FAQs Numbers 1 and 2 for Pipe Welding
As always, our first and second FAQs have to do with (pipe) welding safety: How do I select a welding helmet? How do I protect my eyes? we answered in our TIG Welding FAQs post, and more about welding safety in last week’s post.
About Pipe Welding
Now we know a lot of welders can be very creative when it comes to purging the inside of a pipe…. We’ve heard of everything from cardboard to (believe it or not) bread being used to stuff the end of a pipe…. But if you’re serious about pipe welding and creating a effective back purge for the ultimate weld, check out this video overview, and the list of various accessories below.
Purging the inside of a pipe can be an expensive process, costing time and gas. Making oxygen monitors extremely useful—they let the operator know when the oxygen content inside the pipe has reached the exact specification. Also, as the technology has advanced, even lower cost oxygen monitors (like the Pro OX-100) have data logging capabilities, documenting exactly what the oxygen content was at the time of welding.
A great product for hobbyists, small shops, and occasional field work. Purge plugs for pipe welding are low cost and extremely effective. Designed with a flow-thru center, run the argon line through the plug on one end of the pipe, and leave the flow-thru center of the opposite plug open. This is a very easy and effective way to purge a length of pipe; but, although the pipe plugs themselves are inexpensive, the entire length of pipe needs to be purged—so the cost of gas could add up quickly. While great for short or small diameter pipe sections, these are not an economical solution for purging a 30’ section of 8” pipe.
Purge baffles for pipe welding are extremely durable and very effective. These double-lip high temp silicon rubber baffles create a tight seal inside the pipe and have specially designed inlet/outlet fittings and an engineered diffuser to ensure proper purging of the weld area between the two baffles. With a modular design, and a variety of connecting arms, these baffle systems can be configured for different pipe diameters and schedules, and they can be pulled around 90’s, Tees, and Elbows. The high temp silicon baffles are incredibly durable, but they are sized specifically for exact pipe diameters (a different baffle size would be needed for 8” Schedule 10 and 8” Schedule 80”). Also, because of the tight fit, these baffles can’t be pulled through sections of pipe where the pipe diameter reduces—for those applications we recommend inflatable purge bladders.
Inflatable Purge Bladders & Dams
While these are a very simple concept that has been around for a long time, many improvements have been made—both to price and design. These inflatable bladders and dams for pipe welding inflate to seal the interior of the pipe, and in the case of the double bag systems, they flood the interior weld zone with purge gas. These are effective and extremely versatile, but can get expensive, and because it’s a balloon being inflated near welding, the service life can be limited. It is worth noting that the newer design elements of the I-Purge and I-Purge X have addressed some of the limitations of previous models, and are considerably more cost effective.
Water Soluble Purge Paper & Film
In applications where the pipe to be welded will be completely sealed off, water soluble purge paper and film is essential. A purge dam can be constructed, and after the welding is completed, the pipe can be flushed with water to completely remove all traces of the paper and the adhesive. The set up can be a bit time consuming, and the paper/tape or the film/adhesive can be expensive, but these products are the only solution for these types of applications.
When possible, the best possible solution is to weld pipe inside of a completely purged chamber where the shield gas coverage is ideal. Although these chambers can be custom made to many different sizes and styles, they start at about $2,300 and require quite a bit of argon to operate. Although this cost usually pales in comparison to the cost of a bad weld on Titanium. Of course depending on the length of pipe you’re welding, this may not be practical! but you’ll get the ultimate weld!