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Observing working postures in industry: Examples of OWAS application
Applied Ergonomics 1981, 12.1, 13-17
Observing working postures in industry: Examples of OWAS application Osmo Karhu*, Reino H'~rktinen**, Pentti Sorvali*** and Pentti Veps'~l~iinen * * * * * ** *** ****
Department Manager, Ovako Oy, Helsinki Director of Administration, Ovako Oy, Helsinki Manager of Industrial Engineering, Ovako Oy, Imatra Head Shop Steward, Ovako Oy, Imatra
A practical method for identifying and evaluating poor working postures, ie the Ovako Working Posture Analysing System (OWAS), was presented in an earlier paper (Karhu et al, 1977). The application of the method is here described by means of two examples. One is a case study undertaken by members of an ergonomics training course, in which a marked improvement in working posture was achieved by OWAS analysis of critical activities. The second illustrates the effect of setting up a multidisciplinary group in order to develop an alternative method for the installation and maintenance of steel mill equipment. In both examples, application of the OWAS method led to improved posture in the situations studied, and to the likelihood of its wider industrial use.
Introduction The development work of the OWAS-method (Karhu
etal, 1977) was started in Ovako Oy I in 1973 and we are now able to present some examples of how the OWASmethod is applied in practice. The steel industry, because of its capital-intensive nature, is struggling with problems created by the need to increase productivity. One of the objectives in a situation like this should be healthy, safe and productive working conditions which would make people willing to work in the steel industry. It is therefore important that ergonomics points are observed in routine decision-making at all levels within the organisation. In our company this philosophy is encouraged by extensive ergonomics training, this being based on management decisions at an operation policy level. The Industrial Engineering Department, co-operating with work safety personnel, is responsible for the ergonomics training in Ovako. The effects of working postures in heavy physical work has become the central object of study and the OWAS-method has been established for this purpose. Two examples, in which the OWAS-method has been used, are illustrative of the progress in the use of the method. The first example is of a training topic given to a working group during a 7-day ergonomics course. The second example is of the results achieved through planning and redesign. The difference between these two examples
10vako Oy is a private company producing steel bars, profiles, wire rod and pig iron. The company consists of two profit centres including four plants in the southern part of Finland. The head office of the company is in Helsinki. The company employs 3500 people. The company's turnover is about 650 million FMK.
0003-6870/81/01 0013-05 $02.00 ~) IPC BusinessPress
is that the first has been produced under the strong influence of ergonomics thinking, while the second applies ergonomics training in the planning work of technical designers.
Bricklaying the deck of an electric arc furnace In the Imatra Steel Works the raw material, iron scrap, is melted for casting in electric arc furnaces. The deck of the furnace is a round arc-like construction made of firebricks. The arc is laid in a separate working spot on a mould. The diameter of the arc is 5.3 m and a deck wears out in approximately one week, A working group on an ergonomics course selected this task for its training case study. The ergonomics course consisted of a lecture period of 5 days followed by a period of 3 - 5 weeks during which the training topic was studied. In the final two days the case studies were reported and criticised as project-work during normal working hours. During this ergonomics course a working group of four persons (with representatives from workers, supervisors and industrial engineering) decided to apply the OWAS-method to their training topic. The working group turned to the Industrial Engineering Department for the study of working postures. The study revealed that the bricklaying was done primarily with the back in a bent posture (Fig. 1) for about 43% of the total working time. Particularly difficult and hard on the bricklayer's back were the working postures after the first layer of bricks were laid and the bricklayer had to continue the laying work standing on the mould with his back extremely flexed. The study provided a new and different starting point for the creation of ideas, and in co-operation with the Industrial Engineering Department the working group
Applied Ergonomics March 1981
13
developed a 'ring-element' for the bricklaying (Fig. 2). Each ring was fitted separately with bricks (Fig. 3) and the rings were lifted by crane. Following this change in the working method, tile check study showed that the bent posture exposure time had decreased from 43% to 22%. The new method has now been used for nearly two years and the workers have given their full approval to this corrective measure which they consider a success.
