TPT May 2009

T echnology U pdate

An important feature is that the coupling is placed in only one pipe-end. This means that the coupling has a clamping side and a centring side. When two pipes run together, the upcoming pipe-end is automatically caught and lined up by conical centring rolls. The standard coupling has a three ‐ point clamping system that consists of two fixed support feet and one adjustable clamping foot. The adjustable foot bridges thermal expansion and ensures strong clamping inside the pipe. In tests and later experience the Standard Model performed well with smaller diameters up to Ø 30" and under normal circumstances. The following circumstances demand better performance of the coupling: large diameters (higher pipe-weights); thin wall thicknesses (risk of deformation); oval pipes; curved pipes; worn out or uneven support rolls; high velocities of rotation; and high friction forces between pipes. To improve performance in these harsher circumstances, the advanced coupling was developed. This coupling has a five point clamping system instead of three, and all five clamping feet move simultaneously. This ensures perfect centring, stronger clamping and less deformation of the pipe. For an even stronger fixing inside the pipe- end, the clamping feet can be covered with a heat isolating material that also increases the friction factor between the clamping feet and the pipe surface. On the centring side of the advanced coupling, there is a pre-centring ring with extra rolls that take the first blows when the pipes are running towards each other. Because of the extra ring the construction of the coupling is much stronger and the extra rolls can handle larger radial movements of the pipes.

Technically the advanced coupling performs well, but there is one disadvantage. For different wall thicknesses the clamping side can be adjusted very easily, but on the centring side the rolls need to be exchanged or re-positioned. This is not only time consuming, but there is also an extra risk of human error. The wrong rolls can be mounted on the coupling, or rolls can be mounted in the wrong position. To solve this issue the premium coupling was developed. This coupling is equipped with a new clamping system that centres both the clamping side and the centring side of the coupling at the same time. When force is applied on the central screw, five clamping feet and centring rolls automatically expand and force themselves against the inner pipe wall. The premium coupling can clamp on only 25mm of pipe surface, taking into account the cutback of an internal flowcoat. The coupling combines all advantages in one solution and is the result of experience with many different coating processes worldwide. Dhatec BV – The Netherlands  Centring and clamping side of a premium coupling

 The standard coupling during coating

the coating is allowed to cool down more before hitting the first support roll, avoiding loss in quality. Secondly, by using a coupling, radial movement of pipes when the weld hits the support roll, is reduced. An equally spread coating application free of air voids is ensured. Normally this is achieved by lowering the line speed, but a coupling also solves the problem and production can run at full capacity. Dhatec has developed three main models: standard coupling, advanced coupling and premium coupling. The basic demands for the design were: reducing radial pipe movements to almost zero; strong, shock- resistant construction; adjustable for a wide wall thickness range; bridge thermal expansion of the pipe in an induction oven (220°C); small contact surface with the pipe, to minimise heat loss; room for cooling water to flow through the pipe; and fast and easy application or removal.

Fax : +31 497 55 53 99 Email : info@dhatec.nl Website : www.dhatec.nl

Coil end weld planisher Kent Corporation, USA, has developed a new coil end weld planisher. The new machine has a fixed upper planisher roll that is hydraulically driven on two linear bearings. The lower anvil is adjusted up and down by a precision screw and wedge assembly. A machine mounted dial indicator allows for the anvil to be positioned to the exact material thickness. This prevents over planishing and eliminates the need to adjust pressure for each thickness. The planisher will flatten TIG welds back to original metal thickness so they can easily pass through roll form, tube and progressive die lines. This also allows for strip processors to sell the weld in their final product. Kent Corporation – USA Fax : +1 440 237 5368 • Email : info@continuouscoil.com • Website : www.continuouscoil.com

 Advanced coupling inside a pipe-end  Premium coupling with movable centring rolls

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M ay 2009

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