Compressed Air Flow Rate And Air Temperature

[urbnsr]

Does air temperature affect compressed air flow rate?

This past winter, I ran my setup without any air flow errors. Maybe ran from 35 deg up to 70 deg. without this problem. Now, with temps in the 80's, I am getting errors that I didn't get before. I'm assuming moisture content isn't part of this problem as the filters don't seem to have any more to drain than a few months ago. At least at this time of the year.

I am running through quite a few 1/4" fittings and am working on eliminating as many as possible, but still wonder if it's common knowledge that air temperature might be a variable for flow rate.

TNX
Paul

[beefy]

Have you got a pressure gauge right at the inlet to the plasma cutter. As long as you have enough pressure there under any conditions (like using the biggest nozzle on a long cut) I can't see why cold air would make a difference. To test my system I put the biggest nozzle in my torch and turn the amps dial to "air flow", then see if the compressor can more than keep up with needed air flow (by monitoring the pressure AT the plasma cutter inlet). In my case the air tank pressure initially drops a bit, the compressor cuts back in, pumps up the tank air pressure, and cuts out again, repeat.

The only possible difference I could guess at is the compressed air is being cooled more after compression, and thus contracts more, but your compressor should simply compensate for that and keep pumping until the cut out pressure is reached.

Don't know how cold you are talking about but you couldn't have any moisture freezing anywhere in the lines filters could you, but then again any such restriction will show up as loss of pressure at the plasma cutter.

Keith

[urbnsr]

Hey Keith,

All is well during the winter. I have a gauge mounted right at the inlet. The pressure drops quite a bit initially (for less than a second, maybe), but pops right back to the 110psi I have the regulator set to. It did that in winter, but no 0-30 Hypertherm error until last week when we got up to 80 degrees. I think the compressor kicks in at 125psi and have a main regulator right out of the compressor set to 120PSI. Generally speaking, the compressor keeps up.

[_Ogre]

I am running through quite a few 1/4" fittings

why? you don't say much about your air distribution system. two 1/4'' fittings on the final air hose connection is all you should have

if your running all rubber hoses your problem is moisture. typically (and obviously) moisture won't show up until the warmer humid months. if your compressor runs constant with the plasma table and your running a water trap at the compressor it will trap little water as the air is very warm.

0-30 can also be a worn out swirl ring; iicrc

[urbnsr]

Well, the filter config comes from a previous setup which was plumbed down to 1/4" for whatever reason. It worked up to now and became one of those "if it isn't broken, spend time fixing things that are broke". Or something like that So, 25' from the compressor starts the first 1/4" fitting into the first water trap, then through a 1/4" "T" which is used to adjust water table level, then into a second 1/4" water trap, 1/4" oil trap, 1/4" desiccant dryer, through a 3/8" hose with 1/4" fittings to the 1/4" gauge mounted at the plasma cutter.

The filter stages can be increased to 3/8" which I am working on now. But even at 80 degrees, the first water trap had a comparable amount of water to winter's operations. And, like winter time, the second water trap doesn't have any water and no moisture noticed after this point, so I assumed moisture isn't the root cause if it plays any part.

And if all those 1/4" restrictions are too much, it did work in winter without error. Maybe it was borderline and the warmer weather pushed it passed it's limits. That's why I asked. I know colder air temperature can hold more oxygen, but I figure pressure volume is pressure volume. Or is it? Compressor can provide more than double the plasma cutters recommendations and doesn't run long to recover.

I did replace all consumables to rule out the swirl ring or anything other part. I read that, too, as electrode siding can get hung up and cause a 0-30.

PK