Respirable dust and gin machinery

Applied Ergonomics 1985, 16.3, 201-207

Ergonomics in agriculture

Respirable dust and gin machinery W.S. Anthony and E.P. Columbus Agricultural Engineers, US Cotton Ginning Laboratory, ARS, USDA, Stoneville, MS 38776, USA

The influence of processing machinery at cotton gins on the respirable dust that is emitted into the gin environment and the respirable dust that remains in ginned lint was investigated during a 3-year study. Dust levels in the air near positions occupied by human operators ranged from 94 to 1251/ag/m 3 . The extractor-feeder/gin stand produced the highest dust levels. Dust levels remaining in the ginned lint ranged from 18.2 to 27.7 mg/20 g lint as a result of different processing machines. Lint cleaners were more effective in reducing dust levels in ginned lint than were other processing machines.

Keywords: Respiration, dust, agricultural equipment

I ntroduction The mechanical and pneumatic procedures that are required during the cotton cleaning, conditioning and ginning processes remove dust particles and other foreign matter from cotton. Dust escapes into the air from the various machines that are used in the ginning process. Dust also remains attached to the individual cotton fibres and is subject to removal during subsequent textile mill processes. The purposes of the study reported here were: (1) to estimate the amount of respirable dust generated by gin machinery near operator work stations, and (2) to determine the respirable dust remaining in cotton lint after processing with specific gin machinery. Dust in cotton textile mills has been shown to cause a respiratory disorder, byssinosis, in susceptible workers (Rooke, 1981). Surveys of gin workers in several countries have not shown conclusive evidence of byssinosis (Wesley et al, 1978). Airborne dust generated during the processing of cotton is usually divided into two types - respirable (15/am or smaller) and non-respirable (larger than 15/am). Some particles smaller than i 5/am are likely to be deposited in the lungs whereas larger particles settle rapidly from the atmosphere and rarely pass the filtering mechanisms of the human upper respiratory tract. Respirable dust levels were measured at three locations inside gins in the Midsouth and Texas by Wesley and McCaskill (1976). Lint cleaner areas generally had the highest dust levels. Kirk et al (1977) conducted a similar study of gins in New Mexico and reported that the highest dust levels were in the gin stand area. Hughs et al (1979) studied dust levels in California gins and found highly variable dust levels at the gin stand areas and near the bale press.

Griffin and Columbus (1982) reviewed several studies pertaining to dust research and concluded that similar dust levels occur among cotton gins, but the actual values are highly dependent upon wind conditions as well as production, harvesting and processing parameters. No clear relationship existed between dust levels and gin capacity (size) or ginning rate. The dust surveys mentioned above were made while the ginning systems were operating near capacity and all the equipment was in use. Thus, the contribution of each individual machine to the dust levels inside the gin was not established. The respirable dust levels were measured with large vertical elutriators and required a minimum sampling period of 6 h. Shofner et al (1981) evaluated a portable continuous aerosol monitor (PCAM)* developed by PPM, Inc, of Knoxville, Tennessee, and concluded that the PCAM readings closely approximated the dust levels measured by the large vertical elutriator (LVE). Respirable dust measured by the PCAM has an aerodynamic diameter of 15 #m or less. The PCAM requires a 15 min time-weighted sampling period whereas the LVE requires a 6 h sampling period. Consequently, the PCAM should be useful in evaluating the effectiveness of machinery modifications on the basis of respirable dust generated by individual machines since much less time and cotton is required. The amount of respirable dust measured by the PCAM will subsequently be termed 'PCAM dust ' in this report.

*Trade names are used in this publication solely for the purpose of providing specific information. Mention of a trade name does not constitute a guarantee or warranty of the product by the US Department of Agriculture or an endorsement by the Department over other products not mentioned.

0003-6870/85/03 0201-07 $03.00 Q 1985 Butterworth & Co (Publishers) Ltd

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201

Ergonomics in agriculture The respirable dust that remains m ginned lint is of considerable importance to the textile industry since mill processing emits some of that dust into the working environment. Anderson and Baker (1979) developed an experimental Cotton Dust Analyser {CDA) to estimate the quantity of respirable dust in cotton lint. lligh-velocity jets of air are used to release dust from a thin batt of cotton lint. Dust removed by the air is conveyed through a sizing screen (pre-filter) that restricts the flow of large dust particles. The respirable dust particles are then collected on a glass fibre filter for gravimetric analysis. Respirable dust measured by the CDA has a physical diameter of 17/am or less. Results of CDA measurements of the respirable dust in cotton lint correlate well with the respirable dust levels in a model cardroom as measured by the LVE. The amount of respirable dust remaining in the ginned lint and estimated by the CDA will subsequently be termed 'CDA dust" in this report.

