Help with big 3 phase compressor

One thing I'd recommend is that you not bolt the compressor down. Don't install the bolts. That could put severe stress on the tank that could lead to failure. There are adjustable steel and rubber pads on the market that work out nicely, so buy a set of them. Be certain to buy a set that is adequate for the load. They come in sizes that are rated by load.

When I built my shop, I constructed a small room that is specifically for the compressor, and a built-in vacuum cleaner system. It's on the opposite side of an interior partition, where we store our RV's, so I don't have to listen to either of them run. I didn't want my compressor outside because we get a lot of rain here, and the relative humidity is always quite high. Your situation may be different. Regardless of how you achieve the end result, it's a great idea to not have your compressor in the shop with you.

My compressor is smaller than yours, only a 5 horse Quincy, with an 80 gallon tank, but is the same age. I bought it new, and have been pretty good about keeping it blown down. It has developed a minor leak around a weld, which seals itself off with rust, so the tank needs replacement. I pulled the large reducer out recently and looked inside. Not a pretty sight. I can't imagine yours will be much better. You can have it tested, but it might cost as much as a new tank to do so. A hydrostatic test may tell you that it is safe to use for the moment, but you'd still be in the dark about the thinnest point in the tank, sure to be somewhere at the bottom where the tank never dries out.

According to the tank nameplate, the

I'd hesitate to suggest to you that the tank is either safe, or unsafe, based on age alone. Could be there are reg's that dictate, but for private use they usually have little to no authority to enforce them. Your first consideration would be your own safety, and that of your family, naturally. Air tanks don't normally fail catastrophically, but they are capable of doing so. If the tank is not safe, and you reduce the pressure a little, I'm of the opinion that may delay the inevitable, but would not make much difference in the outcome should it be a catastrophic failure.

Because I'm in the same boat, I'd be interested in what you learn, and decide to do, so please post your decision.

Regards,

Harold

So these are rubber isolators or something like that? How do they prevent the compressor from moving around?

I didn't want my compressor outside

I'm planning on a lean-to over the compressor. We get plenty of rain here, but the shop doesn't have conditioned air, so it doesn't much matter if the humidity is high, the compressor will see it. My major concern is the cold temps in the winter, but I know you can get synthetic oils that help a great deal at startup.

It has developed a minor leak around a

Hmm. I've got the plugs out of both ends, and it's pretty nasty in there, I imagine that the Quincy tank is of similar build quality to the Curtis, so I guess I'll have to take my chances, and if I find it leaks, just bite the bullet and replace the tank. The cost savings on this compressor pretty much rules out doing a whole lot more than just simple R/R stuff to it. If I start spending big money, it'd make more sense to buy a smaller new compressor.

The shop sits back by the woods, at least 300 ft back from the house, and if it's behind the shop, it's likely to have to do quite a lot of damage before it got into the building.

I guess that's the dilemma then, to put it into service or not. I'm of the opinion that any leaks will be pinholes at this point, my main concern is to prevent the continuation of any rusting. Are there any coatings or treatments I can do to this tank? I know there are some for gas tanks. Seems like something similar would be of benefit.

I'll most certainly post here with conclusions.

Regards, Mark

On Sun, 04 Apr 2004 20:26:54 -0400, Mark vaguely proposed a theory ......and in reply I say!: remove ns from my header address to reply via email

If the concrete is literally going to be right onto the building, you will get very efficient vibration transmission. Can't you move the pad just a foot or so away, or even a few inches? That would make a huge difference, unless you're on rock.

I went on a guided tour not long ago.The guide got us lost. He was a non-compass mentor.........sorry ........no I'm not.

I'd bolt it down, but I'd use rubber pads between the feet and the slab. A section of tread cut out of an old tire would do. Oh, and a rubber washer on the top side where the bolt bears too. If you forget that, the vibration will just be transmitted through the bolt.

If you want to get fancy, you could invest in some anti-vibration machinery mounts. Those have a separate stud to connect to the machine from the stud that comes out of the concrete slab. But I think that would be overkill in your application.

There's always some crud in the bottom of old tanks. You could try a pressure washer to clean it out, or have it steam cleaned. It is probably Ok to ignore it, but to be safe, cleaning it will let you inspect the condition of the metal underneath for evidence of heavy pitting.

If you want to protect it, you could slosh some tank sealer around inside after it is cleaned and inspected. POR makes a tough one. But again, I think that would be overkill, and it would make it tough to visually inspect it the next time.

