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Thread: Coating Inside of air tank
10-18-2006, 04:30 PM #1
My friend and Ijust came across a Quincy 325 10 for sale on Craig’s list for 300 bucks. After hearing some of the thing you guys say about those compressors i figured it would hard to go wrong at 300 bucks. Well, so far we haven’t hard any huge issues, just a few small things.
I have tore most of the compressor apart, we are planning on doing a full rebuild. the only issues I have noticed is one bolt holding the exhaust valve assembly together snapped off in the lower part, I found that to be an odd failure.
Also there was a good amount of water in the tank, i would guess between a gallon and two. I drained it, and have left the tank open now for a few days hoping it would sort of dry out. Does anyone recommend a coating i can dump in there, or spray or something?
Any hints from someone that has rebuilt a 325 before?
Does Quincy have a rebuild manual with things like torque specs available at all?
Thanks for your time and help.
10-18-2006, 05:57 PM #2
I haven't rebuilt one of these and I can't answer your other questions but you can probably use one of the products made for sealing gas tanks against water.
10-18-2006, 06:04 PM #3
With all due respect, I strongly urge you to be ultra-cautious with regard to air compressor tanks. Like Boiler Safety Codes, the Safety Codes for air tanks are "written in blood", meaning that people get killed or injured if the rules are not observed.
Check the thread about the "rivetted air tank" for more info.
Even a small compressor tank can inflict injury to the eardrums if it lets go.
10-18-2006, 06:11 PM #4
Im aware of the dangers involved. It sounds stupid, but if i were to buy a brand new tank it would triple or better the budget for this project, and judging by how many people run older air tanks with no issues, its not a big concern for me.
I do however want to make my tank as safe as i can from this point forward, which is why i ask about various rust eaters and sealers.
I apreciate your concern.
10-18-2006, 06:32 PM #5
I expect smarter people than me will chime in and tell you to not take this lightly.
Tanks can be tested, I would think. You have to have a scuba tank tested.
I think they use fiber optics to look inside, and then pressure test to way more psi than the tank will ever see.
I have an old tank that scares me, and it's soon to become something other than a pressure vessel.
10-18-2006, 06:45 PM #6
If pressed hard, most manufacturers will mention 20 to 25 years average service life on a tank. Remember, the tank starts rusting the minute it is welded shut - with or without daily draining.
Hydrotesting is the only way to be certain it's safe. Companies that test and certify fire extinguishers may be able to do this for you.
10-18-2006, 07:24 PM #7
You might be able to get the bottle tested at a supplier of diving equipment. Here in the UK, I have a divers bottle with a din fitting so it has to be tested every five years, two years for bottles with A-clamps. my bottle was bought and is topped up with air at a diving equipment centre. My bottle contains air compressed to 200 - 230 bar though which isn't so far from 3000psi - a lot higher than the average workshop air compressor and tank.
10-18-2006, 07:50 PM #8
Somewhere on PM, Forrest Addy posted a thread about homebrew hydrotesting by filling the tank with water and then finishing the job with a modified grease gun.
10-18-2006, 08:11 PM #9
compresser tanks fail at the point where the feet are welded. You get done for the day and you hear an anoying hiss. When you go to investigate you will find a pin hole at one of the feet. At this time the tank has done all it will do. John
10-18-2006, 08:37 PM #10
Coatings on steel intended to retard corrosion often achieve the opposite. The phenomena is referred to as an oxygen concentration cell.
10-18-2006, 08:53 PM #11
Jared do u have a power washer? if so u can use it to hydro the tank but turn it down to 400 psi
and plumb it it to the tank with a bleader valve so u can get all the air out test it with all water no air
air will make a bad air tank ruputure like a bomb
ps also the welding supply houses here hydro their tanks under water for saftey
10-18-2006, 08:57 PM #12
Whollymacros! Please elaborate. I have often seen rust prevention attempts only invite dissaster. My attack on rust prevention for my air reciever is to not drain it often. I drain it every couple of months. My theory is rust happens at the line where air and water are present. I allow this line to constantly change by allowing it to creep at a constant rate. I then drain it and start the process again. So far, so good. If I ever spring a leak, I will buy a new recievr. John
10-18-2006, 09:34 PM #13
We hydratested our tank using a 12V emergency air pump that went up to 225psi. Just fill the tank with water and attach a standard tire-valve fitting on it. Clip on the air pump (ours had the little lock that kept it on) and turn it on. Pressure builds fast but will also cause the little POS air pump to bog down. It did go to 200psi before we stopped it and let the tank set for a few minutes. Dumped the water afterwards and hooked everything up. Set the cut-off at 125psi. Works great.
