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Pressure Drop

01/06/2009 9:01 AM

Right now we run a 2" header line at 90 psi that feeds air to 10 5-axis machines. If I were to install something that consumed approximately 700 cfm, would this starve the air line and cause a disasterous pressure drop that would ultimately lead to the failure of all machines?

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Pathfinder Tags: CFM Pressure starvation
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#1

Re: Pressure Drop

01/06/2009 10:38 AM

Google this; EARS - Exhausted Air Recycling System

It may be a solution to your problems if you can make it apply, if it is please tell them I sent you, always nice to get a commission when you are semi-retired, I am also a big supporter of their system, and the usual disclaimer I do not work for them, I am just an automotive journalist that really likes the idea of the exhaust air recycling.

Kevin

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#6
In reply to #1

Re: Pressure Drop

01/07/2009 9:03 AM

How exactly does this work? Or, in other words, what would it take to implement this into a machine shop with over 50 machines?

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#13
In reply to #6

Re: Pressure Drop

01/08/2009 9:43 AM

Rather simple concept actually, the air that is commonly vented to atmosphere is captured at the vent and piped back to the compressor.

The savings is realized in less power consumption, three phase power is expensive, since the compressor is not running as often to provide the required volume of air for the machines to operate. As you are aware a compressed air system is relatively inexpensive to build, the operation of the system is by far a greater cost. Typically air is compressed is piped to a component and vented, some form of work is completed, but the air volume and associated cost is lost, by capturing and piping it back to the compressor some of that initial cost is recovered. Recycling the air to use a currently popular term.

Another addition to the system that will save you money in the long term would be air dryers, descant types are the least expensive to use. Dry air in the system will facilitate longer life for the components.

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#2

Re: Pressure Drop

01/06/2009 10:46 AM

What is supplying the 2" header (capacity)?

How much air does each CNC machine take? At what interval? Continuous?

How much/length of piping is it to each machine? Length of header?

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Anonymous Poster
#3
In reply to #2

Re: Pressure Drop

01/06/2009 10:49 AM

............... after asking these questions I had a quick look at some numbers.

At first glance, without details, it looks like you are going to have a problem.

But please supply the requested info to confirm that.

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#5
In reply to #2

Re: Pressure Drop

01/07/2009 9:02 AM

We have two massive compressors that supply the compressed air (I am not sure how much power).

I am not sure how much air each CNC takes, but it is the normal amount used for the pneumatic system - they are 5 axis machines. Furthermore, this would be continuous or 10 hours a day.

The length of the header is very difficult to estimate unless I spent a significant amount of time measuring. I can tell you that the length of the pipe from the header to each machine is about 50 feet, straight down.

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#4

Re: Pressure Drop

01/06/2009 11:03 AM

As stated in earlier posts, What is your CFM supply. How far is the supply from your needs. is the air conditioned, And even if it was, you should still have drip legs. and Wye Strainers.

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#7
In reply to #4

Re: Pressure Drop

01/07/2009 9:05 AM

The air is not conditioned.

My supply is okay. I am not worried about starving the supply. What I am worried about is starving this one header that is supplying this particular cell of mahines.

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#8
In reply to #7

Re: Pressure Drop

01/07/2009 9:54 AM

Seems like a simple calculation.

the machines work on CFM more than pressure.

Calculate the capacity of the header and then the requirement of the machines on the header, that number gives you your surplus.

Calculate what the new bank requires and there is your answer.

Like I posted earlier, you can make the whole system more efficient by recycling the air in the system, it is also nice and Green, which seems to be the trend these days.

You also get to be a hero for saving the company a load of money on the electrical cost of the compressors.

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#9
In reply to #8

Re: Pressure Drop

01/07/2009 10:42 AM

That is what I planned to do...I just don't have the time to calculate lengths, etc. It was a debate that was brought up on whether we should run a new header to supply the increase in cfm.

About the EARS, accolades and status are things that do not motivate me. However, new technology and improving the company are. This is something I will look into and see if it is feasible for the company. Thanks.

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#10
In reply to #9

Re: Pressure Drop

01/07/2009 10:52 AM

You don't need too much detail for the first calculation, by calculating CFM totals you get a fast go, no-go answer.

Should the CFM supply be sufficient, then you can do a pressure drop calculation.

Good luck

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#11
In reply to #7

Re: Pressure Drop

01/07/2009 11:12 AM

You can't starve a supply if your supply. Yopur supply at the source is what it is. Example; lets say the CFM coming out of your supply 800 CFM, and your have lets say 100 cfm losses in the line due to frictional loses, it all depends on the length and fittings in the line.

And since the air is not conditioned, do you have drip legs to remove condensate?

You may have condensate pockets on the low points in the main that can starve the one header your concerned about.

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#12

Re: Pressure Drop

01/07/2009 12:00 PM

Neglecting friction losses it should just be a matter of supply minus cfm required by machines. This should be found in equipment O & M.

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