With the increasing use of automation, requirements for protecting machinery and operators have evolved and become more complex. The improper use of machines can lead to safety hazards when the correct operating protocols are not followed. Thankfully, advancements in technology have allowed for integration of protection devices into the work process, helping to reduce safety risks and improving productivity.
In this blog we’ll define machine safety and take a look at the 5-Step Process to Safety, as well as look at ways of assessing risk, which was originally presented by Fortress Interlocks at Steiner’s 2016 Automation Technology Summer Symposium.
Defining Safety and Assessing Risk
Safety is the freedom from unacceptable risk as defined in IEC 62061 with respect to machinery operation. This provides a definition of safety in terms of risk, and makes clear the importance of assessing risk to achieve safety. [i]
Since the key term in the definition is “unacceptable risk”, a value on a range that determines the threshold between acceptable and unacceptable needs to be established. Various standards can provide guidance on how to determine when acceptable risk has been achieved. Keep in mind that acceptable risk may differ between organizations, so this value is not purely defined in any standard or methodology. The main takeaway is a threshold should be identified prior to starting a risk assessment.
We can also define risk in terms of the following equation.
The severity of possible damage + the probability that it will occur = risk in terms of the respective hazard.
To measure the probability, we would need to look at a few factors:
- frequency and duration of exposure to the hazard
- available options for avoiding the hazard
- the probability of an event that can cause the damage to occur
Breaking Down the 5-Step Process to Safety
Step 1: Risk or Hazard Assessment – This initial step requires the limits of machinery to be determined. Next, the hazards are to be identified, followed by estimating and evaluating the risk. Once all these items have been established, if the risk has been adequately reduced, the first step is considered complete.
Step 2: Safety System Functional Requirements – After assessing the risks, the next step identifies how the machine is supposed to operate in each mode of operation for each person that uses the machine. It identifies special modes such as safe-speed, zone control, etc. In other words, the second step is to confirm that the machines are doing what they are supposed to be doing.
Step 3: Safety System Design and Verification – Evaluate the risks and select control measures for the machine. For instance, if the overall system stopping performance is greater than the access time, a prevention device such as an interlocking guard with guard locking can be added. When applied, opening of the guard shall be prevented unless all hazardous functions covered by the guard have stopped. The goal is to protect both the process and to protect people.
Step 4: Safety System Installation and Validation – Document all stages, design a validation plan, test the installation safety functions and record the results and issue documentation.
Step 5: Maintain and Improve Safety System – A study by the HSE found that more than 50% of all accidents occur during maintenance and machine modification, so the safety cycle process must be used during machine upgrades.
The 5-Step Process to Safety provides a framework for identifying potential machine operating risks and mitigating the occurrence of safety issues through preventative measures or other actions. The process is continuous as risk findings must be regularly reviewed. Once an action is taken to remedy an identified risk, that action must be monitored to confirm the potential risk remains at an acceptable level and no other issues have crept into the process that may have raised the risk level.
For more information on automation and machine safety and to speak with one of our application engineers please call 1-800-STEINER (783-4637).
[i] “Why Do We Need Safety?” Henry Toal.: Fortress Interlocks, 2016. PPT.