Comparison of bricklaying with the new and old method; OWAS-analysis In the study the back, upper and lower limbs were analysed. The most important result of this study was, however, the comparison between operative classes 3 and 4 (Karhu et al, 1977). Operative class refers to urgency of corrective action, 4 being the most urgent (Fig. 4). From Table 1 we find that a definite decrease had been achieved in those postures, which belong to classes which imply a most urgent need for correction.
Trolley for adjusting guides in a roll stand The objective of the working group was to develop alternative working methods for the maintenance and installation of a roll unit.
Fig. 2
Ring elements for bricklaying the deck of an electric arc furnace. The mould consists of three elements which fit into one another. The diameter of the outer ring is 5.3 m and the total assembly weighs 5000 kg
Fig. 3
Each ring element is fitted separately with bricks. This allows the use of more acceptable working postures
The rolling of billets in the Light Rolling Mill is carried out by roll stands. In the Medium Section Mill the three high mills together with bearings and rest bars form a fixed
Fig. 1
The old method of bricklaying. The first layer of bricks is being laid
14
AppliedErgonomics
March 1981
(3)
(2)
(1)
IBACKI
(4)
I)
,dl• I
straight and twisted
bent
straight
bent and twisted
Old Method %
18,5
42,6
1,4
12,7
New Method %
43,5
22,3
2,9
2,2
(1)
UPPER LIMBS
(3)
(2)
both~l iJ limbs .8 k limbs~ ~ . above shoulder on or below shoulder level °~ao°u~~1b°~eevei level both
|
I Old Method %
64,1
10,0
1,1
New Method %
63,3
6,9
0,6
LOWER LIMBS
(2)
(1)
Fig. 40WAS-analysis of the old and new method of bricklaying
(5):
(4)
(3)
/
/
"I'P
Old method %
New method %
loading on both loading on one loading on both loading on one body is moved limb, bent by the limb limbs, straight limb, straight limbs, bent 12,1 4,7 48,0 5,4 5,0 6,8
54,9
Table 1
Operative class
2
3
4
Old method
13.9
3.2
5"6
New method
7.2
1.5
0"6
roll stand. With the help of guides the billet is guided into the groove. The maintenance and adjustment of the 30 ton roll unit is done in a separate working area, where the unit is lifted by crane (Fig. 5). This is an example of setting up a working group to solve a certain problem. The working group comprised six people; a planner, an industrial engineer, two supervisors and two
1,3
0,2
7,7
workers, and the group reported their results to the co-ordinating group (a department manager, representatives of supervisors, workers and the Industrial Engineering Department). Table 2 shows the ergonomics training situation at the time of the study at Imatra Steel Works. In addition to the training shown in this Table, members of the working group were given a 1 - 4 h lecture during rationalisation and work safety seminars.
Comparison of the old and new methods of working The old method for adjusting the guides was carried out on a fixed mounting stand in the rolling mill hall. This situation was hot, noisy, the air was dust-laden and draught
Applied Ergonomics March 1981
15
was continuous. The working postures were difficult and included stretching and bent postures as well as lifting of heavy objects. The new method allowed the installation work to be carried out in a van with an adjustable working platform.
have not succeeded in eliminating all poor postures but some of them can further be eliminated by making small changes in the trolley (Fig. 7). Conclusion
A comparative OWAS-analysis (Fig. 6) shows that working postures changed from bent postures (2) to straight and twisted (3) and bent and twisted (4), but the share of operative class 4 had decreased by about 50%. We
Because people should be considered as 'units' it is important to observe working postures as a unit by combining the postures of the back and limbs in one observation and analysing the working posture as a whole (Fig. 8).
Table 2
Course
Persons
In the two examples presented the main consideration has been on the reduction of 'bad' postures and their time share. Two more considerations should be taken into account
Total I matra Steel Works
Co-ordinating Working group group
(a) (b)
Ergonomics course (7 days)*
2
1
77
OWAS-course (5 days)*
1
1
25
Ergonomics course (4 weeks)**
1
reduction of posture-caused disorders or diseases, and productivity.
