Pipeline Welding Machine


    david - Posted on 22 May 2010

    Snaking across the landscape for hundreds of miles like the arteries of the internal combustion engine society, oil pipelines are among the most dramatic welded objects visible in the everyday world. The subject of controversy and debate, the root of many economic and technological processes, these immense pipes need to be welded together to extremely high standards. Millions of gallons of extremely heavy oil will flow through each pipeline in a given month, putting the welds that hold the innumerable sections together under great stress. With these characteristics, and with the rugged outdoor working conditions under which pipelines must be assembled far from the level, well-lighted confines of a factory floor, special pipeline welding machines are used for the welding process.
       
    Surprisingly, much of pipeline welding – unlike other welding involving large pipes – is carried out by hand rather than with orbital welding machines. Each weld is made by a team of highly skilled welders, and requires five passes, using a shielded metal arc machine with DC reverse polarity. The joint is prepared by being preheated to around 400 degrees Fahrenheit with propane torches. The shielded metal arc process, otherwise known as MMA welding or stick welding, involves using consumable electrode rods with a heavy flux coating that vaporizes during welding to produce a cloud of shielding gas around the weld point. Stick welding is especially good for outdoor operations and is used for this reason, as well as its ease and slight cost savings.

    When the weld is complete, it is inspected both visually and with x-rays to ensure that it has been made properly and will not rupture when the oil is pumped through the pipeline. The welders, in the meantime, have moved on to the next joint in the pipe, keeping up their assembly-line welding procedure.

    Special Design Features of Pipeline welding machines
       
    Since a pipeline welding machine is inevitably used in the field, rather than in a factory or workshop, it has several differences from the machines manufactured for use in these controlled environments. The first design feature that is likely to be noticed by an observer is that pipeline welding machines are equipped with a diesel engine. Typically a four-cylinder, water-cooled engine, this is necessary because there is simply nowhere to plug in the pipeline welding machine, so it must generate its own power. Placing the generator inside the machine rather than in a separate device means that there are less pieces of equipment to handle, no problems with connecting the generator to the welding machine, and less maintenance to be carried out. Fuel tanks of up to fifteen gallons are included to ensure that frequent refueling will not be necessary.
       
    Other features include a pure DC power generation, which can supply 200 amperes or more for 7/32” low-hydrogen electrodes. The machines are built with versatility in mind and can switch over to MIG and TIG welding, as well as carrying out arc gouging. Most are set up to shut down automatically when oil pressure becomes low or the water temperature of the water cooling system becomes dangerously high. These features allow the welder to work with confidence, knowing that they will not burn out their system on the demanding work that is involved in pipeline construction. Pipeline welding machines are tough, flexible, and self-contained – qualities that are necessary to handle these intensive welding jobs which are carried out in less than ideal conditions.