Machine & Operator Safety
Functional safety: Are we getting good ROI?
By Doug Nix
By Doug Nix
Machine builders put a lot of time, effort and component costs into reliable safety systems for machinery. The requirements for these systems are increasingly complex, with some practitioners estimating as much as 90 hours of design and documentation time required to meet the standards requirements. This begs the question, “Is industry getting good return on investment for the cost associated with functional safety?”
Why do we need standards?
Machine safety is about protecting workers from injury. Many studies have shown the extremely high cost of workplace injuries. Machine safety experts began to realize in the 1970s that effective machine guarding could provide significant risk reduction for workers. Even in 1974, some types of safety-related controls, like two-hand, anti-tie-down controls on power presses, had been in use for many years.
It soon became clear that requirements covering the design of the control systems were needed, and since the machinery sector had little direct experience with these kinds of requirements, work done in the aerospace and nuclear industries was used to develop the basic requirements. It was reasonable at that time to implement some structure to the design of safety systems without knowing whether or not the end result would be reduced workplace injuries, when the balance of probabilities said that it would, and the practice was accepted. Oddly, government and industry failed to monitor the effectiveness of these new measures, with the exception of a few small studies.
Machine safety standards have continued to evolve. We are now almost 20 years downstream from the introduction of EN 954-1, and we still don’t know if our efforts have reduced injuries in the workplace.
The need for data
It has long been said that you can’t manage what you don’t measure, but when it comes to the effectiveness of control reliability as a risk control technique, this is exactly what we are doing.
In 2012, VDW, the German Machine Tool Builder’s Association, conducted a study of injuries related to machine tools, and produced a report that showed that the majority of injuries occurring to users of machine tools were not happening during normal operation. In fact, most injuries were happening to maintenance and service technicians when they were attempting to troubleshoot or repair the machinery when the safety systems were bypassed intentionally or offline for some reason. It is reasonable to say, based on this, that safety systems reduce injuries when they are working, but nothing more.
If the results from the study could be generalized to all machines, we might say that we have gone above and beyond to address the risks posed to workers using machine tools. The problem we have is this: There is no data that supports the idea that today’s machines are measurably safer than those built 15 years ago. We have absolutely no way to gauge the effectiveness of the increased reliability of these systems on risk reduction. To answer this question, we need data that discriminates between injuries that occur due to safety control system failures and those from other causes.
At the moment, we cannot say that we are getting a good return on our design and compliance investment in this area. Government regulators need to be pressed to gather this information.
The bigger question
The VDW study brings up another question: What is being done to reduce injuries occurring when the machinery should be under lockout or some other hazardous energy control procedure? Based on VDW’s data in German industry, the injury rate in this phase of the life of the machinery is hundreds of times higher than during the normal operation, set up and related phases.
Standards like ISO 12100 require machine builders to consider all aspects of the life cycle of their machinery. To achieve significant risk reduction for maintenance and service workers, focus needs to be placed on these parts of the life cycle. For the moment, this continues to fall on employers and machine users instead of machine builders, with an unacceptable level of workplace injuries as a result.
Doug Nix is managing director at Compliance InSight Consulting. He has more than 25 years of engineering technology expertise, though he has focused on risk assessment and machinery safety since 1996. Read his blog at machinerysafety101.com.
This column originally appeared in the March/April 2014 issue of Manufacturing AUTOMATION.