Have you ever had issues with re-welded steel hydraulic lines? Here’s a piece of information we learned the hard way. We have a customer that has had a problem for several years with cracking welds on 2 ½” OD supply lines. These oil lines are on a Logemann paper baler, and have several bends for positioning and mounting. Generally what happens is when they have a leak, they call for service and repair. Then someone grinds and re-welds the damage fittings as a repair. These socket welded fittings, are not always positioned straight with the pipe angle. So generally the repairs are left to just that, re-welding the busted weld without removing the fitting.

When we came into the picture, we thought we would be smarter and better that the last repair shop. So we made a layout template and proceeded to remove the entire fitting from the end of the pipe. We machine the entire old weld from both parts, and then proceeded to re-weld the fitting on the jig. We assured the customer that all was fixed correctly and they should be cured of any ongoing problems.

Well, needless to say a few months went by and the fittings started re-cracking. I found out later, after discussing the situation with several ESA members during a recent convention that I needed to leave a thermal expansion gap before re-welding the fittings onto the pipe. They told me if I didn’t leave at least a 1/16” gap, the thermal expansion would push and pull on the weld from inside the fitting, causing it to crack again and again. “And they were Right!” Now with our new found knowledge, we are able to fix socket welded pipes and be assured that it won’t be coming back. Recently, I also found a company that supplies a spacer for making sure you have the proper expansion gap, when welding these types of fittings. You can check them out at www.galgage.com.