Got the air compressor going!

[CJDave]

[img]/forums/images/icons/tongue.gif[/img] Waaay last August I was in the right place at the right time to bag a nice, 5 HP, Sanborn, 60 gallon, upright air compressor for free. The motor was only about a year old, but the pump was blamo. The tank check valve had come unscrewed internally and the valve innards fell into the tank. With no check valve the unit drained back through the unloader circuit and restarted against 90 PSI head pressure over and over ad infinitum until the motor finally tripped a breaker. By that time the crank and rods were blamo from starting dry against high head. I bought a new compressor from SURPLUS CENTER in Nebraska for a hundred bucks plus freight, but the late harvest and never-ending winter made it difficult to do much until things warmed up a little. I got the base re-drilled to match the new pump, and made up new piping a couple of weeks ago. Today I finally got the electrical all set up and energized. I'm using a mag starter that I built up with a 24V control circuit so I can run a remote toggle switch. This compressor is in a separate equipment room so to get it on line all I need is to do is flip on the bat-handle toggle switch on the interior wall of the shop. The unit runs nice and smooth with no leaks. This unit replaces a tiny one that I made out of a refrigeration pump taken from a Borden's Ice Cream freezer in 1971. [img]/forums/images/icons/crazy.gif[/img]

[Pat]

Good job, Dave! I never used a frige compressor for a pressure pump before. A couple times I used one for a vacuum pump. Once to make a linear accelerator and once to lower the pressure in an air filled flash tube to cause it to arc over (flash) so as to not have to switch 15KV from a fast discharge pulse capacitor in my home brew pulse LASER. I teed in a plastic hose that when you put your thumb over the end the vacuum started to pump down till you reached the partial pressure where the 15KV would discharge between the electrodes in the quartz flash tube. Had to use a scatter shield as you never knew if the tube would explode or not.

I have a new upright compressor sitting on its pallet waiting for me to install it and plumb it into the shop, garage, etc. Not nearly the compressor you have but should be enough for me. Until or unless a trusted source (like you) tells me different the plan is to plumb everything with black iron pipe. I have heard all sorts of excuses for using PVC but I'm not interested. I will check the price of copper and powder coated aluminum too.

I may get a small refrigeration type drier. Never used or had one before. Do they sense the compressor running and come on or what?

Are we safe with compressed air?

Here is food for thought...

Compressed Air Piping Precautions:
1. A blast of air under 40 psi from 4 inches away can rupture an eardrum or cause brain damage.
2. As little as 12 p.s.i can pop an eyeball from its socket.
3. Air can enter the navel, even through a layer of clothing, and inflate and rupture the intestines.
4. Directed at the mouth, compressed air can rupture the lungs.

The following guidelines will reduce the risk of injury when using compressed air piping systems:
1. Examine all hoses and connections to see that they are in good condition before turning the pressure on.
2. Never point the air hose nozzle at any part of your body or at any other person.
3. Never look into the end of a compressed air device.
4. No horseplay with air hose.
5. Never kink the hose to stop airflow - turn it off at the control valve.
6. When using air for cleaning, make sure the pressure is no higher than 30 p.s.i.
7. Always wear eye protection when using compressed air.

I won't go into details but I have violated some of these but am trying to be a better (safer) citizen.

Pat

[CJDave]

