TWI Frequently asked questions
by Julian Speck
Risk based inspection (RBI) and maintenance (RBM) are management practices employed to identify plant equipment most at risk of failure. The criticality ranking derived through RBI and RBM consequently forms a framework within which inspection and maintenance resources can be allocated to plant equipment in a cost-effective manner, without compromising safety. In other words, RBI and RBM permits a shift of inspection and maintenance resources to provide a higherlevel of coverage on the high risk items and an appropriate effort on lower risk equipment. A potential benefit of RBI and RBM programs is to increase the operating times (run lengths) of equipment while reducing, or at least maintaining, the same level of risk.
In 1998, TWI developed a software management system called RISKWISE TM as a tool for implementing RBI and RBM. RISKWISE TM calculates the likelihood and consequence of failure for pressure equipment to produce a criticality ranking. The key advantages of RISKWISE TM are -
- overall user-friendliness
- based on well known risk assessment models
- incorporates an inspection and damage mechanism 'knowledge base'
- contains a tracking system for inspection actions
The risk model is semi-quantitative, so it can be easily learned and is convenient to use. The software has a user-friendly Microsoft ® style graphical user interface (GUI), and was developed for the Microsoft Windows NT 4.0 operating system (OS) platform, for use on a Client-Server or Standalone basis.
RISKWISE TM is available in several versions, for application to equipment in 'Process Plants', 'Boilers', 'Pipelines' and 'Tanks'. The risk models, for each equipment-specific version of the software, are based on thebest elements of the risk-based management procedures presented in published documents, i.e. ASME CRTD Vol.20-1, API BRD 581, API RP 580, and EEMUA Publication 159.
The software includes a regularly updated knowledge-base of over 30 relevant damage mechanisms, as well as in-service inspection and non-destructive testing.
RISKWISE TM uniquely evaluates the change of risk of failure with time for each damage mechanism, which provides an indication of remaining life and is the only rational basis for establishing the maximum period between major inspections and maintenance activities. By identifying the most likely damage locations in equipment, RISKWISE TM enables assessors to properly target their inspection or maintenance plans and schedules.
Further information
