Validation, expansion and standardisation of procedures for high temperature defect assessment (HIDA)
The HIDA project has resulted in the development of a draft ‘HIDA Procedure’ which is a unified and software based (or Knowledge-Based) European high temperature crack assessment procedure. It is a unified Procedure as its development has involved partners from a number of European countries who used the knowledge of their own country procedures/ codes to develop this procedure. This Procedure is expected to lead to the establishment of a European Standard. The Procedure is aimed at underwriting the structural integrity and fitness for purpose of all types of (cracked) industrial components operating at high temperatures (within the creep range) under steady state (creep) or fluctuating (fatigue) stresses. The HIDA Procedure is a simplified methodology for crack assessment and is based on both the validated methodologies of the existing European Procedures and those developed through the project. Five materials from ferritic through martensitic to austenitic steels were tested. These were P22 (or 2.25Cr1MoV), P91, 316 Stainless Steel, 1CrMoV steel for forgings, and 1CrMoV steel for castings. A comprehensive programme of lab specimen and diverse range of feature specimen tests was undertaken to assess crack initiation and growth criteria and their applicability under steady and cyclic loading conditions. A large database of tests from the non-HIDA published and un-published sources has also been put together and scatter bands established for a number of high temperature plant materials and their weldments. The HIDA Procedure provides a route for crack assessment in industrial components through the use of a Knowledge Based System. It also provides a large amount of materials data and guidance on how and where to use it. The direct industrial need of end-users in respect of a validated and easy to use defect assessment procedure, (HIDA Procedure), is to improve the capability of extending the useful life of components and in particular to enhance the decision making process in run/repair/replace situations enabling the development of cost effective maintenance and plant rehabilitation strategies. The HIDA Procedure is useful in reducing risk in high temperature plant due to unstable fracture by taking appropriate safety precautions early in time. The Procedure also points out the situations where the use of existing procedures leads to a high degree of conservatism. Industrial targets for the HIDA Procedure are to achieve reductions in production costs by reducing the frequency of unplanned outages, increasing the operating periods between scheduled inspections, increasing plant availability and efficiency and avoiding the costs associated with the replacement of expensive high temperature components. Initially, the achievements of the project will be directly applicable to the steels studied. Of these, the tubing and piping steels P22, AISI 316 Stainless Steel and the 1CrMoV rotor and casing steels are amongst the most commonly used high temperature materials within the power generation, nuclear, chemical, process and oil refining industries. The fifth steel studied viz ASTM P91 is a newly developed steel for advanced applications (higher temperatures and pressures) for which currently little data are available. The deliverables of the project are: a) The HIDA Procedure, b) The KBS or Knowledge Based System which is a software version of the HIDA Procedure, and c) a Databank on creep and fatigue crack growth in high temperature plant components and cracking in industrial components.