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Risk assessments needed for automation |
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Automation doesn’t mean automatically safe
Properly installed machine automation systems can boost productivity and worker safety. But researchers say that manufacturers still need to do proper risk assessments and evaluations to ensure that workers are kept safe.
Present in a wide range of industries such as food processing, pulp and paper, petroleum, textile and automobile, automation offers greater productivity, reduced production costs, improved quality of product, greater manufacturing flexibility as well as workers being alleviated from repetitive tasks, tedious and hazardous labour.
Under normal operating conditions, workers usually do not access danger
zones and are kept away from many hazards since the automated machines,
controlled by programmable logic controllers (PLCs), are designed to
operate without any human intervention.
Automated systems should inherently improve the safety of workers by
eliminating the need to reach into dangerous zones. In spite of
technological advances in the field of automation, these systems cause
many serious injuries because workers still need to intervene in
automated systems for various reasons.
Tasks such as maintenance, setting, commissioning, training, loading
and unloading of materials, changing or adjustment of tools,
adjustments during production, removal of jammed materials and repairs
or interventions following malfunctions of automated systems can put
workers at risk. All of these interventions remain potentially
dangerous.
Factors in automation related accidents
Based on studies and accident reports, it can be said that some of the
contributing factors in automation related accidents are as follows:
• Unexpected start up or machine movement. This can arise from an
inappropriate design of the control system of the machine, the presence
of a worker in the danger zone where a sensor used for production
purposes gets accidentally activated by the worker and resulting in a
hazard, human error on the control panel, software errors in the PLC or
restoration of the energy supply after an interruption;
• Insufficient or incorrect safeguarding of the automated system;
• Insufficient training of workers who are often asked to deal with
many complex and potentially hazardous situations involved with the
automated systems;
• Workers underestimating or unaware of the risks;
• Insufficient risk assessment of the automated system at its design stage;
• Workers tampering with existing safety devices for reasons such as
reducing downtime caused by frequent disturbances to normal production;
and
• Evolution of the automated systems due to modifications in the
software of the PLC, to the addition or removal of sensors and to
changes in safeguarding methods of the system, without the worker being
kept informed.
The need for risk assessment
It is important to perform a risk assessment of the automated systems
at the design stage in order to identify all the hazards that workers
can potentially face, as described in ISO 14121 for example.
An essential part of the overall process to ensure the safety of
automated systems, a risk assessment is divided in two phases (i) risk
analysis and (ii) risk evaluation. The risk analysis consists in
determining the limits of the machine (considering all phases of the
machine life, i.e. design, construction, transport, installation,
commissioning, operation, starting up, shutting down, setting or
process changeover, cleaning and adjustment), identifying the hazards
(workers can get injured by different hazards including mechanical,
thermal, electrical and chemical) and estimating the risk (taking into
account the frequency and duration of exposure to the hazard, the
probability of occurrence of a hazardous event and the possibility of
avoiding the harm).
The risk evaluation enables decisions on the machine’s safety to made
i.e. is the risk level tolerable or does risk reduction methods need to
be used.
How to perform risk assessment?
Guidance to perform risks assessments can be obtained from ANSI
B11.TR3-2000 and ISO 14121. Workers should participate in the risk
assessment and in the evaluation of the safeguards, once these are in
place. The experience of operators, mechanics, set-up personnel,
electricians and other workers who intervene on the automated machines
is crucial for good results.
A small team consisting of one or more operators, maintenance
personnel, safety engineer, technician and representative from the
management of the plant should be set up for the risk assessment part.
The team approach is favoured since it is improbable that a single
person will possess all the necessary knowledge about the various tasks
performed on the automated systems and also have the necessary
technical background to conduct a proper risk assessment.
Using a video camera and photographs to study interventions requiring
access to dangerous zones of automated systems is very useful because
the tasks can then be analyzed carefully, in a less stressful
environment.
This article was provided by the Institut de recherche Robert-Sauvé en
santé et en sécurité du travail (IRSST). This article is excerpted from
the article of Chinniah Yuvin., Bourbonnière Réal. Automation Safety:
Assessing the Risks and Understanding Safeguards, Journal of the
American Society of Safety Engineers- Professional Safety. For more
information visit www.irsst.qc.ca
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Product Features |
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Omron Scientific Technologies Inc.’s MiniSafe MS4800 series safety light curtains are designed to satisfy simple or complex machine safety applications. The MS4800 is available in advanced, standard and basic versions. A cascaded configuration reduces cabinet space requirements and provides an effective guarding solution in multi-sided and dual-axis guarding applications. Optical scan codes eliminate cross talk, which enables OEMs to consistently build identical machines without staggering the transmitter and receiver position. Individual beam indicators simplify alignment, external device monitoring ensures control reliability and machine test signal allows the machine control system to confirm proper operation of the light curtain safety outputs.
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