Management of Change That Actually Catches Changes

By the Aetso Technical engineering team · Reviewed November 2026 · 8 min read

Change is constant in industrial facilities: equipment is replaced, procedures revised, chemicals substituted, controls reprogrammed and people reassigned. Investigations of serious incidents frequently find that a change introduced a hazard nobody evaluated. Management of change (MOC) is the process that is supposed to catch it.

What the regulations require

OSHA PSM (29 CFR 1910.119(l)) requires written procedures to manage changes — except replacement in kind — to process chemicals, technology, equipment and procedures, and changes to facilities that affect a covered process. Before a change, the procedures must address the technical basis, the impact on safety and health, modifications to operating procedures, the time period of the change and authorization requirements. Affected employees must be informed and trained, and process safety information and procedures must be updated. EPA RMP Program 3 contains parallel requirements.

What counts as a change?

The most common MOC failure is not a poor review — it is a change that never entered the system. Make sure your program recognizes:

• Equipment modifications, including "like-for-like" replacements that are not truly identical
• Changes to operating limits, setpoints, alarm and trip settings
• Control system and safety system logic changes, including bypasses
• New raw materials, suppliers, catalysts or concentrations
• Procedure changes and new non-routine tasks
• Temporary changes and temporary equipment
• Organizational changes: staffing, shift patterns, roles and contractor scope
• Changes to buildings and occupancy near process units

The replacement-in-kind trap

"Replacement in kind" means a replacement that satisfies the design specification. A gasket of a different material, a valve with a different trim, or a pump with a different curve may look equivalent but is not. A clear, documented definition with examples — and a quick way to ask "is this in kind?" — prevents many changes from bypassing review.

A workable MOC process

1. Initiate

   Anyone can raise a change request with a description and a technical basis.

2. Classify

   Determine the type of change and the review needed — a simple change should not require the same effort as a new process unit.

3. Evaluate hazards

   Use a checklist, What-If or HAZOP as appropriate to the complexity and risk.

4. Authorize

   Approval by people with the authority and competence to accept the risk.

5. Implement and update

   Update PSI, procedures and training, and communicate the change.

6. PSSR and startup

   Where required, a pre-startup safety review before introducing hazardous materials.

7. Close

   Confirm all actions are complete; for temporary changes, confirm restoration by the expiry date.

Signs your MOC system needs work

• MOCs remain open for months after the change is in service.
• P&IDs and procedures lag behind field conditions.
• People describe MOC as "paperwork" rather than a safety review.
• Temporary changes become permanent without review.
• Organizational changes are never assessed.