Saving weight under water

Tom Shelley reports on the redesign of formerly naval equipment for civilian applications using aluminium



Aluminium alloy is key to the success of a new manipulator for operations undersea, part of a range that has been redesigned from naval to more cost sensitive civilian applications.
CSIP, formerly Remote Technology, and based in Weymouth, introduced its latest five function manipulator arm at the recent Oceanology International event at London’s ExCel exhibition centre.
Design engineer Mike Robinson told us: “It’s made out of aluminium alloy 6082 because steel corrodes. It’s a very corrosive environment under sea. Stainless steel would be too heavy and too expensive to manufacture.”
According to Aalco Metals, 6082 has the highest strength of the 6000 series alloys – 130MPa tensile and 60MPa 0.2% proof stress. Its composition is 0.7-1.3% silicon, 0.4-1.0% manganese and 0.6-1.2% magnesium plus small amounts of iron, copper, zinc, titanium and chromium. While it is difficult to form it into thin walled, complicated extruded shapes, it machines well – so is ideal for the manipulator arm.
CSIP managing director Simon Gilligan added: “This is a new release of an old product. Its original version used to go on a remote controlled mine disposal vehicle for the Royal Navy. We have since changed the design, to give it a wider field of operation and made it into a commercial arm that is now very much easier to maintain and repair. You get a kit of parts and you can mend it yourself.”
He said that the increased field of work was achieved by using longer actuators, and that the company had also “strengthened it slightly”. He added that the company could also offer a version with positional feedback.
“We also do a six- or seven-function arm – which we are also re-engineering to give a bigger field of action and taking cost out of it. We have recently delivered one to Japan that is rated to 6,500m depth,” he said.
CSIP supplies its parent company ECA with all components for complete marine vehicle production. Standard units are electric, hydraulic or water powered and are built for small object retrieval and articulation. The five-function manipulator arm has an integral centreline extender and has been designed for small, high power electric remotely operated vehicles (ROVs). The function manipulators are expected to have life spans of more than 25 years.
In addition to the function manipulators, the company also offers a low cost pan and tilt unit that features a fully enclosed drive system, capable of oil or water hydraulic operation. Constant rotation speed is given on both axes to achieve 180 deg tilt and 360 deg pan. Position feedback is an initial or retrofit option and uses standard rotary potentiometers. All hose runs enter a single point within the electrics allowing simple integration into a camera whip.
The company still has a large involvement in the naval Remote Controlled Mine Disposal System as well as its growing commercial civilian business. The company is accredited to BS EN ISO 9001. Other uses for alloy 6082 include: trusses, bridges, cranes, transport applications, ore skips, beer barrels and milk churns.

Pointers

* Alloy 6082 is sufficiently corrosion resistant to permit use under sea

* It is less heavy and cheaper to manufacture parts in than stainless steel

* It is nonetheless suitable for critical applications

Author
Tom Shelley

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