Risks related to electricians’ work on telecommunications and electricity transmission masts

Päivinen, Minna; Niemelä, Tanja; Nieminen, Markku; Mattila, Markku

Tampere University of Technology / Occupational Safety Engineering / P O Box 541 / Fin-33101 Tampere / Finland

+358 3 3652 669 / minna.paivinen@tut.fi

ABSTRACT

In the Nordic countries, weather conditions during wintertime can be extremely demanding, but despite this many jobs must be done outdoors. The aim was to analyze risks experienced by electricians on telecommunication and electricity transmission masts when their work is performed in a cold weather. The analysis was based on work-safety analysis and action-error analysis and on using several methods of ergonomics analysis. Such problems as falling tools and ice were considered the greatest risk in electricians’ work. Moreover their physical workload is high, especially in regard to postural load and heart rates.

Keywords

Electrician, risk, telecommunications, ergonomics

INTRODUCTION

Electricians in telecommunication and electricity-transmission system companies perform various tasks and work in varied environments. For this study the tasks to be analyzed had to be specified and be chosen to represent those most typical. Weather conditions during which the work can be performed depend on company rules. Some companies do not specify weather conditions allowing work. An example of a part of a work-related safety program in one telecommunications company is as follows: during thunderstorms working on masts is forbidden, during continuous rain, work on masts should be avoided, and some limitations also apply for strong wind. Cold is defined according to wind-chill factor, for example, if wind speed is 0 to1 m/s, the lowest working temperature is –20°C, given that the relative humidity is not high.

Work tasks in this study were chosen to represent typical tasks. For telecommunications, work was analyzed during the mounting of new antennas and the maintenance of telecommunications masts 83 to 90 metres tall. Maintenance work included inspection of the structure of the masts and tightness adjustment of bolts and backstays. For electricity transmission, risks were determined during the assembly of 110 kV electricity transmission masts (Figure 1).

Figure 1. Electricians performing tasks related to assembly of electricity transmission masts (left) and the maintenance of a telecommunications mast (right).

MATERIALS AND METHODS

Risk analyses

The risks of the work were analyzed by work-safety analysis and action-error analysis [5,6,7]. Work safety was analyzed in general, with risks due to a cold climate also taken into consideration.

Risk analyses were made jointly by the researchers and the electricians. Before the risk-analysis meetings, the work was divided into subtasks; then the electricians, together with the researchers, decided what kinds of risks were related to such tasks. After this the cause of the risk as well as its possible consequences were determined. Later, current safety measures were evaluated, and proposals for improvements created.

The risks were rated in five categories according to probability (P) of an accident and seriousness of consequences (C) (Table 1). Overall risk (R) was obtained by the equation:

R = P x C (Equation 1)

Table 1. Rating of probabilities and consequences in risk analyses

Ergonomics

The physical work load was evaluated by means of EMG (electromyography), heart rate measurements, and work-posture analysis by OWAS (Ovaco work posture analysis system).

Heart rates were measured with a Polar Vantage NV^TM heart-rate monitor, and for the analysis a Polar Advantage Interface System^TM (Polar Electro Ltd. Finland) was used. The transmitter was attached to each subject’s thorax and the subject carried the receiver on his wrist.

The EMG was measured with the Mega Electronics ME3000P (Mega Electronics, Finland) as an averaged signal with a frequency rate of 1000 Hz. These values were chosen, so as to obtain the highest possible accuracy with the longest possible measuring time, which was defined by the capacity of this device’s memory card (1 megabyte).

Activities were measured in the arm flexor (m. flexor digitorum superficialis) and extensor (m. extensor digitorum) muscles, and activities of the trapezius muscles (pars descendens) was measured, as well, from the right and the left side. The recommendations of Zipp [8] served to define the placement of the electrodes. Disposable self-attaching electrodes were used (Medicotest M-OO-S, Denmark), with an interelectrode distance of 35 mm. The electrodes were fixed bipolarly. Before the electricians began working, the maximal voluntary contraction (MVC) of each measured muscle was recorded during isometric muscle contraction, and the results presented as %MVC. The results are average muscle activities during the entire work period.