[img]/forums/images/icons/tongue.gif[/img] Pat, I have probably scanned a hundred compressor-drier arrangements with INFRARED, but to be honest, I never noticed the setup as far as how and when the drier ran. I just assumed....... there's that word again,.... that it ran with the compressor motor, using a "rider" on the contactor that was a part of the control circuit of the drier. When the compressor contactor ran, it engaged a delay and then a few seconds later, the drier came on. The delay would be to reduce inrush current. [img]/forums/images/icons/tongue.gif[/img] My interior piping will be in sweated copper; it's easier and holds up well. I have a wall-mounted tank 6" diameter and two feet long that goes inside the shop and THAT tank has the regulator for low pressure and the usual gauges. Most of my blow guns are the OSHA type with the reducing device at the business end. Air can be very dangerous, and nobody who has spent their life around shops has not seen real stoooopidity at work. As confident as I am with my setup, I still don't feel real comfortable with leaving the air compressor "on" when I'm not in the shop. Too many things can and do happen; which is exactly why I now have this "free" compressor. This unit holds air well enough that it would just take a half a minute to pump up to shut-off pressure even if it sat for a week, and in any case there would always be enough residual pressure for inflating a tractor tire. [img]/forums/images/icons/tongue.gif[/img] Yes, this IS kind of an overkill setup with a mag starter and 24V controls, but what the heck. I bought everything out of the surplus catalog, and already had the 24V transformer out of a scrapped HVAC unit, so why not eh? [img]/forums/images/icons/crazy.gif[/img] Oh, and one more thing to keep in mind when wiring your unit, Pat: when you think the wiring is the heaviest you should use, bump everything up one size. Compressors, both large and small, want your BEST STUFF in the power supply department. I'm pulling 14.1 AMPS and all of the motor supply is ten gauge wire. I have a 30A breaker in the supply panel, and 20A Fusitrons in the compressor overcurrent device, a superb, vintage, SqD fusible 3-Phase disconnect. I use the first two legs of that SqD for the motor and the third leg has a 6 AMP fuse in it for the control circuit. That leg feeds the 24V transformer. The magnetic starter is built in a GE can that used to be an enclosed outdoor breaker. The transformer is in the same can as the mag and there is a double-throw switch on the can for Local-Off-Remote. Local is just as it sounds, and Remote is the bat-handle toggle switch inside the shop. [img]/forums/images/icons/smile.gif[/img] Those little old refridgeration compressors are amazing. This one I have will hold 25" Hg. for as long as you want to sit and watch the gauge. I use it for pulling a vacuum on refridgeration piping. [img]/forums/images/icons/cool.gif[/img]

[Pat]

So,the day after my 4 1/2 inch angle grinder died the portable 35 gal air compressor on wheels wouldn't go above 30PSI. I ran temp 240VAC to the new compressor sitting on its pallet for a loooooong time but to be installed real soon now and it worked for almost two days before malfunctioning.

The pressure switch relieves head pressure and turns the unit on when pressure sags. The unit now runs till it reaches shut off pressure but the head unloading air passage leaks air continuously until the pressure switch tries to turn the unit back on. It stalls and does not spin the compressor because the head pressure isn't relieved. I am well out of warranty. Lesson learned: maybe you should test stuff before letting it sit for a couple years.

I suppose I will be able to buy a new part for it and get it going. It is a Craftsman vertical 60 gal with 9 HP and 175PSI.

Pat

[egon]

Pat; don't touch anything expensive till the third item breaks down! [img]/forums/images/icons/grin.gif[/img] [img]/forums/images/icons/grin.gif[/img]

Egon [img]/forums/images/icons/grin.gif[/img]

[Pat]

Hey, Egon...Well DU-UH... I listed three things that broke in the email to which you replied.

Why didn't you warn me before I wired up the new compressor? A fat lot of good the bad-luck-comes-in-threes warning is when you wait until I have already had three failures before you say anything!

Hey Dave... Assuming I get the 175psi Craftsman compressor fixed, should I put a regulator on the output to hold it down to a more moderate value? I noticed the refrigeration type drier I was thinking about is rated for less pressure than that and the advertising copy suggests a working pressure of 100 PSI.

I could, but would rather not have to run seperate "dry drops" separate from higher pressure not dry ones. Oiled and oil free drops are enough redundancy.

Do you think I really need more than 100 PSI for most general purpose shop stuff. I rarely exceed 100 PSI on my truck tires (rated for 110PSI)

If I can't get by OK with 100 PSI then I have to go to alternate means of drying the air. One alternative is absorbing cartridges.

