residence time

Did you revise ISA standard (ISA - 7.1.01-1996 Quality Standard for Instrument Air). It may be useful??

I perused this standard and I could not find any figure about my request in it

Taking the definition of Residence time as surplus air supply duration (maintain the air pressure between upper & lower pressure) even when the air compressor fails to operate by any reason.

Such requirement may not be appreared in standard including ISA since it is not the standard requirement. It is specific requirement as I believe.

Since the air pressure in air receiver is not always maintained at upper pressure, the same air receiver can durate various residence time.

I would recommend you to take Min. 5 min. for residence time based on my experience, whatever specified in the specification of the plant. Sometime, 3 min is not sufficient to control all air-operated instruments since some of them are relayed several mins by the logic.

Hope it will help you!!

I'm not aware of any standard governing this.

There are two questions I would ask myself here:

1. How long does it take my redundant air compressor to come online (if you have one)? That will set my bottle size and then I would add some buffer.
2. How long does it take an operator to go out there and give it the 'ole restart try? Again, this time lag will set the bottle size and then add some buffer.

Sometimes, you have a system that will interlock on instrument air pressure (in my experience, a PSA system had a low IA pressure interlock) that may also affect receiver sizing.

Hi Hossein

I would suggest Try this link, may help.

www.isa.org/intech/20090102

OR

http://www.isa.org/InTechTemplate.cfm?Section=Features3&template=/ContentManagement/ContentDisplay.cfm&ContentID=73680&CFID=694495&CFTOKEN=47111252

Neat article, thanks for the link!