The mechanical integrity (MI) element of the U.S. Occupational Safety and Health Administration’s Process Safety Management (PSM) Standard [29 CFR 1910.119(j)] has been difficult for many facilities to implement. Indeed, PSM audits by OSHA have consistently demonstrated that MI accounts for a large number of citations at most facilities. In some cases, it has been the last PSM element to be fully addressed.
This is not to say that inspection, testing and preventive maintenance (ITPM) programs do not exist at PSM-covered facilities nor that the maintenance programs can be characterized as “breakdown only.” The chemical industry has used preventive and predictive maintenance programs for many years. What have been lacking in some cases are complete integrated MI-management-system programs that address all of the sub-elements of MI as defined in the PSM Standard. There are several reasons for this situation:
The MI element of the PSM regulations is written in very broad performance-based language – even more so than the remainder of the Standard. Interpretation of these broadly stated MI requirements and the matching of these requirements to actual facility policies, practices and procedures can be a difficult process.
Some companies interpret MI to mean only preventive maintenance and therefore assign MI solely to the maintenance group. Actually, because MI includes a wide variety of tasks and activities, the responsibilities for MI activities are spread widely across a facility and many personnel may not realize that their jobs involve a portion of a regulated MI program.
MI activities encompass the entire lifecycle of the covered equipment, including engineering, construction and spare parts, not just the ongoing maintenance activities; therefore some of the requirements of the MI element may not be completely implemented.
Currently, there is no overall industry-published consensus guidance on establishing and implementing a MI program (although the American Institute of Chemical Engineers’ Center for Chemical Process Safety plans to issue a comprehensive guidelines book in 2005).
This article will explore these issues, including the interpretation aspects that confound some sites, the responsibilities of various plant groups for executing MI activities and typical weaknesses in MI programs.
The PSM Standard states in 29 CFR 1910.119(j)(1) that the MI element is applicable to the following process equipment:
• pressure vessels and storage tanks;
• piping systems (including piping components such as valves);
• relief and vent systems and devices;
• emergency shutdown systems;
• controls (including monitoring devices and sensors, alarms and interlocks); and
OSHA’s wording of the standard may have caused some confusion because it appears to be an incomplete list of equipment. Most of the equipment types listed above are self-explanatory. However, several clarifications are appropriate:
Pressure vessels that are not registered vessels and are operated at less than 15 psig should also be included in the MI program if they contain PSM-covered materials.
Heat exchangers are either pressure vessels or components in a piping system and therefore should be part of the MI program if they cool or heat PSM-covered materials.
Piping system components include any mechanical device that is installed in-line in the piping system and is exposed to PSM-covered materials inside the piping — e.g., filters, strainers, flanges, gasket materials, valves of all kinds and mechanical portions of instrumentation.
Relief and vents systems and devices include all components that are used to control pressure — e.g., relief valves, rupture disks, conservation vents, vent systems, vacuum breakers and flares.
Controls also include mechanical systems or devices that are intended to terminate or regulate exothermic reactions, pressure transients or other types of process safety scenarios, or to mitigate the results of such a scenario — e.g., a water curtain or quench system. Controls might also include local instrumentation to help operators handle abnormal conditions. The 2004 version of ISA Standard S84.01 recognizes manual actions as valid components of safety instrumented functions (SIFs).
Pumps include all rotating machinery containing or exposed to PSM-covered materials, e.g., pumps, compressors, fans, blowers and agitators. It would also include any non-rotating machinery, such as an eductor, that is used to move PSM-covered fluids.
However, you also should seriously consider adding to the MI program other equipment types that impact process safety. Examples include:
• employee alarm systems;
• structural and civil systems (including foundations, anchor bolts, supports, pipe hangers, pipe bridges, etc.) that support the weight or movement of equipment otherwise included in the MI program;
• key utility or service systems or components for equipment included in the PSM program, including electrical power, air, steam, nitrogen/inerting, cooling water, refrigeration/chilling, explosion suppression, quenching, etc., where the utility failure could contribute to a process safety scenario or prevent properly dealing with one;
• fire protection equipment;
• fixed and portable area monitors for detecting releases of toxic or flammable materials;
• secondary containments for tanks and vessels containing PSM-covered materials;
• ventilation systems in buildings designated as safe havens or as assembly points during emergency evacuations;
• test, measurement and evaluation equipment (electrical, electronic or mechanical) for equipment in the MI program, since the proper functioning of this test equipment is essential for accurate ITPM results;