Machine Safety: Do safety and security converge or intersect?

Machine safety and security each involve potential hazards that can result in personal injury, damage to property, and / or interruptions and unplanned downtime in manufacturing. While the outcome can be the same, machine safety and security differ in causal behaviors based on intent.


If the two worlds of machine safety and security are synonymous then why even discuss whether their applications either converge or intersect? Does it really matter? It seems to me that there is some confusion in industry in understanding the two worlds of machine safety and security. Both involve potential hazards that can result in personal injury, damage to property, and / or interruptions and unplanned downtime in manufacturing. Even though the outcomes are common, I believe machine safety and security differ in causal behaviors based on intent.

For example, machine safety hazards can be caused by things like stored energy, gravity, unexpected motion, electrical shock, intermittent connections, component failure to dangerous, lack of redundancy, flying objects, lack of guarding, unprotected pinch points, and many others. Most often in machine safety the goal is to provide protection from injury or loss caused by circumstance, accident or negligence. And there are lots of variations and extensions of these very broad terms. The primary point of differentiation is that these hazards generally lack the intention to do harm.

That differs from the world of security. Security related hazards can be related to the examples above but might also include hacking into networks, breaking into locked control cabinets, releasing a virus into a control system, or intentionally altering the machine control. Installing a jumper wire over a machine control relay (thereby disabling the function of that relay) is an example of a security violation that also is a machine safety hazard. It is a security issue because the hazard is caused by a deliberate human intention to disable the control element. Therefore, the security differentiation could be described as the protection from injury or loss caused by a deliberate human action.

Based on this discussion, wouldn't it be proper to summarize the differentiation between machine safety hazards and security hazards as people related problems and intention? But, do these hazards converge or intersect?

They often do overlap, I believe, as the example shows! One reason is because the goal of a risk assessment is to identify all hazards for a given machine. Of course, a guard is required to protect an operator from flying objects on a lathe. Clearly this is a machine guarding issue. Also, control cabinet locks, and key control procedures also are required to "guard" against a deliberate human action to jumper a control element regardless of a viable "reason." Clearly this is a security related issue. However, they often overlap because either can be protected by the safety culture within a company and thorough "best-in-class" machine guarding solutions.

Has this presented you with any new perspectives? Do you have some specific topic or interest that we could cover in future blog posts? Add your comments or thoughts to the discussion by submitting your ideas, experiences, and challenges in the comments section below.

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C.G. , FL, United States, 03/29/14 09:54 AM:

You're right that the "worlds" of security and safety overlap -- in many ways. I disagree, however, that, for example, jumping a lockout switch to streamline a maintenance procedure is a security issue. Generally, people consider security breaches to involve malicious intent. That doesn't obtain in the example. I'd just call it unsafe behavior.

Deliberately leaving the jumper on as a booby trap to zap an unwary technician with 200,000 volts, however, is a security breach. It's actionable and people go to jail for it.

While intent is the main differentiator between safety and security problems, it is very difficult to fathom after the fact. That's what keeps criminal courts busy.

The controls engineer, however, doesn't really care. He or she needs to prevent both.

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