Procedures The objectives of this report were approached with three

separate studies. Studies 1 and 2 were identical except for the year, and they considered the influence of individual machine treatments on the PCAM and CDA dust levels when only those machines were operating. However, study 3 was conducted only in 1982 and considered the PCAM dust levels near each machine while all the machines were operating. PCAM dust levels reported herein are timeweighted averages of 15 min duration.

Studies 1 and 2 The effects of two types of cotton (early, cotton 1 ; and late season, cotton 2) and two levels of lint moisture on the dust emission of the following gin machinery treatments were considered in 1981 and 1982: (1)

Extractor feeder and gin stand (EFGS) only

(2)

Cylinder cleaner and EFGS

(3)

Stick machine and EFGS

(4)

Cylinder cleaner, stick machine, cylinder cleaner, EFGS, and two lint cleaners

DOOR G - GIN STAND L - LINT CLEANER S - STICK MACHINE C-CYLINDERCLEANER

'CONSOLE' 4 i

2 ~

'

EFGS and one lint cleaner

(6)

EFGS and two lint cleaners

The PCAM was used to detect the concenirat,on ol respirable dust at different machinery sites [Fig. 1 ) during ginning as follows: • Treatment 1 -PCAM location at gin stand • Treatment 2 --- PCAM location at cylinder cleaner •

Treatment 3 - PCAM location at stick machine

•

Treatment 4

PCAM location at console

• Treatment 5 - PCAM location at first lint cleaner • Treatment 6 - PCAM location between first and second lint cleaner The minimum auxiliary equipment necessary to convey the cotton to the gin machinery was used. Fans and screw conveyors were used for conveying the cotton within the ginning system. When fans were used, cotton/air separators were required to remove the cotton from the air stream. Some foreign matter, including dust, is usually removed from the cotton by the fan and separator. Treatments 1. 2, 5 and 6 required two separators, whereas treatments 3 and 4 required three separators. The cotton was processed through a drier for all treatments but no heat was applied for the higher moisture level. The PCAM was used to measure the airborne respirable dust concentration about 0-7 m from each machine while the machine was processing cotton. When the conventional machinery sequence (treatment 4) was used, levels of respirable dust near the machinery control console were measured. Machine treatments were assigned at random to the 18 bales in a cotton-moisture class so that each machine treatment occurred exactly three times. The 72 bales (2 cottons x 2 moistures x 6 machines x 3 replications)were assigned a random number from ! to 72 and a random number table was used to assign the ginning order of the 72 bales. Thus the design was completely randomised with a factorial arrangement of treatments. The linear model used in analysis of the data included the overall mean. the

3 ~ DOOR

DOOR

NF]

N' @

s

FN NN N, N] rN H° NN Fn 202

(5)

Applied Ergonomics

September1985

Fig. 1

PCAM dust levels were measured at six locations about 0-7 m from the gin machinery

Ergonomics in agriculture

fixed effects of cotton, the fixed effects of machine treatment, the fixed effects of moisture, the fixed two-way interactions of cotton with machine treatment, the fixed two-way interactions of cotton with moisture, the fixed two-way interactions of machine with moisture, the fixed three-way interactions of cotton, machine and moisture, and the random effect of bales nested in cotton, machine and moisture. Normal assumptions of normality, independence, additivity, etc, were made in analyses of the data. Each replication consisted of about 650 kg (one bale) of seed cotton. Each replication required about 15 min for ginning which allowed sufficient time for measurements of respirable dust with the PCAM. The lower moisture level was achieved by increasing the drier temperature from atmospheric to 93°C. Five cotton samples were taken at the gin input (trailer), extractor-feeder apron and bale press for moisture and foreign matter determinations. Lint samples for analysis of respirable dust with the CDA were also taken before the bale press. A CDA similar to that developed by Anderson and Baker (1979) was constructed and used to evaluate the respirable dust in the cotton lint. Procedures for the CDA were the same as those reported by Anderson and Baker (1979) with the following exceptions: (1)

Trash particles larger than 17/am were prefiltered by a sizing screen.

