Leave compressor pressurized between uses?

[seaplaner]

Here's a basic question for the experienced and learned power tool users.

I have an oilless Craftsman 33 gal compressor, works great, (noisy as a buzz saw, though). My problem is that it's a pain to discharge the pressure each evening when I know I'll be using it again the next morning.

So, is there any major harm to the compressor in leaving it partially charged for, say, a weekend? (Followed by draining, etc.)

I know that high pressure condenses water that can cause corrosion if left in the tank, but does a day or two of water, here and there, make a difference?

One other thing, this unit is secure, in a garage, and the kids are grown and gone.

Thanks much - - - this is a great site

[mdredmond]

I have the same compressor.

Leaving it charged is fine. The water that's in there will be there whether you charge the tank or not (i.e., it's there until you drain it).

Replace the crappy drain valve with a 90 degree elbow, a 4-5" straight length of galvanized pipe, and a ball valve. It will make draining (or rather, 'blowing the water out') much easier. Costs maybe 5 bucks at HD or Lowes, plumbing section. Use teflon tape.

Blow out the water after the air in the tank has cooled (it heats up when it's compressed and the water condenses out as it cools).

[mlw450802]

Originally Posted by seaplaner

Here's a basic question for the experienced and learned power tool users.

I have an oilless Craftsman 33 gal compressor, works great, (noisy as a buzz saw, though). My problem is that it's a pain to discharge the pressure each evening when I know I'll be using it again the next morning.

So, is there any major harm to the compressor in leaving it partially charged for, say, a weekend? (Followed by draining, etc.)

I know that high pressure condenses water that can cause corrosion if left in the tank, but does a day or two of water, here and there, make a difference?

One other thing, this unit is secure, in a garage, and the kids are grown and gone.

Thanks much - - - this is a great site

No harm in leaving it fully charged. Almost all the condensation occurs very shortly after a compression cycle, so just drain the water before you go on a trip and no worries.
I don't know of any machine shops that discharge their air tanks when they go away for the weekend.

Fatigue failure is not REALLY an issue in these but if you were counting loading cycles (goes into the fatigue life calculation) you certainly get more and larger cycles by depressurizing the tanks than by leaving them full. The static pressure on the tank is inconsequential.

-mike

[AltonD]

I have the same compressor. I leave it full pressed up all the time. I think the confusion comes from the instructions supplied with the compressor. It says "Drain tank after each use". I believe the are telling you to drain the water from the tank, not to blowdown the whole tank.

[cnpeters]

Leave it compressed, but periodically discharge the water.
For the noise you mention (mine is oil free and noisy, too), you can make an insulated box. I built one in MDF and particle board on 2x4 frame, lined it with thick rubber mats (good sound absorber), then dense carpet pad (some absorption and reflection attentuation), then finally carpet (mainly reflected sound). Lid is very dense, and seals with two rubber seals. Access doors and vent passages were added - now the beast is tamed to a dull hum. I estimate at least 20dB attentuation, though haven't measured. It gets warm inside, and I will do temp measurements and consider a quiet fart fan as Dan Checkoway did ( http://www.rvproject.com ). But, then again, if it burns up, I will have an excuse to get an oiled quiter compressor. Some pics in my website, first entry.
Carl
http://mykitlog.com/cnpeters

[N674P]

I agree with all of the above. HOWEVER, turn the compressor off when you won't be around! No personal experience, but have heard that if a hose or fitting blows, the compressor will fire up and run until it burns your shop down.

[briand]

I have a 26 Gal 5 HP oiled comp. (which is also very loud) and leave it on and full ALL the time. Sometimes it wakes me up in the middle of the night (its in my basement) but I just put my pillow over my head and fall back asleep.

[zspivey]

In a previous life, I was a National Guard company commander. My unit was an engineer company. We had the normal 2 1/2 ton trucks as well as M920 tractors that we used to pull the lowboy trailers with the D-8 Dozers. One of the biggest maintenance problems we had was getting the young soldiers to drain the tanks for the air brakes. If they did not, the brake valves would get rust particles in them and lock the brakes.

It may not be applicable to the air compressors we use, but I drain the tank after each use and leave the valve open until the next use. That procedure eliminated the brake problem on our trucks, so I suppose it will help with these tools.

I agree with the post suggesting adding a 90 degree street el with a short section of pipe to get the drain valve in a convenient location.

[N162RV]

I leave the compressor fully charged but have a ball valve on the outlet. When finished for the day I would close the ball valve and shut off the power at the pressure switch. Just be sure to drain the condensation once in a while...

[sf3543]

If you really wanted to get anal on this, you could add a valve immediately at the tank drain, then a length of pipe to create a trap, and then another valve. The trap could be on a 90 degree angle as proposed. Leave the top valve open and the bottom valve closed. When you want to drain the tank, close the top valve and open the bottom valve. You could drain the tank without losing the compressed air in it. After draining, close the bottom valve and open the top one again. It would also keep water out of the tank itself.