Compressor Choices

Replace the 50 hp with a 50 or 60 hp.

Shop for a new , small , stationary diesel , like a Kubota , Briggs & Stratton ,

etc.

(1) My suggestion is number 1 if you have only 3 options unless future demands will not vary.

(2) Buying 50 + 50 is alternative since the lower compressors (20, 30) have the lower efficiency.

(3) Final suggestion is to buy new 50 compressor but do not remove the old one. you can keep it as back up (or vice-versa) It can be also the answer when the future demands will slightly go up even more than 100 HP

Provided your budget is limited, I do not see any bid differences between (1) and (3).

In conclusion, my best recommendation is (3)

The special advantage to yeonhu's GA is that if any of the four compressors is down for service, the remaining ones can handle the total load.

You should be looking at the volume of air you use in making the decision on a replacement. These old compressor probably do not produce anywhere near the air out put that a new one does. Purchase one that will produce all your air needs plus some for future expansion. I would all so recommend a rotary screw compressor with VFD. It will save money as it will only produce on demand. Save the the other for back up to service the new one and if it should fail.

Definitely check how much and how the air is used.

What pressure do you compress the air to? What pressure do you use the air at? A large difference is money being wasted somehow.

How many cfm air do you produce? How much air does the equipment require? Again, a large difference is energy being wasted.

Whether the old equipment is saved for "backup" or traded in for credit on new equipment is an ecomonic choice. Will the old machine be ready to operate if needed? How much will the compressor salesman give for the old equipment?

I would suggest replacing the old 50HP because it will be more expensive maintaining the old one.However you keep it as back-up compressor. The replacement compressor will depend in your budget and usage. If your current usage is around 80HP ,a 50HP I think will be enough + your 30HP. Preferrably, you may want a 50HP with VFD drive (inverter) so you can save some power during intermittent usage. The VFD will run as to what the demand in production is needed, meaning it will intelligently deliver air only of the right amount from 30% to 100% of your intermittent demand. If you foresee additional air in the future you may require a bigger unit. Please check also leakages in pipes which may lessen your demand for air. A small pinhole waste around 25 cfm of air.

Before you do anything you need an air audit to determine what your requirements are. Until then you will be throw money at guesses. Once you know what your air needs are then evaluate the units you have with an Air Systems Specialist who can reccomend options. Also include your utility company in as there may be rebates, low interest loans available.

Air audit is good idea. Even a second opion from different local compressor supplier.

More details would help. What type of compressors are they. Reciprocating or screw type? How often do each of them run. Do you have large intermittant requirements or steady requirement. How large are your receivers? If screw type they may be running but unloaded or partially loaded which still consumes a large amount of power.

Many local power providers will provide rebates for buying a new variable frequency drive compressor. It saves on power only turning the screw when air is required. They are pricy but the cost of power is the main cost in using compressed air.

If you have leaks fix them, You should also have the compressor running at as low a pressure as you can and still function. ie don't have them unload at 150psi if you run at 100psi.

Lots of variables to consider. Ask other users of compressed air users in your vicinity to recommend a couple of different vendors.