Have you ever just watched a welder work? Not too closely, of course. The arc they draw to weld with is more than bright enough to blind a person. Sitting there and watching an accomplished welder work in between arcs or while wearing some heavy-duty eye protection is fascinating. It’s a curious blend of brute force, precision, and artistry. Of course, before getting to the point of turning on the welding machine, there is a lot that has to happen.
Take the seemingly simple task of welding a flange onto a length of pipe for an HVAC system. Before the welder even turns on his machine, he has to make sure that the pieces are prepared correctly. Often, materials will come with a protective coating. This coating will need to be removed before the welding can even begin. There are a lot of tools that will work for that. For smaller pieces such as the flange itself, it usually makes the most sense to put it in a sandblaster. The tiny bits of sand is blown into the unit at high pressure, blasting away the paint lest it messes up the weld. Once the surface is prepared, it should be rinsed with demineralized water or some other neutral solution to ensure that sand is completely removed.
Sometimes though, your parts are too big for the shop’s sandblaster. Don’t worry; there are plenty of other options available to get the paint off and prep the edges. Depending on the pipe’s diameter in our scenario, you could take it over to the bench grinder. Put on a face shield and just let the brush take the paint off and then move over to the grinder wheel and put a bevel on the pipe. Of course, our pipe might be big enough for the bench grinder to be not really a practical option. That’s when you will probably have to break out the side grinder and either a tiger’s paw or a grinder wheel (depending on the metal’s hardness and how aggressive you are comfortable being). Find the angle you need and get to grinding. The process should only take a few minutes before you are left with a nice, bright, shiny beveled edge.
Grinding tends to throw off showers of sparks creating a fire hazard. We discussed the safety precautions to take when getting ready to do any grinding in a previous posting. Here, it is enough to say that combustible material should be removed from the area. A fire extinguisher should be present.
Once the edges of the flange and pipe are prepped, they need to be lined up. That sounds pretty simple, but it requires a high degree of care and precision. Perhaps the simplest method is to take the pipe length and run it across a workbench and hold it in place with a pipe vise. The flange then is lined up with an adjustable pipe stand. Of course, it’s also verified to be square in relation to the pipe with a framing or carpenter’s square.
To maintain the gap between the flange and the pipe, all you need to do is use a bit of weld rod between the two parts. Finally, everything is set, and the actual welding can begin. The face shield is dropped, the welding machine is turned on, and the arc is struck. At first, the welder tack welds the flange into place. This is done by quickly welding two to four evenly spaced spots together. The weld quickly cools, holding the flange to the pipe. The purpose is to keep the flange from moving if it is accidentally bumped while welding.
Now, the welder really gets to work. Depending on the method used, he might feed the welding rod manually or feed it through the welder’s actual handle. Either way, he bends close, gently working the rod around the gap, filling it in and permanently connecting the flange to the pipe. Again, depending on size, this might take one rod or several. Along the way, he may need to brush off slag or grind out an imperfection. When the process is completed, an excellent welder will have an even metal seam around the pipe, marked by evenly spaced lines that look like ripples in the metal. When done correctly, the bond is as strong as if it were all cast as one unit.
How does one acquire this skill? Next time, we’ll look at how someone can get the necessary training and certifications to become a welder for Schaus-Vorhies.