From: <Myers.Ron@epamail.epa.gov>

To: MDMARET@mactec.com

CC: Sorrell.Candace@epamail.epa.gov; WCGRAY@mactec.com; Segall.Robin@epamail.epa.gov; 

Ray.Merrill@erg.com; Westlin.Peter@epamail.epa.gov; . . .

Date: 7/10/2009 5:00 PM

Subject: RE: Duct diameter re OTM 27

Attachments: Pages from OTM27_PM2.5cyclone dimensions.pdf; PM2.5 Cylcone Sketches.pdf

Mike:

Thanks for all the work and thought into the measurements and

applicability to sampling real stacks. I guess we should not have

assumed that the CTM40 (Which was based upon the PRE-4) methods were

correct in all their aspects. I guess this means that the area of 20.5

square inches that is in the method for the combined PM10 and PM2.5

cyclone, filter and Pitot are a little (greatly) off. As a result, for

our response to comments, we would need to think about how we will

address this in the final rule. Also, we will need to think real fast

to provide guidance to those recipients of the ICR. I think that we

might be able to segway into the issue of PM2.5 testing only with the

comment from CT that comments on sampling in very hot stacks and the

commentors suggestion to place the PM2.5 cyclone in a heated box

external to the stack and use a traditional heated probe to get the

sample to the cyclone. I think we would need the expertise of a

particle physisist (Joe McCain who designed this in the first place).

Another option would be to revert to single point sampling based upon

the assumption (probably pretty good) that PM2.5 behave very similar to

a gas and that isokenetic sampling may not be required. I'm open to

other suggestions.

When I used the measurements in the Method, I did not think about the

cyclone being backward and that the filter and probe were as wide as

they are. Also, I did not think that the machinist would not trim down

the external dimensions to parallel the inside dimensions.

I am also attaching a copy of the page in the Method with some annotated

dimensions from Mikes measurements.

I'll see Ray on Monday and we can discuss the next step.

I wonder what other glitches lurk in all the equations and procedures of

the particle sizing method.

(See attached file: Pages from OTM27_PM2.5cyclone dimensions.pdf)

_________________________________

Ron Myers

U.S. Environmental Protection Agency

Office of Air Quality Planning and Standards

Sector Policy and Programs Division

Monitoring Policy Group, D243-05

RTP NC 27711

Tel. 919.541.5407

Fax 919.541.1039

E-mail myers.ron@epa.gov

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 |"Maret, Michael" <MDMARET@mactec.com> |

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| To: |

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 |Ron Myers/RTP/USEPA/US@EPA |

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| Cc: |

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 |"Werner, Arthur" <ASWerner@mactec.com>, "Gray, Walter" <WCGRAY@mactec.com>, Barrett Parker/RTP/USEPA/US@EPA, 
Peter Westlin/RTP/USEPA/US@EPA,|

 |Jason Dewees/RTP/USEPA/US@EPA, Robin Segall/RTP/USEPA/US@EPA, <Ray.Merrill@erg.com>, "Joe Fanjoy" 

<joe.fanjoy@erg.com>, "Danny Greene" |

 |<Danny.Greene@erg.com> |

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| Date: |

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 |07/10/2009 12:38 PM |

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 |RE: Duct diameter re OTM 27 |

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Hi Ron,

As we discussed yesterday on the telephone, I have made numerous

measurements on a PM2.5 cyclone head, a 47-mm filter holder, and a probe

assembly in order to calculate the projected area (i.e., blockage of the

stack cross-section) when the OTM27 components are inserted into an

18-in diameter stack.

One interesting item of note is that since the inlet to a PM2.5 cyclone

is located about 2.75 inches from the end of the cyclone, the tester

would be unable to collect a stack gas sample from traverse points 5 or

6. The traverse points would be located 2.6 and 0.8 inches from the far

wall of the stack, respectively. So, aside from the blockage issue, one

might say that the minimum stack diameter for which a PM2.5 cyclone head

could be used (and still sample at all traverse points) would be about

62.5 inches.

Using a PM2.5 cyclone only, the minimum blockage would be approximately

4.82 square inches (in2) at the first sample point. The maximum

blockage would occur when the cyclone head is inserted into the stack to

a depth of 18 inches, and would be approximately 19.6 in2. These values

would correspond to a minimum blockage of about 1.9 percent, a maximum

blockage of 7.7 percent, and an average blockage of about 4.8 percent.

These values include the contribution to blockage of the cyclone as well

as the probe sheath.

When you add the pitot tube assembly (a 3/8-in diameter tube) the

minimum blockage for the example above is about 5.32 in2 at the first

sample point, and about 30.8 in2 when the assembly in inserted all the

way into the stack. Minimum blockage would be about 2.1 percent,

maximum would be about 12.1 percent and average would be about 7.1

percent.

