Compressing ambient air vs cooled room air?

[BackwoodsGA]

Got my compressor in the shop and wired up over the weekend. My shop is 16X24 and is heated and cooled. I live in the country so should have low CO levels. My decision is whether I will draw the air from inside of my shop where CO levels may be alittle higher and humidity will be lower of draw from outside and deal with the 90 degree/90 percent humidity S GA air in the summer and the increased moister to remove.

 

[rcontrera]

Unless you have a car running or something burning in the shop, I sure don't know why the CO levels would be any higher. Air conditioning is GREAT for your compressor. Drier air and a cooler running system... just better all around.

 

[k ellis]

Agreed. As far as the compression itself it wont make much difference since the tanks heat up anyway during the fill. But if your talking equipment wise all equipment always works better in climate control. The thing I would be concerned over is if something does go wrong such as seizing up it could cause alot of smoke inside the shop which since its rubber belts could become toxic!

 

[aHeavyD]

The thing I would be concerned over is if something does go wrong such as seizing up it could cause alot of smoke inside the shop which since its rubber belts could become toxic!

I really wouldn't worry about the rubber belts. If it's seized up it's not pumping air anyway.
I have my air inlet out side the compressor in the room. I also have a fan blowing across the top of the compressor. It really keeps the heat down around the compressor.
it looks like this and they move a lot of air Shop Lasko 12.6" 3-Speed High Velocity Fan at Lowes.com=

 

[Peter_C]

A CO meter installed inline and continuously monitoring it would allow you to know if it is pumping CO for any reason. Having gotten bad air tainted with CO (Failed compressor internally), I became a believer in CO meters for my own protection.

 

[NAM001]

I dont htink you should have a problem pumping inside air. Although humidity is part of the compressor cooling. (removing internal cylendar heat) it should not be a problem as most compressors can function pumping relativily very low humidity air 10% or better. If i had your set up i would pump cool air and use a fan to increase air flow across the cylendar fins. Cooler air should shorten fill time a bit. your first astage should love the shop air. second stage probably not so much but the 3rd and 4th probably little if any difference. Given that you might see some extended life in the desicant. You should definately see a lot less discharge from the moisture seperator's.

 

[iain/hsm]

CO, Carbon monoxide is hardly the issue inside a building but CO2 carbon dioxide is, especially in your 16x 24 foot unit IMHO.

Inside a busy dive shop internal shop air can have up to double the average ambient air levels of background C02 at levels exceeding 1000ppm just by the number of folk in the room while the compressor is running.

In the country I would expect your outside CO2 level to be around the 250 to 350ppm mark as an outside ambient background total.

For breathing air 500ppm is the maximum allowable. At least it is in my neck of the woods therefore the air intake should IMHO be outside in a adequately large diameter intake hose and air intake particulate filter that is capable of 4 times flow to avoid back pressure.

Regarding cooling this is pretty much dependent on the size of your compressor the required working pressure divided by the piston diameters and the piston stroke by the number of stages.

Calculated against this is the ambient air inlet temperature, and compression ratio with the number of compression stages together with the approach temperature and interstage cooling efficiency.

The drier the intake air the hotter the gas due to the wet compressive stages condensing water vapour to water condensate acting as a heat carry over. In experimental compressors a small continuous water "spray" into the 1st stage air intake can half the 1st stage head temperature provided the water doesn't hydraulic the head and the plant has to be designed to condense downstream of the head valves to avoid hydraulicing. Water also aids lubrication reduces friction in the pistons and wear.

Additional fan cooling always helps.

The trick for long chemical filter life is to reduce the gas temperature from the compressor prior to the separator with an mechanical aftercooler even a tube within a tube type heat exchanger or chiller and use a good final stage water separator.

This coupled with a high back pressure regulator setting and a non return valve before the chemical tower will give progressively better filtration and longer life than any pre compression air conditioning.

An proper active molecular sieve can also achieve 30 % more filtration alone than the common low grade industrial sieves typically used in throw away cartridges. Iain Middlebrook

 

[NAM001]

here is an atricle to read. a great laymans terms explanation of compressorsNeptuno's World Articles - Understanding SCUBA Compressors and Filtration