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. 

Pipe line removed (Pump side of the flange) 

Sometimes, you just need 4' of leverage

Capped and ready for air

Stitch welding done by my coworker 

Regulator attached and shop air 

Hours: 40

Running Total: 362

Custom Tool Box Table (5/30-6/3)

We had a slow day at the shop and I asked if I could use some scrap aluminum to make a table for my tool box. My shop lead was fine with it so that I could get more practice with aluminum welding. After making the measurements my lead gave me some advice to set the support arms that were going to be welded on an eighth of an inch smaller than my measurement to compensate for the welder pulling the metal. Seeing as my box is too thin to tap for bolts I got to learn how to use a thread insert gun to use mounting bolts. Fun little project and got to practice aluminum welding. 



Hours: 40
Running Total: 342

Tank Removal/Valve Rebuild (5/23-5/27)

We serviced a truck this week that had a unique issue. The truck had a 750 gallon tank with a foam cell that contained 100 gallons of foam concentrate. The truck was found to be overweight by the area standards where the customer had the truck in service. They requested a new tank to be created at the factory that held 250 gallons of water less to meet the weight limit. I was able to help removed the old tank. This process included completely disconnecting the pump housing from the tank as well as fabricating a custom welded hoist to remove the tank. Cool project.





Our massive drill press with a 1 1/4" drill bit...
 


I also got the opportunity to rebuild leaking discharge valves on a truck that came in for service. To diagnose this we charged the pump with shop air and discovered a few leaks including the #2 discharge valve on the pump. Over time the ball valve in the valve housing wears down from debris in the water scoring it in addition to hard water breaking down the seals. It's a pretty easy but fun process of removing the valve to rebuild it, a very satisfying end result I might add.

Hours: 40
Running Total: 302

Poly Welding (5/16-5/20)

Couple of cool projects that week. I had the opportunity to an old aerial truck. It is a 75' ladder than extends by means of a series pulleys with steel cables all being pulled by a hydraulic motor. A section of the the ladder had some steel cable that was beginning to fray and needed to be replaced. In order to access the cable the ladder was fully extended down the length of the shop and supported by a stand at the end of ladder in case the trucks hydraulic stands failed.




We had a slow day that week and my shop lead to advantage of the time to train me to plastic weld. A lot of the trucks we service have poly plastic tanks and will require repair from time to time. As with all welding surface preparation is key, the surface must be buffed out an clean as possible. The equipment is essentially a glue gun on steroids. After the gun pre-heats a rod is inserted in the tip of the gun and with steady pressure and speed a pass is made along the two pieces of poly plastic are joined together. Pretty straight forward process.

Hours: 40
Running Total: 262

Week 6 (5/9-5/13) Pump Overhaul

Started my new job and first day found myself helping the shop lead remove and rebuild a pump out of a truck. The pump was leaking according to the operator. Upon removal of the outboard bearing cap housing we found water had made it past the seal and ruined the bearing on the discharge side. The pump relies on packing to seal water inside the pump rather than a mechanical seal. The problem was that the packing inside of the stuffing box had overheated and become a solid black mass allowing water to seep by. We replaced the stuffing box and installed new gaskets and o-rings.

The advantages to using packing vs a mechanical seal is that packing is more user friendly and are more robust against hard use. Mechanical seals a very sensitive and can be damaged very easily while installing them in addition to being more at risk to wear and tear by untrained operators.

Fire Truck! 

Pump Compartment (Half of pump removed)

Stuffing Box

Hours: 30
Running Total: 222