4 replies to this topic

[GTE]

Salutations to all,

I am working on this project which uses "instrument air".

I need to size the receiver.

Could you please provide a method to size these air compressor and receivers?

Any information on air system will be usefull.

 

Many thanks,

 

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[shan]

The instrument air receiver should have 15 minutes supply to allow all the instruments shutdown safely in case the instrument air compressors fail.

[thorium90]

You can estimate the amount of air used in each section of the plant. Consider advice from the following website.

 

http://instrumentati...on-calculation/

 

Next, consider different scenarios and the usage during those times. Eg: Normal scenarios, trip scenarios. For example, during plant trips, many valves will start moving, air consumption may increase.

 

Next, one has also to take into account that instrument air is dried and some air is used for purging purposes and is not actually usable. This may range from 15 to 20%, values which would be better left to the vendor to provide.

 

With all this in mind, one would be able to make a suitable gauge of the required compressor size you need. Final selection would depend on the vendor and their models available since air compressors are typically standard packaged units.

 

 

As for the size of receiver, that would depend. It may not be 15 mins. An analysis of the plant systems like safety systems may be necessary. For example, critical valves may have its own receiver beside the valve to provide just enough air for one final push to close. Also 15 mins may not be enough or may be too much. Analysis of the reliability and redundancy of the air system would be advantageous. For example, a plant may feel that it is better to have 2 * 100% compressors and very high reliability than to have large air receivers to last a plant trip.

 

It may be possible for you to work with your vendors for your sizing needs too.

Edited by thorium90, 10 May 2013 - 11:33 AM.

[Bobby Strain]

If you have a good nitrogen supply it can serve in a pinch. I would generally provide 20 - 30 minutes in the receiver operating between the normal pressure and 50 psig. Instrument engineers are best equipped to estimate air requirements. If you don't have them, look for a similar processing facility as a guide.

 

Bobby

[GTE]

Shan, Thorium anad Bobby Strain. Thank you for info