Machine & Operator Safety
Designed for safety: Risk assessment should be considered during the earliest stages of a machine’s life
September 20, 2010 by Rick Sauer
In Canada, and North America as a whole, the standards surrounding machine safety – particularly from a mechanical focus – are rather muddy.
While the Occupational Health and Safety Act (OSHA) ensures the protection of workers from injury while on the job, and the Canadian Standards Association (CSA) has established the Safeguarding of Machinery standard Z432-04, which assigns responsibilities for the proper safeguarding of machinery, there are currently no standards that address mechanical machine safety, such as forced control (including contours and cams), and pneumatics and hydraulics in an automated system.
While Europe has its own set of standards, North American manufacturers are left only with a standard developed by the International Electrotechnical Commission (IEC), the IEC61496, which is an international standard for all electrical, electronic and related technologies that is accepted as the default standard by the Underwriters Laboratories.
But just because there aren’t defined Canadian standards doesn’t mean owners of manufacturing equipment aren’t responsible for malfunctioning or harmful machines. In the past decade, there has been increased regulation and enforcement by the Ministry of Labour on machine guarding and safety, particularly regarding machinery and operator interfaces. In many cases, it’s the owners of these machines – not the designers or manufacturers – that face hefty fines and potential jail time if an employee becomes injured on the job as a result of them.
Over the past few years, there has been a steady increase in the penalties available under provincial legislation relating to health and safety, and this trend seems to be on the rise. This has led to a push to ensure machines are safe before they’re built – namely in the design stage. This trend appears to be driven by customers who will evidently be held responsible for any risks that could become a safety concern during a pre-start safety inspection or through the lifespan of a piece of automated equipment.
This is a good place to start. To prevent potential penalties down the road, it’s wise for buyers of automation machinery to ensure that, during the design of new machinery and the upgrade of existing machinery, measures are implemented to protect the worker and machine from moving devices through security and interlocking principles.
The problem is, this stage of the process is identified through a thorough risk assessment, which is nothing more than a calculated forecast of possible recognized risks and severity of injury. The individual phases of a machine’s life present different hazards, which would not be evident through a normal operating risk assessment.
A thorough assessment should also consider the following factors:
• Initial position standstill: What are the potential hazards when machinery is pressurized for the first time from a pre-exhausted state?
• Set up and service operation: What are the associated risks when machinery needs to be set up and serviced? What are the potential hazards that may exist when compressed air and/or power have been shut off?
• Emergency: The emergency condition can present different hazards, such as losing control of motors and drives that continue to move under momentous forces when an emergency event has been triggered. How will your machinery respond to emergencies? Safe stopping, safe exhausting and protection against unexpected startup need to be considered when an emergency condition has been triggered.
In all of these phases, there is the need for risk assessment and the identification of hazards. This results in design measures that reduce risk, and technical protective measures that will ensure that the residual risk is at an acceptably low level.
The life expectancy of machinery also needs to be addressed, and mean time to failure calculations should be carried out to determine that the components that are used in critical applications will perform as required during the life cycle of machinery.
Rick Sauer is a product manager with Festo Inc. He can be reached at Rick.Sauer@ca.festo.com.