What about running the drier on the input to the compressor instead of the output? I thought that since the drier works by cooling the air below the dew point to let moisture drop out and since the input air is cooler than the compressed air that it might dehumidify better on the input.

This might not be true in the case of air in the tank that has cooled over time and is now being let out of the tank but in a high duty cycle run time situaation I think it sould dry better in the input side,

Whatcha think?

Pat

[CJDave]

[img]/forums/images/icons/tongue.gif[/img] Dear Pat, The air compressor malady as described in your recent post is a symptom of a tank check valve stuck open. Those valves are usually screwed into the the threaded flange on the tank, and may or may not have a separate 1/8" NPT fem tap for the unloader line. So the valve is stuck open and the tank pressure escapes back thru the unloader line till it reaches the set point and then the contacts in the pressure switch close and the compressor tries to start against high head pressure which it cannot do. The compressor that I have here was a victim of that same anomaly, wherein the check valve came apart and the innards fell into the tank, precipitating the chain of events which subsequently led to the demise of the compressor crankshaft. [img]/forums/images/icons/frown.gif[/img] While you are working on your compressor and repairing or replacing that tank check valve, how about adding more "chamber" to the piping between the tank check and the compressor discharge? Anything you do to give the pump more "running room" before it has to push that check valve open means more oil on the crank and rod bearings before they get a big load on them. I doubled the amount of pipe on mine, but I have also seen little tanks added and "weenie" sections added just to give more cu in. There is actually NO REASON to have any more tank pressure than 100 if that will do your job. High pressure just means more storage so most people go for it. Unless you are running two-stage unit, run the tank pressure as low as you can and still get by. Yes, it may cycle a bit more, but so what, you aren't running a body shop and using gobs of air. MOST pressure switches will adjust down to 75-on, 100-off, BUT NOT ALL. [img]/forums/images/icons/tongue.gif[/img] SqD makes two different switches, one is for single stage units and is adjustable over a 75-125 PSI range and the two-stage style has a 100-200 PSI range. Both have unloader ports and an outside over ride lever. The single stage unit is good for 3 HP, although a purist like myself would never direct-start a unit that size, I would have a magnetic contactor. [img]/forums/images/icons/crazy.gif[/img]

[CJDave]

[img]/forums/images/icons/tongue.gif[/img] With regards to the dryer.... [img]/forums/images/icons/tongue.gif[/img] You would not want to put that dryer on the suction side of the compressor as it is rated at a given CFM @ working pressure, not free air pressure. You can employ a regulator ahead of the dryer and lower the pressure to 100, but still have tank pressure at rated capacity. I just noticed that your post said Craftsman 175 PSI. That is a two-stage unit, so instead of lowering the tank pressure down to 100, just tee a line to the dryer with a regulator to get the lower pressure. That way the high upstream pressure on that regulator will provide more consistent flow. The Caddy way to do this is to use that liddle 35-gallon tank from the other compressor as your LOW PRESSURE source by feeding it from the big guy via a regulator, and THAT low pressure air is then passed thru the dryer. [img]/forums/images/icons/crazy.gif[/img]

[Pat]

Yup, Dave, I see you confirm my initial analysis. That is good because it was my first time and I could use the confidence boost. The end of the little tube goes to a fitting that is held on the side of the "control box" by two internal spline head screws (security type screws but so what as I have the $5 HF security screw bit set.) There is a gently pointed plastic thingy that is supposed to do something to the air but apparently doesn't.

I could just get a new part, install it, and be done but that violates rule number 121.305-B so first I have to take the controller/air switch apart. Then if it is beyond my understanding or some spring loaded part flies across the shop never to be seen again or the equivalent (before the compressor is working) then I can declare the control to be non-repairable and buy the new part and get it running again.

How about giving me some background motivation for the lowered pressure setting and all the on-off cycling to follow. This unit is a single stage (I didn't know any better at the time) factory set for 175 PSI. I figured that would give me extra capacity for meeting peak loads. It has a 60 gal vertical tank and it does not recover fast. I think it is a BIG tank and a not too capable compressor. What can I say, it is a Craftsman.

