Particulate testing of compressed air

[Pearse29]

Hey folks, wondered if anybody could help. I am currently project managing a compressed air system test(for breathable air). I have a met one laser particle counter which is giving me particle counts in microns/cubic feet (u/ft3). However the client would prefer the results presented in u/m3. I have obtained a conversion factor for cubic feet to cubic metres, multiply by 0.0283(i.e. divide by 35.315) but the client seems to think that the u/ft3 needs to be multiplied by 35.315. I was wondering if anybody has dealt with particulate testing of compressed air, and where i could get confirmation in writing of the correct conversion factor to use.

 

[RWF7437]

http://joshmadison.com/software/convert-for-windows/

 

[bimr]

You have to make the unit conversion at standard conditions since you are dealing with a compressible gas.

http://www.eng-tips.com/viewthread.cfm?qid=252997&page=1

 

[Ron]

Pearse29...think about it for a minute. Let's say you have a particle density of 1 micron per cubic foot. 1 cubic foot is significantly smaller than 1 cubic meter, so how could you end up with a smaller number to convert? In fact, 1 cubic meter is 35.315 times larger than 1 cubic foot. So if you have 1 micron per cubic foot, you'll have 35.315 microns in a cubic meter.

Your client is correct....multiply your value by 35.315

 

[bimr]

NOTE: Conversion factors- mppcf x 35.3 * million particles per cubic meter

http://books.google.com/books?id=WM...ult&resnum=4#v=onepage&q=mppcf X 35.3&f=false

http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=standards&p_id=9994

 

[Pearse29]

Ron, I understand the logic and this is the way I am looking at the situation, but whenever you have the manufacturer giving you the response outlined below, its gets slightly confusing. Considering METONE are the munufacturers of the particle counter, I was thinking that they would know the conversion factor.


Hello Pearse,
The standard conversion from cubic ft to cubic meter is a multiplier of 0.02831685. This is a standard conversion like converting liters to gallons. Any conversion program or spreadsheet that has volume conversion will give you this result. Hope this helps.

Best regards,

Mike Putnam
Service Manager

Met One Instruments, Inc.
ISO 9001:2000 Certified Company
Ph. (541) 471 7111 (Ext. 133)
Fax (541) 471 7116
service@metone.com

 

[Ron]

Pearse29..yeah, that would certainly throw you off; however, it is like checking results of a computer program. As engineers, we have an obligation to validate "black boxes". That includes obtaining calibrations and in the case of computational software, using some other means of checking the result, such as running the same data on two separate programs or hand-calculating a validation problem. You obviously can't validate their counting process, except through calibration.

In this case the manufacturer has it exactly backwards, which didn't make you look very good to your client. You might want to point that out to them.

I won't go on a rant about metric conversion...we should have been there long ago, but we're not.

Measure twice, cut once.