System approach to risk assessment in safety assurance of machinery with regard to Directive 2006/42/EC.
Industrial machinery is associated with high number of occupational accidents causing high social costs connected with incapacity of employees to work. This situation is reflected in the ever-increasing strictness of the requirements on machinery safety. On 29 December 2009, the current machinery directive 98/37/EC will be replaced by the new Directive 2006/42/EC of the European Parliament and of the Council of 17 May 2006 on machinery, and amending Directive 95/16/EC (recast). This new directive toughens up the requirements on performance and documentation of the risk assessment process for all phases of the life cycle of machinery prior to issue of declaration of conformity.
The concept of safe design and construction of machinery has already been integrated into a number of scientific design methods (Krause et al.,1993; Bernard & Hasan, 2002; Marek, 2004; Eder & Hosnedl, 2007). However, these methods can be successfully applied only by highly qualified specialists (Marek, 2006). Especially for small and medium enterprises it is a problem to fulfil the strict legal requirements as they usually do not have enough specialized personnel and financial resources for consistent and effective performance of the risk assessment process in the newly-developed machinery or for application of scientific design. These producers often confine to subsequent risk analysis of the already finished machine that fulfils the requirements of the type C standard (if it exists). Risk analysis is then carried out in such a way as to provide a positive result for the specific machine. With this approach, of course, some significant hazards remain unidentified.
The current legislation as well as the new Directive specify the general procedure of the risk assessment process, not describing the method of realization of its individual stages. Therefore, the problem of risk assessment lies in the absence of methodology for hazard analysis and risk estimation that would provide objective results and support the fulfilment of all current legal requirements.
This paper presents a system approach to risk assessment, which provides a tool for trouble-free handling of risks associated with all life-phases of a machine; besides, it does not require high specialization of the realization team members.
2. SYSTEM APPROACH TO RISK ASSESSMENT
2.1 Strategic risk management
The policy of risk perception must be clarified on the level of top management. The team responsible for realization of the risk assessment process then determines the limits of risk levels for evaluation of their seriousness and categories of probability of risk occurrence and works out the tables of risk significance and the risk estimation graph.
2.2 Planning of risk analysis and assessment
It is necessary to gather information on the current state of the art of science and technology, solutions of safety risks in comparable products, information on previous occurrences of risks (i.e. accident occurrence) in similar equipment etc.
2.3 System analysis of machinery
In this phase, the team elaborates a comprehensive description of the machinery including a written section and a block diagram on suitable level of resolution (Fig. 1), showing all relevant interactions between its individual elements. This helps the team members to obtain a thorough idea of the construction and functions of the machinery.
2.4 Determination of limit values of machinery
Limit values express the possibilities of the machine or staff (limits of use, spatial and time limits). Special attention must be paid also to any reasonably foreseeable misuse of the machine.
2.5 Identification of hazards
Identification of hazards in machinery stems from the previous two steps and is performed in accordance with the relevant EN standards for the whole life cycle of the machine. Using the previously elaborated block diagram, the team determines all relevant hazards associated with the machine (Fig. 2) and analyzes the significant hazards (Fig. 3). For individual types of hazards they assess the basic requirements on health protection and safety according to 2006/42/EC, relevant type B safety standards and corresponding paragraphs of type C standard where applicable (Fig. 4).
[FIGURE 1 OMITTED]
[FIGURE 5 OMITTED]
2.6 Risk estimation
It is convenient to estimate the level of risk with the use of risk estimation graph (Fig. 5) for all identified significant hazards. If the hazards arise at more places within the machinery, estimation of risk must be done for all places of their occurrence in separate forms. The estimated size of risk and its individual elements are then entered into the Risk estimation form (Fig. 6).
2.7 Proposal of risk-reducing measures
This step is performed in accordance with the requirements of EN ISO 12100-1 (iteration method). First, the measures built in design are proposed, followed by safeguard measures reducing the risks; finally, information for users is provided. Each proposal of a measure must include a detailed written description of the risk reduction method and estimation of the residual risk (Fig. 6).
