air compressor shut off

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mike33

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Location
Irvine, CA
I recently had an air compressor overheat and it now has to be replaced. I am looking for safety shut-off options for the new compressor. I found that some higher end compressors have thermal protection but I wonder if by the time it shuts itself off there may be damage done. In the case of an undiscovered hose burst, has anyone seen anything to keep the compressor from running for hours?

How about some kind of timed outlet that will keep it within it's duty cycle?
 
I recently had an air compressor overheat and it now has to be replaced. I am looking for safety shut-off options for the new compressor. I found that some higher end compressors have thermal protection but I wonder if by the time it shuts itself off there may be damage done. In the case of an undiscovered hose burst, has anyone seen anything to keep the compressor from running for hours?

How about some kind of timed outlet that will keep it within it's duty cycle?

This usually happens when the delivery capacity - usually expressed in scfm - is exceeded. Simple, small compressors are built around high/low pressure controls with a storage tank.

Operating within it's rating, when the pressure in the system/tank drops below the setting the compressor turns on and start running at a fairly low loading level, say 60% or less. As the pressure increases, so is the load and by the time it reaches the high pressure cutoff, the loading can be as high as 130% or higher. Since the compressor is sized to cycle and therefore allow for the motor to cool down the average loading will remain within the thermal limits of the motor. If the compressor is operated above its rating, the overloading will be sustained and the motor will eventually fail.

Unfortunately the overload often over-sized when the compressor start shutting off and it is re-sized to the current reading at the high pressure cutoff. The resulting eventual thermal failure of the motor is the inevitable result. If your smaller motors would have built-in Klixons or larger medium voltage motors would employ CT's and RTD's the motor can be appropriately protected to their true thermal capability. Otherwise make sure that a good thermal overload element is sized to the motor nameplate current.
 

mike33

Member
Location
Irvine, CA
It's in an indoor home basketball court. You can't hear it unless your in the court. It was designed to remain on because it runs a retractable basketball hoop and if someone is ready to play, they won't have to wait for it to fill up.
 

copper chopper

Senior Member
Location
wisconsin
ok heres 1 idea, there must be times that this facility is open. so when its closed you have a solinoid on the air line that is run from a 24 hour timer and is only on during normal buisness hours and off when closed. This way when no one is there and something happens the air cant leave the tank causing the compressor to keep running. or even do the same but 30 minutes on and 30 off all day long. just an idea
 

hurk27

Senior Member
Most home or Small air compressors are not designed to have the power removed from them other then the switch on the compressor, this is because this switch is also the pressure switch and has a release valve that releases the head pressure when you shut it off or it shuts off on pressure, its the P'ssss you hear each time it shuts off, if you just unplug it or was to design a timer to turn it off, the next time you start it it will try to start under a high head pressure and can lock up, most of these low cost air compressors are made very cheap, while I would think the would have a thermo cut out as most of the ones I have seen did, I'm not too surprised if it didn't have one, the only thing I can say is if the piping and controls don't leak any air then shutting it off at night should not be a problem as it should hold the pressure, other wise fix the leaks so it can be shut off and hold the pressure, also as an added measure, put a ball valve on the output of the tank, let them shut this ball valve off when not in use, at least that way it cant leak down or any hose bursting would not let it run down, put the ball valve right at the tank port.
 

mike33

Member
Location
Irvine, CA
I went back with a "loaner" air compressor from my distributor to test the noise level and CFM. I found that the air gear motor was seized up.

Does it have a storage tank and does it cycle on/off as I described it in my other reply?

Yes. And since the motor wasn't spinning, the air from the tank just slowly passed through and the pump kept pumping and the air compressor is toast.

I cleaned/lubed up the motor and got it spinning again but I think the bearing is shot. Before I spend any more time on it I am considering changing the air motor to an electric motor. I don't know yet how to find an electric equivalent. The existing is a Gast 4AM-RV-GR25 1.25HP 15:1 Ratio

The new motor needs to be reversible. IMG_4022.jpg IMG_4025.jpg
 

hurk27

Senior Member
I went back with a "loaner" air compressor from my distributor to test the noise level and CFM. I found that the air gear motor was seized up.



Yes. And since the motor wasn't spinning, the air from the tank just slowly passed through and the pump kept pumping and the air compressor is toast.

