Analysis and prevention of serious and fatal accidents related to moving parts of machinery
Introduction
A machine is defined as an assembly fitted with or intended to be fitted with a drive system consisting of linked parts or components at least one of which moves, and which are joined together for a specific application (ISO 12100). Machines contain hazards of different nature and exposure to those hazards can result in injuries or deaths. Different types of machinery hazards are listed in (ISO 12100, 2010, CSA Z 432, 2004, ANSI B11-TR3, 2000, Bluff, 2014). These are structural (e.g. sharp edges, projections), mechanical (e.g. entanglement crushing, cutting), physical (e.g. electricity, pressurized content, noise and vibration, hot or cold temperatures), ergonomic (awkward working positions, manual handling, repetitive movements), slip/trip/fall (e.g. poor walkways, railings), chemical (e.g. gases, fumes, liquids), end use conditions (e.g. location, impact on workplace layout) and biological (e.g. bacteria, mold) (Bluff, 2014). Since workers intervene on machinery in all the phases of its life cycle, i.e. installation, operation, maintenance, troubleshooting, repairs, adjustments, set up, handling production disturbances, cleaning and dismantling, they are exposed to hazards. Actually, numerous accidents are related to machinery.
Machine related accidents in the US caused 8505 fatalities between 1980 and 1989 with an average annual fatality rate of 0.8 per 100 000 workers (Pratt et al., 1996). The highest industry-specific rate was noted in agriculture, forestry and fishing. Etherton et al. (2001), while citing US Bureau of Labor Statistics data, report that 464 occupational fatalities occurred in the US between 1966 and 1998 resulting from being caught in running machinery. The Bureau of Labor Statistics in the US (BLS, 2014) revealed that a total of 717 fatal work injuries occurred as a result of contact with objects and equipment in 2013. This number includes 503 workers who were fatally injured after being struck by objects or equipment. Out of the 503 workers, 245 workers were struck by falling objects and equipment other than powered vehicle and 29 workers were struck by discharged or flying object. 131 workers were caught in or compressed by equipment and objects, including 105 workers being caught in running equipment or machinery. 78 workers were struck, caught or crushed in collapsing structure, equipment or material. The HSE reports that 50% of accident related to moving parts of machines in UK occurred in printing presses and conveyors (HSE, 2006). Bulzacchelli et al. (2008) report that in 2005 just over 1000 (i.e. 18%) of workers fatally injured in the US were by contact with objects and equipment. Bellamy et al. (2007) report that annually about 400 accidents, i.e. 21% of total accidents per year in the Netherlands, are caused by contact with moving parts of machinery. Gardner et al. (1999) report that in Australia, mechanical equipment injury accounts for 28% of all compensation injuries. Gerberich et al. (1998) report that agricultural machinery has been identified as a principle source of non-fatal injuries in the rural sector.
In Canada, there were approximately 3 occupational fatalities each day of the year in 2008 (Gilks and Logan, 2010). Also in 2008, approximately 1 worker out of every 13 805 workers covered by provincial or territorial compensation systems died from an occupational injury. On average, 1 out of every 46 Canadian worker covered by provincial or territorial compensation systems was injured severely enough to miss at least one day of work in 2008. The working compensation boards paid $7.67 billion in benefit payments or an average of approximately $22 845 per each new compensated time-loss injury or fatality. In addition, $2.03 billion in health care and vocational rehabilitation payments were made in 2008. Including these costs, the total direct annual costs of occupational injuries and fatalities to the Canadian economy were approximately $9.7 billion in 2008. If the indirect costs are included, the total costs of occupational injuries to the Canadian economy can be estimated to be more than $19 billion annually. In Canada on average 177 hospitalizations per 100 000 people are reported annually due to agricultural machinery injuries (Brison et al., 2003). A total of 159 machinery related injuries on 2390 farms in the province of Saskatchewan in Canada were reported in 2006 and these agricultural injuries were due to machinery such as tractors (23%), transportation equipment (16%), harvesting equipment (16%), augers (11%) and combines (11%) (Narasimhan et al., 2010). In Canada, national statistics on the number of machinery-related accidents, apart from agricultural machinery injuries, are not available.