2.8 Risk evaluation
Estimated risks must be evaluated and classified as acceptable or unacceptable. If the level of risk is not acceptable, further risk-reducing measures must be proposed. The hazards, whose risk can not be totally eliminated must be listed in information on residual risks.
The presented system approach to risk assessment objectifies to a great extent the identification of hazards and estimation of risks and supports realization of risk analysis for all life-cycle phases of a machine. The block diagram of interactions between individual elements increases transparency of the whole risk assessment process and helps to estimate the risks correctly and thoroughly. The possibility of overlooking a hazard or underestimating a risk is minimized. Even the persons not involved in the machinery development can perform risk evaluation on highly professional level as they are guided by the described procedure. The documentation obtained throughout the risk assessment process enables the manufacturer to prove that the machinery matches the requirements of the Directive and that adequate effort to ensure safety of the machine has been made.
The approach has been successfully applied in industry on multifunctional machine tools. Further work will concentrate on methodology of elaboration of the instructions for use.
This research was supported by the Ministry of Education, Youth and Sports of the Czech Republic (project 1M0507 "Research of Production techniques and technologies").
Bernard, A. & Hasan R. (2002). Working situation model for safety integration during design phase, Annals of the CIRP, Vol. 51, No. 1, 119-122, ISSN 1726-0604
Eder, W. E. & Hosnedl, S. (2007). Design Engineering--A Manual for Enhanced Creativity, CRC Press--Taylor & Francis Group, ISBN 1420047655
Krause, F.-L.; Kimura, F.; Kjellberg, T. & Lu, S.C.-Y. (1993), Product Modelling, Annals of the CIRP, Vol. 42, No. 2: 695-706, ISSN 1726-0604
Marek, J., 2004, Management of risk at design of machining centres, Proceedings of Machine Tools, Automation and Robotics in Mechanical Engineering, Housa, J. (Ed.), pp. 91-98, ISBN 80-903421-2-4, Praha, 2004, CVUT Praha
Marek, J., 2006, How to go further in designing methodology of machine tools? Proceedings of AEDS 2006 Workshop, Hosnedl, S. (Ed.), pp. 81-88, ISBN 80-7043-490-2, Plzen, 2006, W. Bohemia University
Fig. 2. List of relevant hazards Name of Position of the Type of hazard component component in the according to system EN ISO 14121-1 belt drive for left motor area mechanical hazard, spindle actuation hazard generated by noise, rupture during operation etc. Fig. 3. Analysis of significant hazards ANALYSIS OF SIGNIFICANT HAZARDS Machine: lathe During transport, assembly and installation Model: XY No. Phase of Type of hazard Description of life cycle description ID hazardous event: 1.1 Unloading inconvenient 8.1, During lilting there is a of lathe, position, 18, risk of fall or overthrow lifting overstrain, 23, of the lathe if the of lathe. fall, 27.1, gravity centre is not overthrow, 27.2, known or is not respected. crushing 27.3, In case of unfavourable AM. 27.6 construction the workers may also suffer overstrain or inconvenient position. etc. Fig. 4. List of significant hazards LIST OF SIGNIFICANT HAZARDS Machine: Date: Responsible: Model: No. of HAZARD repeated hazard EN 292 Part 2-A1: Part 1: Part 2: 1995 1991 1991 Hazards, hazardous