10-18-2006, 09:45 PM #14
I think you would be better off forgetting about sealing the inside of the tank. Unless you get all of the rust out, it will continue to rust, even though coated since you will, in effect, only be sealing the rust in.
Someone above mentioned an oxygen concentration cell. I never heard that before but it sounds like a good term.
10-18-2006, 10:01 PM #15
I have put together several air compressor outfits using recycled freon or propane tanks for receivers, and I have never been really comfortable with just a bare steel interior. My method of treating them was to wash them out thoroughly with hot water and detergent, then with phosphoric acid, then after baking the tank dry between 2 portable kerosene heaters, I would let it cool and then fill with about a gallon of Rust Oleum red primer. Slosh it around well, drain and then bake between the heaters again until fumes are no longer seen from the outlets. The tank should be set with the drain opening point straight down and a can underneath to catch the drips, of which there will be plenty of. There may be better products available for this but Rust Oleum has worked well for me, and has kept one tank free from rust for over 15 years.
10-19-2006, 10:08 AM #16
Necessity being the mother of invention, this worked for me to remove corrosion in a tank.
Quick tale; Did a project in a to-remain-unnamed all island state, a long way from Rhode Island, for unnamed entity.
Isolated job site, two diesel gensets, one 500 gallon fuel tank, custom spec.
Fuel tank arrived late from non-island state at a dock, 2 month delivery! 1/2 mile across a bay, job site accessable only by boat or helicopter.
Rolled tank off dock, pulled across bay with boat. Sloshing and heavy upon arrival, glad it wasn't ten miles. Loose plugs, salt water on new steel, dope slap! Propped up and drained, couple of days to solution, alarming corrosion.
Cobbled up a frame, V shaped, rocking bottom. Couple of two wheel crotches, small pneumatic tires, (used, mini bike), fifth and sixth wheels against end bells. Chain drive with electric gearmotor off generator, abrasive mixture of bottled water, sand and gravel, yeah, found abrasive onsite. elevated one end, then the other to scour end bells. Caution; 500 gal tank w/ some water and gravel is heavy, duh.
Got it it all shiney inside, more water and TSP, 3 times, to scour out all abrasives. Taped rag on conduit to check, wiping in juncture between cylinder and bell ends until rag came out clean. One week to 'new' tank, no doubt cleaner than original.
More bottled water and small amount of water soluble oil, more spinning, orient to drain and set blower to one outlet, opposite outlet lower, ran all day. Worked well for light corrosion but I'll bet more spinning would work on heavy corrosion before sealing inside, leave out water soluble oil step.
Oh yeah, for you greenies, formed basin under, lined w/ plastic to catch water/oil, let basin evaporate under rain tarp, (rain every day), rolled up plastic and hauled away.
Left 3 spare fuel filter paks, 2 more than spec of one. A check years later, still running on original. Radio monitoring to a distant, very tall, skinny building with slanted windows all the way around the top.
Never put salt water a new fuel tank Bob
10-19-2006, 01:50 PM #17
My company mainly deals with Quincy compressors, along with other lines. To stay in laymens terms, there will pretty much always be water accumulating inside of the air receiver because of the humidity of the air being compressed along with the air itself. These tanks are considered "wet tanks", and are setup underneath and inline with the compressor before an air dryer. If you drained the tank and found water, did you notice any runt colored water come from the inside of the tank? An 80 to 120 gallon tank would only run you a few hundred dollars, so if you are really worried, and if you do find rust colored water from inside the tank, i would recommend replaceing the receiver, which is not as big of a job as you would expect. You can find your local quincy distributor at www.quincycompressor.com, or just go to any tank manufacturer and give them the specs for the tank. I agree with the other guys, an internally rusted tank can be VERY dangerous, because you cannot see the damage until it actually bursts through. Hope this helps. Good luck.
10-19-2006, 08:42 PM #18
See if you can find someone with an Ultrasound tester. Recertifing most old boilers requirers this be done. Most boiler shops have a very basic one now. Also boat surveyer who deal in steel hulls. Federal RR Inspectors require that you do a hydro and and hammer test under pressue locomotive tanks once a year.
10-19-2006, 10:25 PM #19
I just ordered some parts from the company listed below. My compressor is a Kellogg 325 TV. This is an older unit.
They faxed me a parts diagram and a spec. sheet on the above compressor.
Air Compressor Equipment Inc.
P O Box 3961
6701-B Ward Blvd.
Wilson, NC. 27895
10-19-2006, 10:26 PM #20