Work postures for both the telecommunication work and work with the electricity transmission systems were analyzed by computer-aided OWAS analysis [3]. Analysis took place in the laboratory by use of video tapes. In telecommincation work analysis was based on 475 observations, one made every 10 seconds, and for electricity transmissions, 340 observations, one every 10 seconds. The work postures and combinations of these were classified into four categories; categories indicate priorities for corrective measures. Postures in category 1 require no corrective measures; category 2 indicates a need to change posture in the near future, category 3 as soon as possible, and category 4 immediately.

Subjects

For telecommunication, six electricians participated in the ergonomics evaluation. Their mean age was 34.2 years, mean height 187.7 cm, weight 78.5 kg, and BMI 24.6 kg/m². An additional six electricians participated in the ergonomics evaluation of electricity transmission, their mean age 41.5 years, height 174.7 cm, weight 78.8 kg, and BMI 25.8 kg/m².

Weather conditions

The measurements were done in early winter. For telecommunications mean temperature during the ergonomics measurements was 2.3°C and relative humidity 87%. Air velocity was on average 1.5 m/s at ground level and on the mast 1-7 m/s. The ground was frozen without snow.

For electricity transmission, the mean temperature during the measurements was 1.8°C and relative humidity 87% with air velocity on average 0.5 m/s. There was some snow, and as the work site was located in a field, there was also some mud on top of the frozen ground, creating very slippery conditions.

RESULTS

Telecommunication

Risk analysis 

Risk analyses were done in cooperation with the electricians. Risks were ranked according to the risk ratio obtained by estimating the probability and consequence of the risk (equation 1). The greatest risks (risk ratio over or equal to 10) were the following:

probability x consequence

• 1. Objects falling from the mast (tools, ice, etc.)                                                        4 x 5 = 20
• 2. Manual materialshandling, lifting of heavy equipment                                     5 x 4 = 20
• 3. Tools falling from the carrier bag during climbing                                                3 x 5 = 15
• 4. Use of ladders when checking the backstays possibly on very uneven ground                                                                                                    3 x 4 = 12
• 5. Working on rooftops, walls, and old masts where equipment is difficult to use in an optimal manner                                             2 x 5 = 10
• 6. Microwaves or other frequencies of radiation on the masts

where other companies’ antennas are located 5 x 2 = 10.

Results indicated that the greatest risks related to the electricians’ work on telecommunication were falling objects such as tools, bolts and ice. Things may fall both when workers are climbing a mast and taking tools with them in a carrier bag, and when they are working on the mast using the tools. In these cases the electricians working lower on the mast or on the ground are in risk of getting hurt by falling objects. Lifting of heavy equipment also poses one of the greatest risks during work on telecommunications masts.

Heart rates

The physical work load was measured when the electricians worked on the ground and when they worked on the masts. During work on the ground heart rates were on average 111 beats/min (range, 103-114 beats/min, n=4). Mean heart rates for electricians working on the masts was 125 beats/min (115-136, n=5) (Figure 2).

Figure 2. Electricians heart rates during working in masts

EMG

The muscle activities for electricians working at ground level (n=3) was in their arm flexor muscles 9%MVC and in their extensor muscles 4%MVC. The activity of trapezius muscle was on the right side 4%MVC, and on the left 5%MVC (n=4).

During work on the mast, the arm flexor muscle activities were on average 17%MVC, and extensor activities 6%MVC (n=5). The average activities of the right and left shoulder were 9%MVC (n=5).

OWAS

The OWAS analysis in the laboratory from a videotaped observations involved a combination of the postures of two workers fixing the same antenna to a mast. Most of the postures were categorized as acceptable (Figure 3). The worst postures were related to twisted back postures (39% of the working time) and elevated arm postures (19% of the time one arm was above the shoulder level, and 2% of the time both arms). It should also be noted that electricians stood on the metal structures of the masts, which is uncomfortable and can create high local pressure on the feet. The electricians also leaned backwards, relying on their protective equipment, this can create fatigue on the back, abdominal, and leg muscles.

