Compressor RPM question

[reman]

Hi guys, I currently have a FS Curtis 3 cyl pump. This a fairly large, single stage ES 50 model. Powered with an old 5 hp Doer motor. The entire setup works great, but it runs at about 875 rpm with my current pulleys. I am thinking it should be a bit slower, maybe at 100-150 rpms less. I find a ton of info on Curtis compressors but cannot find the recommended rpm range for this unit. Do any of you guys know for sure what the rpm range should be? Thanks

 

[Fixnair]

You could take an amperage reading on the motor. If it is too high then you need to slow it down. Conversely, speed it up. If it agrees with the motor nameplate leave it alone.
That compressor is probably only good for 90 psi.

 

[larry_g]

http://www.ebay.com/itm/FS-CURTIS-ES50-BASIC-COMPRESSOR-PUMP-/121213017626

This ebay sale has the spec sheet on your compressor. I am unable to copy the chart and cannot find it elsewhere. Can one of you computer gurus copy it into this thread? The chart says 900 is the correct speed. So if the amp check says your motor is not over-currenting then your good.

lg
no neat sig line

 

[zkling]

reman, realize that compressor flow rate is a function of pump RPM so if you drop RPM you will lower the output flow of the compressor. I'm not familiar with that particular compressor, but most of the somewhat older units were sweet spot in the ~700-800RPM range. YMMV.

http://www.ebay.com/itm/FS-CURTIS-ES50-BASIC-COMPRESSOR-PUMP-/121213017626

This ebay sale has the spec sheet on your compressor. I am unable to copy the chart and cannot find it elsewhere. Can one of you computer gurus copy it into this thread? The chart says 900 is the correct speed. So if the amp check says your motor is not over-currenting then your good.

lg
no neat sig line

Sir yes sir. Please see attached.

 

[Thorold]

FS CURTIS ES50 Bare Compressor Pump. Single Stage 95-125 PSI, 5 Horse Power, 19.5 CFM OR 7.5 Horse Power 23.4 CFM at 125 PSI. Weight 157 LBS, 18.1 x 23.3 x 16.7 Dimensions

STANDARD FEATURES: * Splash Lubricated * Cast Iron Crank Case * Heavy Duty Ductile Iron Crankshaft * Dynamically Balanced Flywheel * Cast Iron Cylinders * Large Intake Filter With Silencers * Heavy Duty Connecting Rods * Suction Valve Head Unloader * Large Main Roller Bearings * Intercooler With Radiating Fins * Oil Sight Glass

 

[larry_g]

reman, realize that compressor flow rate is a function of pump RPM so if you drop RPM you will lower the output flow of the compressor. I'm not familiar with that particular compressor, but most of the somewhat older units were sweet spot in the ~700-800RPM range. YMMV.



Sir yes sir. Please see attached.

Thank you for the attachment. I think that everyone starting to mess with compressors ought to study that chart and understand the relationship between pressure, cfm's, and HP required. I've said many times that when mixing motors and compressor heads you can fine tune either the speed or operating pressure to make a motor of a given HP work.

(can you explain how you captured the chart from ebay?)

lg
no neat sig line

 

[zkling]

I agree larry. That chart is too simple though. Quincy used to put out graphs with basically the same data but it had multiple trends superimposed on the same plot space. It was a real trip to try and find something fast. Exhibit A, attached.

 

[larry_g]

I agree larry. That chart is too simple though. Quincy used to put out graphs with basically the same data but it had multiple trends superimposed on the same plot space. It was a real trip to try and find something fast. Exhibit A, attached.

I agree it is a simple chart, hopefully simple enough for some members who are asking very basic questions.

What is exhibit A ? I see no attachment

lg
no neat sig line

 

[zkling]

I agree it is a simple chart, hopefully simple enough for some members who are asking very basic questions.

What is exhibit A ? I see no attachment

lg
no neat sig line

: Check it now. I had to convert the file to JPG as the attachment feature here on GJ wouldn't allow me to upload it as a tiff.

 

[b-body-bob]

Thank you for the attachment. I think that everyone starting to mess with compressors ought to study that chart and understand the relationship between pressure, cfm's, and HP required. I've said many times that when mixing motors and compressor heads you can fine tune either the speed or operating pressure to make a motor of a given HP work.

This doc from Champion shows the various HP motors used on 2 of their pumps, the pump speed, and the CFM output. Note all the motors are turning at 1725 RPM, so it includes the pulley size used to attain the pump RPM. As the motors get stronger, the pump RPM increases, as does the CFM. Also note they offer 125 and 175 PSI units, and they slow the pump down for the higher pressure models.

 

[rburke65]

I have a 5hp, 2 stage Champion and I think it turns at 805 rpm. Very quite.

 

[reman]

http://www.ebay.com/itm/FS-CURTIS-ES50-BASIC-COMPRESSOR-PUMP-/121213017626

This ebay sale has the spec sheet on your compressor. I am unable to copy the chart and cannot find it elsewhere. Can one of you computer gurus copy it into this thread? The chart says 900 is the correct speed. So if the amp check says your motor is not over-currenting then your good.

lg
no neat sig line

Thanks everyone. The ebay ad tells me what I needed. I had seen that sometime in the past, but when looking a couple weeks or so ago I could not find it. This compressor works great....it will pump up the empty 60 gal tank to 120 in four minutes......just sounds like its running kinda fast to me. The rest of my reasoning is that I figured that less rpm would be less heat and less long term wear and tear. I am hoping this thing will last as long as I need a compressor. I am going to go ahead and put it in a permenant place and not worry about it. Thanks to everyone for the responses, a lot of good info. Ron