The overarching objective of an effective inspection process should be to ensure that an unintentional release of stored energy or the release of hazardous contents from a pressure system or containment system are eliminated.
The usual reasons for implementing a Risk Based approach to the Inspection process are the following:
- To improve the management and compliance of Health and Safety on Site and to reduce risks of plant failure
- To identify and repair or replace deteriorating equipment in a timely manner, and
- To produce cost savings
In addition to these goals, other less obvious positive outcomes can also be achieved.
Health & Safety Benefits
In order to calculate risk, a better understanding of the consequence of loss of containment is required. This better understanding can be used to complement several other safety disciplines on site such as Process Hazard Reviews and Hazard and Operability Studies. Consequence calculations can also be used to develop the risk assessments required before maintenance tasks are started.
RBI is a collaborative, team approach, as opposed to the management of Pressure Systems Safety Regulations (PSSR) which usually relies solely on the Competent Person to make decisions. With the emphasis on interaction between Process Experts, Operations and Maintenance, it then becomes easier to discuss Integrity Operating Windows (IOWs) and how process parameters affect corrosion rates. Considerations of how changes in process or equipment materials of construction may affect the inspection program as part of a Change Management process also become routine. As the organization understands risk, it also becomes easier to have the open discussion that is required to define what is "Acceptable Risk" and how the site can reduce risk to an acceptable level.
Risk is a useful measure to identify the priority or order that maintenance or inspection tasks should be completed. This prioritization becomes particularly useful where resources such as time or money are limited and where difficult choices need to be made. Risk matrices are a good visual tool that can quickly show how risk compares between different pieces of equipment to enable these choices to be made.
One part of the Consequence of Failure calculation process is to consider the time required to detect and isolate a release. With these established timings, it becomes easier to focus on areas for improvement and justify spending on more efficient equipment or processes. These improvements and the adoption of Risk Based Inspection can form part of a Sites Major Accident Prevention Policy (MAPP) and should be included in the Control of Major Accident Hazards (COMAH) report too. These changes and improvements also demonstrate that the Site is reducing risk to As Low As Reasonably Practicable (ALARP) or As Low As Reasonably Achievable (ALARA).
All these measures are activities which are focused on preventing and reducing failures. This approach should lead to a reduction in the number of adverse incidents. In turn, this approach should lead to a reduction in incident investigation costs and a reduction in insurance premiums. Furthermore, it should also reduce legal action costs and any fines due to safety breaches from the regulator. An improved safety record will mean that the relationship between the regulator and the site becomes less adversarial. An improved safety record will also mean that the site is a better place to work and encourage more applicants to apply for advertised jobs on the site.
Identifying Deteriorating Equipment
In addition to these primarily Health and Safety benefits, the use of Risk Based Inspection processes means that a systematic approach to the inspection of equipment will be adopted. This systematic approach will produce more important information and knowledge about the equipment and the materials of construction being used.
The first part of this systematic approach should be to identify damage mechanisms for the process and materials of construction involved. In some cases, this may mean that a Corrosion Expert needs to be consulted and this approach may identify damage mechanisms that have not been considered before.
Using a Failure Modes and Effects approach, once damage mechanisms have been identified, it becomes easier to specify the correct techniques that need to be used to inspect the equipment and to write the equipment Inspection Plans. This grouping of equipment together with the same materials of construction and process conditions and as a result the same damage mechanism leads to the grouping of piping into piping circuits. Grouping piping into piping circuits is a more efficient way of inspecting piping than inspecting piping using line numbers.
Risk Based Inspection requires corrosion rates to be calculated and inspection plan intervals to be determined using risk and remaining life. This approach is based more on facts than "inspector intuition" and is less likely to develop an inspection regime that will produce a failure. Corrosion rates of piping under insulation will be affected by the type of insulation that is used. Using Risk Based Inspection it becomes more obvious which types of insulation are better at reducing potential for CUI (Corrosion Under Insulation). This discussion will probably lead to changes in insulation policy on the site as well.
This systematic approach can be adopted for new equipment as well as existing equipment. When starting an RBI program for new equipment, corrosion rates used may be taken from historic data from other parts of the site or rates may be specified by a Corrosion Expert during the damage mechanism identification process.
On sites which use RBI, risk results can be used to justify plans to replace deteriorating equipment and justify capital expenditure.
This Risk Based approach to inspection of pressure equipment may lead to a similar approach being used to inspect pipe bridges/supports, bunds/dikes or other structures on site too.
Finally, it is likely that the introduction of Risk Based Inspection on site will lead the Inspection Team to develop an interest in API (American Petroleum Institute) or other inspection qualifications. So, as confidence increases in the Inspection Team due to the reduction in loss of containment incidents, the site confidence will be further boosted as Inspectors gain industry-recognized qualifications.
As stated at the beginning of this article, one reason for the adoption of Risk Based Inspection is for a site to save money. It is possible, using RBI, for sites to reduce inspection costs, reduce maintenance costs, and increase turnaround intervals. One good example of this can be found on the Asset Optimization Consultants website under the title "RBI Yields Big Savings". In this example, a Chemical Plant on the Gulf Coast with just over 300 pressure vessels was able to reduce costs by changing their conventional API program into a Risk Based Inspection program. They reduced their inspection requirements by 65% which was estimated as a saving of $3.2 million in maintenance costs over the next 10 years. These savings would be preparation costs such as erecting scaffolding or cleaning tank internals. In addition, they were also able to increase turnaround intervals. These savings were estimated at around $8 million over the same 10-year period.
When planned inspections (and their costs) are known, organizations are more likely to try to reduce the number of unnecessary inspections. This includes inspections that are completed to confirm equipment integrity when an inspection recommendation task has not been completed by the Maintenance Dept.
Increasing turnaround intervals will have the obvious positive effect of improving plant availability and the site's productivity. Shutdowns and Start-ups, before and after maintenance activities can be problematic and can have a negative effect on plant availability and productivity. For example, sites may struggle to commission equipment after an outage. Maintenance activities can also leave the site with a greater chance of a leak due to there being a greater chance of an unsecured flange or a gasket being badly fitted during a maintenance activity for instance.
Another positive affect of extending the turnaround interval is to reduce the amount of time an inspector or a cleaning team needs to spend inside a Confined Space. There is an emphasis from the regulator to reduce this time and as a result reduce the safety risk to personnel from working inside a Confined Space.
Cleaning can sometimes have a negative effect on the corrosion rate of a pressure vessel. If for instance the inside of a vessel is subject to atmospheric moisture or jet washed for inspection reasons instead of it usually being blanketed with nitrogen, then corrosion rates will have the chance to increase.
The adoption of Risk Based Inspection is an opportunity to grade the effectiveness of the inspection regime. Ineffective inspection tasks should either be eliminated or replaced with tasks which are more effective at addressing identified damage mechanisms. Short, limited inspection tasks are more likely to be replaced with more effective inspection tasks which have a larger scope and, as a result, then have a longer inspection interval.
This overall reduction in inspection and maintenance tasks means that these manpower resources can be used to tackle other issues including improvement work.
Finally, all these positive changes to the inspection process will help promote a culture of Continuous Improvement on the site.
There will no doubt be other good outcomes that can be gained from an RBI process than the ones that have been mentioned in this article.
In summary, the usual and more obvious reasons for implementing an RBI process are to improve the safety of a site, improve inspection effectiveness, and reduce costs by improving inspection efficiency. However, what has been shown is that there are many less obvious, but still positive outcomes that can also be achieved by adopting Risk Based Inspection.
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