(2)

Dust particles 17/am and smaller were collected on a glass fibre filter.

(3)

20 g samples were used instead of 10 g samples.

Analyses of variance and Duncan's Multiple Range Test (DMRT) at the 5% level of probability were used to analyse the data. The year-to-year variations that occur in the characteristics of cotton, such as foreign matter and dust content, are common occurrences in the field of cotton ginning, and the variable year is usually included in the experimental design to obtain a measure of variability due to yearly differences. As a result, interactions between years and treatments are usually significant and serve to illustrate the fact that cotton responds somewhat differently to machine and moisture treatments across growth years. General responses, however, remain the same. Thus, results reported here will consider data pooled across years and the significant interactions where the variable year is involved will be identified but not addressed in detail. Specific emphasis will be placed on the machine-moisture relationship. Study 3 Since a time lapse occurs before steady-state dust conditions are achieved near individual machines, all the machines were operated simultaneously and continuously

Table 1: Analyses of variance for studies 1 and 2 combined

F-value for Source of variation

Degrees of freedom

Initial foreign matter

Lint foreign matter

Dust PCAM

CDA

Year (A)

1

19-10"

239-02*

29.10"

482"22*

Cotton (B)

1

215"71 *

666.54*

65-53*

60"55*

Machine (C)

5

1-83 ns

284-64*

97.75*

28"68*

Moisture (D)

1

3.14 ns

14.02"

9.39*

AB

1

4-76*

2.66 ns

93.59*

11-95"

AC

5

1"35 ns

3.58*

34.72*

3.55*

AD

1

0-11 ns

101.11"

BC

5

2-00 ns

10-97"

BD

1

0"01 ns

0"82 ns

CD

5

3"86*

0"91 ns

13"82"

1"89 ns

ABC

5

0"30 ns

0"93 ns

61"70"

5"95*

ABD

1

0"12 ns

2-56 ns

9"33*

0-72 ns 34"23* 0.72 ns

1.17 ns

4.15" 3'34* 13"47"

0"80 ns

ACD

5

2"28*

3"03*

0"38 ns

2"60*

BCD

5

2"33*

1"55 ns

1.90 ns

2"99*

ABCD

5

0-94 ns

4"60*

6"55*

1-70 ns

Error

96

* Indicates significance at the 5% level of probability, ns Indicates lack of significance at the 5% level of probability.

Applied Ergonomics

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203

Ergonomics in agriculture

in study 3 and the PCAM was moved randomly to the six measurement points. Study 3 was conducted similarly to studies 1 and 2 except one type of cotton, one level of moisture and four replications were used in a randomised complete block experimental design. Results and discussion Studies ! and 2 Foreign matter levels before processing were significantly different for years (Table 1) and averaged 6.5 and 7-3%, respectively. Foreign matter remaining in the lint (Shirley Analyser method) after processing was significantly influenced by year, cotton, machine, moisture and the interaction between machine and moisture. The interaction was due to the fact that the cleaning efficiencies of machines 1,2 and 3 are not affected as strongly by moisture as are the cleaning efficiencies of machines 4, 5 and 6. Lint moistures were 5-0% and 7"1%, respectively, for moisture levels I and 2. Foreign matter and grade characteristics for studies I - 3 are given in Table 2.

indicates that the respirable dust removal characteristics ~1 the machines respond differently to changes in the dust content of the fibre. Since the cotton/machine and machine/ moisture interactions were significant, the machine means within each cotton and machine treatment are compared in Table 3. The significant cotton/machine interaction for respirable dust was due to the unusually high dust levels near the EFGS for cotton 2 and the difference in the dust levels near the two lint cleaners (Table 3). Differences in the magnitude of the dust levels near the EFGS for moisture 2 as well as the difference in the dust levels for the conventional treatment apparently caused the significant moisture/machine interaction. The differences in the dust levels that caused the significant interactions were not large, thus the overall treatment means for machines in Table 4 are indicative of the relative contribution of each machine to the dust level. The averaged effect of machine treatments is summarised below:

Machine treatment

PCAM dust, tag/m 3

EFGS PCAM dust Dust levels averaged across replications varied from 68 to 4265 tag/m s as the treatments were applied. Year, cotton, machine, moisture and the cotton/machine and machine/moisture interactions significantly influenced the dust levels (Table 1). The amount of dust emitted by each machine changed substantially as the cotton changed which

1309 a

One lint cleaner

451 b

Two lint cleaners

327 bc

Cylinder cleaner

204 cd

Conventional

192 d

Stick machine

177 d

Table 2: Foreign matter and grade characteristics of the cottons in studies 1 - 3 Cotton characteristics for machine treatment

Year/ Study

Cotton 1"

1

2

5.1 8-3 5.6 9.8 2.0

5.1 8.4 6.0 8.4 2-0

3

4

5

6

5-6 8.4 5.4 8.6 1.9

5-5 7.1 5.3 8-0 2.0

4"1 5"9 5-3 7"6 2-9

3"3 5'0 4"6 6'3 2'8

Initial foreign matter (%) 1 1 2 2 3

1 2 1 2 1

5.4 7.8 5.7 9.6 1.9

5.0 7.9 6.0 9-1 1.9

Lint foreign matter (%) 1 1 2 2 3

1 2 1 2 1

6'6 9"4 7"9 11-7 2"9

6"0 8-8 7"6 10"8 2"9

5"6 8"2 7"0 9"8 3"0

3"2 4"8 4"0 5"4 2"8

Grade * 1 1 2 2 3

1 2 1 2 1

*LM = Low middling,

LM SGO LmLtsp GO SLM+

LM GO LM+ GO SLM+

LM SGO LM GO SLM+

SLM LM LM+ LM SLM+

SLM LmLtsp LM+ SLmLtsp SLM+

SLM SLMsp SLM SLM SLM+

SLM = strict low middling,

SGO = strict good ordinary, GO = good ordinary, Ltsp=

light spot and + = plus

tCotton 1 was harvested early during the. season, whereas Cotton 2 was harvested late in the season.

204

Applied Ergonomics

September 1985

Ergonomics in agriculture

Table 3: Comparison of treatment means for PCAM and CDA dust where interactions were statistically significant Machine treatment* Year

Cotton

Moisture

1

2

3

4

5

6

PCAM dust, btg/rn 3 t land2 1 and 2

1 2

-

644a 1974 a

206bc 202 c

153c 202 c

199c 185 c

360b 542 b

223bc 432 b

1 and 2 1 and2

-

1 2

922 a 1696a

198 c 210cd

190 c 165cd

250 c 134d

450 b 452b

318 bc 337bc

19-5a 21-4 b 20.1 c 26.2 a

13-6b 16.6 c 21.5 c 21.3 b

CDA dust, mg/20 g lint t 1 and2 1 and 2 1 and 2 1 and 2

1 1 2 2

1 2 1 2

21.5a 27.4 a 33"6 a 28-4 a

18-9a 21.1 b 29.8 ab 26.0 a

19.1 24.1 27-8 25-0

a ab b ab

16.8b 16"3 c 18-8 c 15.3 c

1"Means w i t h i n each row not followed by the same letter are significantly different at the 5% level as judged by Duncan's Multiple Range Test. *Dust concentrations were measured near the gin stand (1), cylinder cleaner (2), stick machine (3), console (4), one lint cleaner (5), and two lint cleaners (6).

The dust levels were highest near the EFGS and lint cleaners. Thus, efforts to reduce the respirable dust liberated by gin machinery should begin at the EFGS and continue to the lint cleaner. The levels of dust in years, cottons, and moistures are given in Table 3. CDA dust

The respirable dust content (averaged across replications) of the lint sample as measured by the CDA varied from a low of 9-03 mg to a high of 40.90 mg per 20 g lint sample. The CDA dust was significantly affected by year, cotton, machine and several interactions as follows (Table 1): cotton/machine, cotton/moisture, and cotton/machine/ moisture. Since the cotton/machine/moisture interaction was significant, the means within each cotton and moisture were compared for each machine (Table 3). For cotton 1 and moisture 1, the following treatments, did not differ from each other: •