I also made several measurements of a PM2.5 head with a 47-mm filter

holder attached. The design of these filter holders varies from

manufacturer to manufacturer, so these blockage calculations should be

considered as estimates of a typical PM2.5 cyclone with a filter holder

attached to the probe. Our measurement for this configuration indicates

that the minimum blockage (at the first sample point) would be about

4.82 inches (identical to the case where only the PM2.5 cyclone is

used). The maximum blockage (when the cyclone head is inserted into the

stack to a depth of 18 inches) would be approximately 20.7 in2. These

values would correspond to a minimum blockage of about 1.9 percent, a

maximum blockage of 8.1 percent, and an average blockage of about 5.0

percent.

When the pitot assembly is added, the minimum blockage for the case when

the PM2.5 cyclone and the 47-mm filter holder is used would be about
5.32 in2 at the first sample point (once again, identical to the first

case) and about 32.0 in2 when the assembly in inserted all the way into

the stack. Minimum blockage would be about 2.1 percent, maximum would

be about 12.6 percent and average would be about 7.3 percent.

When only the blockage area calculations are taken into account, it

would seem that when the PM2.5 cyclone head (without the filter holder

or pitot tube) is inserted into the stack, a 16-inch diameter stack

would be the minimum diameter which would yield an average blockage of

less that 6 percent. However, the tester would still not be able to

locate the nozzle at all of the required sample points due to the

geometry of the cyclone head. When the blockage due to the pitot tube

is added, the minimum diameter is approximately 19.5 inches.

Lastly, in the case where the PM2.5 cyclone head and the filter holder

are inserted into the stack, a minimum diameter of about 16.5 inches

would result in an average blockage of less than 6 percent. When the

pitot tube is included, a minimum diameter of about 20 inches would

result in a average blockage of less than 6 percent.

I have attached two rough sketches of the two configurations for you.

Please feel free to call or e-mail if you would like to discuss this

issue further.

-M

Michael D. Maret, PE | Project Manager

MACTEC Engineering and Consulting, Inc.

5001 S. Miami Boulevard | Suite 300 | Durham, NC 27703

P.O. Box 12077 | Research Triangle Park, NC 27709-2077

Office 919-941-0333 ext. 234 | Fax 919-941-0234

E-mail mdmaret@mactec.com | Web www.mactec.com

From: Myers.Ron@epamail.epa.gov [mailto:Myers.Ron@epamail.epa.gov]

Sent: Wednesday, July 08, 2009 2:02 PM

To: Maret, Michael

Cc: Werner, Arthur; Gray, Walter; Parker.Barrett@epa.gov;

Westlin.Peter@epamail.epa.gov; Dewees.Jason@epamail.epa.gov;

Segall.Robin@epamail.epa.gov; Ray.Merrill@erg.com; Joe Fanjoy; Danny

Greene

Subject: Duct diameter re OTM 27

Mike:

We received a question on the use of OTM 27 in a small duct. Paragraph

8.3.2.2 provides procedures for adjusting the velocity pressures for

ducts between 18 and 24 inches due to blockage effects when the sampling

device blocks between 3 and 6% of the duct area. In addition,

Paragraph 8.7.2.2 describes the basis for needing the adjustment and the

basis for evaluating the blockage amount. In this paragraph, the

average combined PM10 and PM2.5 cyclone projected area of 20.5 square

inches is provided as the basis of calculating the 3 to 6% blockage.

While not stated, these adjustments imply that OTM27 can not be used in

ducts less than 18 inches in diameter. In other parts of OTM27, the use

of this method with only the PM10 cyclone or only with the PM2.5 cyclone

is supported. Under these conditions, the use of the blockage area of

20.5 square inches is incorrect and the need for velocity pressure

adjustments would occur at different diameters than stated in paragraph

8.3.2.2. Here is a link to the proposed methods (

http://www.epa.gov/ttn/emc/proposed/m-201Ar1.pdf ) and OTM27 (

http://www.epa.gov/ttn/emc/prelim/otm27.pdf ). The existing promulgated

Method 201A has no stated blockage area but has the same duct diameters

where velocity pressure adjustments are required.

For OTM27 where only the PM2.5 cyclone is used, what is the projected

area (maximum, minimum and average) for the cyclone, filter holder,

probe assembly and the assembly including the pitot tube? What is the

smallest duct diameter where the average blockage is less than 6%?

Lastly, would it be appropriate to use only the PM2.5 cyclone in ducts

smaller than 18 inches if the blockage is less than 6%?
(Ray - for the promulgation package we need to consider the revision of

the paragraphs on blockage to include the various projected areas,

blockages etc. for the promulgated rule)

Mike - By my estimation, the total projected area of the PM2.5 cyclone

and filter holder is about 12 square inches and average 6 square inches.

This would mean that the minimum duct diameter where the cyclone is

useable would be about 12 inches (duct area = 113 square inches). If

the pitot tube was also included in the projected area this would add

about 1 square inch to the projected area and require a duct diameter of

about 16 square inches.

_________________________________

Ron Myers

U.S. Environmental Protection Agency

Office of Air Quality Planning and Standards

Sector Policy and Programs Division

Monitoring Policy Group, D243-05

RTP NC 27711

Tel. 919.541.5407

Fax 919.541.1039

E-mail myers.ron@epa.gov(See attached file: PM2.5 Cylcone Sketches.pdf)