organisation (NATO).
HG Molenaar is a worthy winner for its work on this multi-national project for an international submarine rescue system that will provide a rescue capability to France, Norway and the UK, as well as to NATO and its allies.
The strict specifications placed considerable demands on the manufacturing process, which showcased South Africa’s ability to meet global standards. This is a project that has not only benefited the local stainless-steel industry, but is one that the entire country can be proud of.
The rescue system is a 72-person, 100 m3 hyperbaric chamber made from 5 mm SAF 2205 duplex stainless steel in order to cut down on the weight, as the chamber has to be flown to its deployment site. It comprises three hermetically-sealed pressure vessels, two of which consist of two chambers each.
Vessel one is 2.1 m in diameter by 5 m high, with four manways, more than 30 other penetrators, and a huge array of lugs and stand-offs. It stands vertically between the other two chambers, and serves as a transfer chamber from the mobile rescue submersible to the other two treatment and waiting chambers. It also serves as a decontamination and pre-treatment chamber.
Vessels two and three are 1.8 m in diameter and 12 m long, with two compartments. Each has four manways, more than 80 other penetrators and more than 450 lugs and stand-offs. Each of these two vessels can decompress its entrance chamber, so as to airlock-admit or discharge staff. They also have separate small airlocks so that medicines, food or tools can be passed in and out without decompressing either chamber of the vessels.
All the vessels are equipped with electricity and electronic communications connections, while all the necessary plumbing from showers to toilets is hyperbaric. The manways and other penetrators in the vessels had to be placed accurately and welded in with minimal heat distortion, and zero defects, as they interconnect to form a pressurised complex, with a central receiving and decontaminating chamber, two (one on each side) treatment chambers, and two waiting chambers leading on from these.
The vessels had to be built to PD5500 specifications and Lloyds shipping rules, which placed particular constraints on the manufacturing. All the pressure-vessel material had to be certified to 31°C and impact-tested at –20°C. The vessels had to be within dimensional tolerance, which was complicated by the fact that SAF 2205 is a duplex stainless steel with marked weld and heat distortion characteristics.
All welds had to be X-rayed, and were done manually by TIG, a very slow process, in a very short time. As the vessels included internal compartments and airlocks, they had to be hydro-tested in numerous different pressure directions.
Despite all these constraints, all three of the vessels passed their hydro tests in Paarl on the first attempt, an event witnessed by HG Molenaar, Rolls-Royce, Lloyds and the British Department of Defence.
The aim of the rescue system is to evacuate stranded submarine anywhere in the world within 48 hours, without any decompression affecting the crew.
In the event of a submarine sinking, NATO will load all the components of the rescue system onto airplanes and fly them to a suitable ship in a harbour nearest the stricken vessel. The ship then anchors near the submarine, with the entire rescue system on its deck.
The crew of the submarine is fetched in a submersible that can attach to the submarine, drill into it, correct the atmosphere, open the hatch and remove the crew eight a time, without any decompression. The submersible surfaces and is then lifted to the central chamber of the rescue system, attaches hermetically, transfers the crew, and then re-submerges for the next batch.
Martin Molteno
H G Molenaar
Tel : (021) 868 2210
Fax : (021) 868 2209
