Reasons for Purging
In the world of orbital welding, purging is referred to as the process of removing oxygen from the inside of tube or pipe before welding, usually by using argon shielding gas. If you try to perform a weld without purging, the oxygen present will cause discoloration and imperfections and will greatly impact the integrity of the weld. This process of oxidation is often referred to as “sugaring” on the backside of a weld. The impact of this result is very problematic in many industries, particularly the process piping industry where this can cause bacteria to grow on the inside of the welded tube or pipe while product is flowing through it. Purging also helps keep the weld from sinking in during wire-add applications by maintaining pressure on the inside of the pipe.
Standard Purging Solutions
Here at MIT, we understand the importance of purging and offer solutions for both standard and unusual purging applications. Considerably advancing from the days of using tape and an argon gas line, MIT can help you make consistent, repeatable, and affordable purges in efforts to make the best welds possible. In mechanized orbital welding, a feature of most weld heads is automatically purging the OD of the tube or pipe. While this is an important feature to have, purging the ID is just as important.
Our standard purge plug kit covers the size range of 1.5” to 4” OD tube. These purge plugs are manufactured from Duravar-Ultra High Molecular Polyethylene, a high-temperature, high-performance plastic, along with silicone rings. Each tube size uses an exhaust (or cookie) and a purge plug with a quick-connect gas line on one side and a diffuser on the other. Just connect your gas line, push the purge plug into one opening of the tube and the exhaust into the other, and you are ready to weld. The diffuser pushes the argon evenly through the entire tube, ensuring there are no pockets of oxygen remaining.
Often paired with our standard purge plug kit is the back purge. This tool comes in handy when you have a long stretch of unbroken tube and do not want to purge the entire run. Pair it with any size purge plug and use the spring-loaded end cap to only purge the final stretch before the weld. Also available is the purge tree, which is ideal for vertical manual welding. If desired, we have the ability to combine all three of these purging accessories into all-in-one hard carrying case.
We often get asked if the different colors mean anything. The primary purpose of the different colors is to differentiate between two different welder’s purge plugs. This helps build accountability and lessen confusion. If a specific size of purge plug gets lost or destroyed, we do have the ability to replace individual parts from the kit. We also have the option to customize larger or smaller OD tube with the same style purge plugs.
Unusual Purging Application Solutions
MIT is not limited to solutions for standard tube sizes. Many of our customers need to purge varying pipe sizes as well. We offer several types of purging equipment for pipe, including purge bladders and nylon expansion purge plugs. Purge bladders are used with large OD pipe or when there are elbows or tees that need to be purged. The expansion plugs are a good tool for purging smaller OD pipe. Our sales team will be able to help you find the best option for your application.
Unique applications call for unique solutions. To meet customer needs, we have fabricated aluminum purge plugs that can be used to purge short ferrules onto a run of tube. Traditional purge plugs cannot hold short ferrules, but with this design, purging them is not a problem. Other specialized solutions include purging for welding small OD tube and purging designs that avoid touching the ID of the tube.
These solutions help demonstrate the range of purging possibilities at MIT. Bring us your application, and we will find a solution. Watch the demonstration video below and contact us to learn more about purge plugs and the purging process.
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