Building an air compressor

[jaybee]

I've been sitting on a compressor and motor for some time now, waiting for the right tank.  Now I just need to buy some small bits and I'm in business.
The motor is a 220v, 3hp CONTINUOUS DUTY motor that I can barely lift.  It has a capacitor cover as big as the cylinder on my 5hp IR oilless.  I stress continuous duty because of course compressor and power tool motors are commonly rated at stall, which is WAY more than they can run continuously without burning out.
The compressor came with it.  Unfortunately it has no data plate but it's a two cylinder single stage with a bore probably twice the size of my existing small compressor.  No idea as to vintage but it is aluminum.  Reed valves and other mechanical aspects check out.  What sort of oil should I use in it?  It'll connect to the tank through a 3/4" hydraulic hose.
The tank is a 33gal horizontal that formerly mounted across the bed of a service truck.  Next task is to sand some places with light surface rust and throw on a fresh coat of paint.  I want to use a check valve on the inlet so the compressor can unload, does it matter what kind I buy?
The plan is to set all of this outside for noise and space reasons which will necessitate some sort of doghouse for the compressor.  I could use some help here.  How much ventilation do I need to build in for proper airflow and heat removal?  Should I duct some fresh air to the fan that's built into the compressor flywheel?  How about the motor?  it'll make a good amount of heat in an enclosed space.
Piping from the tank will include a union so the thing is removable, then about 25' of 3/4" copper pipe up the wall and across the ceiling, then down.  From there into a T with drip leg down and air back up.  Is red strip copper sufficient, or do I need the blue?
I have a 6gal tank that came from a semi tractor.  I'll mount it end up on the wall.  Air will enter through a pipe thread opening in the bottom end, and there are 4 pipe threaded openings along the length of it.  I'll take my air out of the uppermost one to a regulator, with a guage to measure system pressure in the next opening down.  Since both ends of this tank are have pipe threaded bungs I can come out the top end later to put another drop in elsewhere.
It seems to me with a sufficient run of copper, and the smaller "auxiliary tank" to serve as a water separator this air should be pretty dry.  If that doesn't prove to be the case I could always splice in a coil of copper in an icewater bucket later if needed.
Have I thought of everything?

[Inprimer]

I've been sitting on a compressor and motor for some time now, waiting for the right tank.  Now I just need to buy some small bits and I'm in business.
The motor is a 220v, 3hp CONTINUOUS DUTY motor that I can barely lift.  It has a capacitor cover as big as the cylinder on my 5hp IR oilless.  I stress continuous duty because of course compressor and power tool motors are commonly rated at stall, which is WAY more than they can run continuously without burning out.
The compressor came with it.  Unfortunately it has no data plate but it's a two cylinder single stage with a bore probably twice the size of my existing small compressor.  No idea as to vintage but it is aluminum.  Reed valves and other mechanical aspects check out.  What sort of oil should I use in it?  It'll connect to the tank through a 3/4" hydraulic hose.
The tank is a 33gal horizontal that formerly mounted across the bed of a service truck.  Next task is to sand some places with light surface rust and throw on a fresh coat of paint.  I want to use a check valve on the inlet so the compressor can unload, does it matter what kind I buy?
The plan is to set all of this outside for noise and space reasons which will necessitate some sort of doghouse for the compressor.  I could use some help here.  How much ventilation do I need to build in for proper airflow and heat removal?  Should I duct some fresh air to the fan that's built into the compressor flywheel?  How about the motor?  it'll make a good amount of heat in an enclosed space.
Piping from the tank will include a union so the thing is removable, then about 25' of 3/4" copper pipe up the wall and across the ceiling, then down.  From there into a T with drip leg down and air back up.  Is red strip copper sufficient, or do I need the blue?
I have a 6gal tank that came from a semi tractor.  I'll mount it end up on the wall.  Air will enter through a pipe thread opening in the bottom end, and there are 4 pipe threaded openings along the length of it.  I'll take my air out of the uppermost one to a regulator, with a guage to measure system pressure in the next opening down.  Since both ends of this tank are have pipe threaded bungs I can come out the top end later to put another drop in elsewhere.
It seems to me with a sufficient run of copper, and the smaller "auxiliary tank" to serve as a water separator this air should be pretty dry.  If that doesn't prove to be the case I could always splice in a coil of copper in an icewater bucket later if needed.
Have I thought of everything?

