Petronas Gas Berhad (PGB), a subsidiary of Malaysian oil and gas firm Petroliam Nasional Berhad (Petronas), is engaged in the processing and transmission of gas to petrochemical plants in Malaysia. The company, via its transmission operations division (TOD), operates and maintains more than 2,000 km of high pressure onshore gas pipelines with nominal pipe sizes ranging from 2 to 48. The firm’s TOD division has taken sufficient measures for ensuring the safety of its pipeline operations.
Gas pipeline networks are vulnerable to risks, particularly those pipeline stretches that are located in remote areas where it is not always feasible to assign adequate manpower for monitoring purposes. With the growth of pipeline lengths, technology is set to play the role of enabler in three verticals: asset management, operations and consumer management.
Asset integrity management can help maintain assets in a functionable condition, while extending their life in a reliable, safe and cost-effective manner. In a gas pipeline company, pipelines are the most crucial assets.
The features of PGB’s pipeline integrity management (PIM) system, which has proved to be quite successful for the firm, are listed below.
Implementation of PRIMS
In 2002, PGB implemented the Pipeline Risk and Integrity Management System (PRIMS), which includes software modules for data management, semi-quantitative risk assessment, risk control cost-benefit analysis, defect assessment, corrosion growth modelling and reporting.
The firm undertook a benchmarking study in which its pipeline integrity programmes were compared to those of international pipeline operators. The study revealed that the implementation of PRIMS put PGB among the top firms in terms of pipeline integrity management best practices.
The system was initially tested on 886 km of pipelines and later extended to the entire network, including onshore and offshore pipelines. The results were positive, with the minimisation of pipeline failure risks and the optimisation of maintenance costs.
Through the system’s interactive modules, PGB has the capability to implement a data management system, perform semi-quantitative risk assessments and prioritise integrity assessments. These are followed by a post-assessment analysis and cost-benefit analysis to optimise preventive and mitigation actions.
The various PRIMS modules implemented by PGB are listed below, along with their details.
Database management
The database module is developed on the basis of the industry standard data model, pipeline open data standards, which can be integrated with other third-party geographic information systems and database systems with the availability of other information. The database runs on the SQL server and can be simultaneously accessed by multiple users at different locations for optimal data manipulation and verification via the PRIMS interface.
The interface enables PGB to add, modify and update new pipeline data at any time and from anywhere with network access. PRIMS extracts all the required data and integrates it in accordance with the system’s specifications. It is later used to perform assessments on PGB’s pipeline systems.
The critical data includes basic pipeline data, historical failure data, cost data (pertaining to the costs of inspection, repair and mitigation activities) and inspection data.
Semi-quantitative risk assessment
PRIMS uses a semi-quantitative approach for pipeline risk assessment. The quantified data includes pipeline characteristics related to design, construction, operating pressure, failure histories and in-line inspections.
External and internal corrosion, construction errors, stress corrosion cracking, third-party intrusions, sabotage and pilferage are some of the threats considered in risk assessment. As part of risk assessment for PGB’s pipeline system, a score is assigned to each category of data on the basis of statistical analysis, the industry’s best practices and engineering judgements. Higher scores are indicative of higher risks. The scores are then combined to calculate each individual pipeline’s probability and consequence of failure and the pipelines are then given an associated risk number. The consequences of these failures are then measured using the scores. PRIMS can extract information from in-line inspection results and other assessment results and then apply it to the risk assessment calculations.
Cost-benefit analysis
PRIMS allows PGB to perform cost-benefit analysis to strategise and optimise preventive and mitigating actions. The risk reduction per Malaysian ringgit (RM) is calculated to obtain the highest benefit per RM ratio by integrating the cost data and risk assessment methodology.
PGB has also implemented a facility for tracking changes via the risk-tracking tool within PRIMS. This allows PGB to perform evaluations for tracking the reduction in a risk score for a specific interval by feeding additional information into the system as it becomes available and when the mitigation action has been undertaken. Comparisons can then be drawn between the risk charts to depict the risk reduction due to a specific action.
Defect assessment
Once integrity assessment is carried out, the information can be fed back into PRIMS. An assessment can then be done on the results using the ASME B31G or modified B31G method for metal loss defects. A standard criterion accepted by the industry is used to identify locations where existing dents can threaten the integrity of a pipeline. PRIMS uses BS7910 Level 1 to assess cracks.
The assessments are then used to determine places or locations that need repair and devise plans for taking preventive action. Once the repair is complete, PRIMS allows PGB to feed the repair information back into the system, indicating that the defect has been corrected and there is no threat to the integrity of the pipeline.
Corrosion growth
PRIMS is also equipped with a corrosion growth module that enables PGB to calculate the growth rate for external and internal corrosion with the following models:
- Full life rate for external/internal corrosion
- Half-life rate for internal corrosion
- The De Waard-Milliams equation for internal corrosion
PGB can apply these corrosion rates to detect growth on all the corrosion defects detected by the in-line inspection. It can also devise a corrosion management plan to better manage its pipeline operations.
Reporting
This module has been customised for the firm to generate excavation sheets and management reports based on corporate requirements. In addition, the inbuilt “query” function in PRIMS allows the extraction of pipeline information with ease. The database can also be filtered when a subset of data pertaining to specific pipelines needs to be evaluated.
Conclusion
PRIMS, the integrated PIM system used by PGB, can perform multiple functions like database storage and management; semi-quantitative pipeline risk assessments; defect assessments and repair plans for critical pipeline defects; and corrosion growth analysis for determining re-inspection and future repair plans. It also has a reporting module to produce low-level and high-level management reporting. Gas pipeline companies across the globe can take lessons from this to enhance their management of pipeline infrastructure.