Figure 3. Action categories according to work posture analysis of workers fixing new antennas to masts

Electricity transmission systems

Risk analysis

The risks involved in the building of new electricity transmission systems were analyzed by a risk ratio obtained by estimating the probability and consequence of the risk (equation 1). The risks were rated as follows (risk ratio above or equal to 10):

probability x consequence

• 1. Objects falling from the masts (tools, bolts, ice)                                                    4 x 5 = 20
• 2. Lifting of heavy equipment or structural elements                                               5 x 4 = 20
• 3. Fingers getting squeezed between the structures during the building of new masts                                                                                                 4 x 4 = 16
• 4. Sitting on cold metal structures                                                                                 4 x 4 = 16
• 5. Traffic in work sites located near roads                                                                  3 x 5 = 15
• 6. Accidents when pulling the cables from mast to mast if cable breaks or comes loose from the pulling vehicle and thus can be hurled nearby with great force                                                     3 x 5 =15
• 7. Communication problems and misunderstanding between electricians and drivers of mobile cranes in erections of masts build on the ground                                                                    3 x 5 = 15
• 8. Sudden and unpredictable explosions of insulation

chains made of glass if safety glasses are not used 3 x 5 = 15

If used, as required by the working instructions, the risk was: 3 x 2 = 6.

As for work on telecommunications masts, falling tools, bolts, and ice and the lifting of heavy equipment and structural elements posed the greatest risks when electricians were working on electricity transmission. The third greatest risk was fingers getting squeezed between the structures of the masts, and the fourth resulted when electricians had to sit on narrow cables and structural elements in order to reach the work target. During winter the cables are always very cold, and the consequences, such as long-term illnesses, may be serious.

Heart rates

The heart rates of electricians working in the building of electricity transmission systems were on average 95 beats/min (range 83-104 beats/min, n=5). The minimum heart rate was on average 73 (range 61-85), and the maximum 118 (range 111-126).

EMG

The electricians’ arm flexor muscle activities were on average 12%MVC and extensor activities 6%MVC. The average muscle activity in the right shoulder was 11%MVC, and average activity in the left was 14%MVC.

OWAS

The work posture analyses were made from videotapes taken at two work sites, the tasks being the assembly of electricity transmission masts and the fixing of electricity cables to new masts. The analysis was a combination of the postures of three electricians working together. Only 19% of work postures are acceptable, and the rest needed corrections (Figure 4). The worst postures, including bent postures and twisted postures or combinations of these were 51% of the back postures; 49% of the time the back was straight. The electricians’ arms were below shoulder level most of the time (97%). Both legs were bent for 13% of the time, and it was recommended to decrease the postural load on the legs in the near future. The workers stood for most of the work period (72%). When fixing cables to the masts only 19% of the work postures were classified to action category 1 thus not requiring any corrective measures.

Figure 4. Action categories according to work posture analysis of workers fixing cables

DISCUSSION

Their working in cold, slippery, and dark conditions means electricians’ work has special requirements. More effort is needed to overcome the resistance of snow, heavy equipment, and cold. Even though the emphasis of this study was on the evaluation of work done in cold environments, most of the risks are present also in warmer climates.

According to the risk analyses, similar kinds of risks were most significant both in mast work in telecommunications and in electricity transmission. First of all, prevention of tools and ice falling from the masts is important. The electricians offered the idea of applying a yo-yo -like apparatus to their personal fall-protection equipment or overalls, to which tools could be attached. Possibilities for improving the handles of tools to be more suitable for different environmental conditions should be noted, as well, because tools should in no way be slippery in any conditions; if possible, they should help the worker to apply force to the work target, not merely to hold on to the tool. Keeping the hands warm is also important, as sensations, and the ability to exert force both weaken in the cold.

The electricians themselves evaluated their physical work load as high in the risk analyses, as it was rated as the second greatest risk in the work. This opinion was supported by the ergonomics evaluation; especially work postures in electricity transmission were problematic, and the maximal heart rates during telecommunication mast work were extremely high. To lower the maximal heart rates the electricians’ should be made aware of the importance of climbing slowly and taking breaks frequently during climbing.

