RE: Copper Tubing on the Intake of CAMs

[Jeff Whicker <jjwhicker@lanl.gov>]

At 12:00 PM 10/31/00 -0600, you wrote:
>I would use as small a diameter as would be compatible with the sampling
>device to minimize particle fallout in the intake lines.


Dan,
If you went with smaller tubes you might actually increase the particle 
loss.  Particle loss occurs through several mechanisms and include 
impaction (i.e., in bends), gravitational settling, and diffusion (either 
turbulent or molecular).  Studies have shown that particle loss in a tube 
is nonlinearly related to the particle aerodynamic size and the Reynolds 
number which is a function of properties of the air (density and 
viscosity), air velocity, and tube diameter.  These studies showed that 
there is a optimal tube diameter for a given airflow velocity in the tube 
that will provide for minimal particle loss.  There are a number of other 
factors to consider when trying to predict or minimize particle loss and 
others have commented on these.  Some useful references are listed below as 
a starting point for those interested.

Strom, L.  Transmission efficiency of aerosol sampling lines.  Atmos. Env. 
6:133-142, 1972

Wong, F.S.; McFarland, A.R.; Anand, N.K.  An experimental study of aerosol 
penetration through horizontal tubes and Strom-type loops.  Health 
Physics.  71:886-895, 1996.

Alvarez, J.L.; Novick, V.J.; Ritter, P.D. Particle transport efficiency of 
sampling lines: theory and practical experience with sample-line 
loss.  (sorry, I have the paper but not the full reference).

Jeff Whicker


>-----Original Message-----
>From: Michael S Ford [mailto:MFORD@pantex.com]
>Sent: Tuesday, October 31, 2000 10:40 AM
>To: Multiple recipients of list
>Subject: RE: Copper Tubing on the Intake of CAMs
>
>
>Just a bit of sanity check....
>
>We usually don't use sampling lines larger than one or two inches in
>diameter for aerosol sampling.
>
>For a one inch line, the volumetric flow associated with a transport
>velocity of 3500 fpm is about 19 cfm.  For a two inch line, the volumetric
>flow rate is about 76 cfm.  For a half inch line, about 5 cfm.
>
>I don't know of too many facilities with CAM sampling in the 20 to 80 cfm
>range, aside from Savannah River which may or may not sample through tubing
>with the impactor CAMs (comments folks?).
>
>Metal tubing can presents problems, especially in high humidity environments
>where the sample stream may traverse significant temperature changes (e.g.,
>outdoor to indoor).
>
>A very good person to consult specifically concerning line losses is Dr.
>Andy McFarland at Texas A&M University.  Jeff Whicker at Los Alamos has
>discussed whether you should even be using sampling tubes - he and his
>colleagues at LANL have studied that issue extensively over the last several
>years.  Lastly, the DOE has an Air Monitoring User's Group that meets
>annually (at least) to discuss air monitoring challenges throughout the
>complex.  You can find a description of the group at
>
>http://www.lrri.org/amug.htm
>
>'Hope this helps,
>v/r
>Michael
>
>
> >>> dhoffman@pangea-group.com wrote 30 Oct 00 11:23:33 AM >>>
>The length of the line is not as critical as its diameter and the number of
>bends/elbows.  In general, unless you are dealing with a particularly large
>or dense particle, a transport velocity of 3500 fpm should keep the
>particulates suspended in the copper tubing, with minimal line losses.  This
>transport velocity is used as a guideline in the air pollution control
>industry.  I'm sure a reference could be found without too much effort. The
>velocity in your system could easily be estimated and compared to this
>value.
>
>Dan Hoffman CIH,CSP,CHMM
>Pangea Group
>St. Louis
>
>-----Original Message-----
>From: Dave Biela [mailto:BielaD@wvnsco.com]
>Sent: Friday, October 27, 2000 8:46 AM
>To: Multiple recipients of list
>Subject: Copper Tuping on the Intake of CAMs
>
>
>We use copper tubing on some of our CAM intakes.  We usually stay below 6
>feet, but have had a few a little longer.  Some questions came up during a
>recent audit and I am looking for data from other sites that may use tubing
>on their CAMs.
>
>1.  How long of lengths?
>2.  Testing that may have been done (ex particle size, line loss etc.)
>3.  Any written guidance that might be out there.
>
>Please respond directly, my e-mail is changing, but I will still receive
>messages at the current address for a few weeks.
>
>BielaD@wvnsco.com
>716-942-4423
>
>Thank You
>Dave Biela
>
>!
>
>************************************************************************
>The RADSAFE Frequently Asked Questions list, archives and subscription
>information can be accessed at http://www.ehs.uiuc.edu/~rad/radsafe.html
>************************************************************************
>The RADSAFE Frequently Asked Questions list, archives and subscription
>information can be accessed at http://www.ehs.uiuc.edu/~rad/radsafe.html
>
>************************************************************************
>The RADSAFE Frequently Asked Questions list, archives and subscription
>information can be accessed at http://www.ehs.uiuc.edu/~rad/radsafe.html
>************************************************************************
>The RADSAFE Frequently Asked Questions list, archives and subscription
>information can be accessed at http://www.ehs.uiuc.edu/~rad/radsafe.html

=========================
Jeff Whicker

Los Alamos National Laboratory
Mail Stop G761
Los Alamos, NM 87545

wk: 505-667-2610
fax: 505-665-6071
email: jjwhicker@lanl.gov

=========================

************************************************************************
The RADSAFE Frequently Asked Questions list, archives and subscription
information can be accessed at http://www.ehs.uiuc.edu/~rad/radsafe.html