Compressor Temperatures

[Scubadoo72]

Hey all, looks like a great board here. I am new to both the compressor and diving world, so please bear with me..lol

I have an older Poseidon P80 compressor that I am now running with a 3hp electric motor, as well as a conversion to a gas motor when on the road.

My questions are these..

Is there an optimum RPM the compressor should be turning at to fill my cylinders, and what should the compressor heads temperature be at while in operation?

Thanks in advance!

 

[pescador775]

I don't have that info but will take a guess.

rpm-2600

Discharge gas temps(65F ambient, 3000 psi)
1-280F
2-250F
3-250F

Heads/cylinders:
1-140F
2-140F
3-140F
All(90F ambient)-160F
3(4500 psi)-150F
3-(4500 psi, 90F ambient)-170F

That is a little, 3 cfm, 3200 psi so I believe those temps would be about the max. The high press numbers are provided for comparison. If that were a Utilus which has similar output but low rpm and much higher heat dissipation the temps would be lower. Just saying, FYI.

 

[Scubadoo72]

That is great, thank you. I was wondering if it was running too hot, but I guess my fan is doing it's job.

My heads are running at (in clockwise starting at 9) 153, 135, 125 degrees...guess the shroud needs to be a bit better on the 9 oclock side...it is more open than the other two heads.

Didn't expect a reply so quick..lol.

I will have to calculate the rpm's now.

Here is another question then, approx how long should the molecular sieve be good for? My intake air is pretty dry, and I have been cracking the water separator approx every 15-20 min..

Currently I am changing my filters (MS/charcoal/pads) every 3 fills...but that seems like a lot...

 

[pescador775]

One ounce of MS is good for about 10 fills provided that the compressor has a condensator or separator chamber and a back pressure valve set to about 2000 psi.

Edit: The above assumes operation in extremely hot conditions. Under average conditions, one could allow a longer run for the sieve, up to 15 tanks (1200 cf) per ounce. The charcoal will last at least as long. The Alkin filter contains 1.75 ozs desiccant according to one board member and the change interval is 3200 cf. He also reports that this recommendation may be optimistic according to his RH meter.

 

[Scubadoo72]

Hmmm..ok, so my electric motor is running at 1725 rpm with an 8" pulley on it. The compressor has a 6" pulley. Without joining a math forum group..lol.. would I be safe to say that the compressor would be running 1/3 faster than the electric motor, or 2200 rpm?

 

[pescador775]

Sometimes, manufacturers arrange an electric powered pump to run at slower speed than gas. That seems to be what is happening. I might install a 3450 rpm motor with a 4.5 inch pulley. But, I am not familiar with the compressor and no nothing of the original logic. Anyway, it looks like the pump is turning at about 2300 which sounds right for that type. If the motor is running reasonably cool then I don't see a problem. I just see a high rpm motor as having a high rpm fan.

 

[oxyhacker]

The P80 is the predecessor to the current P100, which is just a rebadged Bauer Junior2. The current Juniors run at 2100 with a 3HP electric and 2300 psi, with a 5HP gas and the gearing (pulleying?) you mention should give exactly 2300. Poseidon runs an electric P100 at 2300, but puts a 5 HP on it. So your 3HP may be a bit overgeared unless it is a very healthy 3 HP.

But why guess? Poseidon compressors has a US distributor, in Vermont, and always been helpful when I've called them, so I'd give them a call or email. 1-800-848-4829

Hmmm..ok, so my electric motor is running at 1725 rpm with an 8" pulley on it. The compressor has a 6" pulley. Without joining a math forum group..lol.. would I be safe to say that the compressor would be running 1/3 faster than the electric motor, or 2200 rpm?

 

[rjack321]

Here is another question then, approx how long should the molecular sieve be good for? My intake air is pretty dry, and I have been cracking the water separator approx every 15-20 min..

Currently I am changing my filters (MS/charcoal/pads) every 3 fills...but that seems like a lot...

Are those really big tanks?? How are you judging when to replace your filters? How big is the filter (the inner parts not the chamber)? How are you filling it (ratio of MS to AC)?

 

[Scubadoo72]

I am filling my steel 72's right now and an alum 80, but wanted to be sure my air was good...and well..lol..this is only the second time I have filled them..changing the filter between them..

Honestly, I wasn't sure when to change the filter components..but I checked it after filling my 72's and 80, not much water had come out of my separator..everything appeared normal..so, I figured I would fill my 72's and 80 twice (6 fills) and then check it..gradually working my way up to noticing a difference...the air is free, so I figured I could waste some if need be...then I was just breathing a few breaths of air off each fill after cooling to check for smell or taste..

The filter itself is about the size of a twoonie around and 4"? long..metal cap with holes at each end..pad on the inside of each end next to the metal washer/cap..50/50 ratio of MS to AC. Right now 120min approx on the oil.

 

[oxyhacker]

That sounds like the nasty old repackable mini cartridge on older Utilises and Mariners etc, not the all-in-one unit used on the P100 and Juniors. They don't hold much, as you have noticed.

Most people I know with them add another canister downstream, and either don't use the little stock cartridge, or keep it filled with 13x as a sort of prefilter.

Some pictures would be real handy at this point since it is hard to say just what you have.

The filter itself is about the size of a twoonie around and 4"? long..metal cap with holes at each end..pad on the inside of each end next to the metal washer/cap..50/50 ratio of MS to AC. Right now 120min approx on the oil.