We have no indication that back pain or other locomotor organ disorders have been diminished. The small number of subjects and insufficient follow-up time do not allow that analysis. Because back pain is often multicausal, we do not expect that even with a greater number of subjects a measurable effect could be achieved. We expect that good working conditions will lead to better health and lower absence figures in general.
11
*Internal training ** Course by the Institute of Occupational Health
Also the productivity in the two examples is made up of several factors from which the purified effect of correcting working postures is not easily separable. In the bricklaying, the total working time decreased by 10%, which seems to come directly from the lightening of the working postures. In the roll stand guide's adjustment task the shortening of the total time is 25%. The concurrent partial mechanisation of the task assists in the shortening of the work time, so that the sole role of changes in working postures is not easily distinguishable. The stand-up time in the rolling mill line shortened considerably. The quality of the reassembly has definitely become better and we regard this as a direct effect of the easing of working postures. For practical purposes the separation of the effect of change in the working postures and in technical equipment and methods is not very interesting, if we recognise that there cannot be a good and productive technical system without consideration of the human aspects.
Fig. 5
Until now, the use of the OWAS-method has been rather selective. In addition to the direct results provided by these studies, they have achieved indirect results by making attitudes more favourable towards working postures.
A diagram of the 30 ton rolling unit. Maintenance and adjustment mechanisms intcude rest bars (B) and guides (G). With the help of guide (G) the billet is guided into the groove (1)
,'A
(I k
I
.41
straight
(4)
(3)
(2)1
i t
straight and twisted
bent
Operative Class
~J
Fig. 6
bent and twisted
Old method (min)
186
60
4
6
15 min
New method (rain)
119
28
25
14
8 min
16
Applied Ergonomics
March 1981
A comparison by OWASanalysis of adjustment and maintenance on the rolling unit with the new and old methods of work
(3)
(2)
(1)
UPPER LIMBS
?he L
both L limbs "" on or below shoulder level
on or above shoulder level
OLD METHOD (MIN)
198
40
18
NEW METHOD (MIN)
137
34
15
LOWER LIMBS
/
(2)
(1)
l)
both L li above shoulder level
(3)
j'
(4)
(5)
(6)
4
d~
loading on both limbs, straight
loading on one limb, straight
loading on both limbs, bent
loading on one limb, bent
loading on one limb, kneeling
body is moved by the limbs
OLD METHOD
134
10
42
4
10
53
NEW METHOD
118
19
16
5
--
26
Fig. 7
OWAS-analysis of positions of the upper and lower elements, before and after modification of maintenance procedures on the rolling mill unit
AN EXAMPLE POSTURE 2t 5
"•••ECTIVE
BRICKLAYING THE DECK AN ELECTRIC OVEN
ADJUSTING THE GUIDE IN THE ROLL UNIT
OLD METHOD (MIN)
1 4,0
1,5
NEW METHOD (MIN)
0
0,5
METHOD
Further information on the OWAS-method in Ovako Oy can be obtained through Mr Osmo Karhu, Ovako Oy, POB 790, SF-00101 Helsinki 10, Finland. In December 1975 Ovako Oy conveyed the OWASmethod to the labour market organisations (The Finnish Employers' Confederation and The Central Organ!sation of Finnish Trade Unions). The organisations have organised a project, financed by SITRA (The Finnish National Fund for Research and Development). This project aims at finding
BACK: bent UPPER LIMBS: both below shoulder level LOWER LIMBS: loading on one limb, kneeling
Fig. 8
Total time involved in Working Posture 215 in (a) bricklaying the deck of an electric oven (b) adjusting a guide in the rolling unit
out the possibilities of applying the OWAS-method to other fields of industry. The project will be completed at the end of 1978. References Karhu, 0., Kansi, P., Kuorinka, l. 1977 AppliedErgonomics, 8.4, 199-201. Correcting working postures in industry. A practical method for analysis.
