Please advise on reappointing an industrial compressor

[frascati]

I'm helping a friend refit his 80 gal DeVilbiss with a newly rebuilt Saylor Beale 705 compressor head. After all refit we'll have it inspected before running to assure proper assembly, wiring, and safety.

He had it serviced last year with tank inspection and motor replacement. Motor is running 230 single phase. He uses it approx 5 to 10 hours a week for pneumatic tools and a small blast cabinet on his blueberry farm.

But the old one lung small DeVilbiss pump remained. As did the ancient pressure switch. So I'm almost starting from scratch.

The SB head is rated to run at 540rpm with 3hp and 845 with 5hp.

I have the appropriate taper loc pulley size fit on the motor.

I wonder if anyone can help me either with a link to a diagram that describes setting up a compressor or can simply describe it here in this thread.

####### I need to purchase the appropriate pressure switch (SB recommends 130 to 175). What switch do I need exactly? Ratings? Why are some pressure switches rated for single or dual stage compressors? What difference could that make where the switch is concerned?

####### Magnetic starter. There are so many types on Ebay and Amazon. How to choose?

####### Manual switch. Isn't this included on most pressure switches? Or are we talking something different? It also appears to be a feature on most magnetic starters I've looked at.

I also need clear instructions as to plumbing the centrifugal unloader valve on the SB as well as other necessary plumbing.

Thanks so much.

 

[Fixnair]

First of all let's get the proper size motor sheave. (Pulley) take the comp speed (540), multiply that times the compressor sheave OD. Now devide that figure by motor speed (1740) and that will yield the motor sheave size OD. When you purchase the sheave it is important to tell them you are giving them outside diameters. Sheaves are sold as pitch diameter so they will have to adjust accordingly.
Call around some electrical Supply stores and get a Square D(this is a brand name ) model # GHG2 pressure switch good for 175 psi. You do not need a bleeder valve with it although it may be the only way they stock it so get it. This switch does not have a manual operator on it so you will need a fusible knife switch or some other means of turning it off & on. A circuit breaker perhaps. Although circuit breakers are not really designed to be service switches.
You do not need a magnetic starter with a single phase motor. The Square D switch will handle 3 HP@ 230 volts.
You will need a tank check valve, with bleeder port, in the tank. Plumb your compressor discharge to the check valve. A 3/4" X1/2" check valve will do. Pick up at a compressed air house. It will need a port in the tank at least 3/4" pipe size.
Now your centrifugal pressure release should be plumbed to the bleed port of the check valve so when the compressor stops the CPR will open and bleed the air off the head of the compressor. If per chance the CPR does not work you can connect the check valve bleed port to the bleeder valve on your new pressure switch and the same thing will occur. When the pressure switch opens and kills the motor, the bleeder valve will open too and bleed the pressure off the compressor.
Hope this helps. If you have any more questions I'll try to help.

 

[PT Doc]

why pressure switch?

 

[frascati]

Motor sheave is taken care of and installed.
Like the idea of forgoing the magnetic starter. Is this because a Square D has beefier contacts than the super cheap imports?

These look good?

Probably the best priced and with the lowest cut-in. Lower cut-in is better, no? Fewer cycle times when using the compressor?
http://www.amazon.com/dp/B000LEQDME/?tag=atomicindus08-20

http://www.ebay.com/itm/Square-D-90...498?pt=LH_DefaultDomain_0&hash=item2334c06d5a

Slightly lower cut-in. Slightly higher price.
http://www.ebay.com/itm/SQUARE-D-90...010?pt=LH_DefaultDomain_0&hash=item4acd1ffeba

There is also a tank check valve with bleeder port next to a pressure gauge on the tank already. I'll include a photo or two here soon of the whole as it is with the SB 705 mounted but unplumbed.

Would this be ok for a manual shutoff? It's 300amp rated with huge copper contacts inside and less than ten dollars.
http://www.amazon.com/dp/B007O0BBFM/?tag=atomicindus08-20

Or this?
http://www.ebay.com/itm/Siemens-Sir...tor-Protector-P-N-3RV1011-1EA10-/141191818583

I'll have to draw a diagram here as far as I understand your comment on the unloader. Each of the SD switches above has an unloader. I understand the SaylorBeall pump centrifugal unloader valve is used to bleed compression off of the head until the motor can get up to speed. So that ought to bleed to atmosphere? The unloader on the pressure switch releases pressure in the lines? I'm confused about the relationship between these two unloaders.

Thanks again so much for your advice.

 

[frascati]

Any more input on this?

 

[compressornew]

Phase :- 2
Voltage :- 208/230
If you can increase phase or voltage capacity of machine then get positive results in future.Try to use machine 12 to 14 hours a week.