[RI [ 8886 [ 

PLEASE IX) NOT REMOVE FRCM LIBRARY 

Bureau of Mines Report of Investigations/1984 

New Bag Nozzle To Reduce Dust 

From Fluidized Air Bag Machines 

By Andrew B. Cecala. Jon C. Volkwein. 

and Edward D. Thimons 

UNITED STATES DEPARTMENT OF THE INTERIOR 
Report of Investigations 8886 

New Bag Nozzle To Reduce Dust 

From Fluidized Air Bag Machines 

By Andrew B. Cecala, Jon C. Volkwein, 

and Edward D. ,Thimons 

UNITED STATES DEPARTMENT OF THE INTERIOR 

William P. Clark, Secretary 

BUREAU OF MINES 

Robert C. Horton, Director 
Library of Congress Cataloging in Publication Data: 

Cecal a, Andrew B 

New bag nozzle co reduce dust from fluidized air bag machines. 

(Report of investigations; 8886) 

Includes bibliographical references. 

Supt. of Docs. no.:: 128.23:8886. 

1. Mineral industries-Dust control. 2. Bagging-Equipment and 

supplies • . 3. Nozzles. 4. Bagging-Dust control. I. Volkwein, J. 

C. (Jon C.); II. Thimons, Edward D. III. Title. IV. Series: Repore of inve~tigations (United States. Bureau of Mines) ; 8886. 

TN23.U43 (TH7697.M56] 6228 [660.2'8] 84-600090 
CONTENTS 

Abstract....................................................................... 1 

Introduction. . . •. .. . . . .. . .. . .. •. . . . .. .• . .. ..•. . .. ..... . ..• . .••.•... . . . . . .. .•. • . 2 

Testing........................................................................ 3 

Conclusions. . . • . . . . . • . . . . . . . • . . . . . . . . . . . . • . . . . • . . . . . . . . . • . . . . • . . . . . . . • . . . . . . . . • 5 

1. 

2. 

3. 

4. 

1. 

2. 

3. 

ILLUSTRATIONS 

New bag nozzle sys tern ...••.•••••..••...••••••••••..•••.•••..•...•.•.•••.••. 

Operator exposure using conventional system and new system ••••••••••••••••• 

"Rooster tail" effect using conventional system •••••••••••••••••••••••••••• 

Elimination of "rooster tail" effect using new system •••••••••••••••••••••• 

TABLES 

Dust exposure at operator position ••••••••••••••••••••••••••••••••••••••••• 

Dust analysis for 325-mesh product ••••••••••••••••••••••••••••••••••••••••• 

Increase in production time using new system ••••••••••••••••••••••••••••••• 

2 

4 

5 

5 

3 

3 

4 
ft 3 /min 

lb 

mg/m3 

UNIT OF MEASURE ABBREVIATIONS USED IN THIS REPORT 

cubic foot per minute 

pound 

milligram per cubic meter 

min 

pct 

s 

minute 

percent 

second 
NEW BAG NOZZLE TO REDUCE DUST FROM FLUIDIZED AIR BAG MACHINES 

By Andrew B.Cecalo, 1 Jon C. Vorkwein,2 and Edward D. Thimons 3 

ABSTRACT 

A new prototype bag nozzle system has been designed under a Bureau of 

Mines contract to reduce dust generated during the bagging operation on 

fluidized air baggers. A field analysis of the new system has shown 

that the bag operator's dust exposure was reduced 83 pet. The amount 

of blowback was reduced 89 pet, which corresponds to a significant 

product savings. The new prototype system has been operating for a 

substantial period of time with no major problems. 

'Mining engineer. 

2p hysical scientist. 

3Supervisory physical scientist. 

Pittsburgh Research Center, Bureau of Mines, Pittsburgh, PA. 
2 

INTRODUCTION 

Many different types of mineral products are packaged into 50- or 100-lb 

bags. In many cases, these bags are 

filled by fluidized air bagging machines , 

which offer a fast and effective way to 

package mineral products into paper bags. 

