Best practices for plant air storage and capacity? 1

[SREisme]

Hi all, I am wondering if there are any "Rules of Thumb" with regards to sizing a plant air/compressed air receiver tank for a multitude of compressors. I have a system with a combined capacity of 10,000SCFM with a normal demand of 8000-9000SCFM, made up of 8 separate compressors, both fixed units and rental units. We are currently using our miles of air header piping as the receiver. My largest compressor has a capacity of 3050 SCFM, the smallest is 675 SCFM. I would like to get rid of all the piddly compressors and install a couple big compressors in the 3-4000 SCFM range to handle all the plant load with fewer pieces of machinery, with one installed spare. Does anyone have a case history of migrating from multiple compressors to a uniform system and if so how did you go about doing it? Are there any recommendations as to having a centralized compressor/dryer location versus a disributed system where the the compressors would be spaced around the plant near core users? Does anybody care about their utility systems? I look forward to your ideas. Thanks

 

[MikeHalloran]

Don't put the air compressor's roof intake right next to where the sandblast booths' discharge air comes out.


( Yep; seen it done. )



Mike Halloran
Pembroke Pines, FL, USA

 

[tygerdawg]

I was tasked with improving our plant air once upon a time. The "previous regime" put in a crazy mix of compressors, dehumidifiers, chillers, receiver tanks. The piping looked like an old hospital: piece-mealed together over time with little overall congruency or capacity planning. The so-called Maintenance Manager had cobbled this trainwreck over the years and refused to listen to any suggestions from any Smart @ss College Boy.

The only thing I was really able to improve was to shut down one of the compressors used in parallel to supply plant air. My local Ingersoll-Rand guy came in and performed a usage analyis (~$500 or so) that showed Compressor #2 was just running, but not contributing any useful volume to the plant system. I got an equation from Dept of Energy website that gave me costs for running an air compressor. By turning it off I saved $75K per year. I also added a couple of receiver tanks in strategic location to provide more constant flow/pressure in certain areas. When I had to put in new piping, I planned it by the numbers with the view to future expansion.

The moral of the story is that your air equipment sales engineer can direct you to a wealth of useful information on this subject. The fact of the matter is that massive improvements may be cost-prohibitive and you just may have to live with the inefficiencies.

TygerDawg
Blue Technik LLC
Virtuoso Robotics Engineering

http://www.bluetechnik.com

 

[TVP]

Lots of information available from U.S. Department of Energy and others. Take a look at these links:

http://www.energystar.gov/ia/business/industry/compressed_air1.pdf

http://www.compressedairchallenge.org/library/index.html

http://www.compressedairchallenge.org/library/casestudies/petrol_cs_mobilvernon.pdf

 

[chief]

a rule of thumb I came across and have found effective is to size the air receivers according
to the SCFM.

ie. total scfm = air receiver capacity (gallons).
The receiver may be a single or multiples in parallel to attain this capacity.
This rule only refers to low pressure ,circa 100-150psi systems

Offshore Engineering&Design

 

[romke]

there are a few rules of thumb:

partloading a compressor is usually very inefficient - you are therefore better of with a combo of a few larger and a few smaller compressors that can be started up as the need arises.

compressed air should be cooled and dryed as soon as possible - therefore a central receiver/dryer is the best way to go - in combination with smaller receivers/dryers down the line

cooling of compressed air is very important from a safety point of view, a compressor fire can have very serious consequences - using the piping system for this spells disaster

keeping the air dry is necessary to prevent corrosion and malfunctioning of airoperated tooling

tygerdawg is right with his suggestion to talk to your equipment sales engineer - serious advice usually can be had from knowledgable people from the compressed air industry

also your luboil supplier might have some useful info about how to locate dryers and coolers to prevent disaster/compressor fire