situations and hazardous events 1 Mechanical hazards caused by: 1.1 Crushing hazard 1.3 4.2.1 1.2 Shearing hazard 1.3 4.2.1 etc. No. of HAZARD EN ISO EN ISO HAZARDOUS hazard 12100-1 12100-2 SITUATIONS Hazards, hazardous situations and hazardous events 1 Mechanical hazards caused by: 1.1 Crushing hazard 4.2.1 1.2 Shearing hazard 4.2.1 4.2.1 4.2.2 5.2.1 184.108.40.206 etc. No. of HAZARD Relevant Corres- hazard articles ponding of B type 2006/42/EC standards Hazards, hazardous situations and hazardous events 1 Mechanical hazards caused by: 1.1 Crushing hazard 1.3.7 1.3.8 1.3.9 1.2 Shearing hazard 1.3.7 1.3.8 1.3.9 etc. No. of HAZARD Relevant Total hazard articles number of C type of standard hazards Hazards, hazardous situations and hazardous events 1 Mechanical hazards caused by: 1.1 Crushing hazard 1.2 Shearing hazard etc. Fig. 6. Risk estimation form Brno UT RISK ESTIMATION FORM machine; lathe FME responsible: (name) date: 10.12.2008 No. of hazard ID HAZARD IDENTIFICATION 1. Mechanical hazards 1.1 3 CRUSHING Phase of LC: USE Danger zone: OPERATING AREA Expend persons: OPERATOR Operational state: MACHINING, ADJUSTMENT Description of CRUSHING DURING WORKPIECE CLAMPING WITH A CHUCK hazardous event: DANGER OF CRUSHING OF FINGERS OR PARTS OF HANDS Initial risk seriousness of S2--serious injury RISK health damage 12 Frequency and A2--frequent to length of threat: continuous Possibility of E3--hardly possible avoiding the hazard: Probability of W3--high hazardous event: STEP 1: MEASURES BUILT IN DESIGN THE DESIGN OF THE MACHINE RESPECTS THE ERGONOMICAL PRINCIPLES REDUCING THE POSSIBILITY OF INSERTING FINGERS OR PARTS OF HANDS BETWEEN THE MOVING PARTS. Reduced risk Seriousness of S2--serious injury Risk after measure health damage: 10 Frequency and A2--frequent to length of threat: continuous Possibility of E2--possible at avoiding the certain conditions hazard: Probability of W2--medium hazardous event: STEP 2; SAFEGUARDS AND ADDITIONAL PROTECTIVE MEASURES DESCRIPTION IT IS POSSIBLE TO ACTIVATE ONLY ONE DANGEROUS OF MEASURE: MOVEMENT AT A TIME IN A CLEARLY ARRANGED SPACE. WORKPIECE CLAMPING WITH A SAFE SPEED of 2M/MIN. USE OF ENABLING SWITCH. DANGEROUS MOVEMENTS OF THE CLAMPING DEVICE CAN BE ACTIVATED ONLY BY A DELIBERATE ACTION OF THE OPERATOR, I.E. PRESSING DOWN THE CONTROL PEDAL REQUIRING PERMANENT ACTUATION. Reduced Seriousness of S1--slight injury RISK risk after health damage: 4 measure Frequency and A2--frequent to length of threat: continuous Possibility of E2--possible at avoiding the certain conditions hazard: Probability of W2--medium hazardous event: STEP 3: INFORMATION FOR USE DESCRIPTION WARNING IN THE INSTRUCTION MANUAL: OF MEASURE: "IT IS NOT POSSIBLE TO TOTALLY ELIMINATE THE HAZARDS ASSOCIATED WITH WORKPIECE CLAMPING BY TECHNICAL MEANS; THEREFORE, BEHAVE IN SUCH A WAY SO AS TO AVOID INJURY OF FINGERS OR PARTS OF HANDS!" Residual Seriousness of S1--slight injury RISK risk health damage: Frequency and A2--frequent to 3 length of threat: continuous possibility of E2--possible at avoiding the certain conditions hazard: Probability of W1--little hazardous event: VALIDATION: MEASURES ARE DATE: SUFFICIENT: (name)
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|Author:||Blecha, Petr; Blecha, Radim; Bradac, Frantisek|
|Publication:||Annals of DAAAM & Proceedings|
|Date:||Jan 1, 2009|
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