7.5hp rotary screw pricing.

[GraphicDisorder]

One last question and I am done with my research I hope. I noticed most compressors you have to specify your psi when ordering, like 125 and 150 psi are most common. What is recommended as it pertains to us since most press specs are xx cfm @ 100 psi. Would a 125 psi compressor run more often than a 150 psi?
I think what im trying to ask what difference would a 125 psi over a 150 psi be since the air is regulated at the press to be about 100 psi?

More PSI in the tank the less it will run. 

[Prosperi-Tees]

One last question and I am done with my research I hope. I noticed most compressors you have to specify your psi when ordering, like 125 and 150 psi are most common. What is recommended as it pertains to us since most press specs are xx cfm @ 100 psi. Would a 125 psi compressor run more often than a 150 psi?
I think what im trying to ask what difference would a 125 psi over a 150 psi be since the air is regulated at the press to be about 100 psi?

More PSI in the tank the less it will run.

Cool 150 psi it is!

[GraphicDisorder]

One last question and I am done with my research I hope. I noticed most compressors you have to specify your psi when ordering, like 125 and 150 psi are most common. What is recommended as it pertains to us since most press specs are xx cfm @ 100 psi. Would a 125 psi compressor run more often than a 150 psi?
I think what im trying to ask what difference would a 125 psi over a 150 psi be since the air is regulated at the press to be about 100 psi?

More PSI in the tank the less it will run.

Cool 150 psi it is!

Will also take a bit longer to get to that PSI from empty, but on these screw compressors it takes no time. 

[Prosperi-Tees]

That shouldn't be an issue with them running so quiet. I am getting really tired of hearing our compressor run and run and run and run

[GraphicDisorder]

That shouldn't be an issue with them running so quiet. I am getting really tired of hearing our compressor run and run and run and run

My Screw is right next to my press. 

[cbjamel]

Isn't it the more psi the less cfm? At least on std piston type.
Shane

[Prosperi-Tees]

I believe you are correct but if you have a regulator at your press regulating air at 100 psi does it matter whether your compressor is 125,150 or 175 psi?

[cbjamel]

But that only controls psi not CFM. That was my point the higher the psi the lower the cfm usually. A regulator doesn't effect that part.  But if the press eats air(CFM) up, then less psi unless you get a bigger compressor to compensate for higher psi if needed. Since I don't have 3 phase I had to biggest 7.5 single phase I could find, and when not in use I disconnect and block of the head I don't run to minimize compressor running more than it has to. That why I keep think of newer press as well as other things.

Shane

[Prosperi-Tees]

I thought the lower the psi the higher the cfm regardless of your compressor of being 125 or 150 psi.

Lets say a compressor puts out:
25 cfm @100 psi
23 cfm @125 psi
20 cfm @150 psi

My thoughts were even if your compressor is running 20 cfm or 23 cfm at 150 and 125 psi respectively that when it gets to the regulator and you regulate that down to 100 psi you would end up at the 25 cfm since the lower the psi the higher the cfm. Im sure im probably wrong as im no expert whatsoever but that's how my brain is processing it.

Although looking at the specs on these 2 machines makes me wonder:
http://www.aircompressorsdirect.com/FS-Curtis-SEG0723012R-Air-Compressor/p11331.html
http://www.aircompressorsdirect.com/FS-Curtis-SEG0723015R-Air-Compressor/p11333.html

[ZooCity]

Our will very likely be for sale in the next month or two.  Also a 7.5hp CPN, total air system. 

One thing about the psi...I would go for the 150.  Unless you have a perfectly laid out, closed loop system with quality, smooth wall pipe and few 90s than your going to see serious pressure drop.  I think common air runs are branched all over and a mish mash of different piping and fittings, so it's something to consider.

I was also surprised at how fast you can outgrow a 7.5hp, looking at 15hp now, would like 25 with extra tanks really.

[cbjamel]

That is my point, I personally would look at the 28 cfm at 90psi first.
Shane

[Gilligan]

Higher pressure = more stress = more heat as well.

But that's all I know, Brian would be the one I'd like to hear from.

[Binkspot]

IMO run higher pressure and larger pipe to the press, give it all you can and let the regulator do it's job. Pressure drop shouldn't be a factor under 100' run, average of 1psi drop per 100' @ 100psi. Each fitting in a system including couplings is equal to 5' of run. That being said 50' of run and 10 fittings is equal to 100' of run.

At this point your splitting hairs on CFM and pressure. Another thing to consider is the compressor outlet, filters and dryers, if they are 1/2" the flow is restricted anyway down to roughly 18 CFM.

Personally I would rather have a free standing compressor unit and remote tanks preferably someplace out of the way like the overhead or wasted space above a office or something. For larger volume add compressors and tanks for redundancy and needs. In a perfect shop two screw compressors with dryers maybe 15-30 cfm each and tow or three 200 gallon tanks. Set it up to have a high and low, the high does most of the work the low kicks in when needed. Go one step further and set it up so you can run one as the high for three months then switch it to be low for three months. In reality if a 10 color press is rated for 20 cfm chances are most of the time it's only consuming maybe 10 cfm. The rated cfm is it running full bore all heads, on an eight color and most of your jobs are three your only using roughly a third of the rated cfm. Not saying to short yourself but consider it.

[GraphicDisorder]

Running our CHIIID 12 color on a 5hp screw.  Never a issue. 

[Prosperi-Tees]

Thanks for the write up Brian.
My current 5 horse delivers about 15 cfm and the M&R tech who assembled the press said that it wasn't enough and could not get the press to index smoothly due to it, so the press runs rough and does not table lift smoothly and hits the reg gates thus my search for a new compressor. I believe he said the press would need at least 28 cfm if I remember correctly for him to be able to get the press to run smooth.

This is what FS-Curtis said the difference between the 125 and 150 psi units are:

When the compressor is assembled for the 150 psi maximum pressure the pulleys are sized for that maximum pressure. The air end will run slower than the 125 psi pressure. You will not see a rise in cfm if you set the un-load pressure lower than the 150 psi because the speed of the air end is the same. Cfm is based on speed and time.