We get lots of questions regarding welding pipe. Whether it’s about welding high-pressure pipe, Erw Steel Pipe for food and beverage industries, or pipe for the oil and gas industries, there are a number of common elements we see in pipe welding and fabrication which lead to problems. These include 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 essential to give attention to many of these basic variables in the pipe welding process that could affect these efforts. In this post, we’ll look at 13 of the most common issues we percieve in pipe welding applications and how to resolve them.
1. Forgetting to grind the joint after oxyfuel or plasma cutting
Both the oxyfuel and plasma cutting processes give a layer of oxide towards the cut edge. This oxide layer has to be removed prior to welding, as the oxide often has a higher melting point compared to the base metal. Once the arc gets hot enough to melt the oxide, it’s too hot for your base metal and can cause burnthrough. The oxides can also remain in the weld and cause porosity, inclusions, lack of fusion along with other defects. It is crucial that welders make sure to grind the joint right down to the parent material before welding, in addition to grind the in and out of diameters of the pipe to get rid of these oxides as well as other potential contaminants.
2. Cutting corners with cutting
When welders assist materials very likely to distortion as well as the affects of higher heat input, like stainless steel and aluminum, a bad cut can cause poor fit-up and create 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, is able to reduce the corrosion-resistant qualities of the base metal. It can also 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 utilized in critical process piping applications should think about buying dedicated orbital pipe cutting equipment to ensure cuts within mere thousandths of an inch in the specified parameters. This precision helps ensure optimum fit-up and keeps the amount of filler as well as heat placed into the joint at the very least.
3. Forgetting to slice out and feather tacks
Tacking is essential to fit-up, and greatest practices suggest that the welder reduce and feather that tack to be sure the consistency from the final weld. Particularly in shops when a fitter prepares the Ss400 Carbon Lsaw Steel Pipe then someone else welds it, it’s important that the welder knows precisely what is incorporated in the weld. Tacks left within the joint become consumed through the weld. If there is a defect in the tack, or if perhaps the fitter used the incorrect filler metal to tack the joint, there is a risk for defects inside the weld. Removing and feathering the tacks helps eliminate this potential problem.
4. Preparing a joint for MIG processes differs as compared to Stick welding
Training welders is actually a main concern for a lot of fab shops, and – for better or worse – many welders bring past experiences with them towards the new job. These experiences could be addressed with adequate training, but one common mistake we percieve is welders with Stick experience not discovering how to correctly make a joint for wire processes common in pipe fabrication applications. Welders trained traditionally in Stick and TIG welding often prepare the joint using a heavy landing area and wish to keep the gap as narrow as you can. As pipe shops switch over 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 than those trained in Stick and TIG processes are used to and can cause several problems: focusing excessive heat into the edges in the weld, an absence of penetration and insufficient reinforcement on the inside of 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 may not be better
Some welders possess a misconception that “more shielding gas is better” and definately will crank the gas wide open, mistakenly believing they are providing more protection for the weld. This procedure causes numerous problems: wasted shielding gas (resources and expense), increased and unnecessary agitation from the weld puddle, and a convection effect that sucks oxygen to the weld and can cause porosity. Each station should be outfitted having a flow meter and each welder should learn how to set and adhere to the recommended flow rates.
6. Buy mixed gas – don’t count on mixing with flow regulators
We have now seen shops that, for any stainless application that requires 75/25 percent argon/helium, create another tank of argon along with a separate tank of helium then depend on flow regulators to bleed inside the proper level of shielding gas. The simple truth is you actually don’t understand what you’re getting in a mix using this method. Buying cylinders of Mild Steel Black Steel Pipe from reliable sources, or investing in a proper mixer, will ensure you understand precisely what you’re shielding your weld with and that you’re adhering to proper weld procedures/qualifications.
7. Welding power sources don’t cause porosity
It is far from uncommon to acquire a call from a customer who says “Hey, I’m getting porosity from your welder.” Plainly, welding power sources don’t cause porosity. We tell welders to recount their steps back from the point where the porosity began. Welders will often discover that it began just whenever a gas cylinder was changed (loose connections, incorrect gas used), a new wire spool was put in, when someone didn’t prep the material properly (oxides contained in the weld), or if the material was contaminated elsewhere along the line. Usually the issue is due to an interruption or trouble with the gas flow. Tracing back your steps will usually lead dkmfgb the variable that caused the porosity.