Management of Change (MOC)

Many industrial disasters start with a change nobody thought through: a different valve, a bypassed alarm, a substituted chemical, a shortcut in a procedure or a smaller crew. Management of change (MOC) is a formal way to ask “what could go wrong because of this change?” before it's made, and to make sure everyone affected knows.

• Plant Engineers
• Operations & Maintenance
• Safety Managers
• Supervisors
• Contractors

What counts as a change

• Equipment: new, replaced or modified equipment, piping, valves, instruments, relief devices and controls.
• Materials and chemicals: a new supplier, grade, concentration or substitute material.
• Process conditions: higher or lower temperatures, pressures, flows or limits, and new operating ranges.
• Procedures: changed steps, new shortcuts and workarounds, and changes to lockout, startup or shutdown steps.
• Software and controls: programming, alarm settings, interlocks and trip points.
• People and organization: staffing changes, shift patterns, and contractor use that affect safety-critical jobs.
• Facilities: new buildings, layout changes and storage changes that affect hazards.

A “replacement in kind” (an identical part for the same design) usually doesn't need MOC, but anything different in design, material or specification does. When in doubt, ask. See Process Safety Management.

The OSHA requirement

For facilities covered by OSHA's Process Safety Management standard (29 CFR 1910.119), employers must establish and implement written procedures to manage changes to process chemicals, technology, equipment and procedures (except replacements in kind), and changes to facilities that affect a covered process. The procedures must address:

• the technical basis for the change,
• the impact on safety and health,
• modifications to operating procedures,
• the time period required for the change, and
• authorization requirements for the proposed change.

Employees involved in the process and maintenance and contract employees whose job tasks are affected must be informed of and trained in the change before start-up, and the process safety information and operating procedures must be updated. Facilities not covered by PSM benefit from the same approach. See HAZWOPER and Ammonia Refrigeration.

Typical MOC steps

1. Request: describe the change, why it's needed and where, on a form or in the MOC system.
2. Screen: decide if it's a real change or a replacement in kind, and whether it's temporary or permanent.
3. Review the hazards: a team including operations, maintenance, engineering and safety asks what could go wrong, using a hazard review method such as a what-if or a hazard and operability study. See Maintenance Technicians.
4. Approve: get sign-off from the right people, with conditions.
5. Prepare: update drawings, procedures and safety information, order the right parts, and plan training.
6. Train and inform everyone affected, including contractors and other shifts. See Shift Handovers.
7. Pre-startup safety review: check that the change was built as designed, procedures are in place, and training is done before startup. PSM requires this for new facilities and modified ones where the change affects the process safety information.
8. Close out: update records and confirm the change worked as planned.

Temporary changes and emergencies

• Temporary changes such as bypasses, jumpers, temporary hoses and disabled alarms need MOC too, with a defined time limit and removal date. Temporary often becomes permanent when nobody tracks it.
• Emergency changes may be needed to stop a hazard right away. Follow the emergency MOC procedure if you have one, make the change as safe as possible, then complete the full review quickly afterward.
• Never override a safety system without the proper authorization. See Emergency Stops and Safeguarding Devices.

Workers' role

• Speak up if you see equipment, materials or procedures that differ from the drawings or training.
• Don't improvise changes or fix problems with unapproved parts or workarounds.
• Ask whether a change has been through MOC, and ask for training before start-up.
• Report unexpected conditions after a change, and near misses linked to it. See Incident Investigation.

MOC checklist

• The change was described and screened for whether it's a replacement in kind
• A team reviewed the hazards and the right people approved it
• Drawings, procedures and safety information were updated
• Everyone affected was trained and informed before startup
• Temporary changes have a removal date and a pre-startup review was done

Last updated: October 5, 2026