The muscular load on the arm and shoulder muscles was mostly at an acceptable level, except for the arm flexor muscles when working on telecommunication masts, if Jonsson’s [2] recommendations are followed. Åstrand and Rodahl [9] recommend that for long-lasting dynamic activity the muscle activity should be under 10%MVC. These values were exceeded for those working on electricity transmission systems.

In the mast assembly of antennas as well as in the maintenance of masts the workers use hand tools. Byström and Fransson-Hall [1] have recommended that muscle activity should be lower than 17%MVC when work requires constant squeezing of the fingers. Muscle activity equal to this level was measured in the telecommunication work, thus indicating that the work load should be reduced, moreover, Malchire et al [4] recommends that the arm flexor activities should be lower than 15%MVC in order to avoid wrist disorders. According to these findings, muscle activity should be lowered by such means as changing work arrangements or trying other tools for the tasks.

In the evaluation of OWAS results in this study it should be remembered that these electricians worked on top of the masts is an uncommon addition, the postures of the neck region were not analyzed but are of importance, especially for those electricians working on the ground and looking high up into the mast.

One of the physiological risks that arose indirectly in this study was the problems caused by coldness in the genital areas. As the electricians sit on cold metal structures they are at a risk of such problems as prostatitis, which can lead to chronic effects. This problem could be reduced by equipment design, for example by adding thermal insulation to the riding patch on the overalls.

In addition to these findings, the electricians’ themselves suggested that more emphasis should be given to development of rain-protection equipment, gloves, use of protective equipment in cold environments and as the most important issue to design the personal fall-protection equipment so as to be useful in all weather conditions and to be as light in weight as possible.

ACKNOWLEDGMENTS

This study was supported by the Finnish Work Environment Fund and The Academy of Finland. Cooperation with Sonera Ltd. and IVO Transmission Engineering is also highly appreciated. Special thanks are expressed to safety officer Aulis Hämäläinen and safety officer Paavo Kesti for their cooperation.

REFERENCES

• 1. Byström, S. and FranssonHall, C. (1994) Accessibility of intermittent handgrip contractions based on physiological response. Human Factors 36(1), 158171.
• 2. Jonsson, B. (1982) Measurement and evaluation of local muscular strain in the shoulder during constrained work. Journal of Human Ergology 11, 7388.
• 3. Karhu, O.; Kansi, P.; and Kuorinka, I. (1977) Corrective working postures in industry. Applied Ergonomics 8, 1977, 199201.
• 4. Malchaire, J.B.; Cock, N.A.; Piette, A.; Dutra Leao, R.; Lara, M. and Amaral, F. (1997) Relationship between work constraints and the development of musculosceletal disorders of the wrist: A prospective study. International Journal of Industrial Ergonomics 19, 471482.
• 5. Saarela, K.L.; Suokas, J.; Lahtela, J.; Maijala, P.; Reunanen, M.; Rouhiainen, V. and  Ukkola, K. (1982) Tapaturmavaarojen turvallisuusanalyysi. Valtion teknillinen tutkimuskeskus, tutkimuksia 173 ja Työterveyslaitos, tutkimuksia 195, Espoo (In Finnish).
• 6. Salo, H. (1984) Inhimillisistä virhetoiminnoista aiheutuvien vaaratilanteiden toimintovirheanalyysi. Valtion teknillinen tutkimuskeskus, tutkimuksia 339, Espoo (In Finnish).
• 7. Suokas, J.; Rouhiainen, V.; Reunanen, M.; and Norlund, K. (1982) Työn turvallisuusanalyysin laatiminen. Valtion teknillinen tutkimuskeskus, tutkimuksia 104, Espoo (In Finnish).
• 8. Zipp, P. (1982) Recommendations for the Standardization of Lead Positions in Surface Electromyography. European Journal of Applied Physiology and Occupational Physiology 50, 4154.
• 9. Åstrand, PE. and Rodahl, K. (1986) Textbook for Work Physiology: physiological Bases of Exercise. Third edition, MacGrawHill Book Company, Singapore.