Fitness-For-Service (FFS) assessments are performed to evaluate the components damaged in service to determine whether it is possible to continue their use. FFS assessment codes were recently standardized, and they are being used in many companies in Europe and the United States. In Japan, the regulation permits the use of FFS codes in nuclear power stations, but not yet in petroleum and petrochemical industries. The PAJ/JPCA FFS task group that consists of the members of petroleum or petrochemical companies has been studying and investigating one of the FFS Codes, API579-1/ASME FFS-1 [1], in an attempt to include it in the high pressure gas safety law [2], which regulates the pressure equipment operating at pressures greater than 1 MPa. We have now completed the adaptation of the FFS code for Japan, and it is in the process of being assessed by the authorities. It is required that the code is modified slightly because Japanese authorities and people are particularly nervous to matters regarding earthquake safety. This paper focuses on cylindrical equipment regulated by the high-pressure gas safety law. The margin for earthquake load of the actual equipment is shown, and the local metal loss assessment procedure according to API579-1/ASME FFS-1 is verified by using experimental burst test data with pressure and/or bending stress in order to determine whether or not the FFS code provides a sufficient safety margin for safe operations in Japan.
FFS assessment technologies for pressure equipment have been studied and standardized in recent 15 years in Japan. FFS assessment of local thin area, LTA, is the most frequently used in process industries. However reliability of thickness measurement of LTA and influence to FFS assessment has not been studied much in the past.
Uncertainty of thickness measurements and Remaining Strength Factor, RSF, were investigated on Round Robin Testing using manual UT and additional new technology such as flexi-alley UT and 3D LED system for LTA in pipes, It is recommended to use suitable combination of Manual or mechanized UT and 3D LTA measurement system in case of assessment of critical flaws and decision making for repair and replacement of pressure equipment.
This paper outlines the technical logic/steps that have been documented in JWES-CP-0902, “Guidelines for Repair Welding on Pressure Equipment”(hereinafter the Guidelines). The paper covers the work flow logic that can be followed by maintenance personnel as they address making a repair welding in pressure vessels/piping made of both ferrous and nonferrous materials after flaw detection during inspection during refinery operation. Material degradation factors that are considered include: strength loss, ductility loss, temper embrittlement, σ embrittlement, corrosion metal loss, stress corrosion cracking, fatigue, and creep.
In recent years in Japan, the concepts of the regulation system and technical standards have been changed a lot with following major items: 1) Changing concept of regulation from specification basis to performance basis. 2) Although specification base regulation had prescribed detailed construction, design method, applicable material and methods of inspection and testing, the performance base regulation only requires total function on reservation of safety and security. If required performance is proved on pressure equipment during manufacturing and/or operation, it will accept to use fundamentally. Performance base regulation will allow applying new technology timely but it is rather difficult in specification basis.
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