Choosing air compressor replacement pump.

[Chaznsc]

So the pump on my delta is gone and it's apparently going to be cheaper to install a new pump. My questuon is what's the magic in choosing a new pump? I'm confused about hp ratings, for instance. I don't know what the electric motor puts out and the tag doesn't indicate. A volt / amp conversion came up with 5ish horses. The specs in my manual only refer to 6.5 but not sure if that's the electric motor or the pump.

Anyhow, would like some thoughts on this, good and bad brands, etc.

Here's my manual: https://www.dropbox.com/s/uu3conpmrbket74/DELTA COMPRESSOR.pdf?dl=0

 

[CGT80]

That is a 5hp motor. The manual says 6.5 peak which is just advertising.

Can you post a pic of the name plate on the motor with the voltage and rpm?

The manual shows 16 cfm at 90 psi.

I would look for a 2 stage cast iron compressor that will run on a 5hp motor. Some pumps run on 2 or 3 sizes of motors. On a small motor, the pump is run at a lower rpm and on the bigger motors the speed is increased. The old pump I have is rated at about 600 rpm on a 3hp and 800rpm on a 5hp motor.

Some people like the Eaton pumps, but they are imports. I thought about buying a compressor from them, but they wanted $500 to ship. For that price, I would have put the shipping money into buying a S&B compressor with free shipping. Just the pump would be much less in shipping.

You will need to know what size belt and pulley is on your motor as well. 1700 rpm motors are better and that may be what you have.

 

[Chaznsc]

Can I replace the pump with a smaller hp rating? I don't need 16cfm, and I'm not looking to spend much.

Attached is the motor plate image.

 

[CompressorWorld]

Yes, some companies rate the motor at peak starting amps, 6.5 hp is probably a true 3 hp electric motor. I'd look at a single stage compressor pump. Schulz has a good 4-5 hp punpbthat can be used.

https://www.compressorworld.com/piston-air-compressors/replacement-pumps/

Either way, stay with a single stage pump (100-140 psi) with this motor and don't go too large as you could over amp your motor and burn it out.

Use non detergent lubricant too

Good luck.

 

[CGT80]

At 23.5 amps and only a 1.0 service factor, I would agree it is only a 3hp. It is crazy how much they exaggerate on the HP. Also, the rpm is high, which is more common on the small motors. My old compressor had basically the same motor and same advertisement, but may have had a lower number for the amperage.

I would not buy a single stage again, but higher pressures require more hp and I don't know if there are any decent two stage pumps that will run on 3hp. It depends on what kind of work you do with air.

 

[md21722]

23A 230V single phase is solidly in 5HP territory. Lots of possibilities, what's your budget? An import pump sounds like what you're after if you're not looking to spend much. It would be better to buy a 3-5-7.5HP pump and turn it slow than rev up a smaller pump. Dual stage is really better, and what you have now. With dual stage your tools generally don't run out of air. With single stage it's always a hassle, bumping up the cut in and setting the cut out. Ideally no compressor used in a garage would cut in less than 110.. It looks like your Delta had a Rol air style pump. If you swapped in a single stage you'd have to adjust your pressure switch accordingly.

 

[redmondjp]

Check at your local Harbor Freight, if you have one nearby, to see what replacement pumps they have.

 

[Firebrand]

Don't forget about Surplus Center! www.surpluscenter.com

Great place for all sorts of stuff for the shop, farm, trucks, tractors.

 

[bugman53]

Yes that is a true 5hp motor, Since it is 3450 rpm motor you will have to check the pulley sizes to make sure you are in range of the pump.

IF you want cheap this pump from HF might suit your needs, It needs to spin 1050 rpm so make sure you motor pulley is the correct size, Let me know if you need help calculating the pulley size. you need a 3.28 reduction.

http://www.harborfreight.com/air-to...-twin-cylinder-air-compressor-pump-67698.html

The above is a 2 cylinder single stage pump so you will have to set your pressure switch to cut out at 145.

PS. For a given HP you can actually get a few more cfm at 90 psi with a singe stage pump, Where a 2 stage puts out more pressure but less CFM typically. IE for ingerosoll rand their singe stage 5 hp pump is 18.1 cfm and their 2 stage is 15cfm at 19psi.

 

[md21722]

PS. For a given HP you can actually get a few more cfm at 90 psi with a singe stage pump, Where a 2 stage puts out more pressure but less CFM typically. IE for ingerosoll rand their singe stage 5 hp pump is 18.1 cfm and their 2 stage is 15cfm at 19psi.

The problem is single stage pumps are rated at 40 and 90 PSI, but tanks fill up to 120, 135, or 150 PSI. Single stage pump output drops 20-30% after about 110 PSI. And most powerful air tools require the regulator to be set over 110 PSI to account for pressure drop through regulators, long hoses, and couplers. In industrial and commercial settings single stage pumps are relegated to fire sprinkler and climate control systems. Dual stage pumps are for shop air, and are rated at 175 PSI. They do not slow down much at all 0-175 PSI.

 

[bugman53]

The problem is single stage pumps are rated at 40 and 90 PSI, but tanks fill up to 120, 135, or 150 PSI. Single stage pump output drops 20-30% after about 110 PSI. And most powerful air tools require the regulator to be set over 110 PSI to account for pressure drop through regulators, long hoses, and couplers. In industrial and commercial settings single stage pumps are relegated to fire sprinkler and climate control systems. Dual stage pumps are for shop air, and are rated at 175 PSI. They do not slow down much at all 0-175 PSI.

Yes, no and maybe is the answer. To put it simply a singe stage pump will have more Displacement that a 2 stage pump at the same HP. This increase in displacement increases the load on the motor so you are limited to a lower pressure but you can move more air and have a higher CFM below 120 psi or so. To put is simply if you need a high volume of continuous air for a blasting cabinet a singe stage will out perform a 2 stage is some cases. If you need short burst of high volume air you will get less cycling out of a 2 stage.

quick example from memory. Comparing the Ingrosoll rand SS5 and TS5 pumps, Both 5 HP both same price range. The SS5 will supply 18.1 cfm at 90 while the TS5 will supply 14.5cfm at 90. The SS5 is 140psi the TS5 is 175. Typically the SS5 is shipped with a 80 gallon tank where the TS5 is shipped with a 60. So comparing the two compressors the SS5 will supply 25% more air when you need it but might cycle more often. It takes until 120+ psi for the 2 stage pump to catch the singe stage pump.

So from the above example a singe stage will walk circles around a 2 stage for a blasting cabinet. Lets say you are using the standard 15 cfm nozzle the single stage will never drop below 90 psi so you will never notice any pressure loss. The 2 stage will because you are using more air than you are supplying and once the pump cuts on you are working well below the PSI the two stage is more efficient and the single stage can supply more air.

If you need 110psi at your regulator there is some bad engineering of the piping system. 10PSI drop at max cfm is considered the standard. But you work with the hand your dealt sometimes and if you are working with an existing system you do what you have to.

This is just one example but it depends on your needs and price range. really what i would do is if you need more than 15cfm just get a 7.5 hp 2 stage and you will be good.