EFGS

• Cylinder cleaner •

Stick machine

• One lint cleaner Respirable dust in the ginned lint from conventional and two-lint-cleaner treatments differed significantly from all other treatments but not from each other. For cotton 1 and moisture 2, similar results were achieved except that the respirable dust after the EFGS differed from the other treatments except the stick machine treatment. For cotton 2 and moisture 1, the respirable dust in the ginned lint from the EFGS treatment differed significantly

from all other treatments except the cylinder cleaner treatment. Respirable dust remaining in the lint did not differ significantly between the cylinder cleaner and stick machine treatments, or between the one- and two-lint cleaner, and conventional treatment. For cotton 2 and moisture 2, the EFGS, cylinder cleaner, stick machine and one lint cleaner treatments did not differ from each other. The respirable dust remaining in the lint after the

Table 4: Treatment means for studies 1 and 2

Treatment

Level

PCAM dust, /~g/m 3 * t

CDA dust, mg/20 g lint1

Year

1 2

346 a 541 b

15"3 a 28-8 b

Cotton

1 2

297 a 589 b

19"7 a 24.5 b

Moisture

1 2

388 a 497 b

21.7 a 22.4 a

Machine*

1 2 3 4 5 6

1309 204 177 192 451 327

a cd d d b bc

27-7 23"9 24"0 16.8 21"8 18"2

a b b c b c

• *Dust concentrations were measured near the gin stand (1), cylinder cleaner (2), stick machine (3), console (4), one lint cleaner (5), and t w o lint cleaners (6). tMeans w i t h i n each treatment not followed by the same letter are significantly different at the 5% level of probability.

Applied Ergonomics

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205

Ergonomics in agriculture conventional machinery treatment differed signilicantly and was lower than all other treatments.

the ginned lint did not dltler ,,,igiliticantl~ ,~:. :t resu]l., treatments and aver,,ged q.q ,n~: 20 g Iil)l

CDA dust averaged 15.3 and 28"8 mg per 20 g lint, respectively, for years 1 and 2 (Table 4). Average levels of respirable dust for years, cottons, moistures and machines are given m Table 4. Significantly larger amounts of respirable dust were present in the lint from the I:;FGS treatment (27-7 rag/20 g lint) than from the other treatments. Differences in the CDA dust are summarised below (each treatment includes the EFGS):

PCAM dust levels ranged [tom zl h~w ol '~_~~g/m" n~'zn tile stick nmchiile to a high ,)1 12.ql/,tgim "~ tlear the 1!t(;S. Dust levels near the lint cleaners did not diile/ trom each other and averaged 157/ag,lm ~ . The dust levels ate summarised below (each treatment includes the I([:(;SI:

CDA dust, mg/20 g lint

Card room dust level, mg/m 3

EFGS

27-7 u

4"0

Stick machine

23.9 b

4"0

Cylinder cleaner

24-0 b

4-0

One lint cleaner

21.8 b

3.7

Two lint cleaners

18.2 c

3" I

Conventional

16"8 c

2"8

Machine treatment

The quantity of dust in the cotton lint after processing through the two-lint-cleaner treatment did not differ from the quantity of dust after processing through the conventional sequence. Dust levels for the two-lint-cleaner treatment and the conventional-sequence treatment were over 34% less than those for the EFGS. Regression correlations were developed from data published by Anderson and Baker (1979) to allow projection of the respirable dust levels in a textile mill card room. Using these correlations, the card room respirable dust levels were projected to range from 2-8 mg/m 3 to 4-6 mg/m 3 as the machine treatments in this study were applied. Human workers in the card room would be exposed to those levels unless positive dust control measures were applied. Individual correlations between CDA dust, PCAM dust, lint foreign matter, feeder foreign matter and initial foreign matter by regression analyses were very low, which suggests that prediction of the respirable dust generation potential of cotton by conventional measurements of foreign matter such as the Shirley Analyser is unsatisfactory. The coefficient of determination between CDA dust and lint foreign matter was 0.62, which indicates that 62% of the variation in fine dust content was attributable to change in lint foreign matter content. Significance of these interactions indicate that the adhesion force between respirable dust and cotton fibres differs for these combinations of cotton types and moisture levels.

Study 3 Characteristics of the cotton used in study 3 such as foreign matter, moisture and grade were not significantly different for the treatments. Foreign matter in the seed cotton and lint cotton averaged 2-0% and 2-9%, respectively. Official classification grades were Middling, Strict Low Middling, and Strict Low Middling Plus, respectively, for leaf, colour and composite grades. Respirable dust levels in

206

AppliedErgonomics September 1985

PCAM location

Dust level,/ag/n¢ .

