Air Compressor

Yes. Pressure does not depend on piston diameter, but flow rate and required hp do.

Do an internet search for this, '7.5 HP two stage compressor head', and pick which one fits your budget.

This should work....

It will be okay but seems to have 90 PSI and work with 5hp electric motor, I already own 7.5hp motor, and required 175PSI, so wouldn't it be little small

That's able to maintain 90 psi @ 14.9 cfm....It has max pressure 175 psi...It will do better with a 7.5 hp motor....What is your cfm and working pressure requirement?

Any small shortage in hp can be corrected by resizing a pulley.

Disagree.

What's the pressure rating on the tank, and what condition is it in? Has it been tested lately?

Whether 5 mm thickness is adequate depends on the diameter of the vessel, and how much corrosion allowance has been applied.

Well, let me give you all an idea about what exactly I am going to use this for, 4 Tire curing chamber( so I would have to air 4 of 12.00X24 tyres and fill the chamber) 1" Impact wrench, Tire changer with one hp motor, a 50 Kg pneumatic grease pump, and inflating other tyres as it come for work

Tank diameter is 22"

The tank requires periodic inspection and testing under a written scheme of examination that is followed by the Surveyor/Engineer from the organisation that is providing burst indemnity insurance cover. For information, cover will be required if the tank is installed in the UK if the energy stored exceeds 215 bar-litres. It is not possible for an anonymous internet forum to become involved in the underwriting of this particular vessel for public safety.

The compressor needs to be selected for the pressure and flowrate that the facility needs. It is not possible for the forum to assess the flowrate from the information given.

It is unreasonable to introduce additional information at a later stage in a thread, as to do so may invalidate the replies received up to that point, which some readers may find offensive. Next time, please include all relevant information at the start of the thread as to do so enables a more concise response to be obtained earlier, saving time, which is a currency, just like money.

A typical air wrench uses 5cfm@90 psi...so if you plan on using several devices at once, you might go to the next larger model which provides 24.4cfm@90psi....requires 7.5hp electric motor....

http://www.northerntool.com/shop/tools/product_200596493_200596493

Your tank at 58 gal is a little small, I would recommend 120 gal...

The tolls you want to supply air to, do not require 171 psi. Sounds like you need more volume, not more pressure. Making this compressor a 2 stage , will not increase the volume of air generated.

At 171 PSI make darn sure your tank is capable of this pressure, there should be a label with this info. RE: the compressor just buy one that matches up to the 7.5 HP you have to drive it, if you need more CFM add a unit probably much cheaper than one big unit. Most industry max is 90 PSI some service shops go to 120 PSI. You should check with authorities especially if you have staff operating in this area.

Safety first.

If you have a 'proper' tank (receiver) then it will have a nameplate telling you the max working pressure. It should also have a matching safety valve and pressure gauge - both essential.

Go for a pulley driven compressor. You match the size of the wheels to give you the necessary torque for the working pressure depending on the piston diameter, from which you get the compressor speed to give you the flow depending on piston stroke/length.

As a rule of thumb, you get 4 scfm per HP. But as others have said. Go through compressor specs for the pressure you want - then pick one that has a 7.5hp motor. You need to note the speed of (this) compressor and match it to the speed of your motor by suitable pulleys.

That will give you the size you want.

So now that the whole concept has been over analyzed here's what I know.

A good 7.5 HP air compressor head should be able to provide at least 25 CFM at 175 PSI and 30+ @100 PSI which on a ~50-gallon air tank should be more than sufficient for most standard shop use.

Especially so being that in normal shop compressed air system the tank is regulated down to 100 - 120 PSI from the compressors normal 140/175 PSI cycle settings.

I have the mil-spec 15 HP version of this one, Two stage V4 Air Compressor head. , and it does ~50 CFM @175 PSI.

Tank wise. Not our problem. OP didn't ask so I am assuming his is fine. Testing wise in reality it's rather rare that any air compressor ever gets any tank retesting done once it goes into operation. I've never seen one get a tank pressure test and some were in use for 20+ years before I ever saw them.

Maybe some places do that but I have yet to ever see any place that does. Heck, I have a number of tanks that are still in service that are pushing 40+ years old and they probably lived a hard life before I ever got a hold of them.

Pressure system regulations are clearly different in Minnesota.

What is mean't by 100/60 piston ? and what units ?

Diameter in mm.

Bore & stroke in mm

IMHO you should consider the overall situation and buy a whole new compressor sized to your needs and scrap the "old" tank.