Inspection using Risk Based Methods

Inspection Using Risk Based Methods

In order to optimise your spend on inspection and maintenance, the first step would be to determine which equipment would benefit from increased surveillance and which would pose no additional risk from reduced inspection.


There are established approaches to developing an understanding of the risk of operating process equipment, e.g. API RP 580/581 as well as proprietary techniques.


It must be noted that quantitative and semi-quantitative RBI approaches depend on obtaining repeatable and reliable data such as process conditions, deterioration mechanisms and rates. With this in mind it is only possible to carry out such studies once appropriate data has been identified, collected and understood. With a lack of data, it is often only possible to carry out a qualitative assessment. 


We follow qualitative (e.g. API 581 annex B) principles however we have also experience of carrying out the semi quantitative and quantitative assessments.

Firstly, we integrate our assessment with the development of the Written Scheme of Examination (WSE). This ensures that the reasoning used during the RBI work process is retained for the inspector to review prior to the examination being carried out. 


Secondly, we recertify our WSEs on the back of each inspection. Recertification is the process of re- reviewing the WSE taking the latest inspection information into account and, if necessary, making any changes as required. This ensures that the assessment remains valid in light of new information, changes to process conditions or repairs/modifications.


Thirdly, we focus our assessment to identifying each failure mode with regard to:

  • Understanding how the equipment will fail
  • Understanding what deterioration will cause the failure
  • Establishing deterioration rates
  • Determining the probability and consequences of failure
  • Developing inspection techniques that will detect the potential deterioration modes.
  • Potentially identifying actions that may be required to mitigate such failure.

By scoring the probability and consequences of failure, we are able to rank the equipment in order of risk which can help justify maintenance spend and timings.

Fourthly, we group equipment together such that the inspector can investigate the potential damage to attached equipment should deterioration be found in one item of equipment.


Normally an Inspection Engineer project manages the process with input from a Materials Engineer and Mechanical Engineer as required.This ensures that the numbers of people are kept to a minimum - e.g. there’s no technical clerk, RBI facilitator, etc.


  • The first step is to carry out a data-gathering exercise where all pertinent information is obtained.
  • Then we analyse available information and develop a proposed WSE for each item of equipment.
  • After this we carry out a series of meetings (normally) or submit technical queries in order to validate and adjust the WSEs as necessary.
  • Once this is complete, the WSEs are sent round for endorsement (electronically).


We use a technical clerk to handle documentation - our experience is that it’s more useful for us to scan in documentation and work off the electronic documentation then issue you the originals back within 5 days of receipt.