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Manual Welding

Published: 10th Apr 2004 in Health and Safety International

Manual Welding

Ergonomics and musculoskeletal health

In the manufacturing, fabrication and construction industries, world-wide emerging joining technologies, new materials and increased quality demands, automation and robotisation are affecting all aspects of planning and operation of production systems. Nevertheless, conventional techniques, requiring high manual operator skills, remain essential for a large proportion of the production. Ways must be found to amalgamate technical demands with demands relating to human factors: management of the workforce, organisation of work, welder qualifications, ergonomics, health and safety" - Richard Ennals: The Welding Industry in Technological Change: A Human Resource Perspective - Work Life 2000, Yearbook 2, Springer Verlag 2000

The role of manual welding

The above observation was made in the context of a work life analysis carried out as part of the preparatory activities for the Swedish EU Presidency in the year 2002. Welding was seen as an example of industrial activities where, amid technological developments, the character of the job was not necessarily developing for the better.

Welding work faced new challenges, linked to the increased demands on productivity, flexibility, and product quality. Even though automation and robotisation of welding production was gradually becoming more important, it was made clear that manual welding will remain an indispensable activity within the welding industry for the foreseeable future.

An international notion is that only very few welders are active as professionals in their trade up to normal retirement age. An important reason for this is that health problems cause early retirement or a transition to unqualified jobs. This situation has been manageable for industry in a period where labour was cheap and accessible, and when qualification demands on welders were relatively low in many types of welding production. However, the situation is now changing rapidly. There is a notion that it is becoming increasingly difficult to recruit young people to join welding school. Moreover, demographics in most industrialised countries imply that there will be an increased competition for workforce in the future. Also qualification demands are changing. This means that the qualified welder must undergo continuous education in order to obtain the formal qualification linked to welding in particular materials, using particular methods, etc. Automation and robotisation require operators who are knowledgeable in welding as well as in programming and production planning. The conclusion to be drawn is that industry needs to recognise that it will have to compete in order to recruit and keep qualified welders on the job.

For continued employability a person must have the right competence, be motivated, and be healthy. In fact, health related problems are extremely prevalent in the context of premature retirement in welders. The following article will focus on the role of the musculoskeletal ailments in welders, and the obvious incentives arising for good ergonomic workplace design.

Musculoskeletal ailments in welders: how frequent are they?

In the The Work Environment 2001 (Annual Report, Swedish Official Statistics), "welders and flame cutters" stand out in terms of heavy exposure and health effects in several respects. For instance, welding constituted one of the twenty occupations where more than half the population reported being "worn out after work" (54%). High prevalence of pain in the musculoskeletal system every week was reported in the following percentages:-

Lower extremity: 38.3%
Upper back: 29.1%
Lower back: 18.5%
Shoulder and arm: 37.0%
Wrist: 23.9%

These figures were significantly higher than what was found in the general male working population, with the exception of the upper and lower back, where about the same prevalence was found in the general population.

In terms of physical load, welding rated number 8 of all occupations reporting exposure to daily lifting of heavy materials weighing 15 kg or more (39%). Flexed or twisted postures were reported by 49% of the welders (rated 9th of all occupations), whereas 40% of them reported work with the hands at or above shoulder level (rated 7th). This very particular strain on the musculoskeletal system comes from awkward postures and the static character of welding work.

Based on questionnaire data, Torell et al. (1988) reported on the 12-month prevalence rate of complaints from the musculoskeletal system in a group of 79 welders, compared with control groups of platers and hull fitters. The prevalence rates were (controls in brackets), neck 59(36,41)%; shoulder 58(40,39)%; elbow 22(20,33)%; knees 53(54,46)%; back 69(65,76)%.

In the Swedish national register of occupational accidents (the ISA system) occupational diseases were also included. For each occupation, relative risk was calculated for men and women separately. Among women, female welders rated 5 among all types of work. Male welders had a rating of 17. There was an over-risk among male and female welders concerning disease in the musculoskeletal system generally. Specifically, male welders had over-risks in the neck (rating 8), back (rating 17), and shoulder/arm (rating 15). Female welders had rating 7, 8, and 9 respectively, also indicating significant over-risks.

In a retrospective cohort study of 550 Dutch shipyard welders, Wanders et al. (1992) reported on the medical wastage in comparison with control groups of shipwrights and engine fitters. It was found that the welders left their job with a disability pension 20% more often than did the controls. The most common medical diagnoses centred on respiratory, cardiovascular, musculoskeletal and mental disorders.

Burdorf et al (1998) studied the prognostic value of pain in the musculoskeletal system in welders with respect to sickness absence the following year, and found that those experiencing symptoms of this kind had a higher risk of subsequent sickness. They reported that neck or shoulder pain and pain of the upper extremities contributed significantly to neck and shoulder absence (relative risk RR=3.35, confidence interval 1.73-6.47), and to upper extremity absence (RR=2.29, CI 1.17-4.46).

