Control system and instrumentation changes, including setpoint adjustments, alarm rationalization, DCS logic modifications, safety instrumented system bypasses, and instrument range changes, frequently trigger MOC requirements that facilities overlook. OSHA has addressed a range of instrumentation scenarios, generally finding that changes to safety-critical instrument functions require the same documented hazard review and employee communication as physical equipment changes. These letters are especially relevant as facilities migrate to digital control systems where changes can be made quickly without the physical evidence that a wrench was used.
What OSHA Has Said
⚡ Key Compliance Takeaway
A keyboard stroke in the DCS is still a change. Instrument setpoint changes, alarm limit adjustments, and SIS logic modifications that affect process safety function require MOC. Implement a formal software change management system integrated with your MOC process.