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A powerhouse in tight spaces

Insulated steel pipes – used for oil and gas and urban heat networks – need to be bent regularly in order to follow a planned route. Maats Pipeline Professionals commissioned VIRO to optimise an Internal Bender that bends the pipes from the inside.

Traditionally, high-quality steel pipes are bent from the outside. Bending from the inside keeps the insulation and protective material around the pipes from getting damaged. Maats Pipeline Professionals decided to take over the existing concept, prototype, and rights from an Austrian pipe manufacturer. In order for the Internal Bender to be used commercially, however, the concept needed to be further developed and strengthened. VIRO was commissioned to optimise this concept.

400 tons of bending force

‘The Internal Bender slides into the pipe until it reaches the point that needs bending. The bender has tractor bending shoes on the front and back. The rear shoe is pushed vertically upwards by cylindrically driven wedges until it secures the bender in the pipe. Afterwards, a compressive force of 400 tons bends the front shoe upwards. It's the front shoe that does the actual bending work. We have also installed shoes in the middle of the Internal Bender that expand to the side by cylindrical pressure. The anti-buckling system ensures that the pipe doesn't kink inwards,’ explains Gertjan Varvik, Project Leader at VIRO. Every upward push of the front shoe bends the tube by 0.2 / 0.3 degrees. Through enough repetition, the pipe can eventually be bent at an angle of up to 10 degrees.

Tensile strength of 1100 MPa

The commission in the trial stage was to bend a 600 mm diameter pipe with 20 mm thick walls, at a strength of 600 MPa. The Internal Bender has to exert an enormous force. The pipe requires a frame made of heavy solid steel that the cylinders in the bender must be able to withstand. The tensile strength in the frame comes to a yield point of 1100 MPa. In Austria, we found a forge that could supply – and also to a large extent mill – such a frame for us. This makes up is the framework for a 4 metre-long Internal Bender that can slide into a pipe with a 60 cm diameter. Within that 60 cm is where everything has to happen,’ says Gertjan Varvik.

Hydraulic energy chain

Gertjan and his colleagues at VIRO made the complete design, calculations, and Finite Element Analysis (FEA). The challenge was to meet all customer queries, requirements, and standards within the minimum diameter. The bender – and all necessary equipment – is built in a standard shipping container. ‘The bender rides from a duct – its resting position – into the pipe it’s meant to bend. Underneath is a hydraulic energy chain for all of the controls and power lines. The control block for the hydraulics is located in the same container as the Internal Bender, because there is not enough room for it in the machine. Pipes over 15 metres in length must be able to enter a tube, making for a huge energy chain,’ explains Gertjan Varvik. Besides their Mechanical Engineering and Engineering Analysis, VIRO was involved as a system architect in the handling of the Internal Bender. ‘In addition to handling the Internal Bender, data must be collected for various purposes, such as predictive maintenance. The control block itself is made by another party,’ adds Gertjan Varvik.