MRO Magazine

Plant Safety: What defines a reliable safety system for machine guarding?


April 14, 2001
By PEM Magazine

The issue of interpreting the CSA standard for machine guarding is being discussed once again in safety circles, thanks to Ontario’s new requirements for Pre-Start Health and Safety Reviews.

These changes require industrial machine owners and lessees to obtain a report from a professional engineer before beginning work. That report must have the engineer’s seal and signature, as well as state that the engineer is satisfied the machine complies with all applicable safety regulations. Failure to comply with these requirements can mean stiff penalties for officers, directors, owners, lessees and engineers — anywhere from $25,000 to $500,000 or a year in jail.

Pre-Start reviews make it very important to have a well-defined machine guarding standard. But the existing standard, CSA Z432, only states that machine safeguards must be "reliable." What does "reliable" mean? People may interpret the word in a number of ways.

The European standard EN-954 both explains and classifies a reliable safety system. The standard demonstrates that different safety system components require different levels of reliability. For example, an area where there is a high risk to human life will have a greater standard of reliability than a lower-risk area.


This European method, in my opinion, is a good engineering practice and one that is needed in the Canadian definition of reliable systems. In absence of a clear definition, the concept of reliable safety components can be difficult to grasp — whether you are reviewing the safety of a new machine or retrofitting an existing one.

The CSA standard is the only one currently available, and we must work with what we have. Since there is no clear definition of reliable, the best practice for Ontario machine owners is to hire an engineer who has a clear understanding of the concept of reliabliity and is registered in Ontario. That engineer can then work with either the owners or directly with the vendor to advise on what safety components need to be part of the equipment to ensure it will pass the Pre-Start review.

For more information about Pre-Start reviews, contact the Ontario Ministry of Labour at 1-800-268-8013, or you can visit their Web site at

Simon Fridlyand, P.Eng., is the president of S.A.F.E. Engineering, a company specializing in Pre-Start Health and Safety Reviews and audits for fire code compliance. You can reach him at (416) 447-9757.