I cleaned/lubed up the motor and got it spinning again but I think the bearing is shot. Before I spend any more time on it I am considering changing the air motor to an electric motor. I don't know yet how to find an electric equivalent. The existing is a Gast 4AM-RV-GR25 1.25HP 15:1 Ratio

The new motor needs to be reversible. View attachment 8358 View attachment 8359

That is an vane type air motor with a planetary gear reduction gear box, most likely designed for the compact space and the fact that from a safety stand point of stopping if something were to hang up in the rack and pinion or the mechanical moving parts of the hoop system, the problem with going with an electric equivalent will be providing the same kind of safety in the forum of a slip clutch or shear pin and have it all fit in the same location, an electric gear motor of the same hp will be much larger, this air system should have an oiler to keep this air motor lubricated, running some 10 weight air oil through the air motor should free it up and the planetary gears should take a 30 weight oil but check on the gear box, there should be an oiler/drier in the air lines just before the motor.

Might contact the manufacture of the equipment to see if they have an electric motor option that would maintain the safety aspect of the system, this is why it can be dangerous to modify equipment like this as it could get someone hurt if not done correctly and without the manufactures blessings.

Most retractable hoops are done with wench's and cable, but they to are designed to stop anytime there is a restriction on movement otherwise they could go till the cable failed or if someone was caught in the movement could have a limb crushed.

Just something to think about.
 

mike33

Member
Location
Irvine, CA
Yeah I really don't know why this motor froze up. I have a lubricator for each flow direction installed right above it. The gear box oil is full and looks good. Safety is a concern. Along with noise level and reliability. A person would have to be on a ladder to be in the path of any moving parts and there are limit switches at each end of the rack. A far as I know this is a custom one off installation.

I have no problem fixing the motor again (this one is only a few months old). There were no lubricators on the last motor. But if I can change it to electric then I wouldn't need such a large compressor. I could just install a small one for the actuators for the doors and hoop pivot.
 

hurk27

Senior Member
After looking on the support tab and looking at the lubricated air motor PDF I see that this is a standard gear reduction unit with just off set gears, the round shape of the gear box led me to believe it was a planetary gear reducer, but it really doesn't matter, it does list that the two oilers should have a 10 weight air oil in them, these I believe are the two box's in the air lines just above the air motor, if they are allowed to run dry the vanes will prematurely wear as will the seals and bearings.

The cost of trying to re-engineering an electric motor to be put in place of this air motor will most likely cost more then buying a good commercial grade air compressor, like I said before placing a ball valve in the output of the tank and keep the compressor always turned on would be the best way to have the air always available and avoid it running all the time if a hose was to fail, then teach them to turn off the valve when not in use, also make sure there is a good quality water trap/drier after the compressor as well as an auto water drain on the tank to remove any moisture from getting to the air motor as water can cause rust in the air motor even with the air oilers.

Just like a car they have to maintain this system or they will always have problems making sure the oilers are kept full of oil and once every 6 months the gear box needs to be checked, I don't care for the fittings on the oilers as as these worm drive type clamps can fail, I would rather see the compression type fittings they used on the air motor its self, you could also find hydraulic hoses to replace these hoses with as they will last much longer especially if the hoses are moved with the rack, sure its an over kill but it would increase the longevity of the hoses.

I have a house that the owner of one of the company's I do work for had a all indoors full size basket ball court built in but they went with the wench cable method of retracting the hoops they are only retracted when they use the court as a volley ball court, the cable wench system has never given them any trouble.
 

mike33

Member
Location
Irvine, CA
image.jpg Thanks for the pointers. I replaced the air motor and installed what seems to be a high quality compressor. It is soooo quiet and has an auto drain on tank & filter & dryer. Come to find out the lubricators supplied with the reversible motor are not bi-directional. So I will replace them with a different model.

Now I will adjust the programmed switches to lock out use with respect the duty cycle. If the head pressure at start up becomes a problem I'm told I can install a separate electrically controlled valve.
 

hurk27

Senior Member
View attachment 8463 Thanks for the pointers. I replaced the air motor and installed what seems to be a high quality compressor. It is soooo quiet and has an auto drain on tank & filter & dryer. Come to find out the lubricators supplied with the reversible motor are not bi-directional. So I will replace them with a different model.

Now I will adjust the programmed switches to lock out use with respect the duty cycle. If the head pressure at start up becomes a problem I'm told I can install a separate electrically controlled valve.

Since this is in the attic, why not install a solenoid air valve on the output of the tank so when they are not using the air they can flip a switch or timer (so it can't be left on) and shut of any air supply from the tank and a busted air line will never be a problem again.
 
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