TPT January 2008

C oating, J acketing & Galvanizing Technology

Automatic zinc coating plant for tube seam

Launch of new all-terrain pipe coating

The Metallizing Equipment Company (MEC), India, is a thermal spray equipment manufacturer and supplier. Arc spray is user-friendly, and one of the more cost efficient thermal or metal spraying processes for applying metal coatings on base materials. Any electrically conductive material in wire form can be arc sprayed.

A contoured/scarfing tool or smoothing mandrel removes weld spatter or excess material from the outer diameter of the tube surface. Many tube makers install a two-wire electric arc spray process directly down line from the scraping tool or smoothing mandrel.

Saint-Gobain Pipelines, UK, is a supplier of ductile iron pipes, fittings, valves, access covers and gratings, and also produces cast iron drainage systems for above and below ground. The company has introduced a new coating solution that offers total protection, no matter what the soil conditions. The TT (Total Terrain) external coating system comprises thick, organic coatings which provide a complete barrier between the pipe and the surrounding soil. The system extends the capability of Saint- Gobain’s water and sewer pipes to all soil conditions. The company’s product manager, Mr Nigel Ward, explained, “ PAM Natural and PAM Integral Plus with their 85 per cent zinc and 15 per cent aluminium alloy coating are suitable for use in 85 per cent of all soil conditions. However, in extreme situations, tape wrapping has traditionally been used for a higher degree of protection. The TT coating is an external protection system that provides a total barrier coating, which offers cost savings through quicker and easier jointing techniques onsite. ” The TT coating system consists of an efficient PEC (polyethylene) or PUX (polyurethane) coating. DN80-700 pipes are supplied with the PEC coating, which is a 2mm thick extruded polyethylene coating applied over 200g/m² zinc using a heat bonding adhesive co-extrusion technique which is electronically tested to ensure it is holiday free. When assembled, the joint area is protected by either an easily fitted rubber sleeve or heat-shrink wrap. DN800-2000 pipes are supplied with the PUX coating, 900 microns thick with the joint area protected by a holiday free epoxy paint requiring no further protection. Conforming to BS EN 545 and BS EN 598, the robustness of the coating system ensures the minimum risk of damage during transportation and installation.

During the process, a wire feeder pushes two electrically charged metallising wires to the gun. The wires meet at the head of the gun and melt in the electric arc, with the molten mass then atomised and blown onto the substrate with compressed air. The particles cool to ambient temperature and coalesce into a high quality metal coating. A rollforming machine draws hot or cold rolled steel through

› MEC manufactures and supplies thermal spray equipment

successive stations and shapes the material into a tube. Electric resistance welding closes the seam left by the butted edges. Although no filler metal is added that would change the chemical composition, the welding process applies temperatures high enough to sacrifice some corrosion resistant properties of the base metal. The process may also vaporise aluminium or galvanised coating previously applied to the rolled steel.

The spray process applies coatings of aluminium, zinc or properties of the tubing. Applying the spray material while the weld seam is still hot assures a metallurgical bond of the sprayed material with the substrate. It improves both the deposit efficiency and density of the sprayed material and allows the coating to blend.

M/s Metallizing Equipment – India Fax : +91 291 2746359 Email : mecpl@sancharnet.in Website : www.mecpl.com

fi The arc spray process

Saint-Gobain Pipelines – UK Fax : +44 115 932 9513 Email :

innovations.uk.pipelines@saint-gobain.com Website : www.saint-gobain-pipelines.co.uk

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J anuary 2008