Any air compressor Guru's. Trying to retro-fit a pump

CalsXS2

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I'm working on an old Speedaire 60gal 5HP set up. I paid $50 for it with a blown up pump. I'm finding out I probably would have been better off buying a new compressor. Oh well. Too late now. :shrug:

There's been some parts robbed off of it that I need to replace. I'm going to need a new pressure switch, check valve, and unloader.

The old set up had the unloader hooked to a secondary 1/8"" copper line hooked directly to the pump. The new pump does not have the small secondary line. I'm hoping I can just go from the pressure switch to the check valve. Does this sound doable.

What my main concern is the in tank check valve. My old one is 1/2"x1/2". It is getting blocked by the new pump. And there's the whole going from 1/2" tank bung to 3/4" outlet on the pump restriction thing. I do have a 3/4" bung on the side of the tank. If I could put a new check valve there, it would make my life easy.

I can't find a rating on the old check valve. The new one that I found is rated for 450 psi. Does the check valve rating have to match the tank max pressure rating. If so, I'm screwed. My tank is rated at 165 psi.

I know this is a lot of rambling. I'm just hoping you guys that have been through this can help me figure it out. Thanks
 
Once in a great while, the many thankless hours I have spent working on smoking hot, oil puking air compressors in any number of dark, dank holes across this land allows me to pass on some pearls of wisdom, so here goes...

First, you do not have to worry about any pressure ratings on the check valve, since a single stage compressor pump should not be putting out much more than 125psi. This is well within the rating of any in tank check valve. Single stage compressors draw in air from atmosphere and compresses it to full discharge pressure in one go, so every cylinder is the same size and draws directly through the air filter. If you set them up to try and produce a lot.of pressure, you just end up generating a lot of heat and they operate very inefficiently. The unloader system must be set up to relieve pressure between the check valve and the pump at shutdown, so the unit will not try to start against full tank pressure at startup, which will overload the.motor and.blow breakers. It does not matter where the bleed line is installed, as long as it blows down the pump and discharge line at cut out. Some pumps have a port in the cylinder head, others plug into a 1/8 npt port on the check valve and bleed it off via a needle valve on the side of the.pressure switch, a common, cheap and reliable system.

There is no problem going into the side of the tank with your discharge line, as long as you use a proper check valve and unloadr, the compressor won't care, and if you plumb it in with copper tubing, it will actually give you a bit of.extra cooling.

A word.to the wise, make sure your pump rpm is correct for the.motor power and pressure setting, so it is not overloaded. Some pulley swapping may be necessary to get the best out of it. Do not put in a safety relief valve with a setting higher than your tank rating. HTH, don't hesitate to ask for any.more pointers. DO NOT USE CONVENTIONAL ENGINE OIL IN A COMPRESSOR. IT WILL CARBON UP THE VALVES. Mobil1 synthetic is a good choice, but regular car.engine oil is a.slow.death.for an air compressor. Sorry for all the periods, damn tablet seems to.want to.put them in everywhere with this stupid predictive typing nonsense.

EDIT. Don't know why there is a red angry face on the post, probably hit something I didn't mean to.
 
Thanks Mac. I always wanted to say that. :laugh:

Now that's what I call a good answer. :thumbsup:

I guess I just don't understand how the check valve works. I thought it ment that the check valve will blow at the rated number. Which in this case is 450 psi. But my tank is rated for 165 psi max.

So will this check valve work for me. I sure hope so.
 
Hint the pressure switchs in the plumbing isle work just fine for compressor duty, usually less than $10 a throw. Easy to adjust them for the cut in/out pressure you want. I have a plumbing isle switch on my 1 1/2 horse that has been working since the early 90's when the original died.

Macmac is the pro here, my motor is smaller than the OP's My compressor does get used, it's 40 years old now, I bought it new! But amazingly it still holds pressure, I leave it plugged in all the time, and it never runs unless I use it. If I hear it run I know I left a tool in the air chuck. Confession; I have welded the tank a time or two to stop leaks from rust where the water sits in the bottom. I'm beginning to think it might outlive me! I have religiously changed the oil, maybe 3 times so far. I made an adapter when I was painting cars and it breathes through a small block chevy air filter.
 
Let's. Be clear on our terminology, the check valve is the spring loaded one way valve that the compressor blows through to fill the tank. When it cuts out, the spring seats the little puck against a seat to keep the air from going back into the pump. There should be some way to attach a blow off line to it that bleeds off the air above it when the compressor shuts down. The safety relief valve is a spring loaded valve that vents to atmosphere when the unit goes over the setpoint pressure of the tank. It should definitely not be 450psi, but 150psi. Set your cut off at least 10 psi below the safety valve set point to prevent the valve from simmering, 20psi would be better still. Water pressure switches may work, but i don't. Think there is an unloader valve on the side to bleed down the compressor on shut down. A small machine might get away without one if it is used sparingly enough that other leaks allow pressure to escape between cycles, but I would rather spend the extra for the proper one.
 
OK. It's picture time. :wink2:



Here's a pic of my old 1/2'' check valve, pressure gauge, and safety relief valve. Check valve on the bottom,,,correct??

And yes, the gauge has seen better day's. :laugh:







Here's the check valve I want to use in the link below. I'm thinking I can just remove the allen screw and attach a line from there to my unloader in the pressure switch,,,right??

http://www.grainger.com/Grainger/CDI-CONTROL-DEVICES-Compressor-In-Tank-Check-6X215?Pid=search





Here's the pump I bought from Harbor Freight.







I know they kinda exaggerate their rating's. But I like the CFM. Hope it's close. Kinda low on psi,,, but I think it will work for me.







Here's what I've got so far.







