RBI: Reducing the risk
01 April 2014
Risk-Based Inspection (RBI) has become a leading industry-wide, approach to optimising inspection regimes. Done well, RBI reduces risk, increases plant availability and improves asset understanding, as well as lowering total inspection costs. Done badly, however, RBI takes up time and wastes money. Here, ABB Consulting’s Paul Jackson explains what makes RBI successful and how it has changed in the last twenty years.
It is no secret that integrity management poses many challenges. Assets today are often operating well beyond their originally envisaged life-span. Couple this with increasing economic pressures to maximise production and a tighter regulatory framework – difficulties can arise. The goal, therefore, is for inspection to deliver better results, and to do so for less money.
Put simply, RBI involves determining an optimum inspection plan for plant equipment that benefits the end user. Plants operating without RBIs are likely to use largely historical, dated and prescriptively driven methods of inspection. With RBI, on the other hand, a plant can reduce costs and increase overall equipment effectiveness (OEE) whilst maintaining legislative compliance.
At present, RBI is often applied only to equipment with the highest health and safety risks. Yet, considering business risk and making the process more efficient, RBI can be justified for most containment equipment too. As assessments advance, the process is likely to be increasingly used for lifting equipment, machines and civil and structural assets.
The evolution of RBI
The concept of inspection can be traced back to European marine insurers trying to protect their assets. In the early 20th century numerous vessels failed to return home, a problem that was eventually traced to caustic cracking around rivets in steam boilers. Explosions of boilers at sea caused ships to sink without trace; hence they were the first pressure vessels to have ‘compulsory’ periodic inspections.
The Factories Act of 1961 set out rules for inspection equipment containing steam and air and prescribed rigid fixed intervals e.g. 14 months for steam raising equipment. At that time all prescribed inspections were invasive - they required equipment to be taken out of service for the inspection engineer to look inside. Whilst there was no guidance for equipment other than steam or air, a period of 26 months became customary practice for many insurance inspections.
In 1989, as a response to the Flixborough incident where a chemical plant explosion killed 28 and seriously injured 36, the legislation for pressure systems was changed. The new legislation was ’goal setting’ as, unlike the prescriptive Factories Act, it did not instruct users how to comply. Instead, it encouraged a risk-based approach and did not give guidance on the scope or interval of inspections. The application was widened to relevant fluids which were essentially compressible fluids above 0.5 barg and steam at any pressure. Although the risks of scalding from steam and stored energy were recognised, the legislation did not cover toxic and hazardous fluids and largely excluded pipework. The 1989 legislation evolved into the Pressure Systems Safety Regulations 2000 (PSSR).
For fluids not covered by PSSR, the Provision and Use of Work Equipment Regulations (PUWER) 1998 apply. These regulations are much less prescriptive than PSSR. Where a site stored more than a given amount of certain chemicals, the Control of Major Accident Hazards regulations (COMAH) 1999 were applied. Like PUWER the regulations are less prescriptive than PSSR but the regulator is able to enforce best practice. Best practice on COMAH sites became accepted as RBI.
In the early years of the new legislation, inspection remained largely invasive and, because of this, a plant shutdown was required to carry out an inspection. Repeatedly shutting down a continuous process plant was neither practical nor economical and therefore the items with the shortest intervals determined the turnaround interval. For planning reasons, other items that could have longer intervals were often set to the turnaround interval and this became the inspection interval. Other factors that influenced inspection intervals were catalyst life and pressure relief valve test intervals.
Focused Schemes of Examination
In 1993 the first process that would be recognised as RBI was used to improve the Written Scheme of Examination (WSE) for critical equipment. This was known as ‘Focused Schemes of Examination’. There was no software to support the process but a short report was produced to record the results.
Prior to focused schemes, WSEs were often produced by the inspection engineers. The WSE was generally produced without specific input from a corrosion engineer, although deterioration types for a plant were well known. This reflected the fact that inspection was invasive and there was limited non destructive testing technology.
