Mechanical Integrity Programs

Mechanical Integrity (MI) is the set of activities that ensures process equipment — pressure vessels, piping, storage tanks, relief devices, emergency shutdown systems, and rotating equipment — is designed, installed, inspected, tested, and maintained to prevent or mitigate releases of hazardous materials.

In the United States, MI is element 6 of OSHA's Process Safety Management (PSM) Standard (29 CFR 1910.119). It is one of the 14 PSM elements and represents a legal requirement for facilities that handle threshold quantities of highly hazardous chemicals.

A complete mechanical integrity program consists of eight interconnected elements:

1. Written Procedures: Documented instructions for inspection, testing, and maintenance activities. Must be accessible, current, and followed.

2. Training and Competency: Personnel performing MI tasks must be trained and competent for their role. Competency verification should be documented.

3. Equipment Inspection and Testing: Systematic inspection and testing against written procedures. Frequency driven by risk, regulatory requirements, and manufacturer recommendations.

4. Inspection Criteria: Clear definition of acceptance criteria — minimum wall thicknesses, allowable defect sizes, test pressures — linked to relevant codes (ASME, API, NACE).

5. Deficiency Correction: Process for documenting, prioritizing, and resolving MI deficiencies. Safety-critical deficiencies must have a safe operating limit (SOL) defined.

6. Quality Assurance: Procedures to ensure new equipment and materials meet specifications. Material traceability, weld procedure qualification, NDE qualification.

7. Management of Change (MOC): Any change to equipment covered by the MI program must go through a formal MOC review before implementation.

8. Incident Investigation: MI-related failures and near-misses must be investigated using RCA methodology. Findings must feed back into the MI program.