7 A S t a n d a r d i z e d M e t h o d for V e r t i c a l E l u t r i a t o r Cotton Dust
Sampling
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ANN L. WALKER and ELLIS E. PARDUE The Hanes Group, Consolidated Foods Corporation, Winston-Salem, NC 27102
Specific equipment and techniques used by The Hanes Group for vertical elutriator cotton dust sampling are discussed. Some accessories were developed for convenience, but the approach to site selection, f i l t e r handling, orifice calibration, and training of sampling personnel were important in obtaining vertical elutriator data with coefficients of vari ation less than 10%. One new sampling method was investigated also, and plant data showed that i t was equivalent to the vertical elutriator method. The alternative instrument used was a Portable Continuous Aerosol Monitor (PCAM) manufactured by ppm, Inc., and dust concentrations measured with the PCAM were 5-15% lower than values obtained with standard vertical elutriators. Calculations and examples for TWA exposures, equivalency tests, and vertical elutriator coefficients of variation are included. Two f a c t o r s are important i f v a l i d a n a l y t i c a l data i s t o be generated. One i s equipment or instrumentation; the other i s technique. These two f a c t o r s are always i n t e r r e l a t e d , s i n c e techniques are a t l e a s t p a r t i a l l y determined by the c a p a b i l i t y of the equipment (Tables I and I I ) . Cotton dust sampling i s a p l a n t s i t e t e s t , normally i n v o l v i n g u n s o p h i s t i c a t e d f i e l d equipment, ever-changing p l a n t cond i t i o n s , and t e c h n i c i a n - l e v e l l a b o r i n performing many f u n c t i o n s . However, w i t h adequate equipment and a t t e n t i o n to technique, we have found that good q u a l i t y data can be obtained f o r each survey. The purpose of t h i s paper i s t o share w i t h you some of the i n s t r u mentation, equipment m o d i f i c a t i o n s and techniques we have s t u d i e d and employed t o o b t a i n v e r t i c a l e l u t r i a t o r (VE) data w i t h average c o e f f i c i e n t s o f v a r i a t i o n l e s s than 10%. 1
Current address: Route 8, Box 5202, Winston-Salem, NC 27106.
©
0097-6156/82/0189-0085$6.00/0 1982 American Chemical Society
Montalvo; Cotton Dust ACS Symposium Series; American Chemical Society: Washington, DC, 1982.
COTTON
86
DUST
TABLE I Cotton Dust Sampling Equipment
Stopwatch VE Rack Walter c r u c i b l e holder Vertical elutriator Balance (to 1 microgram) Vacuum pumps Tweezers Orifices M o d i f i e d arbor press Chains and/or brackets F i l t e r support stand Thick w a l l e d rubber tubing Static eliminator Hose connectors Diagrams of p l a n t l a y o u t E l e c t r i c a l tape Employee l i s t s Ladder Storage c a r t F i l t e r boxes F i l t e r s , backup pads, c a s s e t t e s , s h r i n k bands F i l t e r data sheets and pens Wet t e s t meter, bubble tube, rotameter, and manometer Assorted spare p a r t s ; pumps, f u s e s , o r i f i c e s , e t c .
TABLE I I Basic Procedures f o r Cotton Dust M o n i t o r i n g
1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18.
Define process area Define work areas w i t h i n each process area S e l e c t and prepare sampling s i t e s Define employee job c l a s s i f i c a t i o n s Define time-in-work-areas f o r each job c l a s s i f i c a t i o n Obtain c u r r e n t l i s t of a l l employees i n each job c l a s s i f i cation Obtain p r o d u c t i o n , v e n t i l a t i o n and system design i n f o r m a t i o n Clean e l u t r i a t o r s Calibrate o r i f i c e s Weigh f i l t e r s and assemble c a s s e t t e s C a l i b r a t e personnel pumps Obtain 6-8 hour e l u t r i a t o r samples i n each work area d u r i n g each s h i f t of o p e r a t i o n Obtain personnel t o t a l dust samples f o r r e p r e s e n t a t i v e employees i n noncompliance areas Reweigh f i l t e r s C a l c u l a t e dust c o n c e n t r a t i o n s f o r each s i t e and s h i f t C a l c u l a t e employee TWA exposures f o r each job c l a s s i f i c a t i o n and s h i f t N o t i f y employees and management of r e s u l t s Clean equipment f o r next survey
Montalvo; Cotton Dust ACS Symposium Series; American Chemical Society: Washington, DC, 1982.
7.
