Risk Based Inspections (RBIs)

The large chemical manufacturer Imperial Chemical Industries (ICI) was founded in 1926 — when it was the largest manufacturing company in the UK and employed roughly 29,000 people.

The company produced petrochemicals, bulk chemicals, paints and speciality products such as polymers and electronic materials.

Manufacturing hazardous and toxic chemicals safely required an effective Inspection Authority (IA) to monitor equipment for containment issues. ICI chose to do this in-house but kept inspection separate from operations to avoid any conflict of interest.

ICI developed one of the largest in-house IAs, setting out inspection regulations and assisting in the formulation of UK regulations on inspection. Later, in 1980, the inspection service was centralised. In 1993, it became part of the independent company Eutech as ICI prepared to divest production of bulk chemicals. Following this, in 2001, ABB purchased Eutech and from then on grew and developed the inspection process.

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, so they became the first pressure vessels to have ‘compulsory’ periodic inspections.

The Factories Act of 1961 set out rules for inspecting equipment containing steam and air, prescribing rigid fixed intervals of 14 months for steam raising equipment.

At the time all prescribed inspections were invasive — they required equipment to be taken out of service for the inspection engineer to look inside. As 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, in 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 (PSSR) 2000.

For fluids not covered by PSSR, the Provision and Use of Work Equipment Regulations (PUWER) 1998 apply. These regulations were 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 these were less prescriptive than PSSR but the regulator is able to enforce best practice. Best practice on COMAH sites became accepted as risk-based inspections (RBI).

Before RBI, inspections in ICI followed company regulations. These used a grading system based on the results of previous inspections with intervals gradually being extended to prescribed maximums for different types of equipment.

Progression was in line with American Petroleum Institute guidance and the maximum interval depended on the equipment type. In practice, there was a conservative approach and relatively few items were extended to the maximum interval.

Inspection was 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 valves.

In 1993 the first process that would be recognised as RBI was used by ICI 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, all WSEs were produced by 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.

While preparing a focused WSE was clearly more expensive for clients, 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 (RBI) in line with what other users called their processes. A key differentiator for the ABB has always been that the WSE was the focus of the process rather than the intermediate step of carrying out a risk analysis.

The RBI process was documented by the American Petroleum Institute (API) publication API 581 (Risk-Based Inspection— Base Resource Document) and published in June 1996, which contained the information necessary for a qualitative or quantitative RBI to be carried out.

The qualitative process 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 programmes 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. 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.

By 2000, RBI was well established and the 5-by-5 risk matrix was now used to identify the likelihood and consequences for business and health, safety and environmental risks.

The process complied with the requirements for a qualitative RBI to API 581 and client operations and maintenance staff then formed part of the team.

The need for a database to make the process more efficient and store the large amount 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.

While 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 directly 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.

The pRIME RBI software was recently used 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 achieved 20 per cent workscope elimination as well as a reduced number of intrusive examinations and reduced safety risks. Other benefits included improved knowledge of the equipment and the greater involvement of operations staff in managing integrity.

Many organisations have only applied RBI to the critical HSE equipment. Considering business risk and making the process more efficient means that RBI is now justified for most containment equipment. It is also likely that the process will increasingly be used more for lifting equipment, machines and civil and structural assets.

This focus on improving the process will continue with further software development, greater use of corrosion circuits, virtual meetings and much better data mining of the many assets already assessed.

Evergreening or reviewing of existing studies has not always been carried out. This is an area where there is significant opportunity and it is expected that many companies will do this in the future.