PHYSIOLOGICAL RESPONSES OF UNDERGROUND COAL MINERS UNDER INIMICAL WORKING ENVIRONMENT

Delivered By ~

Dr. Netai Chandra DeyPROFESSOR(MINING)

BENGAL ENGINEERING AND SCIENCE UNIVERSITY, SHIBPUR, HOWRAH

Reasons to take up Ergo based research work

Objectives of the study

Unit operations in UG mine

Provision of ergonomic study in DGMS circular

Selection of subject for the study

Physical characteristics of Roof Bolters

Threshold limit values of different environmental parameters

An overview on physiological status w.r.t some strain indices

Time element of roof bolting activity in spell and shift

Determination of work load as per various scientific classification

Adequacy of job duration in mines

Possible R & D initiatives

Conclusion and recommendations

Lecture Content

WHY ERGONOMICS-BASED RESEARCH WORK IN MINING IS IMPORTANT?

Huge base of workers constituting more than 80% of total

work force in mining industry.

Huge absenteeism about 30-35%.

Significant report of sufferings from MSD’s and postural

problems, which indicates poor health of miners.

Considerable compensation is being paid to the miner by

private and public enterprises.

Poor OMS of underground miners which is around 0.5-0.6

since last 10-15 years, indicates poor efficiency of UG

miners.

Mine reserve sustainability in India for at least next 100

years

OBJECTIVES OF THIS PARTICULAR STUDYOBJECTIVES OF THIS PARTICULAR STUDY

Determination of workload of selective category of miners

Optimization of job duration of different mining operation with respect to given environmental inputs.

Determination of workload of selective category of miners

Optimization of job duration of different mining operation with respect to given environmental inputs.

Executive: 15,431Supervisor: 36,855Workmen: 3,28,359 (86%)

Total: 3,80,645

MANPOWER OF CILMANPOWER OF CIL

Open cast

Under ground

MANPOWER OF SCCLMANPOWER OF SCCL

Executive: 2477Supervisor: 14,568Workmen: 49,041 (74.3%)

Total: 66,086

As per DGMS Circular & Xth conference on safety in mines held in

New Delhi during 26-27 Nov.2007 following ergonomic study have

been made mandatory:

1.Assessment of work processes

2.Assessment of posture

3.Assessment of tools/aids

4.Cardio- vascular assessment

5.Vibration studies of machines as per ISO

As per DGMS Circular & Xth conference on safety in mines held in

New Delhi during 26-27 Nov.2007 following ergonomic study have

been made mandatory:

1.Assessment of work processes

2.Assessment of posture

3.Assessment of tools/aids

4.Cardio- vascular assessment

5.Vibration studies of machines as per ISO

PROVISION OF ERGONOMIC STUDY IN DGMS CIRCULAR

How ergonomics can help industryHow ergonomics can help industry

Work load determination and adequacy of workload to an Individual.

Work optimization can be done through changing environmental

parameters.

Work station designing.

Designing of HEMM’s and other machine operator’s seating, cabin etc.

Handling of heavy tools.

Postural study to minimize musculo-skeletal disorder(MSD) related

troubles.

Work load determination and adequacy of workload to an Individual.

Work optimization can be done through changing environmental

parameters.

Work station designing.

Designing of HEMM’s and other machine operator’s seating, cabin etc.

Handling of heavy tools.

Postural study to minimize musculo-skeletal disorder(MSD) related

troubles.

STEPS INVOLVED IN THE CONVENTIONAL UNDER GROUND DEVELOPMENT DISTRICT

Priority based criteria that have been used to select the different mining operations for the present study are as follows:Priority based criteria that have been used to select the different mining operations for the present study are as follows:

1. Activities that are quantitative in nature.

2. Activities where the miners have to devote a significant time at a stretch in the allocated working area.

3. Activities that are supposed to be relatively physically demanding under adverse conditions of mines.

1. Activities that are quantitative in nature.

2. Activities where the miners have to devote a significant time at a stretch in the allocated working area.

3. Activities that are supposed to be relatively physically demanding under adverse conditions of mines.

Category BMI range (kg/m²)

Severly underweight <16.5

Underweight 16.5-18.5

Normal 18.5-25

Over weight 25-30

Obese classes >30

Stages of human BSA values (Acceptable

limits)For men 1.9 m²

For women 1.6 m²

REFERENCE:1. Adapted from US EPA 19852. WHO recommended body weight based BMI values for

adults.

PHYSIOLOGICAL PARAMETERS (DIRECT & DERIVED) IN ROOF BOLTING FOR TWO DIFFERENT MINE

PARAMETER Mine A (n=5) Mine B (n=5)

WHR(bpm) 123.8±3.77(120-130)) 109.8±3.77(105-115)

RCC (%) 54.08±4.80(48.11-61.45) 52.18±4.75(47.11-60.45)

NCC(bpm.) 53.2±3.34(51-59) 28.2±3.34(22-30)

OT(0F) 99.2+0.4(98.4-99.8) 99.3+0.4(98.6-100.2)

It is observed that roof bolters experience the highest responses in both spells except

net cardiac cost.

