Air compressor question

[Morgan RedHawk]

Not sure if this is the right forum for this, but here goes.

I have this old air compressor that someone gave me (30 gal, 200 psi). The tank is rusty on the outside and sounds like it is half full of rust so I have decided it is too risky to pressurize.

I found a replacement tank online at ecompressedair.com (ASME specs, outfit looks pretty reputable, price is decent). Have any of yall ever done business with them before?

I am also wondering about the ports. From the pics all of the ports are open on the new tanks, and you have to add your valves, plugs and whatnot. Should anything be put on the threads for the stuff you are screwing into the ports? Loctite or anti-seize or anything? I was just going to use rated valves from Northern Tool and steel plugs from the hardware store to stop up the ports I am not going to use.

I'm also wondering about pressure. The tank I'm looking at says 200 psi and the compressor that is donating the pump and motor has a tag that says max working pressure is 200 psi. Max working pressure and max pressure is the same thing, yeah?

Is there anything I'm overlooking or should be aware of?

Thanks for yall's input, and sorry if this is in the wrong forum.

Morgan

PS I am also open to suggestions of things I could do with the old horizontal tank besides scrap it. I already have a grill, though.

 

[gotogojo]

air tank

take the tank down to your local scrap dealer and watch how fast he will find the the rust and dirt in side. they are hard to get a head of.gotogojo

 

[Terrywerm]

Please pardon me for writing this at a basic level. It may be a good way for those who know little about compressors to learn a bit about them.

First, there are some basic fittings you should have, if your old compressor did not have them:
1. Pressure control - This switch is pressure controlled and it starts and stops the compressor motor. The type with the unloader valve built in are preferred.
2. Pressure gauge - allows you to see how much pressure you have in the tank.
3. Pressure relief valve - This safety device will dump excess air if the pressure rises above a certain preset point.
4. Outlet valve - This is the valve where you will draw air from the tank.
5. Condensate drain - Valve at the bottom of the tank where you can drain out any condensed water that accumulates in the tank.
6. Inlet Check Valve - This check valve is where air from the compressor enters the tank. The valve is designed to allow air to enter, but not to escape.

All fittings should use some sort of thread sealant. There are several kinds available, with Teflon thread sealing tape being the easiest to use.

As for working pressure, you could safely run your system at 175 PSI, but that would consume excess energy. There are two basic types of reciprocating compressors, and they generally fit into two categories, each with its own typical system pressure:
1. Single stage - This is the most common for home use and light industrial systems. The compressor will typically be one or two cylinders, and in some cases three, with all cylinders being the same size. These systems typically run between 90 and 125 PSI. They are more than adequate for home shop use.
2. Two stage - Multicylinder compressor, many times they are three cylinder, with one cylinder being smaller in diameter than the other two. The two large cylinders compress the air up to about 100 PSI, while the smaller cylinder brings the pressure up to 175 PSI (or whatever the desired set point is). These systems are typically used in large installations with long pipe runs, which translates into pressure drop when in use. They are significantly more expensive to purchase, operate and maintain. The higher pressures require greater horsepower and greater energy consumption also.

There are also other types of compressors, such as pancake and rotary screw, but they are generally outside the realm of what we are talking about here. There are also constant run systems where the compressor runs constantly, but the governor unloads the compressor when system pressure is reached. They are usually used only in high volume industrial systems.

 

[Morgan RedHawk]

Thank you for the info, especially about the pressures. I was under the impression this compressor worked at a higher pressure than the garden variety home shop compressors. Given that it works at the same pressures as most other single stage, dual cylinder, reciprocating compressors, and that I will have to replace the check valve, drain, and other hardware on the tank(because everything is rusted so good....liquid wrench, kroil, break free, a cheater pipe, copious amounts of cursing, and even making the right face made no headway in getting them unstuck), combined with the cost of a replacement tank and shipping puts the cost only a few dollars less than just buying a new compressor.

I am just going to replace it. I'm sure I can find some use for a 220v 2 hp single phase motor..

 

[Terrywerm]

You are most welcome!

After submitting the info, I got to thinking that you might be better off just purchasing a new compressor, but did not come back to mention it.

If the old compressor only had a 2 HP motor on it, it was probably single stage, and running about 120 PSI and not much more. Takes too much power to get the higher pressures.

Good luck in your hunt for a new compressor! I recently bought a new, very quiet one from California Air Tools just for in my basement shop, and I love it. I still have my big, noisy, 6HP unit for out in the garage, but don't need anything like that for the shop downstairs.