Technical Minimum size compressor for shop work?

Don't they use water pressure to test compressor tanks?

 

most pressure vessels are hydro tested.
Since a liquid doesn’t compress should a burst occur it’s more of a nuisance, where as the bursting of a pipe or tank or a tire releasing compressed air is lethal unless protected by distance, enclosing, or blind luck being behind a big machine.
Hydraulic hoses and lines burst all the time while seeing thousands of lbs of pressure. Not really a big deal just messy. A very small, tiny itty bitty amount of compressed air can put a pellet thru a phone book.

 

Also am told buy a HAMBER here to note the direction of rotation. Nothing on the motor notes that. How do I determine the rotation?

 

On the old motor if there is nothing marked externally ,look inside the junction( wiring) box , especially if its a reversible motor , the schematic will show for which way its presently wired ..

 

I think the problem with pvc pipe is degradation due to being open to the elements. Extreme temp chances (summer vs winter), uv/sunlight etc.

Under a house in theory there should be a smaller temp extreme and hiden from direct sunlight.

I considered pex myself. It has better burst control and flexibility. Talked to a plumber friend of mine and his main concern was uv rays.

 

The rotation of the compressor blows air over the compressor for some cooling, usually LH or CCW rotation.. Sometimes there is an arrow on the compressor pulley.. If you are looking at a motor advertised as "compressor grade" then its rotation should be LH, CCW. Haven't found a compressor that isn't LH, CCW rotation.

 

My son and I are thinking about running an underground line from the shop to the ought we might bury some PVC and if it blows probably the lawn would cushion any energy. On the hand rubber hose is cheap, just picked up 50' of 3/8" for $15.00 CDN.

 

What about those RapidAir kits with the nylon tubing? They're sold for plumbing air lines but is nylon safer than PVC? I'm a copper tubing guy myself...

 

Is black pipe cost prohibitive ? Years ago I salvaged about 300' of 1/2 black pipe out of a newer building that went down in a storm , mostly 20' sections, took 20 years to use it all ..!

 

PVC pipe may have a high working pressure does not mean that it is fit for compressed air service. An inquiry with the PVC or PEX manufacturer would verify that their plastic pipe is not recommended for compressed air. Compressed air and gases are stored energy and when the piping fails that energy is destructive. The compressed air expands until the energy has expired when a pipe fails so it is a powerful force when it is released. Water looses it energy as soon as it is released. Compressed air is regulated in industry and if air systems was required for homeowners then the codes for power & pressure piping would be have to be followed. Since home installations do not require an inspection then everyone is free to use whatever they want. The code drives standards & codes are a minimum standard of safe construction. Using the right grade of copper, steel pipe or a light wall pipe air system sold for garages are safe options. Another factor is the service life of the materials. Plastics have a shorter life than copper or metal pipe. I remember when plastics were all the rage in home piping and the plastic of the day became a problem. I am going to do some renovations and will go all copper as opposed to PEX. I have an 80 year old house and a now a 60 year old house where the copper piping is still in great condition.

Here is one reliable source.
https://www.cp.com/en-us/compressor...use-pvc-piping-for-your-compressed-air-system

 

PCV pipe is intended for water. Which is forced into your house by gravity. Turn on your water all the way and see how much pressure there is. No turn your Air release valve on all the way and notice there is considerable more pressure. 34Larry, get someone to help you change your piping in your garage if you can`t do it yourself. If it`s easier, just run air hose instead.

 

If you can afford one a Saylor-Beall, 7.5hp.

 

I've hesitated to get involved. Somewhere on here, I mentioned having been a tool salesman. My truck always had a air compressor on it. Emglo was very popular in our area back then. Never buy what you need. Always think ahead. How fast the compressor turns is important. More rpm's means more heat and noise.

 

I’d really like to be able to decipher the advertised out puts for a direct comparison.

I’d really like a high out put (equals my current unit) at half of the 3400 rpm mine runs at that runs on single phase power. It works very well but loud.

