Question about "Best" compressor setting

Boswell

Hobby Machinist since 2010
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I just got my compressor back together today. Same old compressor (1958 2 stage Curtis but just rebuilt it with new gaskets and an overall good cleaning)) on a new tank (80 gal) with a almost new motor, new pressure switch and plumbing. The old pressure switch was set to cut out at about 150 PSI. The new switch I bought defaults to just under 180 PSI. The tank and all are rated at 200 PSI. I am curious what others think is the ideal pressure. The primary use of pressurized air is for a Fog Buster system on the mill to cool the cutter and help evacuate chips. I also use to air up tires. I have a few air tools. I don't do any painting or sand blasting. Will it last longer if set to 150 PSI? Will cycle more often or less often when set to 175PSI? Thoughts?

Thanks all
 
Curtis are very durable compressors, I owned a 2 stage Cutis for years and sold it with my old house. Lots of iron in those compressors. The standard pressure cutoff setting for 2 stage compressors is 175 PSI, but +/-5 PSI is within the normal window. Turn on pressure is around 125 PSI. As long as everything is sound, I see no reason to turn down the upper pressure shutoff. Just means that the motor will run a little longer and the compressor will cycle on/off less frequently. The air pressure requirements for the Fog Buster are pretty low. You might have the tank inspected to make sure it is sound, I think if it were to go then the difference between 150 and 175 PSI would make little difference. I currently have a Champion compressor with an Auto-Drain, opens the drain at the end of each compressor cycle. If sitting for long periods I also will purge the drain valve. I have an after-cooler which drops out a lot of the moisture into the tank. They also indicate not to rigidly mount them to the floor, they need some form of flexible feet or idolators to allow movement and absorb some of the vibration.
 
Sounds like a great set-up.

I have an older 80 gal. unit and when I had to replace the pressure switch I discussed it with my local compressor service company. Was worried about the old tank and generally wanted to make it last as long as I could so I dropped the max pressure down to 125psi. I rarely use enough air to even cycle the compressor a second time after it's full and can't think of any application where I need more pressure. It'd definitely easier on the pump and motor if you go lower.

And yes, mounted on some "feet" made out of 2x4 scraps.

Just my two cents....


Cheers,

John
 
Thanks for your thoughts mksj and John. This all started when I decided to replace the original tank, so now I have a brand new 80 tank. I also have an automatic drain valve to install and I also raised the new tank/compresor up on a 4x4 platform to give more clearance for the drain valve.
 
You also need to consider the psi of your safety relief valve
 
Safety relief valve on output tank is 200 PSI and new. There is also a relief valve between the stages. It appears original and I am not sure what it is set to. there is the number 70 stamped on the side so possibly it is 70 PSI.
 
If the tank max is 200 & the cutoff psi is 180, what is the SAFETY VALVE set at?? If I serviced your machine it would be, 150 cutoff, 25 differential, 175 safety valve. Everyone has an opinion but that's mine.
 
I'm not sure who you bought the tank from but in my town there's a local compressor service company that's super easy to ask questions. I follow their advice since they are in the business and I trust them....

John
 
Will it last longer if set to 150 PSI? Will cycle more often or less often when set to 175PSI? Thoughts?
Like many things, the harder you work it, the shorter its life is. I would put my money on a compressor lasting a lot longer, only working to 150, then being pushed to 175. The question, is how much longer, and is it significant difference in the compressors life.
 
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