Pipe Purging FAQ: What Welders Need To Know
More than 50% of products made in the U.S. require welding, making these skills more in-demand than ever. Most welders understand that in order for their work to stand the test of time, the metal work piece must have a clean joint. Purging equipment is used to eliminate any oxygen in the material that could otherwise lead to corrosion. Although you can treat the metal after it’s been welded, preventing oxidation in the first place is typically the better option. However, some welders may want to know more about the purging process or whether purging equipment for welding is actually necessary. We’re answering a few of these FAQs below.
What materials need to be purged prior to welding?
Most often, welders us purging equipment on steel tubes. Stainless steel and titanium will also benefit from purging prior to welding, as will other types of corrosion-resistant materials. Purging the material before starting the welding process will keep the heated weld seam from being exposed to oxidation later on.
What are the proper time and flow parameters for purging?
Purging flow rate should depend on the volume of materials required. Ideally, the welder should have enough flow to gently force the oxygen out of the material while keeping the pressure inside the purge chamber slightly higher than the pressure outside of it. Doing this will keep oxygen from coming back in to the purged area through the weld seam while keeping the welding arc stable.
The proper time for purging can vary as well, and many welders will use calculated formulas to determine what they think works best. Typically, purging may take somewhere between two to four minutes when using purge monitors. Keep in mind that the material, volume of material, and even humidity will play a part. If you are using purge monitoring equipment, you should continue purging until the oxygen sensor shows the right value; for stainless steel, the value should be below 70 PPM, while titanium’s value should be below 50 PPM. However, purging should continue until the weld seam has cooled enough so that oxidation is no longer a factor.
Is purging actually effective?
One common method for purging is to tape up the ends of a pipe and purge its entire length. This may not be as effective as some welders think, considering it takes a lot of time, wastes purging gas, and doesn’t produce the best results. Using a real purging unit, which contains temperature resistant aluminum tape, a purging monitor, and a tungsten electrode grinder, will usually produce much more desirable results. When a unit like this is used, it can create a clean weld that has no risk of oxidation and subsequent corrosion. Using purge equipment like monitors can give you a much more exact idea of how well the process works for a given weld and can provide more accuracy.
If you want to know for certain that your weld will be clean and stand up to corrosion, purging beforehand is a must, as is purge monitoring. To find out more about this process or how our equipment can help you ensure a high-quality product, contact us today.