welding a hydraulic tank

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I have a 80 gallon hydraulic tank on a drilling rig that feeds 4 pumps Im upsizing one circuit from 18 gpm to 29. the hydraulic tank is precharged with 10 psi of air to help feed the pumps. I have a 3/4" port for the feed line to the pump it had a 3/4" hose for the intake. Im thinking I need to upsize the port in the tank. its .250 wall on the tank. the question is how can I weld a bung on it while it has about 20 gallons in it. i was thinking about welding the bung and then drilling with a hole saw through the middle of it. just trying to figure out how to make sure it doesnt go boom. pulling the tank out and draining it is a 40 hour job needing a crane. so I need ideas if its possible to do it in place I dont have access to the inside to put in a bulkhead fitting. thanks for any advice.Do not argue with an idiot. He will drag you down to his level and beat you with experience.
Reply:.Get a crane....  Hydraulic oil is moderately flammable when cold but you'll never get the metal clean enough for a good bond anyway (with fluid in it).if it was me, I'd pull it and install an bulkhead fitting anyway.  Maybe it needs an inspection cover added for access.
Reply:You are going to need to clean the inside of the tank after you drill the penetration in it. Hydraulic pumps and components are not very fond of metal particles.
Reply:It's a tank feeding different pumps that are not mounted directly to the tank?Make a new tank for the new ungraded pump.  Leave the old tank feeding the ones it's hooked to.Minimal down time.Dave J.Dave J.Beware of false knowledge; it is more dangerous than ignorance. ~George Bernard Shaw~ Syncro 350Invertec v250-sThermal Arc 161 and 300MM210DialarcTried being normal once, didn't take....I think it was a Tuesday.
Reply:Reminded me of the time I dumped about 100 gallons of hydraulic oil in a gravel parking lot (I had a main line break on a rolloff when I was pulling a heavy box of scrap).  It emptied the holding tank in about 5 seconds.  The plant manager was going crazy about the oil.I told him, one it keeps the dust down and two, it supposed to rain tomorrow, it will be gone.  Hydraulic oil dissipates in water......  quite nicely.Not sure if dropping the level and welding a port in the tank would cause it to explode but I'd pull it anyway or fab a replacement beforehand and switch it out.
Reply:I would like to build a new one but this thing has about 16 ports on it, internal filters, baffles, and other things on it. I know they weld on main gas lines live just trying to figure out how its done. as for the fitting I can weld it to the outside before the hole is bored so its just welded to the outside of the tankLast edited by idacal; 08-05-2013 at 10:06 PM.Do not argue with an idiot. He will drag you down to his level and beat you with experience.
Reply:Originally Posted by idacal I know they weld on main gas lines live
Reply:Originally Posted by idacalI would like to build a new one but this thing has about 16 ports on it, internal filters, baffles, and other things on it. I know they weld on main gas lines live just trying to figure out how its done. as for the fitting I can weld it to the outside before the hole is bored so its just welded to the outside of the tank
Reply:Cut about a 4" circle out of 1/4", drill holes around the outside for 5/16 bolts every 3" or so. Weld your fitting into the circle. Drill and tap corresponding holes in the tank and hole saw a center hole to fit in the fitting. Make a gasket with some silicone on both sides and your set.
Reply:I knew someone here would have a duh fix for it. thank you welderj that will work perfect.Do not argue with an idiot. He will drag you down to his level and beat you with experience.
Reply:Glad I could help. Done a few that way over the years. Just to clarify on the gasket make sure you make a gasket out of materiel you can get at the auto parts store, just silicone won't work well.
Reply:Originally Posted by welderjCut about a 4" circle out of 1/4", drill holes around the outside for 5/16 bolts every 3" or so. Weld your fitting into the circle. Drill and tap corresponding holes in the tank and hole saw a center hole to fit in the fitting. Make a gasket with some silicone on both sides and your set.
