TPI July 2012

products & developments

Demagnetising transport pipelines on location

magnetic transport, induction heating, tear tests, magnetic grippers, etc. The magnetisation is also strengthened by electrical welding, mechanical vibrations, grinding, sawing and cold deformation. The consequences are diverse: plasma soldering is usually impossible, small metallic particles and metallic dust remain sticking, increased wear, fallout and waiting time in case of automatic processing stations due to clinging materials, problems with electrical welding, unevenness and thickness differences in case of electrical zinc coating and chroming, sharp edgeswhen galvanising, etc. In the abovementioned case the pipelines could not be welded together because of arc deflection. This can cause lack of adhesion and is therefore not desirable. Undesired remanent magnetism costs time and money, and influences the quality of the end products. To prevent this, the company has developed a number of demagnetising systems in tunnel form and table form (with slat conveyor, if required), as a manually operated device or low frequency as mobile unit. When the investment in these systems is not cost-effective, the magnet producer also offers the possibility to perform the demagnetisation on location or in-house. Goudsmit Magnetic Systems BV – The Netherlands info@goudsmit-magnetics.nl www.goudsmit.eu

magnetic field in the pipelines that decreases in strength to 0.

Goudsmit Magnetic Systems recently demagnetised PE coated pipelines, delivered by the Dylan Group Netherlands, for a new oil refinery to be built in Southeast India. The pipelines could not be welded due to the present remanent magnetism, and this caused the construction of the oil refinery to come to a standstill. To have this remanent magnetism disappear or to reduce it to a workable level, the company developed a system that consists of a low frequency generator and a specific cable system. The cable system is wrapped around the pipelines as a coil, which causes a strong variable

The consequence is that the remanent magnetism disappears or is reduced to a workable value of approximately 35 gauss. In this case it concerned around 40 pipelines of carbon steel, each with a length of 12m and a diameter of 470mm, and the activity took four days. The causes of remanent magnetism of materials can be various and difficult to classify in practice. However, it is usually caused by magnetic fields in the area, intentionally or unintentionally, for example by clamping surfaces,

Transport piping is demagnetised by a Goudsmit Magnetic Systems technician

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Tube Products International July 2012

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