Applied Ergonomics
March 1981
17
Observing working postures in industry: Examples of OWAS application Osmo Karhu*, Reino H'~rktinen**, Pentti Sorvali*** and Pentti Veps'~l~iinen * * * * * ** *** ****
Department Manager, Ovako Oy, Helsinki Director of Administration, Ovako Oy, Helsinki Manager of Industrial Engineering, Ovako Oy, Imatra Head Shop Steward, Ovako Oy, Imatra
A practical method for identifying and evaluating poor working postures, ie the Ovako Working Posture Analysing System (OWAS), was presented in an earlier paper (Karhu et al, 1977). The application of the method is here described by means of two examples. One is a case study undertaken by members of an ergonomics training course, in which a marked improvement in working posture was achieved by OWAS analysis of critical activities. The second illustrates the effect of setting up a multidisciplinary group in order to develop an alternative method for the installation and maintenance of steel mill equipment. In both examples, application of the OWAS method led to improved posture in the situations studied, and to the likelihood of its wider industrial use.
Introduction The development work of the OWAS-method (Karhu
etal, 1977) was started in Ovako Oy I in 1973 and we are now able to present some examples of how the OWASmethod is applied in practice. The steel industry, because of its capital-intensive nature, is struggling with problems created by the need to increase productivity. One of the objectives in a situation like this should be healthy, safe and productive working conditions which would make people willing to work in the steel industry. It is therefore important that ergonomics points are observed in routine decision-making at all levels within the organisation. In our company this philosophy is encouraged by extensive ergonomics training, this being based on management decisions at an operation policy level. The Industrial Engineering Department, co-operating with work safety personnel, is responsible for the ergonomics training in Ovako. The effects of working postures in heavy physical work has become the central object of study and the OWAS-method has been established for this purpose. Two examples, in which the OWAS-method has been used, are illustrative of the progress in the use of the method. The first example is of a training topic given to a working group during a 7-day ergonomics course. The second example is of the results achieved through planning and redesign. The difference between these two examples
10vako Oy is a private company producing steel bars, profiles, wire rod and pig iron. The company consists of two profit centres including four plants in the southern part of Finland. The head office of the company is in Helsinki. The company employs 3500 people. The company's turnover is about 650 million FMK.
0003-6870/81/01 0013-05 $02.00 ~) IPC BusinessPress
is that the first has been produced under the strong influence of ergonomics thinking, while the second applies ergonomics training in the planning work of technical designers.
Bricklaying the deck of an electric arc furnace In the Imatra Steel Works the raw material, iron scrap, is melted for casting in electric arc furnaces. The deck of the furnace is a round arc-like construction made of firebricks. The arc is laid in a separate working spot on a mould. The diameter of the arc is 5.3 m and a deck wears out in approximately one week, A working group on an ergonomics course selected this task for its training case study. The ergonomics course consisted of a lecture period of 5 days followed by a period of 3 - 5 weeks during which the training topic was studied. In the final two days the case studies were reported and criticised as project-work during normal working hours. During this ergonomics course a working group of four persons (with representatives from workers, supervisors and industrial engineering) decided to apply the OWAS-method to their training topic. The working group turned to the Industrial Engineering Department for the study of working postures. The study revealed that the bricklaying was done primarily with the back in a bent posture (Fig. 1) for about 43% of the total working time. Particularly difficult and hard on the bricklayer's back were the working postures after the first layer of bricks were laid and the bricklayer had to continue the laying work standing on the mould with his back extremely flexed. The study provided a new and different starting point for the creation of ideas, and in co-operation with the Industrial Engineering Department the working group
Applied Ergonomics March 1981
13
developed a 'ring-element' for the bricklaying (Fig. 2). Each ring was fitted separately with bricks (Fig. 3) and the rings were lifted by crane. Following this change in the working method, tile check study showed that the bent posture exposure time had decreased from 43% to 22%. The new method has now been used for nearly two years and the workers have given their full approval to this corrective measure which they consider a success.