In the province of Quebec in Canada, between 2000 and 2004, there were 770 agricultural machinery related injuries, which represented 12% of the 6604 occupational injuries in the agriculture sector (CSST, 2006). In Quebec, between 1989 and 2003, 12% of fatal injuries on farms were caused by moving parts of machinery. In 2005, the OHS regulator for Quebec, the CSST, revealed that around 13 500 machinery related accidents and 20 deaths occurred annually in the province (CSST, 2006). Moreover, the CSST has introduced in 2005 a safety of machinery action plan to educate machine suppliers, employers, workers and other associations about the risks associated with machinery. The action plan focused on access to moving parts of machinery. In 2010 the CSST revealed that 3552 workers were injured as a result of an accident linked to a machine. Between 2006 and 2010, on average 12 workers were killed each year as a result of work accidents related to machinery. Due to the action plan of the CSST which began in 2005, the number of annual machinery accidents has dropped significantly. In Quebec, section 21 of Occupational Health and Safety (OHS) regulation, the RSST, addresses safety of machinery (regulations 171–226). In essence, the RSST states that machines must be designed and built so as to make their hazardous zones inaccessible. Hazardous zones relate to any area in or around a machine that presents a risk to the health and safety of the worker. The law on OHS states that employers have legal responsibilities when purchasing machinery, installing machinery and supervising employees operating and intervening on machines. Employers need to identify and manage risks associated with machinery. Machine builders and suppliers need to ensure that their machines are safe. Workers using and maintaining machines need to abide to safety procedures and take all necessary measures to prevent injuries to themselves and others. In Quebec, if the health or the safety of an employee is directly and seriously compromised by the use of a hazardous machine, the employer may be liable to a fine ranging from 15 000 $ to 300 000 $ CAD. The employers can also face criminal charges for negligence.
The literature in the field of safety of machinery is rich and consists of machine safety standards, regulations, peer reviewed and non-peer-reviewed journal and conference papers, books, guides, leaflets and checklists. The CSST has compiled a list of 415 safety of machinery standards from ISO, IEC, CSA, ANSI and EN. Increased pressure to comply to existing regulatory framework, more frequent OHS inspections in companies by CSST inspectors, availability of information from the literature as well as training of engineers, CSST inspectors and OHS personnel in the field of safety of machinery combined with research on safety of machinery have all contributed to the reduction in machinery related injuries and fatalities in Quebec. It is important to understand the causes of accidents in order to identify potential solutions to further reduce the number of injuries and fatalities. The causes of machinery-related serious and fatal accidents in Quebec have not been studied.
Backstrom and Doos (2000) report problems related to safety devices from 76 accidents in automated production obtained from 21 work sites in Swedish manufacturing industry over a two year period (1988–1990). The study reveals that a production installation should not be regarded as safe simply because it possesses safeguards. The latter include barriers, interlocks, hold to run control, two hand controls and presence sensing device. The study identifies four levels of problems namely: (i) no or low level of safeguarding, (ii) non-use of safeguards (remove, circumvent, defeat, decouple), (iii) failure of safeguards to stop all machine movements in the danger zone (residual energy, inertia) and (iv) failure of safeguards to provide protection under all prevailing circumstances (e.g. work requiring machine to be energized). It is shown that all types of safeguards have their problems. Safeguards do not always function adequately in conjunction with the handling of production disturbances.
In another study, 592 lockout/tagout related incidents in the US resulting in a total of 624 fatalities were reviewed (Bulzacchelli et al., 2008). In the majority of cases (70%), lockout procedures were not attempted at all. There were very few incidents in which a lockout attempt was made and a fatality occurred due to human error (5.2%) or mechanical failure (1.2%). This small proportion suggests that lockout/tagout procedures, when properly used, do indeed prevent fatalities. Several strategies to increase the use of lockout/tagout are proposed. The author recommends further research on understanding barriers to following lockout/tagout procedures and finding ways to increase usage of these procedures.
Shaw (2010) reviewed 100 incident investigation reports in the UK spanning the period 2002–2007 and identified a number of contributory causes. The review revealed that inadequacies in design, failures to isolate (lockout), defeating protection system, inadequate fault reporting or maintenance were major contributors.
Blaise and Welitz (2010) retrieved from the French EPICEA database, 88 accidents between 1998 and 2007 involving machinery during non-production phases (i.e. maintenance). The study reports that operators also perform maintenance actions. The distribution of non-production phase machinery accident according to the risk factors were classified as: (i) organisational aspects (69%) corresponding mainly to compliance with procedures, in particular isolation/lockout, (ii) technical aspects (51%), i.e. maintainability, lack of protection or inadequate protection and (iii) human aspects (15%), i.e. operator has insufficient knowledge associated with risk assessment in particular. The phase during which the accident occurred was analyzed. The distribution of non-production accidents according to phase were classified as: (i) preventive maintenance (32%), i.e. cleaning, setting, testing, inspection activities, (ii) corrective maintenance (30%), i.e. combination of repairs and troubleshooting activities, (iii) diagnosis (15%), (iv) re-commissioning (14%), i.e. adjustments and tests after maintenance and before returning to equipment operation phase, (v) malfunction (8%), i.e. activities aimed at rectifying unforeseen production incidents mainly due to jamming of raw materials.
