TPT November 2022

T E CHNOLOG Y

Why a proper welding preparation is essential to stop pipeline accidents from occurring

any type are also to be removed prior to any welding operation. The pipeline machinery available on the market, applying cold-cutting processes, allow to achieve repeatable high quality weld end preparations within a few seconds and are perfectly suitable for manual or mechanised welding processes. Their main advantages are: suitable for facing, bevelling I, V, J, compound bevelling, counterboring, severing, surfacing; suitable for all kinds of materials: carbon steel, stainless steel, exotic alloys such as Incoloy, Hastelloy, Duplex, Super Duplex, P91 and so on; improved weld volume; finishing works can be processed individually or simultaneously; wide size ranges; self-centering clamping; speeds pipe alignment, cold machining process, no heat affected zone; safety chips guard, burr-free, no vibrations; very powerful motors suitable for the machining of large wall thicknesses; fast machining for high production rates, high accuracy and performance, versatile and reliable, easily transportable, they can be placed on the ground with an optimum stability, modular design, possibility to be used in all positions, horizontal, vertical, overhead; easy to handle and set up, safe use on-site or in prefabrication workshops; and adapted for extreme conditions. Pipe facing machine Protem PFM HSB-620 operated on-site. Pipeline operators have criteria that enable them to select the most proper pipe facing machine according to diameters, wall thicknesses, materials, defaults of ovality, very fast operations, extreme conditions, ease of use, reliability, versatility etc.

PIPELINES remain the safest way to transport oil & gas and they are nearly omnipresent in everyday life. However, several accidents due to poor welding or poor welding preparation have marked history. Bevelling and chamfering are applied to thicker pieces of metal prior to welding. Different types of joints can be performed according to the welding process applied or to qualified welding procedure applying to meet the application´s requirements. The bevel provides a smooth clean edge to pipe and allows to achieve a correct shape preparation. What are the risks of unproper welding procedures? • Line pipe weld misalignment • Incorrect pre-heat or interpass temperature • Improper cleaning of the pipes prior to the welding operation • Improper bevel and wall thickness sections • Out of roundness due to cut induction bends • No consideration of the influence of extreme temperatures or extreme working conditions • Other improper welding practices • Improper welding preparation and welding inspections Controversial welding and welding preparation techniques do represent the main reasons of the accidents occurred in the pipeline industry. Today, certain preparatory operations for welding are done with a grinding wheel or other equally unsuitable tools. Poor preparation will affect the end quality of the weld and lead to rejects, breakage or even leaks in use if defects are not detected in time. Good preparation for welding is even more

important when mechanically welded structures are subject to heavy loads when in use (pressure, heat, mechanical stress and so on). For example, this is the case in nuclear power or oil & gas industries, two domains where welding needs to be perfect. Edges for welding are to be performed when parts and assemblies require definitely strength. To achieve a perfect welding penetration, the edges of the metal must be properly prepared. The welding material will then replace the removed material and does represent a kind of bridge between the parts which are to be joined. Many different welding processes are available. For the pipeline industry, four types of welding are generally applied: MIG, TIG, stick and flux-cored arc welding. Besides the welding preparation itself, the pipes have also to be cleaned prior to any welding operation. This enables to avoid the risk of hydrogen inclusions. If the welding preparation was made while using lubricants, it is also essential to clean the pipes. If this welding preparation was made with a flame cutting process and not with a cold cutting process, slags or oxide may have stayed on the edge. The main advantage of a cold cutting process is that a perfect welding preparation is possible with no heat affected zone. Therefore, it is the most proper process to maintain the integrity of the pipeline material. Paints, dirts of

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NOVEMBER 2022