Two things I can answer, use blue copper, 3/4 " and silver solder the joints.  the rest will pipe up( np pun intended) and tell you their experience.

[wayne petty]

i would think that instead of a hydraulic hose to connect the pump to the tank...  the air coming out gets really hot...

you might want to use some kind of pipe with a flex joint in it..  the pipe will expand and contract... not good if its rigid...

there are also large check valves that screw into the tank inlet ...  this prevents tank pressure from backing up into the pump outlet...

on the tank... before you paint it.... examine all the welds....    look for cracks in the paint...   use a wire brush to remove paint from the welds...   the tank end welds are usually not a problem... but where all the brackets and feet are welded to the tank...

remember.. that tank rode on a truck for who knows how long..     was it stressed... probably... are there any cracks in the welds.. ?    are they dangerous.. YES... easier to inspect before putting the tank in service..

can you verify that the unloader works... the what...   when the motor turns off... the compressor comes to a stop.. this bleeds off  pressure from the cylinders and outlet ports... so when the motor cycles back on...  the compressor is not trying to start against a big head of air...   sure to burn the motor out... or worse... this is usually a copper line to a fitting on the crankshaft end plate...

tank drain...    some place easy to get at... so it gets done often... weekly...  with a way to drain it into a bucket...  instead of across the floor...

if you hate the noise of draining the tank or discharging the air nightly...  you can make a muffler for the drain.. with some bell reducers, nipples and some stainless steel scrub pads wedged in to reduce the sound..


just ideas ...

[jaybee]

Inprimer, thanks for piping up (there it is again) about the blue copper.

Wayne, the hose I'm planning to use worked for years without issues when this compressor was hooked to a 100# propane bottle, that's why I'm going to use it again.

"there are also large check valves that screw into the tank inlet ...  this prevents tank pressure from backing up into the pump outlet..."

Yup, that's what I want to do.

"on the tank... before you paint it.... examine all the welds....    look for cracks in the paint...   use a wire brush to remove paint from the welds...   the tank end welds are usually not a problem... but where all the brackets and feet are welded to the tank..."

Good thinking, I'll look all those points over very carefully.  Compressed air tanks can be dangerous.  That's why I didn't reuse that 100# propane bottle after 25yrs collecting water with no drain.

"can you verify that the unloader works... the what...   when the motor turns off... the compressor comes to a stop.. this bleeds off  pressure from the cylinders and outlet ports... so when the motor cycles back on...  the compressor is not trying to start against a big head of air...   sure to burn the motor out... or worse... this is usually a copper line to a fitting on the crankshaft end plate..."

It has never had an unloader, but my pressure switch can accommodate that.

"tank drain...    some place easy to get at... so it gets done often... weekly...  with a way to drain it into a bucket...  instead of across the floor..."

Handled.

"if you hate the noise of draining the tank or discharging the air nightly...  you can make a muffler for the drain.. with some bell reducers, nipples and some stainless steel scrub pads wedged in to reduce the sound.."

I built a muffler for a compressor unloader once.  It was built from a gallon paint can with holes drilled in it, filled with steel wool surrounded by shop rags.  It worked pretty well.


"just ideas ..."

And I thank you for them.  I can't come up with enough good ideas of my own, and if I could I still wouldn't be too proud to steal other people's ideas.   :?

[kb426]

The only thing that I would add is about compressors in general. The main thing that cools them is the actual air volume that they pass through as they pump. If you have bad valves or wore out rings, they could fail from heat build up in short order. As far as cooling requirements on your doghouse, safe than sorry comes to mind. It needs really good flow through to allow for cooling. I'd put a thermometer in the doghouse and see what you have and adjust accordingly.