Charpentier (2005) retrieved 457 automation accidents covering a period of 20 years from the French EPICEA database. The reports were analyzed to provide information on the type of industry, characteristics of injuries, factors leading to the accidents, protective devices existing on the equipment and prevention or corrective measures adopted. The nature of injuries suffered by victims of automation accidents were amputation (27%), fractures (28%), various wounds and injuries (30%) and bruises (10%). The activities involved in the accidents were: usage or operation (36%), handling (8%), assembly (9%), adjusting (7%), supervising (12%), repairs (9%), cleaning (10%) and informing, testing and inspecting (5%). Safeguards being absent accounted for 32% of the accidents. Guards (i.e. fixed, moveable with or without locking, moveable with timed opening, automatic) and safety devices (i.e. light curtains, pressure mats, and other presence sensing devices) were present in 45% of the accidents. Emergency stops, lockout procedures and other preventive measures were present in 20% of accident cases. The reasons behind accidents occurring in spite the use of guards were: inadequate guards or improperly dimensioned, installed and utilized (35%), bypassed guards (30%) and malfunctioning of guards (15%). In 82% of cases, corrective measures following the accidents were to use safeguards.
Villard (2003) described accidents caused by the failure of safety components. In that paper, 4 accident reports from Switzerland were presented namely: a fatal accident during the cleaning of a horizontal mixer; amputation of a finger during operation of a metal guillotine; a fatal accident during repairs on a palletiser and injury during repairs of machine used in tobacco industry. Those accidents occurred due to failures of guard operated interlocking switches.
Dzwiarek (2004) analyzed 144 machine related accidents which took place in the period 1996–2002 in Poland. He found that 54 of those accidents were caused by improper functioning of machine control systems. The different causes of accidents caused by improper functioning of the control system were: no safety function, i.e. no guard position control and presence sensing in hazardous zone (58%); incorrect choice of category of safety control system, i.e. random failures of a safety-related element of the control system due to either an improper choice of the category of control system or inadequate fulfilling or the category requirements (26%); error in controller software (6%); devices not resistant enough to environmental impacts (6%) and incorrect definition of safety function (4%).
Gardner et al. (1999) identified, as primary causes of mechanical equipment injuries in small manufacturing businesses in Australia, the incorrect work practices and the failure of operators to follow safe work procedures. Additional causes revealed were design problems and conditions of machinery as well as inexistent or inadequate guarding. In that study, interviews were carried out with 35 managers from 35 businesses in Sydney Australia, 145 employees returned completed questionnaires and 76 accidents were analyzed. Machinery design issues included existence of nip points and closing dies (93%), exposed rotating parts (73%) and poor control panel design (66%). Machines needed additional guards (49%). Guards were frequently removed since it was difficult to do the job with guards in place. Finding or making new guards for old unguarded machines was difficult.
Lind (2008) analyzed 33 accident reports of fatal and severe non-fatal accidents in industrial maintenance from Finland. The author found organizational factors, local workplace factors and unsafe acts are main causes of accidents and recommends (i) additional information and training, (ii) planning interventions, (iii) employer’s supervision, (iv) safe working methods, (v) hazard identification, (vi) checking condition of the machinery including its safety, (vii) prevention of unintentional start-ups, (viii) good condition of working surfaces, (ix) the right choice of proper tools and (x) following orders and instructions.
Section snippets
Research objective and method
The objective of the paper is to identify the main causes leading to serious injuries and fatal accidents involving machinery as well as proposing solutions. In this paper, 106 accident reports of fatal and serious injuries involving machinery in the manufacturing and processing sector covering the period 1990–2011 in Quebec have been analyzed.
Accidents reports for serious or fatal injuries to workers were available from the CSST website and accessible to the public. On the CSST website, the
Results and discussions
The main findings from the analysis of 106 accident reports are summarized and discussed in this section.
Conclusions
The objective of the paper was to understand the various reasons causing serious and fatal accidents related to moving parts of machinery and to discuss prevention strategies based on the findings of the study as well as on the existing literature. Therefore, 106 accidents reports (31 serious and 75 fatal) related to moving parts of machinery from the province of Quebec in Canada were analyzed. Conveyors and different types of saws caused 32 accidents. It was found that 12.3% of accidents were
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