.

.

.

.

.

.

.

.

.

.

.

liFGS Lint cleaner(s) Average for cylinder cleaner, stick machine, and console

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

125 ! ,i

157 !, ~4 c

Dust levels near the EFGS were 8 to 13 times greater than elsewhere in the gin.

Analysis Different types of gin machinery generate widely differing levels of respirable dust into the air. Highest dust levels were consistently measured near the EFGS, followed by those near the lint cleaner. Thus the human operator should be positioned so as to minimise exposure until engineering controls to reduce dust levels can be applied. The respirable dust that remains in cotton lint correlates with the type of gin machinery through which it is processed but does not correlate well with the foreign matter in the lint. Little correlation exists between the fine dust generated and emitted into the gin environment by the gin machinery and the respirable dust that remains in the cotton lint. Lint cleaners reduce the level of respirable dust remaining in ginned lint significantly more than seed cotton cleaners. The respirable dust that remains in ginned lint will be available for subsequent generation during mill processing and mill dust levels will change accordingly.

References Anderson, J.D., and Baker, R.V. 1979 Trans of the Am Soc of Agr Engineers, St Joseph, MI. 2 2 . 4 : 9 1 8 - 9 2 1 , 9 2 5 . Development of experimental cotton dust analyzer. Anthony, W.S., and Columbus, E.P. 1982 Preliminary investigation of the effect of gin machinery on fine dust. Proc of the 1982 Beltwide Cotton Res Conf (Special Session on Cotton Dust), Las Vegas, NV. Wakelyn, P.J., ed (National Cotton Council, Memphis, TN). pp 67-70. Griffin, Jr, A.C., and Columbus, E.P. 1982 Dust in cotton gins: An overview, p 27-36. In: Dust - Controlling an Occupational Health Hazard, American Chemical Society Symposium Series 109, Joseph G. Montalvo, Jr (ed), Washington, DC. Hughs, S.E., Urquhart, N.S., and Smith, D.W. 1979 Occupational dust levels in California cotton gins. Am Soc of Agr Engineers Paper No 79-3553, 24 pp.

Ergonomics in agriculture Conf (Special Session on Cotton Dust), New Orleans, LA. Wakelyn, P.J., ed (National Cotton Council, Memphis, TN). pp 55-62.

Kirk, I.W., Leonard, C.G., and Brown, D.F. 1977 Trans of the Am Soc of Agr Engineers, St Joseph, MI. 20.5: 962-968. Air quality in saw and roller gin plants.

Rooke, G.B. 1981 Tex ResJ, 51.3: 168-173. What is byssinosis? A review.

Shofner, F.M., Kreikebaum, G., and Miller, Jr, A.C. 1981 Gravimetric certification and equivalency demonstration protocols for alternative samplers to the vertical elutriator. Proc 1981 Beltwide Cotton Res

Wesley, R.A., and McCaskill, O.L. 1976 The Cotton Gin and Oil MilI Press, Mesquite, TX. 77.20: 20-22. Total and respirable dust levels inside gins processing spindle-harvested cotton. Wesley, R.A., Hatcher, J.D., McCaskill, O.L., and Cocke, J.B. 1978 Am Industrial Hygiene Assn J, 39, 368-377. Dust levels and particle-size distributions in high-capacity cotton gins.

microprocessorsand

mlcrosystems S p e c i a l I s s u e o n a i d s for v i s u a l l y h a n d i c a p p e d - December 1984

There are 44 million blind people in the world - - but only 20,000 electronic aids known to be in use. What is the reason for this shortfall: lack of production facilities, lack of funds, or lack of interest? What are the advances in technology - - so beneficial and even vital to the business community - - contributing to the job prospects and private lives of the visually handicapped? These, and other questions about provisions for the visually disabled are addressed in this special issue of Microprocessors and Microsystems. For further information contact: Anne Browne, Editor,

Microprocessors and Microsystems, PO Box 63, Westbury House, Bury Street, Guildford, Surrey GU2 5BH, UK. Tel: (0483) 31261 Telex: 859556 SCITEC G

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