Saturday, August 29, 2015

13 Most Common Pipe Welding Mistakes and Best Preventions (Part 2)

A tight grasp of most common mistakes in pipe welding process and how to avoid them will benefit tremendously your process of new welder training, raising quality and productivity and improving safety.

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7. Think welding power sources cause porosity

Some welders blame welding power sources for porosity in welding. Indeed, they are not the culprit of this problem. If welders track back their steps from the point that porosity began, they will often find that this problem began when a wire spool was changed, a new gas cylinder was used (loose connections, wrong gas used), when someone failed to prepare properly the materials (oxides appears in the weld), or if the material suffered contamination from somewhere else along the line. Most often, the problem results from an interruption, or trouble with the gas flow. Looking back their steps, welders will often realize the variable causing the porosity.

 8. Use wrong type or size of drive roll

While flux cored wires should be employed with the knurled drive roll, a standard V drive roll should be used for solid wires. Critically, welders remember to change those out when changing types of wires in their machines. Welders that wrongly use the standard V drive roll with the flux cored wire will often notice this wire slipping, crank down on the tension of drive roll to hold it in place, thereby crushing the cored wire. When incorrectly using the knurled drive roll with solid wire, welders will notice the roll chip off the outer coating on the wire, and that induce plugging up the liner. Then welders tend to crank on the tension; that just worsens the problems.

If welders find themselves having to crank on the wire tension, it indicates something else wrong with the process – incorrect drive roll, incorrect drive roll size, clogging in the liner. Work the process, ensure using the right drive rolls, and they will likely find the cause of the problem.

 9. Add cleaning solvent or lubricant to the dust pad

Some shops add the dust pad (i.e. a small piece of fabric) just before the drive roll system to get rid of any final contaminants from the wire. This is fine on its own, but some shops have been seen to add cleaning solvent or lubricant to the pad to further enhance feeding or clean the wire. That turns out to have the opposite effect – those oil, indeed, contaminate the wire, and can induce weld defects. For added protection or as an alternative, welders can also add a spool cover to save the spool of wire from the airborne contaminants.

10. Use wrong nozzle size

There require different types and sizes of nozzles for different Mig processes. For example, a tapered nozzle is recommended for the regulated metal deposition process. Still, that same tapered nozzle can’t address the gas flow requirements of pulsed Mig process, and will induce inappropriate gas coverage of the weld. Seize which nozzles is suited for each process/ variable, and use accordingly.

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11. Fail to select a Mig gun rated for handling peak amperage when pulsing, and mixed gases as well

When shops specify a Mig gun for the pipe applications, they will often choose a Mig gun by the average amperage of their application. They may purchase a Mig gun of 250 amperage, and have 250 amps as the average amperage. But they are applying substantially higher amperage to that gun during the peak of pulsing cycle. Those guns aren’t designed for that peak amperage and then can burn out more quickly. 

Likewise, Mig guns are often rated for use with 100% CO2. That is fine for the applications welding with 100% CO2 though, that available amperage on that gun reduces once the mixed gas common in pipe welding applications is applied.

Many shops find for low amperage guns as they are lighter and less costly, but that isn’t good in the long run. They should select the Mig gun rated for dealing with peak amperage when pulsing, and mixed gases as well.

12. Jump into mechanized/ automated processes without seizing why

One common mistake is the desire to apply mechanized or highly automated robotic process without doing the homework. The automated welding processes can just as effective as upstream and downstream processes in a shop. The automated cell isn’t helpful when sitting idle because upstream processes are still slow, or when creating new bottlenecks downstream.

There are 2 important things that a shop must do first – Seize the issue they are trying to handle through automation, and them make everything else in the operation simple to make sure of the appropriate workflow as well as optimal efficiency at each station. 

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13. Rely on smaller, less expensive machines

There are shops that use 250-amp shop welders and believe they will give the needed power and performance to carry out any pipe welding applications. They may be right, in some cases.

Still, those smaller, less costly machines would feature lower duty cycles, fewer capabilities. If your shop takes pipe fabrication seriously, and desires to maintain high levels of productivity, operating at the higher duty cycles will guarantee consistent use. It’s far from similar between 250 amperage at 20% duty cycles (2 mins on out of a 10-min cycle) and 250 amperage at 100% duty cycle (10 mins of continuous welding in a 10-min cycle).


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