Pipe in Pipe IDEAfix
Offshore contractors Heerema were using a 2 tonne machine to weld oil pipes. Idea's newly designed and constructed replacement weighs in at just 35 kilos!
The brief
Heerema, a leading contractor to the oil and gas industry, lay sea-floor oil pipelines from a ship. The pipes are welded together sequentially on the ship. Traditionally, single walled pipes have been used, but nowadays the oil companies will sometimes call for double-walled pipes where great depths are involved.
Holding the inner pipe in position in heavy seas presents a major challenge. In bad weather, Heerema would rig a 2 tonne machine above the welding station. Obelix, as the operators called it, would then clamp onto the inner and outer pipes, and hold them steady.
Heerema brief to Idea called for a simpler, smaller and more manageable alternative to Obelix. And time was short: Heerema's pipelaying vessel Balder was contracted to lay double-walled pipes at a depth of a couple of kilometres in the Gulf of Mexico.
Concept
"We have a reputation as engineers who enjoy the challenge of developing new things," says Project Leader Marcel Smits. He is the young mechanical engineer responsible for the concept, engineering and production of the new machine.
Idea set about brainstorming the problem with a team of four staff. "Throwing out ideas and racing through calculations," as Smits puts it. As each idea emerged, the calculations for the hydraulic cylinders and the quantity of steel required were carried out on the spot. "In a session like this, as soon as you discover you will need a hundred kilo cylinder, you know that idea isn't going to be a runner."
After a couple of hours of brainstorming, the engineers settled on a design involving a clamp and a double wedge arrangement. A double-action hydraulic cylinder would move the twin wedges in and out. Ideafix, as they dubbed the device, would handle all three of Obelix's operations using a single mechanism, with a tremendous saving in weight.
A device weighing 23 kilos, the maximum can be lifted by a single person under the Health and Safety legislation, proved not to be feasible, but a 35 kilo version was a real possibility, and could be safely lifted by two people. "Simple, small and handy."
Engineering
"The next step was to turn the prototype model into a finished product," says Smits, "and that had to be done to a very tight deadline." He carried out the force and friction calculations, prepared 3D CAD drawings and completed FEM calculations on the frame. "The secret here is to achieve the largest possible force on the wedge, and the smallest possible reaction moment on the frame. It isn't easy, because you are working right on the edge. If the weight wasn't an issue it would be a lot simpler. Sometimes you leave the office thinking 'this isn't going to work', but then a possible solution comes into your head when you are sitting at home."
Fabrication
The hydraulic cylinder was the only major component that came out of a catalogue. All the other large items had to be made from scratch. During the initial engineering phase, basic design, Smits was already sending drawings out to engineering companies asking if they could deliver work to a short deadline. To make the wedges for example he needed to find a firm with a five-axle CNC machine capable of machining high-strength steel.
Ideafix consists of a black frame supporting a yellow lifting boom. The boom's point of rotation is a precisely dimensioned slot, to compensate for lateral displacement. "But that's just a detail," says Smits nonchalantly.
A factor of ten cheaper
Before six months had passed, Heerema were starting tests on the Ideafix at Vlissingen. As well as being far easier to use, the new machine is a tenth of the price of its predecessor. The Obelix machine cost hundreds of thousands of euros, Ideafix came in in the tens of thousands. Heerema have now successfully deployed the Ideafix machine in the Gulf of Mexico, while Idea have developed another rather larger device for heavier seas. Logically enough, that one is called Asterix.