Compressor question

[trooper1954]

Hi,
I have a Campbell Hausfeld 60 gal 5 hp 2 stage compressor that runs 13.5cfm @ 90psi, and has a 80/20 duty cycle. I'm using this in a sandblasting setup, and it runs for about 4 minutes before it kicks in. How long should I continue to blast after the compressor kicks in before I would be doing some damage? Is it better to run 4 mins then give it 4 mins rest, or run it for awhile after the motor kicks thereby saving the stop/start situation?
Thanks for any advice

 

[Lightning rod]

trooper
not sure if I got your situation correctly

the 80/20 duty cycle

does this mean it can run 80 % "ON" time ?

if this is the case, it sounds like you don't have to worry since it's so close to 100%
that you probably will never use up the full duty in practical situation

in any event , the motor will have to eventually kick in (start stop)to keep the tank full

or are you saying you want to modulate the air usage so that the motor stays on all the time
and you avoid the start stop when you are blasting a part?

the compressor pump and motor is designed to handle this situation for 10,s of thousands of operations so I'm not sure if you appreciably increase life span by modulating usage

sorry I guessing a bit at your question

 

[redmondjp]

You are better off keeping the motor running continuously. The motor is only rated for so many starts per hour (typically 4-5) because that high current during starting heats up the windings and it takes a long time for that heat to dissipate.

Put a box fan blowing over the pump and motor to help it stay cool. Your bigger problem is that the compressor will start putting out a lot of water vapor after 10-15 minutes of continuous operation (I have a compressor that is the same size). You really need a bigger compressor if you want to sandblast for very long. Search on this site - this topic has been extensively covered.

 

[nadogail]

Keeping the motor from being overheated will extend the life of your compressor.

 

[pancho400cid]

How long is a start/stop cycle while you are blasting continuously?

Meaning this: First start of the day the compressor runs until the pressure switch trips it off at full pressure. You start blasting, and "X" minutes later the pressure switch trips and the compressor starts running. You keep blasting continuously and the compressor eventually catches up and trips off after time "Y" - IF the compressor makes more air than your blasting set-up uses. That's a big "if" and by no means guaranteed. If not you continue to lose pressure down to some equilibrium point and the compressor never shuts off.

Assuming your compressor will keep up, what is time "Y"?

...

 

[islandkent]

Great explanation pancho!

 

[trooper1954]

Thanks pancho....
It runs for 4 minutes while I'm blasting, then the compressor kicks in and the pressure slowly drops to around 80psi and stays there, but the pump just keeps running. I guess this means that it cannot keep up to continual use and replenish the tank if I just keep blasting.

 

[firebirdparts]

That's pretty common with blasting. It takes a lot of air. They do get really hot, but I just let mine run. I mean I don't monitor the time.

 

[Ilikeike]

We stepped up to a 7.5hp champion advantage series from a 5hp tractor supply Ingersoll two sage because of the blast cabinet usage in our small shop at work.

I'm pretty sure I have the same campbell hausfeld two stage 5 hp at Home as you do OP,although my tank is 80gal, I just stop for a bit when I use an air hog tool like a DA. have a sip or two on the beverage and get back to it.

 

[pancho400cid]

I guess this means that it cannot keep up to continual use and replenish the tank if I just keep blasting.

That is exactly what it means, and really if it's blasting OK at the pressure it CAN keep up with (80 PSI or so) it may be OK. I mean, not for 3 shifts per day in an industrial setting, but for even pretty frequent home/hobby use. Worst case is you stop blasting for a couple of minutes to get the pressure up, then blast/stop while minding the pressure (motor running the whole time pretty much). Very common, and it's what I have to do, but I don't blast much and have a crude set up.

I'm not sure how your motor manufacturer is defining duty cycle. If you truly ran continuously for 48 minutes out of an hour and let the motor rest for 12 minutes, that is one interpretation of an 80/20 duty cycle with minimal effects from frequent starts as others mentioned. You may be able to get specific info from a manufacturer's manual specific to your motor, but I don't know if it's worth the trouble.

As for the moisture issue mentioned that is definitely true, and you need serious moisture control hardware for your set up.

 

[csp]

I guess this means that it cannot keep up to continual use and replenish the tank if I just keep blasting.

Not necessarily. It only means that the pump isn't capable of enough CFM to exceed the use of the blaster and build pressure to the shutoff point in the pressure switch.

If it is able to maintain the pressure that you're blasting at you're fine to keep using it. If it drops and continues to drop, then you have a problem.