Fitness for Service


		AcuSafe -> May 2000 Newsletter
		Fitness for Service

Many facilities have discovered that while implementing OSHA's PSM program that the design basis and "pedigree" of certain equipment cannot be established. Most often, this occurs when implementing the mechanical integrity (MI) program, and/or while attempting to document the good engineering practices (in the process safety information element of PSM) used to design, install, and operate critical equipment. Pressure vessels represent a special problem in this regard because in order to certify that a vessel meets the ASME code requirements, original design documentation (i.e., the U-1 form), or at least a stamped nameplate are required. Also, the use of the vessel in certain applications may require its certification as a pressure vessel under state law in many jurisdictions.

In these situations, what can a facility do if they have a vessel that operates under conditions that would require a certified pressure vessel but cannot produce either the documentation or valid nameplate data? In the extreme, the vessel would have to be derated from its current service, or replaced. However, there is a process to recertify a vessel for pressure vessel service and essentially create a new design "reference point." This process is called a "Fitness for Service" (FFS) evaluation. It is a physical inspection of the vessel internals to determine its suitability for the service conditions to which it is exposed. The American Petroleum Institute (API) has developed a guideline for performing a FFS, Recommended Practice 579. RP-579 covers the following issues:

Fitness-For-Service Principles
Overview of Damage Mechanisms
- Assessment of Equipment For Brittle Fracture
- Assessment of General & Local Metal Loss
- Assessment of Pitting Corrosion
- Assessment of Blisters and Laminations
- Assessment of Weld Misalignment and Shell Distortions
- Assessment of Crack-Like Flaws
- Assessment of Components Operating in the Creep Regime
- Assessment of Fire Damage
Stress Analysis Techniques for FFS Assessments
Material Properties for FFS Assessments
Interaction of FFS Assessments with risk-based inspection programs
Opportunities for FFS Assessments in Day-to-Day Plant Operations
Opportunities for FFS Assessments in Shutdown/Maintenance Planning

But, there are some cautions regarding FFS evaluations:

Persons holding valid API-510, API-570, or API-653 inspector qualifications must perform the inspections.
If the vessel is regulated under state law, the agency having jurisdiction must approve of the FFS evaluation, its conduct, and the qualifications of the inspectors. The agency may have other requirements that must also be satisfied.
Although the purpose of a FFS evaluation is to re-establish the design basis documentation for a vessel, a FFS evaluation may reveal that remediation is necessary to further operate the vessel in its current service, or that the vessel must be replaced.

Facilities interested in learning more about FFS evaluations may contact API for a copy of RP-579 (or its companion training course) or write to Mike Hazzan.