Comparison of bricklaying with the new and old method; OWAS-analysis In the study the back, upper and lower limbs were analysed. The most important result of this study was, however, the comparison between operative classes 3 and 4 (Karhu et al, 1977). Operative class refers to urgency of corrective action, 4 being the most urgent (Fig. 4). From Table 1 we find that a definite decrease had been achieved in those postures, which belong to classes which imply a most urgent need for correction.
Trolley for adjusting guides in a roll stand The objective of the working group was to develop alternative working methods for the maintenance and installation of a roll unit.
Fig. 2
Ring elements for bricklaying the deck of an electric arc furnace. The mould consists of three elements which fit into one another. The diameter of the outer ring is 5.3 m and the total assembly weighs 5000 kg
Fig. 3
Each ring element is fitted separately with bricks. This allows the use of more acceptable working postures
The rolling of billets in the Light Rolling Mill is carried out by roll stands. In the Medium Section Mill the three high mills together with bearings and rest bars form a fixed
Fig. 1
The old method of bricklaying. The first layer of bricks is being laid
14
AppliedErgonomics
March 1981
(3)
(2)
(1)
IBACKI
(4)
I)
,dl• I
straight and twisted
bent
straight
bent and twisted
Old Method %
18,5
42,6
1,4
12,7
New Method %
43,5
22,3
2,9
2,2
(1)
UPPER LIMBS
(3)
(2)
both~l iJ limbs .8 k limbs~ ~ . above shoulder on or below shoulder level °~ao°u~~1b°~eevei level both
|
I Old Method %
64,1
10,0
1,1
New Method %
63,3
6,9
0,6
LOWER LIMBS
(2)
(1)
Fig. 40WAS-analysis of the old and new method of bricklaying
(5):
(4)
(3)
/
/
"I'P
Old method %
New method %
loading on both loading on one loading on both loading on one body is moved limb, bent by the limb limbs, straight limb, straight limbs, bent 12,1 4,7 48,0 5,4 5,0 6,8
54,9
Table 1
Operative class
2
3
4
Old method
13.9
3.2
5"6
New method
7.2
1.5
0"6
roll stand. With the help of guides the billet is guided into the groove. The maintenance and adjustment of the 30 ton roll unit is done in a separate working area, where the unit is lifted by crane (Fig. 5). This is an example of setting up a working group to solve a certain problem. The working group comprised six people; a planner, an industrial engineer, two supervisors and two
1,3
0,2
7,7
workers, and the group reported their results to the co-ordinating group (a department manager, representatives of supervisors, workers and the Industrial Engineering Department). Table 2 shows the ergonomics training situation at the time of the study at Imatra Steel Works. In addition to the training shown in this Table, members of the working group were given a 1 - 4 h lecture during rationalisation and work safety seminars.
Comparison of the old and new methods of working The old method for adjusting the guides was carried out on a fixed mounting stand in the rolling mill hall. This situation was hot, noisy, the air was dust-laden and draught
Applied Ergonomics March 1981
15
was continuous. The working postures were difficult and included stretching and bent postures as well as lifting of heavy objects. The new method allowed the installation work to be carried out in a van with an adjustable working platform.
have not succeeded in eliminating all poor postures but some of them can further be eliminated by making small changes in the trolley (Fig. 7). Conclusion
A comparative OWAS-analysis (Fig. 6) shows that working postures changed from bent postures (2) to straight and twisted (3) and bent and twisted (4), but the share of operative class 4 had decreased by about 50%. We
Because people should be considered as 'units' it is important to observe working postures as a unit by combining the postures of the back and limbs in one observation and analysing the working posture as a whole (Fig. 8).
Table 2
Course
Persons
In the two examples presented the main consideration has been on the reduction of 'bad' postures and their time share. Two more considerations should be taken into account
Total I matra Steel Works
Co-ordinating Working group group
(a) (b)
Ergonomics course (7 days)*
2
1
77
OWAS-course (5 days)*
1
1
25
Ergonomics course (4 weeks)**
1
reduction of posture-caused disorders or diseases, and productivity.