WALKER
Sampling
AND
PARDUE
Vertical Elutriator Cotton Dust Sampling
87
Site
Perhaps the most b a s i c and important p a r t o f the techniques i n c o t t o n dust sampling i s the process o f choosing sampling s i t e s . In the rush to o b t a i n VE r e s u l t s , i t i s easy to overlook c e r t a i n c o n d i t i o n s i n the workplace. Meaningless data can o f t e n be t r a c e d to n o n r e p r e s e n t a t i v e s i t e s . Instead, the f i r s t step should be a thorough review of processes, machinery v a r i a t i o n s , employee job f u n c t i o n s f o r a l l a f f e c t e d job c l a s s i f i c a t i o n s , dust generation p o i n t s , dust c o n t r o l equipment, and a i r handling systems (1). With t h i s data i n hand, and an accurate l a y o u t of the p l a n t , one can begin the three-stage process of s e l e c t i n g p l a n t sampling p o s i t i o n s . Process Areas. The f i r s t stage i s easy: d i v i d e the p l a n t i n t o s p e c i f i c process areas, such as opening, c a r d i n g , r o v i n g , s p i n n i n g . The second stage draws upon the accumulated i n f o r m a t i o n to determine whether or not a given process area should be s u b d i v i d e d i n t o s e v e r a l work areas (Figures 1 and 2 ) . This d e c i s i o n i s based on answers to the f o l l o w i n g types of q u e s t i o n s : 1. Are dust l e v e l s c o n s i s t e n t throughout the area? Do c e r t a i n areas tend to have higher or lower dust concent r a t i o n s due to machinery dust generation p o i n t s , waste handling o p e r a t i o n s , etc.? 2. How do a i r h a n d l i n g systems and dust c o n t r o l u n i t s a f f e c t dust l e v e l s throughout the area? 3. Where do employees spend most of t h e i r time? 4. What j o b f u n c t i o n s tend to generate the most dust? 5. How many d i f f e r e n t job c l a s s i f i c a t i o n s are represented i n a given a r e a , and are t h e i r work p a t t e r n s s i m i l a r or d i f ferent? S i t e S e l e c t i o n . The t h i r d stage examines each work area f o r s u i t a b l e and r e p r e s e n t a t i v e s i t e s . The number of sample s i t e s depends on work area s i z e , dust c o n s i s t e n c y , equipment generation p o i n t s , and any other f a c t o r s t h a t seem a p p r o p r i a t e to c o n s i d e r . Since process areas may be subdivided to a s s i s t i n the c a l c u l a t i o n of employee time-weighted average (TWA) exposures, i t i s necessary to have at l e a s t one VE i n each work area where c o t t o n dust i s present. Larger numbers of sample s i t e s per work area give more r e p r e s e n t a t i v e i n f o r m a t i o n about dust l e v e l s throughout the a r e a , but u s u a l l y there must be a compromise between the amount of data that might be d e s i r a b l e and the amount of time, e f f o r t and equipment a v a i l a b l e to o b t a i n necessary i n f o r m a t i o n . Some problems t o avoid i n choosing sampling s i t e s are as f o l l o w s : strong a i r c u r r e n t s , l o c a t i o n s p r o t e c t e d from normal a i r c u r r e n t s , areas w i t h shutdown machines, and l o c a t i o n s that i n t e r f e r e w i t h machinery o p e r a t i o n or maintenance, t r a v e l i n g c l e a n e r s , m a t e r i a l h a n d l i n g , or employee e f f i c i e n c y (1). Column and w a l l l o c a t i o n s should be c a r e f u l l y examined, s i n c e p e c u l i a r i t i e s i n a i r c u r r e n t s o f t e n give
Montalvo; Cotton Dust ACS Symposium Series; American Chemical Society: Washington, DC, 1982.
Montalvo; Cotton Dust ACS Symposium Series; American Chemical Society: Washington, DC, 1982.
Figure 1.
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WORK [AREA 2B
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WORK AREA IB
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'WORK AREA IA
PROCESS AREA: OPENING (I)
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Sample plant layout of opening and picking process areas including subdivisions into work areas and sampling locations.
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WORK
WORK AREA 2A
PROCESS AREA: PICKING (2)
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Montalvo; Cotton Dust ACS Symposium Series; American Chemical Society: Washington, DC, 1982.
Figure 2.
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WORK AREA 3B
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WORK AREA 3A
WORK AREA 3B
WORK AREA 3A
Sample plant layout of card room subdivided intofivesections representing two work areas with sampling sites.
WORK \AREA 3A
WORK AREA 3C
PROCESS AREA: CARDING (3)
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