Mean WHR for both group gets elevated around 70-75% compared to their resting

responses. Both the elevation is statistically significant.

PERCENTAGE OF ROOF BOLTING WORK EXCEEDING THE RECOMMENDED LIMITS OF PHYSICAL STRAIN

INDICES ACCEPTED LIMITS Mine A Mine B

WHR(bpm) 110 100 60

LCW 35 beats over resting pulse 100 100

RCC (%) 30% 100 80

NCC(bpm) 30 100 60

The average work load of individual roof bolter of two different mine during their bolting activity is judged against various recommended indices of cardiac strain.

It is seen that in mine A 100% of bolters remain above 30% level of RCC whereas 80% of mine B remains above 30% RCC.

WHR of mine A is 100% beyond the limit whereas in mine B it is 60%. The same effect is observed in case of NCC.

Parameter Reference

Classification of workload

Light Moderate HeavyVery

heavy

Extremely

heavy

Roof

Bolting

Driller

(n=5)

Remarks

Working

Heart rate

(bpm)

Astrand <90 90-110 111-130 131-150 151-170 *123.8Roof Bolters are in

heavy category.

Energy

expenditure

(Kcal)

Ramanathan

,et al1.0-2.5 2.6-4.0 4.1-6.0 6.1-8.0 >8 *4.15

Roof Bolters are in

heavy category.

Net cardiac

cost (bpm)

Chamoux, et

al≤20 20-30 31-40 41-50 51-60 *53.2

Roof Bolters are in

very heavy

category.

Physiological workload classification & comparison with observed values(Mine-A)

* Mean values are given

Parameter Reference

Classification of workload

Light Moderate HeavyVery

heavy

Extremely

heavy

Roof

Bolting

Driller

(n=5)

Remarks

Working

Heart rate

(bpm)

Astrand <90 90-110 111-130 131-150 151-170 *109.8Roof Bolters are in

moderate category.

Energy

expenditure

(Kcal)

Ramanathan

,et al1.0-2.5 2.6-4.0 4.1-6.0 6.1-8.0 >8 *3.75

Roof Bolters are in

moderate category.

Net cardiac

cost (bpm)

Chamoux, et

al≤20 20-30 31-40 41-50 51-60 *28.2

Roof Bolters are in

moderate category.

Physiological work load classification comparison with observed values(Mine B)

* Mean values are given

A glimpse of heart rate at different states of mine A Roof Bolter

28%28%

71%71%

A comparison of cardiac indices & energy expenditure of Roof BoltersA comparison of cardiac indices & energy expenditure of Roof Bolters

Mean±SDRoof Bolter (n=5)

P1 P2 P3

 (Range)112.6±5.74

(98-118)98.8±5.24

(90-104)90.6±5.17

(82-97)

Recovery heart rate pattern of Subjects (Mine A)Recovery heart rate pattern of Subjects (Mine A)

Mean ±SDRoof Bolter (n=5)

P1 P2 P3

(Range) 

99.2±6.83 (95-106)

87.6±5.50 (82-98)

82±5.41 (78-86)

Recovery heart rate pattern of Subjects (Mine B)Recovery heart rate pattern of Subjects (Mine B)

Brouha’s fatigue assessment techniquesBrouha’s fatigue assessment techniques

Condition Criteria

Normal state P1 - P3 ≥ 10 bpm and P1, P2, P3 ≤ 90

bpm

No – recovery state P1 - P3 < 10 bpm and P3 > 90 bpm

Inverse recovery state P3 > 90 bpm and P1 - P3 ≤ -10 bpm

No increasing cardiac strain P1 ≤ 110 bpm and P1 - P3 > 10 bpm

BOLTER (Mine A) TIME(MIN) NUMBER

work duration per shift 101.12±2.43(99.4-102.84) -

spells per shift - 4

spell duration per shift 25±0.06(25-26.99)* -

% time spent by different job elements in an activity of a spell

walking with machine & accessories - 5.61

Considering 5 effective hours in a

shift

roof checking - 5.98

drilling in roof - 21.52

Soaking , pushing of cement cartridge and insertion of bolt - 12.6

Tightening of bolt nut - 2.5

BOLTER (Mine B) TIME(MIN) NUMBER

work duration per shift 63.8±2.6(61.4-65.3) -

spells per shift - 3

spell duration per shift 21±0.12(20.2-23.4)* -

% time spent by different job elements in an activity of a spell

walking with machine & accessories - 3.2

Considering 5 effective hours in a

shift

roof checking - 4.34

drilling in roof - 12.4

Soaking , pushing of cement cartridge and insertion of bolt - 6.8

Tightening of bolt nut - 1.6

UNDERGROUND MINE ENVIRONMENT PARAMETERS (Mine A)

PARAMETERS DB(°c) WB(°c) NWB(°c)AIR VELOCITY

(m/min)

WBGT(°c) HUMIDITY (%) ET(°c)

