Harbor freight air dryer.

Here's a question I've been meaning to ask since the subject of compressor tanks exploding has come up.

Is it better to discharge all of the air from a compressor tank daily, or leave the tank full of air at the end of the day. I leave my tank full of air 24/7, however, I discharge the air pressure in the air dryer, copper lines and regulators at the end of the day.

My thought was by leaving the tank under compressed air, I wouldn't be flexing the tank walls by draining and refilling each day?

Thoughts?
 
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My thoughts are that a complete drain and pump back up in the morning is just going to add to heat buildup and thus moisture content. On my tank I have a cutoff valve right at the tank that gets shut off at the end of the days work, (All my lines are black steel) and all rubber hoses get disconnected whenever leaving the building, including over lunch. Let the fitting come off the end of a hose and it will flop and beat the shit out of anything in it’s reach.
 
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MJM said:
Here's a question I've been meaning to ask since the subject of compressor tanks exploding has come up.

Is it better to discharge all of the air from a compressor tank daily, or leave the tank full of air at the end of the day. I leave my tank full of air 24/7, however, I discharge the air pressure in the air dryer, copper lines and regulators at the end of the day.

My thought was by leaving the tank under compressed air, I wouldn't be flexing the tank walls by draining and refilling each day?

Thoughts?
Click to expand...
Your very good observation about pressurization cycles is something similar to aircraft ascent and landing and holds true for some aluminum pressure vessels but not for low-carbon steel air tanks designed with simplistic engineering. I suppose it is how comfortable you are being around bombs. Any acetylene cylinder has a rupture disk in it for fire but no welding gas cylinders do or oxygen ones. The larger sizes are somewhere north of 220 CUFT @2200psi and potentially one mile range missiles if the valves get knocked off. No one overly worries about those too much--but they have been known to take out firefighters and others in a fire.

Today--I disconnect the electrical for an air-compressor via a shut-off box--not the breakers in the panel and remove all pressurization from the tank and drain it when I go home. I leave the bottom drain valve open too for a morning blow-off. The attached is an example that a person may not think about with a dated compressor pump and modern lubricants loaded with additives.
 

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I have wondered why IR says to use their oil, this makes loud and clear.
 
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D.A.T. said:
Likely the bulk of the weight on your old service station compressor was not the tank but the industrial pump itself and a very well made 5-7.5 single phase motor loaded with copper windings and a continuous duty cycle. Many were vertical tanks of 80-120 gallons with slow speed pumps that worked well for the pneumatic operated cylinders in-ground car lifts of the day.

All prepackaged air compressors (common names) sold use commodity tanks and they are thin to keep their costs lower. For the 33 years i have been involved in such things--all have an additional 1/16" of provided metal for internal corrosion allowance. I would encourage you to find someone to either ultrasonically test it to see what remains after all these years--some are like brand new--others are tissue paper thin--seen dozens both ways. Ingersoll Rand buries it in their owner's manuals to hydrotest (pressurized water test) every year. You can disconnect everything isolate the tank and do a 30 minute hydrotest @70F to what it is rated for in pressure on the nameplate.

Leaks are that--the danger is rupture down the long way of the shell cylinder when it is too thin and on a cold morning. An 80 gallon tank at 175 psi is about 2.5 sticks of 1"x 12" Dyno-Nobel dynamite when it ruptures. Farmers used to have a hard time believing a typical small 40 gallon air tank at 100 psi was about 1 stick of dynamite at rupture and one of the Ag publications a awhile back helped get that word out. More than a few have been obliterated with ruptures in the back of their farm service trucks in cold climates especially. Unless you have insurance policy for boiler and pressure vessel casualty--you are uninsured with respect to rupture and its consequences at your home/business.

I do all that--if I lived closer and was retired, I would come over and do it for you gladly.
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nah its heavy with nothing on it at all. horizontal tank. im not sure who nearby does that kind of testing.......i should probably consider it though.
 
D.A.T. said:
Your very good observation about pressurization cycles is something similar to aircraft ascent and landing and holds true for some aluminum pressure vessels but not for low-carbon steel air tanks designed with simplistic engineering. I suppose it is how comfortable you are being around bombs. Any acetylene cylinder has a rupture disk in it for fire but no welding gas cylinders do or oxygen ones. The larger sizes are somewhere north of 220 CUFT @2200psi and potentially one mile range missiles if the valves get knocked off. No one overly worries about those too much--but they have been known to take out firefighters and others in a fire.

Today--I disconnect the electrical for an air-compressor via a shut-off box--not the breakers in the panel and remove all pressurization from the tank and drain it when I go home. I leave the bottom drain valve open too for a morning blow-off. The attached is an example that a person may not think about with a dated compressor pump and modern lubricants loaded with additives.
Click to expand...

That report was interesting, especially the consequences using the wrong type of oil in your compressor.

I don't have an electrical disconnect box between my air compressor and breaker panel. My compressor is hard wired directly to my breaker panel. Why shouldn't a breaker be used to disconnect power to the compressor?
 
MJM said:
That report was interesting, especially the consequences using the wrong type of oil in your compressor.

I don't have an electrical disconnect box between my air compressor and breaker panel. My compressor is hard wired directly to my breaker panel. Why shouldn't a breaker be used to disconnect power to the compressor?
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Breakers are not designed to be used as a switch. Doing so can cause wear that could affect the ability to protect from overload or shorting.

I have done it myself many times without any ill effect, as have many others. In one of my shops it was the only way to turn on certain lights, so I did it frequently without a problem.

IIRC, the NEC codes explicitly state that it is not an allowable use.

One of those things that are fine until they aren't.
 
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