Odd Ball IR Type 30 Model 41 Compressor Questions

[DougWil]

I picked up a IR type 30 model 41 compressor a couple of years ago and haven't done anything with it.
It looks in great shape and turns easily.

The model 41 is a high pressure 3 stage pump, rated for 1000 psi max with 2 cylinders and the 2nd piston has a 3rd piston and 3rd stage cast on top of the 2nd.

Anyway this beast was made by GE in 1958 and has a 9/16" thick tank rated at 400psi working pressure.

The GE tag says low pressure system 255 psi, and high pressure system 350psi.
The relief valve is 400psi.

The tag also says 9 cubic feet of free air at 350 psi.
Looking at the IR performance specs it says at
600 rpm, 300 psig, 8.6 ACFM.
600 rpm, 400 psig, 8.4 ACFM.

Not sure why GE's values aren't closer to IR?
Maybe GE ran higher rpms than IR values?

Anyway, if I was to draw out air from the tank at 100 psi for sand blasting wouldn't I have closer to 20 cfm?

 

[DougWil]

Nobody??

I think some of you compressor gurus are holding out on me.

 

[Packard V8]

Anyway, if I was to draw out air from the tank at 100 psi for sand blasting wouldn't I have closer to 20 cfm?

Far from a compressor guru, but I don't think it works that way. The IR high volume pumps designed for sand blasting supply have two large equal size pistons. The high pressure pumps have one large, one smaller. Your very high pressure has one large, one small and one very small, doesn't it?

jack vines

 

[jallyn]

The Ideal Gas Law says if you have 9 cubic feet at 350 psi then you would have 31.5 cubic feet at 100 psi. Air is not an ideal gas so it is closer to the 20 cubic feet you guessed. It won't be as energy efficient as a lower pressure compressor, but it can work. Basically the inefficiency goes into wasted heat at the compressor.

 

[DougWil]

Far from a compressor guru, but I don't think it works that way. The IR high volume pumps designed for sand blasting supply have two large equal size pistons. The high pressure pumps have one large, one smaller. Your very high pressure has one large, one small and one very small, doesn't it?

jack vines

The pistons are 4" and 1-1/2" and unknown on the 3rd, all with 3-1/2" stroke.

Agreed that the ideal sand blasting compressor would have high volume, and a very high hp motor too.

But what I am thinking is if it takes 5hp of energy to run my HP pump and compress the air to 375 psi or 5hp of energy to compress the air to 225 psi with a different pump only to be regulated down to 100 psi for blasting, what is the real difference?

Granted the latter doesn't waste as much energy over compressing the air, but would it be significant?

 

[DougWil]

The Ideal Gas Law says if you have 9 cubic feet at 350 psi then you would have 31.5 cubic feet at 100 psi. Air is not an ideal gas so it is closer to the 20 cubic feet you guessed. It won't be as energy efficient as a lower pressure compressor, but it can work. Basically the inefficiency goes into wasted heat at the compressor.

That is what I am thinking, just not as efficient.

 

[jallyn]

That is what I am thinking, just not as efficient.

Yep. If you have to push a loaded tool cart up 100 feet in elevation and you push that same tool cart up 350 feet of elevation and let it roll down to 100 feet you will have accomplished the same amount of work, but which way will you be more tired (wasted effort)???

 

[bad_idea]

Am I missing something? If you intend to use the air at 100 psi, why not reset the pressure switch? ON at ~140 psi to ~175psi. Even better, repipe the unit to bypass the 3rd stage. Take the air pipe from the second stage and run it into the tank. Each stage adds additional heat from compression, I would think it ideal to skip the extra heat.

 

[DougWil]

Am I missing something? If you intend to use the air at 100 psi, why not reset the pressure switch? ON at ~140 psi to ~175psi. Even better, repipe the unit to bypass the 3rd stage. Take the air pipe from the second stage and run it into the tank. Each stage adds additional heat from compression, I would think it ideal to skip the extra heat.

I have considered those ideas, just don't know enough about compressors and the friction/heat losses to know if it is worth the trouble??

I think w/o bypassing the 3rd stage it would still compress the air in that chamber requiring the energy and work. Only discharging it into a tank of 175 psi would require less energy than into a tank of 375 psi.