MEAN±SD (RANGE)

28.84±0.72(28-30.5)

27.74±0.68(27-29.5)

28.23±0.71(27-30)

4.92±4.65(1-18)

28.41±0.69(27.3-30.3)

92.07±1.68(89-98)

29±0.35(28-29.5)

Classification of environmental zone at various level of ET

Classification ET(0C) Observed value(0C)

Very hot zone >30

29*Hot zone 28.33-29.94

Warm zone 26.67-28.28

Comfortable zone 21.11-26.61

*Values are given °C, ET & WBGT

Permissible Heat Exposure Threshold Limit Values: - (By ACGIH)

Work Rest Regimen Light Moderate HeavyContinuous work 30.0 26.7 25.075% of work; 25% of rest, each Hr. 30.6 28.0 25.950% of work; 50% of rest, each Hr. 31.4 29.4 27.925% of work; 75% of rest, each Hr. 32.2 31.1 30.0

Observed WBGT values

28.41*

UNDERGROUND MINE ENVIRONMENT PARAMETERS (Mine B)

PARAMETERS DB(°c) WB(°c) NWB(°c)

AIR VELOCITY

(m/min)

WBGT(°c) HUMIDITY (%) ET(°c)

MEAN±SD (RANGE)

31.5± 0.96 (28.5-33.5)

29.9±0.94(26.5-31.5)

29±1.02(27-32)

22.2 ± 0.12(12.6-42.6)

27.8 ± 1.06 (26.5 -31.5)

88 ±3.5(75-93)

27.95 ±0.35

(26.5-31.5)

Classification ET(0C) Observed Value(0C)

Very hot zone >30

27.95*Hot zone 28.33-29.94

Warm zone 26.67-28.28

Comfortable zone 21.11-26.61

Classification of environmental zone at various level of ET

Permissible Heat Exposure Threshold Limit Values: - (By ACGIH)

Work Rest Regimen Light Moderate HeavyContinuous work 30.0 26.7 25.075% of work; 25% of rest, each Hr. 30.6 28.0 25.950% of work; 50% of rest, each Hr. 31.4 29.4 27.925% of work; 75% of rest, each Hr. 32.2 31.1 30.0

*Values are given °C, ET & WBGT

Observed WBGT values

27.8*

Category of work

Actual work (in

each hour) Mine A

Recommended work (in each hour) Mine

A

Actual work (in each hour)

Mine B

Recommended work (in each hour)

Mine B

Roof Bolter 20.22Min.* 15 Min. 12.76 Min. 45 Min.

* Effective time in a shift is considered to be 5 hrs.

In Mine A the roof bolters are doing more work (though this may not be adequate)

than the recommended work limit. Hostile Environment is responsible.

In Mine B the roof bolters are doing much less work than the recommended work limit.

The hostile environment of Mine A is responsible for increased job demand and hence

the bolters are in heavy work load category. So, the mine unit is deprived of effective

utilization of system inputs whereas, the humanizing environment of Mine B helps to

reduce the job demand to moderate category.

The roof bolters of mine B are heavily under loaded and the jobs should be increased

accordingly.

The environment of Mine A should be monitored and improved adequately so that

their work limits can be enhanced appropriately.

In Mine A the roof bolters are doing more work (though this may not be adequate)

than the recommended work limit. Hostile Environment is responsible.

In Mine B the roof bolters are doing much less work than the recommended work limit.

The hostile environment of Mine A is responsible for increased job demand and hence

the bolters are in heavy work load category. So, the mine unit is deprived of effective

utilization of system inputs whereas, the humanizing environment of Mine B helps to

reduce the job demand to moderate category.

The roof bolters of mine B are heavily under loaded and the jobs should be increased

accordingly.

The environment of Mine A should be monitored and improved adequately so that

their work limits can be enhanced appropriately.

Job duration optimization of Roof Bolters in MinesJob duration optimization of Roof Bolters in Mines

Possible R&D initiatives required in mining field

Workstation designing in under ground and open cast.

Ergonomical designing of HEMM’s operators cabin

Postural study regarding operators reach/ control with respect to

HEMM’s

Determination of workload and adequate work rest regimen for

miners in different working conditions and work environment.

Nutritional study

Delay in onset of fatigueness to maximize worker’s efficiency in

mines

CONCLUSION & RECOMMENDATIONS CONCLUSION & RECOMMENDATIONS

Decreases Injury Frequency so that the compensation made towards

the employee is drastically reduced.

Increases production and productivity

Ergonomic study helps to scheduling and optimizing the work bouts to

reach the companies objective comfortably.

Decreases Absenteeism.

Increases Health and Comfort which will have direct impact on the

work efficiency of employee.

Decreases Injury Frequency so that the compensation made towards

the employee is drastically reduced.

Increases production and productivity

Ergonomic study helps to scheduling and optimizing the work bouts to

reach the companies objective comfortably.

Decreases Absenteeism.

Increases Health and Comfort which will have direct impact on the

work efficiency of employee.

Thank You