Mechanical Integrity 101 | 5-Year Inspections

There seems to be a lack of clarity regarding the frequency that Mechanical Integrity inspections must be performed on ammonia refrigeration systems and more specifically whether a 5-year MI inspection is required by the PSM regulation.

Title 29 CFR §1910.119(j)(4)(iii) requires that “the frequency of inspections and tests of process equipment shall be consistent with applicable manufacturers’ recommendations and good engineering practices, and more frequently if determined to be necessary by prior operating experience.” Per the above mentioned requirement, one would have to consult with both manufacturer’s manuals and literature outlining good engineering practice to determine how often to perform inspections. In this post we will only consider the good engineering practice requirements.

In regards to good engineering practice for ammonia refrigeration systems, the two primary documents that are considered RAGAGEP (recognized and generally accepted good engineering practice) are:

• IIAR Bulletin No. 109 Guidelines for: IIAR Minimum Safety Criteria for a Safe Ammonia Refrigeration System
• IIAR Bulletin No. 110 Guidelines for: Start-up, Inspection and Maintenance of Ammonia Mechanical Refrigerating Systems

Here is what each of those documents has to say about a 5-year mechanical integrity inspection:

IIAR Bulletin No. 109 §5.3
A more thorough inspection of an ammonia refrigeration system should be conducted by a competent ammonia refrigeration engineer and/or fire safety official and/or other authority every five years.

IIAR Bulletin No. 110 §6.4.4.1
At least every five years, the annual inspection of the vessels and heat exchangers shall be carried out by a competent person independent of immediate commercial and production pressures for that installation, who shall carry out whatever examinations and tests he may consider necessary in order to determine that the equipment is safe for further use or in order to specify such repairs that may be necessary.

To summarize, the references above speak for themselves in requiring 5-year mechanical integrity inspections to be performed on all ammonia refrigeration systems.