Optimising PSSR inspections using RBI+©

Implementing an integrated integrity management system to comply with HSE RR509 and reduce inspection costs.

The client operates one of the UK’s largest onshore gas storage facility. The asset consists of nine man-made salt cavities that have been leached into a salt layer 1.8 kilometres below the surface creating 325 mcm of gas storage capacity.

The pressure vessel inspections on this top tier COMAH site were previously carried out by an insurer to comply with the Pressure Systems Safety Regulations (PSSR). The client required a UKAS accredited supplier to instigate an integrity management system on the site to fully meet the requirements of HSE RR509 - plant ageing: management of equipment containing hazardous fluids or pressure.

ABB carried out a high level criticality study and RBI reviews to fully understand any potential deterioration mechanisms. We then prepared Written Schemes of Examination (WSE) to enable ABB inspectors to carry out detailed examinations of the equipment and report their findings.

ABB carried out a piping and vessels criticality and opportunity screening process. This allowed the pipework to be categorized and ranked in order of criticality, risk and opportunity to provide the operator with a greater understanding of key pipework issues. It also acted as a feeder for the long term integrity management strategy and RBI+© study. Examples of learning included:

  • Annual maintenance of sight glasses and instruments on the micro-scrubbers and of the ROPs in the pipework from the microscrubbers to the dump tanks is essential for the prevention of gas break-through causing brittle failure of this pipework
  • A methanol storage tank was converted to an atmospheric tank under a plant modification. The atmospheric vent is sat on a valve which should be locked open (confirmed) and then removed at the next available opportunity

The RBI+©  methodology concentrates on determining: 

  • What - to inspect. i.e where failure is unacceptable  
  • Where - to focus effort  
  • How -  the right techniques to use  

When - optimise the examination interval

In addition, we considered what the impact of any potential failures would be on either, the business, the environment or safety.

Detailed Risk Based Inspection (RBI) reviews were undertaken to fully understand any potential deterioration mechanisms of individual items of equipment. By doing this, ABB were able to highlight and prioritise items that were key to the operation, and focused inspection activities accordingly. 

As part of the data review and analysis stage we also challenged the scope of the Non-Destructive Testing (NDT) to ensure the inspection regime was optimised and appropriate for the relevant deterioration mechanisms to provide the most cost effective solution.

Bespoke WSE were prepared for ABB inspectors to carry out detailed examinations of equipment, which included recording thickness measurements at key locations. From the RBI reviews and the subsequent inspections ABB were able to recommend a number of changes to inspection practices and frequency of inspections:

  • Inspection intervals for PSSR vessels were increased from 58 months to 82 months and inspection intervals on COMAH vessels were increased from 60 months to 86 months. This reduces costs and strain on operator time
  • Only 5 COMAH vessels and 90 PSSR vessels had inspection schemes this has now been updated to 50 and 115 respectively
  • The current inspection schemes called for NDT by Alternating Current Field Measurement (ACFM) of all the welds of over 50 vessels, following the study only the welds with the potential for deterioration were specified for inspection 

On completion of the inspection programme the findings were reviewed to determine any changes to the written scheme and, if required, to the RBI data. This continual review of inspection findings will ensure that the requirements of HSE RR509 are embedded in the integrity management system.

All RBI reviews undertaken by ABB were delivered using the RBI+© pRIME tool. The web-based software further enhances the RBI+© process as it:

  • Allows a number of team members to work concurrently in capturing the input data electronically to enable review during multi-disciplinary meetings. This functionality also allows the information to be reviewed by specialist engineers outside of the immediate project team
  • Ensures a consistent workflow and management reporting - Each equipment item review is subject to a series of secure stage gates to ensure that all of the necessary input data has been collected, analysed and the recommendations captured. This structured work process facilitates the tracking and reporting of project status by means of the progress dashboards
  • Provides a risk assessment according to SSE’s criteria 
  • Automatically generates customisable reports

Main data

Customer:  Major gas storage company
Site:  Yorkshire, UK
Customer need:  High level criticality study and RBI reviews to fully understand any potential deterioration mechanisms
Scope:  Piping and vessels criticality and opportunity screening process
Application:  Oil and Gas
Customer benefits:
A 40% reduction in inspection costs
Average inspection intervals for vessels increased
Greater understanding of the equipment
Compliance with PSSR requirements
Commissioning year: 2014
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