Over the past few years, there have been several PDC presentations on machine safety, the impact of ANSI B11.TR3, and the need to incorporate safety into the design stages of a machine or process. Earlier presentations have focused upon task and hazard evaluation and determination of risk. This paper explores various " protective measures" that may be taken to reduce risk, their strengths and weaknesses, and provides guidance for selecting those measures that are most appropriate to degree of risk reduction you wish to achieve.
For years, safety pundits have taken the position that any hazard should be safeguarded to highest possible standard. This has resulted in a squandering of valuable resources, and provided fuel to plaintiff's attorneys in this litigious environment. A more logical and scientific approach is to analyze risk and select protective measures appropriate to the degree of risk reduction desired.1
Fred Manuele, CSP, PE has pointed out in several of his books that " all hazards are not equal, and all risks are not equal." In the development of ANSI B11.TR3, we ultimately came to the conclusion that:
" Zero risk" does not exist
Achievement of " tolerable or acceptable risk" for a given task/hazard combination usually requires a combination of incremental protective measures
Protective measures provide varying degrees of " risk reduction." If your risk level is high, you need a higher level of protection (or safety effectiveness/reliability)2 to assure that it is brought to a tolerable level.
In every case of risk reduction, some residual risk will remain that must be communicated " down the line." Although figures do not exist to substantiate this claim, failures to communicate residual risk may pose the greatest single cause of injury.
In his presentation at the 2002 PDC, John Etherton, Ph.D, of NIOSH, points out:
" A fundamental tenet of risk assessment is to see to it that high risk tasks, such as workpiece or scrap jam-clearing, are matched with high reliability protective measures. The hierarchy of risk control measures is to 1) eliminate the hazardous task; i.e., no jams or fewer jams; 2) provide a well-engineered safeguard; i.e., not easily bypassed; and 3) train. If training is to be used, it must be highly reliable. Well-trained and supervised personnel can be a solution. Unfortunately, they are often the weakest link."
" Because of these shortcomings with the training solution, the two strategies that are higher on the risk control hierarchy warrant further consideration. NIOSH and industry partners, within the framework of the National Occupational Research Agenda (NORA), have developed priorities for finding such alternative measures (NIOSH, 1998). The NORA Traumatic Injury research agenda calls for:
designing workplaces, machines, and equipment to remove the possibility of making unsafe choices or actions (engineer-out hazards); and
in designing and modifying workplaces to improve safety, " passive controls," those which do not require choices or actions by workers in order to be protective, should take priority over " active controls," which require workers to take action or change behavior."