TPi October 2012

products & developments

Increasing life expectancy of pipelines Alan Robinson, managing director of Arc Energy Resources, discusses the benefits of weld overlay cladding to protect the internal surfaces of pipe systems, and reviews the options available using corrosion resistant alloys.

can choose from a number of welding processes and a wide range of cladding alloys. The final choice will depend on the size and geometry of the components to be clad and the alloy best suited to combat the surface degradation. Even in systems that do not suffer anything worse than normal aqueous attack and where pipes are internally protected by other methods, it is well worth considering the application of weld overlay cladding to the system’s seal areas. For example, on flange seal faces where mechanical damage may be caused during construction and subsequent maintenance activities, a conventional and inexpensive stainless steel deposit would be adequate. Where the medium is more corrosive or can be variable in content, the use of either a higher grade stainless steel or oneof themorecomplexnickel chromium alloys is normally recommended. Whilst these may be prohibitively expensive for use in solid form, a 3mm thick layer on the affected surface will offer the same working performance and could lead to significant savings from the extended life of the equipment. Mechanical wear is normally limited to areas where a directional change of flow takes place – for example at a bend or diversion point, or where the medium is physically propelled by pumping or other means. In these areas of wear, weld overlay cladding offers clear advantages because protection can be applied specifically to the areas under attack. The overwhelming advantage of weld overlay cladding is its versatility. Whatever the shape or size of the component there is a process that can be applied, and whatever the medium, there is an alloy to counteract its corrosive or abrasive properties. Significant developments by equipment suppliers to improve productivity and quality have helped to ensure that weld overlay cladding is now widely accepted as a versatile and economically viable process with which to protect pipe systems against corrosion.

Corrosion is the ultimate dirty word, leading to a waste of precious natural resources and creating problems for those entrusted with the containment and handling of aggressive liquids and ecologically damaging toxins. Paints and coatings are readily available to protect the external surfaces of piping systems and equipment from the atmosphere; but what can engineers do to ensure the integrity of the internal surfaces and maintain an efficient and reliable service, when the transported media can, for chemical or mechanical reasons, degrade pipes, valves and other equipment? In such applications, what techniques are available to enhance the life of new plant or refurbish worn or corroded equipment, and what are the cost benefits compared to expensive base materials and/or replacement parts? Engineers have a number of options when considering corrosion protection for the wetted surfaces of a pipeline system. However, the final solution will depend in part on an evaluation

6m pipe cladding

of factors such as the presence of chemically aggressive compounds; the level of suspended solids, if any, in the product; the installation deadline; and budget restraints. Where budget is not a constraint, engineers can simply specify components in corrosion or wear resistant alloys known to withstand the specific service conditions. However, this is rarely the case and other, more cost-effective options must be sought. Where standard, off-the-shelf carbon steel components such as pipe, flanges or fittings are used, weld overlay cladding is certainly the most versatile option, providing the assurance of a heavy-duty metallurgically bonded protective layer that will not be undermined or dislodged in service. After first identifying the areas within the system that need to be protected, and the properties of the medium from which protection is required, engineers

Steel pipe from China Tianjin Nolite Steel Co, Ltd is a manufacturer of ERW, SSAW and LSAW steel pipe and strip steel. The company supplies high quality petroleum and gas line pipe, water pipe and construction pipe. The company’s ERW steel pipes range from 21.3 to 457.2mm (½" to 18") o utside diameter, and 1.5 to 14.27mm wall thickness. SSAW steel pipe is available in outside diameters from 219.1 to 3,048mm (8" to 120"), with wall thickness ranging from 5 to 30mm. LSAW steel pipe OD ranges from 219.1 to 1,820mm (8" to 72").

Tianjin Nolite Steel Co can manufacture according to certificates API 5L PSL2, API 5CT, EN 10217-1, 2, 5, EN 10219-1, and ISO 9001:2008.

Tianjin Nolite Steel Co, Ltd – China sales@nolitesteel.com www.nolitesteel.com

Arc Energy Resources – UK sales@arcenergy.co.uk www.arcenergy.co.uk

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Tube Products International October 2012

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