Reply:If you find the closest weldolet to the size of your out put pipe,  You can weld it on the tank and then hole saw right through the weldolet.  Ive done it more than once.  The small pieces of steel that fall in the tank will be picked up by the filter or just lay on the bottom. The hydraulic fluid will boil a little at the weld point but it dose not carry heat away real well so you do not have to worry about hardening the tank.  Mac
Reply:most of the cuttings will flow out when the bit passes through I already have dumped about 40 gallons of oil on the floor from leaks(this is a new rig to me and we are doing all the repairs from years of abuse and from a couple of years of sitting). A couple of big magnets on the base of the tank aught to trap everything else right?Do not argue with an idiot. He will drag you down to his level and beat you with experience.
Reply:tool maker I was worried about having a poof, my wifes a widow moment. when you did those was the tank full of fluid above your welding point or was it below I can fill the tank back up above the port height if needed? its a pressurized  tank very little air movement when the compressor is not running. there is over pressure relief but no fresh air intank without the rig runningLast edited by idacal; 08-06-2013 at 12:03 AM.Do not argue with an idiot. He will drag you down to his level and beat you with experience.
Reply:When you are drilling (not welding) the tank, put a strong magnet on the tank just below where you are drilling or threading. It will collect the chips for you.  It will collect the chips inside too, but this will only help if you have an access hole to remove them through, but in my experience, very few chips will be found inside of where the magnet is located. They almost all seem to accumulate on the magnet outside.CharleyMiller MM252Miller Bobcat 225NTMiller DialArc HF / DIY Cooler2 Victor O/A TorchsetsMilwaukee 8" Metal SawMilwaukee Dry Cut "Chop" Saw 5 Ton Wallace Gantry Various Grinders, Benders, etc.
Reply:Originally Posted by idacal . . . the question is how can I weld a bung on it while it has about 20 gallons in it. . . .
Reply:I have done this to a few tanks myself but some good ideas here   @ tool maker  I would never trust a hydraulic filter to pick up rubbish out of a tank as a lot of hydraulic systems are filtered on the return which meens the oil will have already passed through the full system ( not good with metal shavings in the oil) I used to do a lot of this work for JCB dealers in Scotland any welding on hydraulic tanks was done with oil in the tank open cap and go at it never had a problem (yet) as for drilling the hole I have a selection of old  speaker magnets which I slip inside my hole saws they catch about 90% of the shavings . Then a magnet tool one of the telescopic ones is put through the whole to collect as much as I can and always flush the tank with diesel afterwards always been good never a fault  so far let us know how u go
Reply:I'd purge the tank with an inert gas before and during welding, would eliminate the concern of the oil being vaporised and exploding. I've welded a few diesel tanks up and never had an issue doing it this way
Reply:Originally Posted by Stroked550I'd purge the tank with an inert gas before and during welding, would eliminate the concern of the oil being vaporised and exploding. I've welded a few diesel tanks up and never had an issue doing it this way
Reply:I filled mine with co2 before welding on it, had no troubles. Hot tap on a gas line is no different, it is just that you have air in your tank. Replace the air with inert gas and it is the same.  Only difference is that you don't have the tools that they use to actually do the tap portion of it, could make them fairly easily if you knew what they were and how they worked.
Reply:I got it welded in. I drilled it out and took the wirefeed bottle plumbed it in and let it run for a 100PSI worth then welded it over a 15 minute stretch with 1/16 +P rod had just a little flame were the oil would boil over and leak out the unwelded part of the weld outlet. a new computer to me so Im having issues with the pictures. thanks for all the advice and helpDo not argue with an idiot. He will drag you down to his level and beat you with experience.
Reply:Hydraulic tank size is primarily determined by the required cooling capacity for the horsepower of all of the pumps feeding from it.  Adding a cooler reduces the size requirement of the tank.  Have you considered adding a fan cooled oil cooler instead of enlarging the tank?
Reply:Originally Posted by idacalI got it welded in. I drilled it out. . .