I suppose I can try it at 100 PSI which will satisfy my impact tools as well as nailer/staplers, spray guns, and virtually all tire inflation tasks but of course it will take some getting used to the idea of having the thing cycle every time you use a couple breaths of air. I may have to compromise back up to 125 PSI like the recently failed portable had to get a little more reserve so the fact that the compressor can't produce sufficient cu ft at pressure will not be noticed so quickly.

Maybe my years of experience using SCUBA bottles distorted my thinking. High pressure yielded good storage volume (steel 72 cu ft at about 2,100 PSI or aluminum 80 cu ft bottles at 3,000 PSI) and two stage regulators to drop it down to ambient.

Anyway, if you could provide some background/motivation for lowered pressures I'd appreciate it.

Pat

[Pat]

Dave, I don't know enough about all this, practical experience wise, to agree or disagree.

Here is some info on the drier:

Advanced 3-in-1 air dryer system features modes for pre-refrigeration, evaporation, air and moisture separation modes to remove up to 90% of the moisture from your compressed air lines.

* High efficiency prerefrigeration system is three times faster, takes 60% less power to operate
* Accommodates compressors up to 21.6 CFM, 140 PSI max
* Lowers the dew point to 36ï½°F


Weight: 73 lbs.
Recommended operating pressure: 100 PSI. Not for medical use. Operates between 35.6ï½°-140ï½°F. Uses R-134A refrigerant. 115 V input; Air inlet: 1/2"-14 NPT;

Here is the product listing:

http://www.harborfreight.com/cpi/cta...emnumber=40211

Here is the PDF manual:

www.harborfreight.com/manuals/40000-40999/40211.pdf


I don't know what pre-refrigeration means in this instance. Apparently it is not cooling the intake air.

My compressor is rated for:

7 HP (max developed)
175 PSI
60 gal tank
it is 2 stage OIL FREE
9 standard cu ft per min at 90 PSI.

I think I see why you don't want it on the input. My compressor will maintain 9 cu ft per min at 90 psi output. That requires 7 times as much (I hope I got it right and it isn't 6 times) intake air as output at 90 PSI. That would be 63 cu ft per min going into the compressor and the drier is rated for 21.6 cu ft per min.

I don't think I need dry air at pressures over 100 PSI. I will use dry air for plasma cutting and painting and I suppose air tools would appreciate it too. So unless or until someone cries foul I will plan on running the compressor, as sold, set for 175 PSI and put a regulator set for 100 PSI between the 60 gal tank and the drier with the output of the drier going into the 30-35 gal tank I can cannibalize from the Devilbiss 125 PSI portable. I will set that regulator at 100 PSI and distribute that air shop wide. I should be able to use the regulator and the dual gauges from the Devilbiss to do the 175 to 100 drop as they are currently installed on the Devilbiss tank.

I can install at least one high pressure outlet in the metal shop and one in the wood shop for just in case some temporary requirement comes up for higher pressure air and depend on hoses to get it to the job.

I liked the idea of running dry air on the input to the compressor but, oh well...

The June-July issue of "Progressive Farmer" has a good but simple piece with good illustrations on workshop compressed air distribution. Their featured installation was built around a 17 cu ft per min compressor with 80 gal tank. It too is a 175 PSI dual stage unit.

The pix show how to plumb for dry and oiled outlets with drains for condensate. They communicate a lot of info with a few paragraphs and pictures taking a page and a half. They hit lots of important issues like black iron not PVC, using flex hose between compressor and rigid piping for vibration isolation, and on and on.

I tell folks these same things and they ignore me and install PVC direct to the compressor and all through their shop because the installer and the owner know PVC is just fine, has never in their experience had a problem and is way cheaper and easier.

Anyone, please chime in. I'd rather know I was wrong about something before doing it not afterwards.

Pat