Compressed air lines - confused!

Luke · 25 Jun 2012 at 11:28

Bit of an odd question for GD but it's the most diverse knowledgebase I can think of

We run a compressor and air lines at work for our plant machinery. It is a big old compressor and puts out 8 bar continous according to the gauges. It is run via a large cylinder which itself is rated to 11 bar.

We don't know the draw (if that's the correct term in this situation) of the existing machinery but know that it works fine with no difference in output regardless of how many machines are on.

I want to get a new mixer unit which has a minimum requirement of 5.5 bar. Clearly our compressor would power it with ease if it was the only thing running, but I have know idea how to go about working out if it would negatively affect the other machines.

If anyone is clued up on these kinds of things I'd really appreciate some advice on determining capacity/load.

Cheers

panthro · 25 Jun 2012 at 11:35

You need to work out the max draw when all existing lines are in continuous operation. Should be easy enough as each instrument/tool should have it written/stamped on its body.

Luke · 25 Jun 2012 at 11:45

The more I read into it, the more complicated it gets!
I'm now confused as I think it's the CFM ratings I need rather than PSI/Bar ratings.
Unfortunately the machines don't seem to state CFM or bar but once I know exactly what to ask I can get in touch with the manufacturer.

PhillyDee · 25 Jun 2012 at 11:48

As said, PSI is the pressure, cfm is Cubic Feet per Minute. This is what each tool needs to draw. Of course, what business is it? A lot of machinery only uses air when required, not continuously. The large cylinder is there to keep the pressure constant (a reservoir). The compressor tops this up.

Luke · 25 Jun 2012 at 11:56

The machines are grinding mills, producing (for arguments sake) ink. The primary power source is electrical but they have a pneumatic mechanical seal so don't use air continuously. We also run pneumatic filters which do run continuously but the flow rate is very small.

Mercenary Keyboard Warrior · 25 Jun 2012 at 12:37

At the rated PSI the compressor will output x CFM (cubic feet per minute)

The cylinder will be at the same PSI as the compressor basically, it cannot be at a higher PSi than the compressor supplies. If you have no leaks and no usage the compressor would fill the cylinder and set it at 8 BAR in your case.

As you use the air the PSI will drop if your using more than the compressor is adding. The air in the cylinder is probably droping in PSI but as long as it doesnt drop below the level the machine that needs the highest PSI rating needs then your dandy.

You need to understand the total CFM usage of your machinery after the new machine is added, If your usage is below the output of the compressor then you have enough supply, your issue then could be demand spikes. If you have demand spikes you can add more capactity to the system (ie another or bigger cylinder to handle the supply when demand is greater than the output from the compressor)

Think of it like a water reservior the rainfall is your compressor, the water reservoir is your cylinder. If you have enough capacity in your reserviour to get round the summer months of high demand and low rainfall then you will be fine if your annual rainfall is greater than your annual demand. But if either of them you cannot say is true you have an issue.