The clinical pattern

In a clinical and experimental investigation of studies performed on tendinitis of shoulder muscles (Hagberg and Wegman 1987), it was found that high relative risk (RR=10) was present in three categories of workers: ship-yard welders, plate workers and pooled groups with work above shoulder level.

Herberts et al (1976) found in a clinical-epidemiological study of 131 ship-yard welders that there was a prevalence rate of 18% of supraspinatus tendinitis, a non-bacteriological inflammatory reaction in the shoulder rotator cuff. It was found that the welders were significantly younger when they acquired the disease (Herberts et al. 1981). It was concluded that welding work accelerates the inflammatory process. It was further demonstrated that the supraspinatus muscle is particularly strained in work at or above shoulder level (Kadefors et al. 1976, Herberts et al. 1984, Järvholm 1990).

The high prevalence rate of musculoskeletal symptoms among welders was further emphasised in a clinical-epidemiological study by Törner et al. (1991) of a group of 58 welders. All subjects investigated had clinical aberrations in the musculoskeletal system. Symptoms in the last seven days included 38% from the neck, 42% from the shoulder, 40% from the lower back, and 20% from the knees. Diagnoses which were more common in the welders than in the control groups (fishermen and clerks) included shoulder muscle atrophy (mm. supraspinatus and infraspinatus), and contractures in the hand (Dupuytren's disease). The static load on the shoulder was highlighted as a major problem.

With respect to neck pain, Eklund and Gunnarsson (1992) referring to ISA statistics, reported that welders had a relative risk RR=2 to acquire neck injuries. They identified dynamic biomechanical loading due to visors as a major cause behind this type of pain.

Nauwald reported (1980) on a clinical investigation of knee-joint changes in 120 ship-yard welders. He found a high prevalence of pathological abnormalities. In this group, 69% had spontaneous pain in the knees. The pain was in most cases load-dependent. There was a clear tendency towards an increased prevalence in welders above the age of 45. Patella and bursa syndromes were the most common diagnoses.

Conclusions

A critical look at the scientific evidence available with respect to musculoskeletal complaints and disorders in welders gives rise to the following conclusions: (a) musculoskeletal symptoms are prevalent in welders; (b) welding work entails an increased risk for shoulder pain due to inflammatory reactions in the rotator cuff; (c) further studies should be carried out with respect to hand and neck problems.

This emphasises the need to reduce shoulder muscle load in welding work.

The summary of scientific studies of musculoskeletal ailments in welders indicates that it is the static nature of the work that causes elevated risk for chronic pain in the shoulder and neck. Static muscle contractions at high effort cause fatigue and pain and limit endurance, and may in the long run result in tissue necrosis due to degenerative processes. Static work is considered ergonomically unsound, which has firm physiological basis. Keeping a constant force at 50% of maximal effort may be sustained for only a couple of minutes, whereas introduction of even very brief pauses extends endurance significantly. This can be interpreted in terms of welding methods. Stick welding introduces a natural rhythm in the loading pattern: 1.5-2 minutes of static work, then some changing of electrode, rinsing, and inspection. Compared to semi-automatic welding, this traditional type of welding work may in fact represent an ergonomically preferable type of job. In MIG/MAG welding, there is a continuous feeding of material for as long as the welding needs to be going on technically. This means that static workload in semi-automatic welding may be present for many minutes at a time.

What can the welding industry do?

On the basis of the scientific results summarised in the previous paragraphs, it can be concluded that welders run a high risk to acquire occupational diseases in the musculoskeletal system. From the point of view of workplace design, this fact must be taken into account in the design of workplaces. However, health concerns must always comply with productivity and quality concerns put forward by the production organisation. In the ergonomic checklist to follow, such aspects have been taken into account. In the present context, we limit the discussion to manual welding of objects in the range of approximately 5 - 500 kg. Smaller objects may be welded on welding tables. Larger objects on the other hand, tend not to be moved around in the welding workshop and there is rarely a special workplace arranged.

  • In production planning, the necessity for a MIG welder not to have to weld long joints without rest must be taken into account
  • In order to reduce musculoskeletal strain, the workplace should be arranged so as to allow welding in the optimal hand position, that is, with the hand between waist and shoulder level, not requiring twisted or bent forward postures. In many cases this will require the ability to manipulate the object
  • In order to eliminate heavy lifting, all handling of objects heavier than approximately 10 kg should be carried out using overhead hoists, balancing devices, lifting tables or similar aids
  • In order to reduce the strain in connection with welding gun and powered hand tool (e.g. grinding machine) operation, all such equipment weighing more than approximately 1.5 kg should be suspended. Welding cables should be balanced
  • In order to reduce the strain on the hands, welding guns should have a swivelling operation. They should be designed to allow for operation with two hands
  • In order to allow for adequate safety, all equipment to be used must comply with the European Safety of Machinery Directives

Roland Kadefors, Ph.D., Professor Industry and Human Resource National Institute of Working Life Box 8850 SE-40272 Göteborg Sweden

Published: 10th Apr 2004 in Health and Safety International

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