We have no indication that back pain or other locomotor organ disorders have been diminished. The small number of subjects and insufficient follow-up time do not allow that analysis. Because back pain is often multicausal, we do not expect that even with a greater number of subjects a measurable effect could be achieved. We expect that good working conditions will lead to better health and lower absence figures in general.
11
*Internal training ** Course by the Institute of Occupational Health
Also the productivity in the two examples is made up of several factors from which the purified effect of correcting working postures is not easily separable. In the bricklaying, the total working time decreased by 10%, which seems to come directly from the lightening of the working postures. In the roll stand guide's adjustment task the shortening of the total time is 25%. The concurrent partial mechanisation of the task assists in the shortening of the work time, so that the sole role of changes in working postures is not easily distinguishable. The stand-up time in the rolling mill line shortened considerably. The quality of the reassembly has definitely become better and we regard this as a direct effect of the easing of working postures. For practical purposes the separation of the effect of change in the working postures and in technical equipment and methods is not very interesting, if we recognise that there cannot be a good and productive technical system without consideration of the human aspects.
Fig. 5
Until now, the use of the OWAS-method has been rather selective. In addition to the direct results provided by these studies, they have achieved indirect results by making attitudes more favourable towards working postures.
A diagram of the 30 ton rolling unit. Maintenance and adjustment mechanisms intcude rest bars (B) and guides (G). With the help of guide (G) the billet is guided into the groove (1)
,'A
(I k
I
.41
straight
(4)
(3)
(2)1
i t
straight and twisted
bent
Operative Class
~J
Fig. 6
bent and twisted
Old method (min)
186
60
4
6
15 min
New method (rain)
119
28
25
14
8 min
16
Applied Ergonomics
March 1981
A comparison by OWASanalysis of adjustment and maintenance on the rolling unit with the new and old methods of work
(3)
(2)
(1)
UPPER LIMBS
?he L
both L limbs "" on or below shoulder level
on or above shoulder level
OLD METHOD (MIN)
198
40
18
NEW METHOD (MIN)
137
34
15
LOWER LIMBS
/
(2)
(1)
l)
both L li above shoulder level
(3)
j'
(4)
(5)
(6)
4
d~
loading on both limbs, straight
loading on one limb, straight
loading on both limbs, bent
loading on one limb, bent
loading on one limb, kneeling
body is moved by the limbs
OLD METHOD
134
10
42
4
10
53
NEW METHOD
118
19
16
5
--
26
Fig. 7
OWAS-analysis of positions of the upper and lower elements, before and after modification of maintenance procedures on the rolling mill unit
AN EXAMPLE POSTURE 2t 5
"•••ECTIVE
BRICKLAYING THE DECK AN ELECTRIC OVEN
ADJUSTING THE GUIDE IN THE ROLL UNIT
OLD METHOD (MIN)
1 4,0
1,5
NEW METHOD (MIN)
0
0,5
METHOD
Further information on the OWAS-method in Ovako Oy can be obtained through Mr Osmo Karhu, Ovako Oy, POB 790, SF-00101 Helsinki 10, Finland. In December 1975 Ovako Oy conveyed the OWASmethod to the labour market organisations (The Finnish Employers' Confederation and The Central Organ!sation of Finnish Trade Unions). The organisations have organised a project, financed by SITRA (The Finnish National Fund for Research and Development). This project aims at finding
BACK: bent UPPER LIMBS: both below shoulder level LOWER LIMBS: loading on one limb, kneeling
Fig. 8
Total time involved in Working Posture 215 in (a) bricklaying the deck of an electric oven (b) adjusting a guide in the rolling unit
out the possibilities of applying the OWAS-method to other fields of industry. The project will be completed at the end of 1978. References Karhu, 0., Kansi, P., Kuorinka, l. 1977 AppliedErgonomics, 8.4, 199-201. Correcting working postures in industry. A practical method for analysis.
Applied Ergonomics
March 1981
17