However , a substantial amount of dust is 

generated during the fill cyc1e. 4 The 

dust generated results from a few specific causes. One is a "r ooster tail" of 

product from the fill nozzle and bag 

valve as the bag is discharged from the 

fill station. Another cause is blowback 

of product a s the bag is fil ling , which 

results in the accumulati on of dust on 

t.he outside of the bag. Also , as the bag 

falls from the fill station and hit s t he 

conveyor belt, a blast of product is 

blown out from the bag valve because the 

bag is under pressure as it leaves the 

fill station. This, combined with the 

blowback, contaminates the outside of the 

bag, resulting in a dust problem for 

workers loading the bag onto a pallet. 

A new system has been designed under 

Bure au of Mines contract H03 18013 by 

Foster- Mi l ler, I nc . , to eliminate t h e s e 

major dust SOULces (fig. 1). The new 

system is composed o f an i mproved bag 

clamp designed to r educe the amount of 

p~oduct blowback during bag filling . The 

clamp reduces blowback because it has direct contact with approximately 80 pct of 

the nozzle. An air exhaust syst em incorporated around the fill nozz l e exhaus t s 

the excess pressure from the bag when i t 

4National Industrial Sand Association . 

Guidance and Solutions to Reducing Respirable Dust Levels in the Bagging 

of Wholegrain Sili~a Products. Silver 

Spring, MD, 1977, 35 pp. 

Volkwein, J. C. Dust Control in Bagging operations. Proc. Industrial Hygiene for Mining and Tunneling (symp., 

Denver, CO, Nov. 6-7, 1978) . Am. Conf. 

of Governmental Indo Hygienists Inc . , 

1979, pp. 51--57 ,. 

has finished filling. The inner nozzle 

is the normal fill nozzle, around which 

is another nozzle used as the exhaust 

nozzle. The exhaust system is powered by 

an eductor, which uses a venturi effect 

to exhaust the bag at approximately 50 

ft 3 /min. The exhaust exits to a bucket 

elevator, which recycles the exhausted 

product. A pinch valve is used to open 

and close the exhaust syst em to t he bag . 

There are four steps to the new system. 

Step 1.--The operator places t he ba g on 

the fill noz z le and activates the start 

button. The bag clamp clos es, the produ ct v a lve opens , a nd t h e bag f ill s normally with no changes . (Fill t i me variable dependent on pr oduc t mesh size; no 

increase in fill time with new system.) 

Step 2. - -The bag is 

filled , the product valve 

clamp r emains closed, and 

opens allowing t h e bag 

(5 s) . 

slightly over -

closes , t h e bag 

t he pinch val ve 

to be exhausted 

- Exhaust -

t 

58~ -Fill nozzle 

Bag clamp 

- Pinch valve 

(open position) 

Compressed air 

To recycle 

FIGURE 1. - New bag nozzle system. 
Step 3.--The bag clamp opens, and the 

bag begins to fall away from the fill 

nozzle. The exhaust system, which is 

still operating, cleans the bag valve as 

the bag falls away (2 s). 

3 

Step 4.--The pinch valve closes, turning off the exhaust system. A new bag 

can be placed on the fill nozzle and the 

cycle repeated. 

TESTING 

A field evaluation was performed on the 

new system during the second week of a 

2-week test on a four-station fluidized 

air bagger at a minerals- p r ocessing 

plant. During the first week, the conventional system was tested to determine 

the amount of dust generated. Over the 

weekend, the new system was installed, 

which took approximately 30 worker-hours . 

During the second week, t he same test was 

performed using the new system. 

Five real- time aerosol monitors (RAM) 

were placed at various locations throughout the bag-loading and transport operation as follows: 

Location 1 was in the exhaust duct of 

the exhaus t vent ilation system for the 

four- station bag a rea that goes to a baghouse collector. I t gave a direct indication of the amount of blowback. 

Location 2 was at t he transfer point 

between t he bag machine discharge belt , 

and the belt to the loading dock to measure the amount of dust on t he outside of 

the bag and belt . 

Location 3 was at the area of intake 

air into t he bag room. It gave an indication of dust f rom the belt and the 

loading dock area and was used as a baseline for bag room measurements . 

Location 4 was on the lapel of bag 

operator to give a direct indication of 

dust exposure at the operator position. 