The new process utilised a team made up of the plant maintenance engineer, the plant process engineer, the inspection engineer, a chartered inspection engineer and a corrosion engineer. Inspection history was examined and as well as the deterioration mechanisms based on the normal operation and start up and shut down. The types of failure expected as well as the controls were recorded. The output of the study was a ‘focused scheme’ that recorded in much more detail than a normal WSE the active deterioration mechanisms, the locations to inspect and the inspection methods to be applied. The inspection interval was set based on an understanding of the equipment condition and deterioration rate. The scope and frequency of the inspection also took account of the consequences such as the effects of loss of containment.
Whilst the cost of preparing a focused WSE was clearly an investment for clients, the savings from avoiding the high cost of lost production in order to carry out inspection, or unplanned repairs if inspection was not effective, gave a very attractive return on investment and the focused schemes process took off.
The focused schemes process continued to be developed and gradually became known as ‘Risk-Based Inspection’ in line with what other users called their processes. The risk-based inspection process was documented by the American Petroleum Institute (API) publication API 581 (Risk-Based Inspection Base Resource Document) published in June 1996 as a preliminary draft API 581 contained the information necessary for a qualitative or quantitative RBI to be carried out. The qualitative process used by ABB included expert judgement to evaluate the most appropriate inspection regime. The quantitative process attempted to gauge risk and the base resource document provided the generic data that was the basis of this. Computer programs quickly followed and that enabled the quantitative process to become manageable.
Whether to use qualitative or quantitative RBI is a subject in its own right: both have advantages and disadvantages. There is no one size fits all approach and each inspection needs to be developed on a case-by-case basis. In some instances a qualitative expert opinion based approach is needed to provide results quickly. For others quantitative analysis is needed to form a basis of the assessment. ABB Consulting believes the qualitative method is best for the equipment it deals with and even a quantitative method will have a qualitative element to it.
Over time, the need for a database to make the process more efficient and store the large amounts of data generated by the increasing number of studies was recognised. ABB Consulting commissioned the production of a database using the proprietary Microsoft software program Access. Whilst this initially met the requirements it proved very difficult to upgrade the software and a decision was taken in 2003 to upgrade to a Lotus Notes package as part of the ABB pRIME (process Reliability & Integrity Management Excellence) software package. Using the Lotus Notes platform meant that multiple users could input data and users could all see the same up-to-date information. It also had further advantages in that data could be transferred direct to the RBI database from the Inspection database for recording inspection history. RBI data could also be exported to other applications in the pRIME suite.
The software continued to be enhanced in particular in the authoritative review section where it became mandatory to provide more detail on how to inspect for each deterioration mechanism. Further software enhancements included: the incorporation of a non-invasive module based on the DNV G 103 standard, automatic generation of the WSE and guidance on inspection intervals based on risk.
A significant upgrade to the software has recently been carried out. Renamed pRIME2 this latest version is fully web compatible enabling clients to interact fully with the system via the internet, using a normal web browser. This enables clients to license the software to view historic data and even to complete an RBI using their own staff.
The next steps
In the future, software development will have a key role to play in RBI. I’d anticipate greater use of corrosion circuits, virtual meetings and much better data mining of the many assets already assessed.
Evergreening or reviewing of existing studies is not always being carried out by companies and could be a missed opportunity for improving practice and reducing risk in many businesses. With this strategy in place, and technological advancements, RBI will continue to have a fundamental role in inspection management services for years to come, and in many cases improve efficiency and give companies a competitive edge.
An ABB client used the pRIME RBI software at an oil refinery to make the major turnaround more manageable. Turnaround man hours were too high and earlier RBI by others had not updated written schemes. Using the ABB software, a team of experts from ABB Consulting critically reviewed 540 items and conducted a full RBI on 164 items as well as producing a WSE for each altered item.
As a result of the technology, the client eliminated 20 per cent of the workscope and significantly reduced the number of intrusive inspections and have reduced safety risks. Turnaround examinations and inspection workload has also significantly reduced.
About the author:
Paul Jackson, ABB Principal Consultant for Inspection and Integrity Management
Paul has over 30 years industrial experience working within the power, chemical and oil & gas sectors. Paul is the functional leader of ABB's inspection services and has held roles in design, maintenance, inspection and consulting on all aspects of pressure systems. Paul is a Fellow of the Institution of the IMechE and Chairman of its Pressure Systems Group Committee.
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