We receive a lot of questions regarding welding pipe. Whether it’s about welding high-pressure pipe, Irrigation Pipe Fittings for food and beverage industries, or pipe for the oil and gas industries, there are a variety of common elements we see in pipe welding and fabrication which lead to problems. These include everything from improper shielding gas and drive rolls to choosing a MIG gun with too low of an amperage rating. As companies push to train new welders, work with new materials, increase quality and productivity, and improve safety, it is important to give attention to a few of these basic variables in the pipe welding process that can impact these efforts. In this article, we’ll take a look at 13 of the most common issues we see in pipe welding applications and how to resolve them.
1. Forgetting to grind the joint after oxyfuel or plasma cutting
Both oxyfuel and plasma cutting processes put in a layer of oxide to the cut edge. This oxide layer has to be removed just before welding, as the oxide often has a higher melting point compared to the base metal. When the arc gets hot enough to melt the oxide, it’s too hot for the base metal and can lead to burnthrough. The oxides can also remain in the weld and cause porosity, inclusions, absence of fusion as well as other defects. It is essential that welders make sure to grind the joint right down to the parent material prior to welding, along with grind the outside and inside diameters of the pipe to eliminate these oxides and other potential contaminants.
2. Cutting corners with cutting
When welders work together with materials more prone to distortion as well as the affects of higher heat input, including stainless steel and aluminum, an inadequate cut can cause poor fit-up and make unnecessary gaps. Welders then compensate by putting more filler metal (thus, heat) in to the joint to fill it. This added heat can lead to distortion and, with corrosion-resistant pipe like stainless steel, can reduce the corrosion-resistant qualities from the base metal. Additionally, it may cause insufficient penetration or excessive penetration. Poor preparation also leads to longer weld cycle times, higher consumable costs and potential repairs.
Shops currently using chop saws or band saws to slice pipe used in critical process piping applications should look into buying dedicated orbital pipe cutting equipment to guarantee cuts within mere thousandths of your inch from the specified parameters. This precision helps ensure optimum fit-up and keeps the volume of filler and also heat placed into the joint at least.
3. Forgetting to cut out and feather tacks
Tacking is critical to suit-up, and finest practices recommend that the welder reduce and feather that tack to guarantee the consistency from the final weld. Particularly in shops where a fitter prepares the Chemical Stainless Steel Pipeline then someone else welds it, it’s important that the welder knows just what is in the weld. Tacks left within the joint become consumed through the weld. When there is a defect in the tack, or if perhaps the fitter used the wrong filler metal to tack the joint, there is a risk for defects within the weld. Removing and feathering the tacks helps eliminate this potential problem.
4. Preparing a joint for MIG processes differs than with Stick welding
Training welders is really a top priority for many fab shops, and – for better or worse – many welders bring past experiences together towards the new job. These experiences can be addressed with adequate training, only one common mistake we have seen is welders with Stick experience not understanding how to properly create a joint for wire processes common in pipe fabrication applications. Welders trained traditionally in Stick and TIG welding often prepare the joint having a heavy landing area and would like to keep the gap as narrow as is possible. As pipe shops transition to easier, more productive MIG processes such as Regulated Metal Deposition (RMD™), we prefer welders take that landing area as a result of a knife’s edge and space the joint at approximately 1/8-inch. This place is wider compared to those trained in Stick and TIG processes are utilized to and can result in several problems: focusing excessive heat to the edges from the weld, too little penetration and insufficient reinforcement on the within the pipe. Shops should train their welders towards the specifics of each application and be sure they understand different weld preparation and operational techniques before they go to work.
5. More shielding gas might not be better
Some welders use a misconception that “more shielding gas is better” and definately will crank the gas wide open, mistakenly believing these are providing more protection to the weld. This procedure causes numerous problems: wasted shielding gas (resources and cost), increased and unnecessary agitation of the weld puddle, along with a convection effect that sucks oxygen to the weld and can cause porosity. Each station needs to be outfitted with a flow meter and every welder should understand how to set and adhere to the recommended flow rates.
6. Buy mixed gas – don’t depend on mixing with flow regulators
We have now seen shops that, for any stainless steel application that needs 75/25 percent argon/helium, set up a separate tank of argon as well as a separate tank of helium and after that depend on flow regulators to bleed in the proper amount of shielding gas. The reality is you actually don’t know what you’re getting in a mix using this method. Buying cylinders of High Quality Ssaw Steel Pipe from reliable sources, or buying a proper mixer, will make sure you understand exactly what you’re shielding your weld with and this you’re sticking with proper weld procedures/qualifications.
7. Welding power sources don’t cause porosity
It is far from uncommon to obtain a call from the customer who says “Hey, I’m getting porosity out of your welder.” Plainly, welding power sources don’t cause porosity. We tell welders to recount their steps back from the stage where the porosity began. Welders will frequently find that it began just when a gas cylinder was changed (loose connections, incorrect gas used), a brand new wire spool was invest, when someone didn’t prep the content properly (oxides found in the weld), or if the content was contaminated elsewhere across the line. Usually the problem is due to an interruption or downside to the gas flow. Tracing back your steps will often lead dkmfgb the variable that caused the porosity.