Location 5 was in the back of the bag 

room to indicate the dust level throughout the bag room, 

Dust from each product me sh size was 

measured separately. Table 1 gives the 

results obtained for the 

tion for the first week 

operator locawith the conventional system as compared with the second 

week with the new bag nozzle system. As 

the product size is reduced (finer product), the dust generated during bagging 

increases; the new prototype system is 

more effective. The dust levels with the 

finer mesh sizes are not lower; in fact, 

dust levels are very close for all the 

mesh sizes with the new system. The increase in percent reductions with the 

finer product sizes is due to the increased dust levels during the first week 

of testing (conventional system) . Table 2 shows the dust reductions obtained 

for the 325-mesh product size, the 

finest (dustiest) product bagged at this 

operation. 

TABLE 1. - Dust exposure at operator 

position 

Product Conventional New Reducsize, system, system , tion , 

mesh mg/m3 mg/m3 pct 

120 • •••••• 0 . 27 0 . 14 48 

180 •• •• ••• .49 . 09 82 

325 ••••••• .42 . 07 83 

TABLE 2. - Dust analysis for 325-mesh 

product 

Measuring Conventional New Reduclocation system , 

mg/m3 

Exhaust • •• >200.00 

Transfer • • . 33 

Intake •• o • .29 

Operator" • .42 

Background .32 

Figure 2 shows a 

measurement at t he 

fo r the first and 

system , t ion , 

mg/m3 p ct 

21.87 89 

.13 61 

.06 79 

.07 83 

.07 78 

portion of the RAM 

operator ' position 

second weeks. The 
4 

rt) 

E 

, 

C'I 

E 

• 

2.0 

Conventional system 

z 

o 

~ 0:: 

tZ 

W 

U 

Z 

o 

U 

ten 

:::> 

o 

1.0 

.2 

o 5 10 

TIME, min 

15 20 

FIGURE 2. - Operator exposure using conventional system and new system. Monitor located on 

operator's lapel. 

threshold limit value (TLV) for this 

operator ranges from 0.17 to 0.20 mg/m3 , 

and peak dust exposure levels remained 

under this TLV value. 

Because of the increased time involved 

to exhaust the bag, the production rates 

for both weeks of testing were monitored. 

The effect on productivity with the new 

system is presented in table 3. The new 

system has increased the time approximately 1.5 s per bag over that of the 

conventional system. The increase was 

attributed to the time the operator 

waited after loading nozzle 4 until he 

could begin loading nozzle 1. Normal 

truck loading time with the conventional 

system was approximately 45 min; with the 

new system, it increased to approximately 

58 min. The time increase had no significant effect on productivity at this 

mill. 

TABLE 3. - Increase in production time 

using new system 

Product size, Per bag, Per truck (480 

mesh s bags), min 

120 •••••••••••• 1.4 11.2 

180 •••••••••••• 1.7 13.3 

325 •••••••••••• 1.5 12.2 

Average ••• 1.5 12.2 

The problem dust areas on fluidized air 

baggers have been significantly corrected 

by this new prototype bag nozzle system. 

The rooster tail has been eliminated because the exhaust system is cleaning out 

the bag valve and fill nozzle. Figure 3 

shows a bag coming off the bag machine 

with the conventional system and figure 4 

shows the same occurrence with the new 

system. The blowback has been significantly reduced because of the new bag 

clamp, which has direct contact with 
FIGURE 3. - "Rooster tail" effect using conventional system. 

approximately 80 pct of the bag nozzle. 

The blast of product when the bag hits 

the conveyor is reduced because the bag 

is not pressurized as it falls from the 

fill station. Because of the foregoing, 

FIGURE 4. m Elimination of "rooster tail" effect using new system. 

5 

and the reduced amount of blowback, the 

bags are much cleaner on the outside as 

they travel on the conveyor belts to the 

loading dock. 

CONCLUSIONS 

The new bag nozzle system was very effective at reducing dust levels during 

the bagging operation at a mineralsprocessing plant. For the finest (dustiest) product bagged at this operation, an 

83-pct reduction was recorded at the 

operator position. An 89-pct reduction 

aU . S. GPO : 1984-705-020 /5026 

was recorded for blowback during bag 

filling, which is also an indication of 

the amount of product savings. The new 

system requires little maintenance and 

has had no major problem in the 8 months 

since installation. 

INT.-BU.OF MINES,PGH.,PA. 27560