My buddy just got a brand spanking new champion. Beautiful!! You would not mind it sitting in your kitchen It’s nice and quiet, but not as much out put as mine . 2 of them would put out more than mine does but then you’ve got 2 times everything including the noises

 

Unfortunately all manufacturers don't use the same rating system , there's CFM , SCFM for output which are very different & there's HP & IPP, again confusing , The only consistent rating I've seen is AMP draw , it takes X amount of amps to make Y HP. The other is single or 2 stage , most single stage are 3450 motors with a max of about 15 cfm , borderline for shop tools and they're noisy. , 2 stage are usually 1750 motors output 20 +cfm , runs most tools ,and they're quieter ... Call the manufacturer sales rep and question the details

 

I like your suggestion of just running hose. I'm contemplating running hose to the present reel position mounted 20 feet away that feeds the filter system then out to the tools of course. I am concerned in doing this that the loss of pressure and volume might be significant however.
I need to thank everyone who has contributed input. My plumbing career ended the second I was discharged Jan. 9th, 1962, so much of my knowledge today is ancient history. I just hated the job. I took to heart the opinion expressed on what you needed to know to be a plumber, IE: Payday is on Friday, Shit runs down hill, and you don't clean your fingernails with your teeth. One you learn and understand that your eligible for your journeyman's card. (with apologies to all plumbers)

BTW, DOR found on motor fan cover. CCW when facing the shaft.

 

Hot is on the left
And cold is on the right
Shit runs down hill
Payday Friday night.

 

The reasons for my limiting my system to 125psi were the old tanks and the pvc lines as limiting factors, and the fact that it was and is a hobby shop where not as much storage capacity of compressed air is needed, and the 140 gallon capacity of the 2 tanks involved. That 140 gal.capacity means I don't need 175psi in the tank to have enough air.
Here in GA the normal humidity is quite high and air tanks need an almost daily draining if in use constantly, and that seldom happens. In the past the automated drain systems weren't seen too often either.
As a consequence, most air tanks here wind up rusting out on the bottom and usually it's pinholes that leak way before there's enough pressure to pop a tank. I'm 82, and the only tanks ruptured I've seen in a lifetime of hanging around and/or working in those shops have been on the internet. Here they all seem to just wind up leaking from pinholes in the bottom way before that point of structural failure.
I did have 2 failures in about 25 years on the sch. 40 PVC, One was early on and due to a less than proper glue joint. The other was a "tee" fitting rupturing with a quite loud and startling pop, but no shrapnel.
Very soon after that "tee" failure I replaced the whole system with sch. 80, and still limit to 125psi.
OSHA would reject it, but WTH, I ain't subject to that bunch of asshole's rules with a hobby shop

 

Water lines into your house are under pressure, usually around 50 psi, only thing gravity is your sewer waste line. Unless you have a tank in your attic that it’s pumped to and have gravity lines from there.


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Also note that air is compressible and water is not. PVC pipe is rated at a working pressure and temperature, as that temperature rises, the pressure rating drops due to the material. I have black pipe in my garage with blow offs at low points and enough pipe to allow water to condense so the water traps work.


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Larry
Fill a balloon with water and set it on the table, poke it with a sharp object. It just goes splat and the water runs out across the table. The balloon probably rolls away with the water.
Now blow up a balloon with air to the same size as the water balloon, poke it with a sharp object. It goes BANG and pieces of the balloon probably fly everywhere.
This is because water does not compress and air does. If you take 1 cubic foot of water and compress it to 100 psi it is still 1 cubic foot of water. In order to compress air to 1 cubic foot of air at 100 psi it would take about 8 cubic foot of air to start with. This is the difference between compressed air and compressed water.
Said in simple terms, compressed air is like a thousand little compression springs all compressed inside a line just waiting to be let go and when the line breaks they are let go!! Sending the balloon or pipe all over the place.
I live in Michigan or I would come over and help you replace your lines. But you are a long drive away....
Greg

 

Got cha Greg thanks.
Larry, retired manufacturing engineer.