To be really safe, you should pressure test the tank. Fill it almost completely with water than pump it up to a pressure higher than you intend to use by some comfortable safety margin. If it doesn't leak, you're good to go.

This is called hydrotesting. Because water is incompressible, and because there will only be a small amount of compressed air in there during the test, very little energy is stored in the tank. It is very much safer than just pumping it full of air and waitng for the explosion.

Gary

I'm one of those "overkill" types. I'll look into it.

That's somewhat comforting... the there's always crud part... :)

The sloshing part would be interesting to try. The thing was so damn heavy, getting it out of my 3/4 ton truck was fun. The loader on the tractor wouldn't lift it. Kept blowing the 1500 psi relief valve on two

I don't know how I'd do that. My only other source of air is a small oilless. Wouldn't it show leakage at 125psi as well as 175psi?

Indeed!

Regards, Mark

I recently went thru this on a large Kellogg-American compressor 120 gallon tank built in 1974. The thing had been neglected for many years and I was told at one point more than 5 gallons of water were drained from it. I removed all the plugs and looked it over pretty good but was still leary of using it. Since it took me some time to rebuild the compressor itself that allowed me the time to search for another tank. I ended up finding a 120 gallon tank that was only about 10 years old and it had only been used as vaccumm storage on a large machine hence no moisture buildup in the tank. Basically I started from scratch on mounting the motor and compressor, the piping, and the fabricating of the belt and pulley enclosed guard. I ended up cutting one end off the old compressor for a guy who is building a blacksmiths forge with it. This allowed me to do a very up close inspection of the interior of the old tank. There were two areas that were pitted fairly badly, right at the very bottom of the tank and then right about the top line of where a constant stand of water in the tank had been. Since this compressor was going to be within an area of fairly high traffic there was little choice but to replace the tank. Had the compressor been in a remote area I might have went and used the original tank but with a good cleaning and also an automatic tank drain (which I installed on the new tank anyway). As far as mounting this compressor is sitting on 4x4 treated timbers which is on carpet on a wood floor. It is also a very quiet running unit with the compressor only spinning around 570 RPM. With the door closed to the back room it is very hard to hear if the thing is running or not. My advise would be to pour your pad and put down quality (P60) treated timbers and then lag down the compressor to those. I am not sure of the weight of our compressor but I had to pick it up on one end and slide it thru a 36" wide door opening, it was all the old IH wanted to lift in that manor. If I can figure out how I will post some pictures in the dropbox of the compressor on the trailer the day I moved it to the shop.

tim

You want to leave a very small air pocket, so you'll only need to inject a very small amount of air, *or more liquid*, once you seal the tank, to get up to proof pressure. You could even pump hydraulic fluid into it using your tractor's auxillary hydraulics. The caution there is *don't inject too much*, since you've got

Gary

Thanks. I'd wondered about that.

Could almost do that with a bicycle pump.

If you are worried about corrosion, ultrasonic inspection is a classic nondestructive way to measure the wall thickness of a tank. If the thickness is uniform, all is OK. If the thickess varies a lot, (typically near the waterline) that is a problem. Whether it is worth it to pay somebody to come out and inspect it is another question, not sure what it would cost.

I think that ultrasonic testing is probably the best way to measure the degree of corrosion.

The hydro test is a very good way to prove that something is safe or not, and maybe is something better suited to a home shop project than hiring an inspector with a ultrasonic tester, in that you could do it yourself without a lot of specialized equipment. It might be a little tricky to fill the tank with water and bleed all the air out, but could probably be done. Not sure what pressure I would use for a hydro test, but a little googling might give you some rule of thumb like "Hydro test at a pressure 50% higher than the highest pressure the tank would see in service". But maybe double is the correct rule of thumb.

Richard

Mark wrote:

I did a hydro test on my air compressor tank. I put a pressure gauge on it, filled it with water from a garden hose and then used a small electric pressure washer to presurize it to around 250 psi. Cobbling up the connection was fun, but it worked OK. You really want to avoid getting air in there. If the tank breaks with water in it, you get a leak. There's a lot of energy stored in compressed air which makes tank ruptures a really bad thing.

Paul

Here in NYC, any pressure vessel holding over 100psi must be hydrostatically certified every 5 years.

The mech fills the vessel with water, pressurizes to 300psi and it must hold for 30 min.

I've had 40y/o, secondhand tanks pass that test. The mech said when (rarely) they blow it's usually out the bottom, so the danger is "minimal" but I noticed he went out for the half hour.