I'm looking at this pressure switch in the link below. But I cant' find a brand on it. If it is the one that Lowes sells,, which it looks like,,,it has very bad review's,,, and I'll pass for sure. If you click on the tech spec's, the last note says:

"If you have a starter the amperage does not matter since you are not running the power through the switch, all it's doing is telling the starter when to turn on and off".


http://www.compressor-source.com/95_125_psi_air_compressor_pressure_switch_p/69mb7ly2c.htm





So that brings me to my motor. Does this have a starter on it. :shrug: All the pressure switches I'm seeing are rated below the 22 amps that my motor is. Except the one linked above. It's rated at 20 amp's. And they all say they are for 3hp. Will they work for my 5hp,,,if I have a starter. Do I have a starter??









And lastly,,,I know,I know,,,thank God. :D Since my pump claims to put out 145 psi,,, should I get a pressure switch that will go that high, or just stick with a 125 psi cut off model.

Please let me know if I'm doing something wrong, or I'm missing something. Thanks
 
Sorry to thread jack here... MY compressor is single stage. Tank rated at 175psi. Something is wrong... seriously wrong. Check valve obviously must be bad, safety valve obviously failed, one day the compressor seemed like it was running WAY too long, gauge read 200psi!! I pulled the drain plug, replaced the safety valve with a new one, and fured it up again... safety valve pops off at 150psi now, but compressor keeps running... now I just shut it off manually, and only use it for inflating tires, and air blowing.

Is this normal? lol... I know nothing about compressors... I do know this stupid piece of junk wont run the sand blast cabinet, which makes me sad that I spent good money on the cabinet.
 
The first thing that should have been asked is :

DO YOU KNOW THE TANK IS SOUND?

An easy test is to seal all openings in the tank, fill it completely with water, put a fitting on one of the bungs and install a grease nipple and gauge. Put in 1.5 times the rated pressure with the grease gun (careful, because it goes up fast) and check for falling pressure or leaks.

gggGary, not to be an ass, but the tank is telling you it has had it's day. I would never use a repaired tank. You have a ticking time bomb on your hands. It's not worth it. Tanks are expensive, I know, but what you have to lose is infinitely more valuable. I nearly took my head off one day opening a filter cartridge pot with 5psi in it. It flipped open that 1" thick steel cover faster than you can imagine.

CalXS2, you do not have a starter. It is a stand alone, heavy switch, activated by a magnetic coil which opens and closes the main contacts feeding the motor itself. A control signal from the pressure switch makes and breaks the power to the coil, which opens and closes the starter contacts. You can get away with using the pressure switch as a starter up to about 3hp, then the arc from starting and stopping will surely weld the contacts closed and the compressor will not cut out. There is also a built in overload protector in the starter, which is sized for the amp draw of the motor. Do not neglect the electrical aspect of setting up the machine. There is far too much liability in terms of fire and negated insurance policies to be worth trying to save a buck here. The setup should be properly fused and have a separate disconnect box. The pressure switch you posted has a small lever on the side which can interrupt the signal to the starter coil which will prevent the compressor from starting, but a main disconnect for the motor leads is advisable, and possibly required in your area.

DO NOT RELY ON INTERNET ELECTRICAL ADVICE! ('cept for XS650's of course) I don't care how much experience the guy has, there is always room for misunderstanding, and there is far too much to lose. I have set up many starters, and hooked up hundreds of single and three phase machines and I refuse to try to tell someone how to do it.

Anyhow, you have the right components. Yes, you remove the littel Allen headed plug from the check valve and install the blow down line from there to the needle valve on the side of the pressure switch. You should be able to set up your machine just fine with the pressure switch and check valve you are looking at. Be aware that the check valve has a ferrule fitting on it, so you will be hooking it up with copper tubing if you choose to use that one. You will need a similar one for the compressor outlet, all easily obtained. They are easy to use and last a long time. Bending copper tubing can be tricky if you haven't done it, but a few tries should be sufficient. It doesn't have to be perfect.

As was stated, now is a good time to replace the water drain before you add all the weight on the tank up high. It's almost guaranteed that the original drain valve is in there, with the crappy pressed steel handle that always jams, resulting in a burred up brass stud full of sharp edges from people using vise grips set to max to get it to open (often turning it the wrong way...) I'd put in a fresh nipple, a 90deg elbow, another nipple to get it out near the edge of the tank, and a proper brass ball valve, maybe with another 90 on the end to direct the water downward. Vertical tanks suffer from plugged drains more than horizontal tanks, since the crap in a horizontal tank can lie in a line all long the length of the tank, whereas all the crap in a vertical tank gets funneled directly into the drain valve at the bottom.

I'd put a fresh 150psi safety valve on the tank. A fresh pressure gauge too, naturally.

If it was me, I'd set it for about 130psi, with a 110psi cut in. You will have to check amp draw at max pressure to see if you are loading the motor appropriately. It is quite easy to overload a motor with improper pulley sizes. This is a 3450 motor, which will have half the torque of a 1725rpm motor. It will need a fairly small drive pulley to make the most of it's power, and not overspeed the pump. In extreme examples, the arc of contact on a small pulley can be insufficient and the belt will slip all the time, or the belt life is short. Try it with what you have and see. I'd do a rough calculation at first to make sure I am not exceeding the pump rpm.

Motor pulley diameter X motor rpm / Pump pulley diameter = Pump rpm, which in your case should be 1050rpm or less.

The best tool you can use for setting up a newly built compressor is a clamp-on amp meter. Just put it around one of the supply leads while it is running and it will give you your amp draw. That motor has lots of capacitors to help it out, which is good, but it is a bit on the small side, which leads me to believe it may be a bit stressed for heavy workloads.

Anyhow, as you said, it can be false economy to try and build your own machine unless the components are nearly free. You can end up with a decent machine here though.
 
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