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Ten Fingers and Ten Toes: Applying Machinery Safety Principles in a Process Plant

by Lauren J. Caldwell, PE(SC), CFSP, CMSE

When performing risk assessments on process equipment, are you reviewing machinery as well? Bag dump stations, conveyors, and various vendor-packaged machinery provided with E-Stops are sometimes evaluated in a Process Hazards Analysis (PHA), but they tend to be reviewed at a high level. Because they do not have process flow, they may not be viewed as having traditional process safety hazards. Machines still have hazards, and there is a need for a deeper dive with respect to machinery-related hazards.

Did you know that machinery E-Stops fall under OSHA’s General Duty Clause? In an interpretation letter from April 28, 1999, OSHA noted, “If a serious injury could result from an

improperly-designed or installed emergency stop device, a citation under the OSH Act’s General Duty Clause could be issued.” This brings the question – how should machinery without process flow be addressed?

There are separate standards available for evaluating machinery hazards and designing their

safeguards appropriately: ISO 12100, IEC 62061, and ISO 13849. Fortunately, functional safety of machinery follows a similar workflow to the process safety lifecycle. Similar to identifying risk gaps in a Process Hazards Analysis (PHA), we can identify risk gaps for machinery. We can define risk targets, determine how to best close the risk gaps, specify a design, and verify the risk has been adequately addressed.

This paper will present a practical example application to demonstrate machinery safety risk

reduction in accordance with machinery safety standards for machinery common to chemical

process plants.


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