p.1 

OAR Box 1168 

Prepped by Ollie Stewart 

Document Number: 

93) ll-C-22 

Docket Number: 

A-89-10 

Printed 4/29/2008 11:23:20 AM Sheet 93 of 131 

$ 
A-89-10 

P.2 

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0Sr% IT- P •>-> 

° mf\ \ UNITED STATES ENVIRONMENTAL PROTECTIO 

Office of Air Quality Planning and Standi 

Research Triangle Park, North Carolina 27711 

MAY 3 0 1980 

Hi 

FEB I f 1991 ti 

To Reg Neg Committee Members j 

j EPA AIR DOCKET 

Enclosed are two bar charts showing flange leak data for-Hre-et'lTyreny 

oxide and butadiene plants, and for plants in the "24 unit study." The latter 

is an early 1980's study of 2 plants at each of 13 chemical processes. In 

each chart, the bars represent the percent of flanges that were leaking in the 

sample from each plant. The value above the bar is the sample size at each 

plant. 

In total, 41 plants were sampled. At a 500 ppm leak definition, samples 

at 10 plants exceeded 5 percent leakers; 17 out of 41 had leak frequencies 

above 2 percent. These data indicate clearly that the number of flanges that 

leak at a facility can be high. Based on estimated emission rates calculated 

by CMA in the EO and BD studies and the high leak frequencies at many of the 

plants, it is apparent that flange emission rates are significant and can 

account for a high percentage of the emissions at a plant where other 

equipment is controlled. These data also indicate that flange leak 

frequencies below 0.5 percent and even approaching zero are possible. We 

believe that these leak frequency data indicate clearly that flange monitoring 

is necessary to assure a low percentage of leaking flanges. In the absence of 

regulation, the data show conclusively that low leak frequencies will not 

necessarily occur. 

We do agree that flange leak occurrence rates should be lower than valve 

leak occurrence rates. However, this is not necessarily so in all cases. As 

such, we believe an extended monitoring frequency is reasonable where low leak 

frequencies are consistently maintained. However, where low leak frequencies 

are not consistently demonstrated, we believe quarterly monitoring is needed. 

Attached is a diagram of a monitoring scheme that would meet our interest. 

We have reviewed the CMA flange discussion dated May 7, 1990, which 

concludes that there is very little to be gained by any flange monitoring 

requirement. However, we find nothing in the discussion that supports the 

conclusion. More specifically, the CMA material does not address the large 

percentage of plant samples that have high leak frequencies. Ron Berglund's 

analysis, for example, considers average leak frequencies; it does not 

consider the large number of plants with frequencies greater than 2 to 5 

percent at 500 ppm. Similarly, the basis for the introductory section in the 

CMA handout is oriented around emission factors and average performance. It 

ignores the actual data reported by CMA that shows high leak and emissions at 

many plants. 

Sincerely, 

rr^^~ 

Bob Ajax 
BD/EO Flanges 

Percent Leakers at 500 ppm 

10 

8 -

CO 

CD 

CO 6 

CD 

C 

<D 4 

O 

O 

GL 

2 -

- 70 

_______________ 

—^H 

- ^H 

- ^H 

—____H 

- ^H 

135 

'^Hi 

•••i 

408 

' fli 

146 

•Hi 

63 

•••Bl 

158 

•H 

158 

- -HHi •7t2" •••<W7 

Pjy. 147 

117 150 181 

,37 f T 328 

bd4 bd8 eo9 eo6 eo3 bdlO eo8 eo4 bd5 bdll eo2 bc_3 bd!2 bd7 bdl eol eo7 

Unit 

CO 
25 

20 -

CO 

CD 

_*_ 

CO 1 5 

CD 

c 

CD 1 0 

O 

24-Unit Study - Flanges 

Percent Leakers at 500 ppm 

CD 

a. 

5 -

1)54 |9 $7 49 T|76 1|83 ^85 

22 28 4 2 11 12 6 31 5 3 20 29 61 1 65 66 60 64 62 32 21 33 35 34 

Unit 

ZJ 

j*. 
P.5 

A Conceptual Approach 

for Flange Standard 

<0.5 

<0.5 

Skip 15 

Quarters 

>0.5 

Quarterly 

<0.5 

\ 1 

Skip 3 

Quarters 

<0.5 

<0.5 2 Quarters 

>0.5 

>0.5 

5/30/90