(111a) Ten Fingers and Ten Toes: Applying Machinery Safety Principles in a Process Plant

When performing risk assessments, are you reviewing the machinery as well? Bag dump stations, conveyors, and various vendor packaged machinery provided with E-Stops may be 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 that, “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: 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 practical example applications in accordance with machinery safety standards for machinery common to chemical process plants (e.g. a conveyor):

• Example hazards around the machinery
• Target risk ranking example
• Requirements for meeting the target Performance Level (PL)
• Safeguarding options such as guarding, E-Stops, and interlocks
• Example of input to the safety requirements specifications
• Example components selected and wired as dual-channel with diagnostics

Practitioners will be introduced to practical applications of risk assessment and functional safety of machinery safety in a chemical process plant.