Intern 5.0: Tank to pump supply line/Stitch welding (6/6-6/10)

A truck came in with complaints of a leak somewhere in the pump housing. We found the leak on the threads of the tank to pump pipe line at the check valve. To remove the section of pipe I unbolted the a flange that housed the tank to pump butterfly valve and on the tank side I had to loosen the clamps on the rubber boot that joins the tank to the pipe. After I got it out of the truck I managed to get the pipe to off of the check valve to find the threads had a decent size crack in them due to rust build up in the pipe. We then cut off the bad threads and cleaned up the pipe and were able to weld a new threaded end onto the pipe so that we would keep the pipe the same length needed. My co-worker informed me that since we were welding pipe we would have to use a stitch weld method. A stitch weld on a pipe requires you to weld uphill in small sections and allowing the metal to cool slightly between welds so that the material does not overheat compromise the integrity of the pipe. The purpose of welding uphill is that it actually has deeper weld penetration and is much stronger than welding downhill. But caution must be taken to not overheat the pipe so that your puddle runs back downhill. So welding in small sections allowing it to cool in between for a moment prevents defective welds. After this is complete the weld must be check. we cap off both ends of the pipe and attach a regulator with shop air to charge the pipe with approximately 20-30psi shop air check the weld with soapy water. Caution must be taken to not overcharge the pipe, because charging a 4' section of 4" pipe with any more than 30psi can be extremely dangerous. ALWAYS use a regulator and make sure that both caps are SECURE.