 

You can get away with something like this... 80 gallon IR 15 cfm unit... Good enough for a one person shop, not good enough to run two tools on. Less than $1300 when I bought it.

 

great idea putting it in a closet; my sears makes me jump every time it kicks on!

 

i've been happy with my craftsman, 6.5 hp, 60 gallon vertical tank. i've had it at least 25 years. as i previously stated, it is loud. i checked out eastwood's "quiet" compressor, but it's something like two grand! the only real mod i did to mine was to run some pipe to a ball valve from the drain--located in the bottom middle of the tank. always hated having to reach under the unit to drain it; we have brown recluse spiders in missouri!

 

Look at the fan on the compressor. You want it to blow over the compressor, so look at the blades and figure out which direction they need to turn to accomplish this.

Anybody want to run a plastic hose from their compressor go to a semi truck parts house. They have plastic hose that is used on trucks that will withstand over 150 psi. It is marked air hose or line, and is double layered. It's available in ID's from 1/4" to 1" or larger.

 

I hate being near it when it comes on. I like the closet but I should have made it accessible from inside the garage. It is kind of a pain to walk out there in the rain to service the desiccant dryer. But it does make my shop a lot quieter.

 

Years ago, I was able to buy a three phase Rotophase, that runs off 60 amp, 220 VAC circuit to my play garage. With the Rotophase, I can run a ten HP "biggie" air compressor. I understand that one three phase motor, when running, acts like an alternator, and kicks even more power back into the supply line, so, while running my ten HP three phase air compressor, I can run another fine to seven HP three phase motor at the same time. This would seem to exceed the available output of my ten HP Rotorphase, but it doesn't. The Rotorphase works well supplying my 10 HP air compressor, a lathe, Pullmax, and power hacksaw with high teens of HP throughout my "play shop." The Rotorphase looks like a great big electric motor, and has a panel full of capacitors and controls. It all works great and doesn't care how much or how little the load motor/s demands. It will power from a little three phase, low HP motors up to my ten HP compressor (I used to run two crank grinders off of it). I have never used the capacitor style three phase converters, but I understand a capacitor three phase converter unit must be pretty well matched to singular particular load it is going to power. Capacitors converters are low bucks to buy, and definitely ARE worth buying if you have only one three phase motor to power. As most folks can't or won't adapt over to three phase power, used three phase air compressors are available at steep discounts.
A sad note: The young guy, that manufactured my Rotophase, got killed in a dragster accident just months after I bought my unit from him. What a waste.

 

If you are trying to determine what the rotational direction of your non-working compressor was/is, look at the vanes on the compressor pulley. They rotate in the direction that forces air toward the pumps fins,

If the motor you want to buy is bi-directional. it will say so on the wiring diagram. Basically it is simply a matter of switching two wires. If it doesn't have a small diagram showing which two wires to switch, then it is MOST LIKELY that it is NOT bi-directional . Lots of motors only turn one direction and in that case you need to make sure its the correct direction. Don't know that it will work on all motors, but I had a motor that turned the wrong direction for my needs and I took it apart and reversed the rotor end for end and reinstalled it. Had to extend the wiring a little, but it turned in the opposite direction and ran fine.

Looking a little further, its also nice if the motor you buy has the same size shaft as tha motor you are replacing, or you may have to buy new pulleys......which can be expensive.

Another tip: Take the largest air consuming tool you have and hook it to the used compressor you want to buy. Turn the compressor on while the tank is empty and see if the compressor will pump the tank up while you have the air tool in operating mode. Obviously the empty tank won't operate the tool, but if it gradually builds pressure in the tank and the tool begins to run until it reaches the point of operating at full speed, the compressor is capable of what you need.

Now, all of that being said, its also possible to sell your compressor to someone who wants to rebuild it, and just go buy a good new one and avoid the hassles in a few years when some other components begin to fail.

Look for one with a magnetic starter and appx 1725 rpms instead of 3450 rpms.

 

big brother is watching. after looking at this thread I had an advertisement for compressors on my main Yahoo page.