Pipeline infrastructure is a critical component of the energy sector, ensuring the safe and efficient transportation of natural gas, petrochemicals, and refined liquids. However, maintaining the integrity of these buried pipelines requires diligent monitoring, maintenance and regular inspections to identify potential threats and degradation mechanisms.
Among the various inspection methods, line walking surveys can detect issues that might not be apparent through other monitoring techniques. Here we outline the key points from UKOPA’s latest Good Practice Guide for those undertaking such surveys.
What is a Line Walking Survey?
A line walking survey involves physically walking along the route of a buried pipeline to establish the condition of the surrounding environment. This practice is particularly effective in identifying localised issues such as ground movement, shallow cover, or encroachments that could pose a threat to the pipeline’s integrity.
While other survey methods like aerial or overline inspections provide a broader overview, line walking allows for a close-up assessment that can reveal subtle changes and potential hazards that might otherwise go unnoticed.
Legislative and Standard Requirements
In the UK, the maintenance of pipelines is governed by the Pipelines Safety Regulations 1996 (PSR), which, while not specifying line walking as a mandatory practice, emphasises the need for regular maintenance and inspection to ensure pipeline safety.
Regulation 13 of the PSR mandates that pipelines be maintained in an efficient state and in good repair. This regulation underscores the importance of regular inspections, including line walking surveys, to validate and maintain pipeline safety.
Industry standards also provide guidance on the frequency and conduct of line walking surveys. For instance, the IGEM/TD/1 standard recommends that pipeline routes be walked at least once every four years unless a risk-based approach justifies a different frequency. Similarly, the ASME B31.8 and PD 8010 standards advocate for regular inspections, with a focus on identifying factors that could affect pipeline safety, such as third-party activities, ground movement, or environmental changes.
Risk-Based Approach to Line Walking
Given the varying environments through which pipelines traverse, a one-size-fits-all approach to line walking is not practical. Instead, a risk-based approach is recommended, where the frequency and focus of line walks are tailored to the specific risks associated with different sections of the pipeline. This approach considers factors such as the potential for ground movement, the proximity of the pipeline to populated areas, and the likelihood of third-party interference.
For example, pipelines located in areas prone to flooding, ground erosion, or significant human activity may require more frequent inspections. Conversely, sections of the pipeline in stable, less populated areas might be inspected less frequently. The risk-based approach ensures that resources are allocated efficiently, with more attention given to high-risk areas that are more likely to experience issues.
Preparing for a Line Walk
Effective line walking surveys require thorough preparation. Before setting out, inspectors must be well-versed in the pipeline’s route, the surrounding environment, and any known issues that could affect the pipeline. Health and safety considerations are paramount, as line walkers may encounter hazardous conditions or difficult terrain.
Inspectors should be equipped with the necessary tools to document their findings, such as GPS devices, cameras, and notebooks. They should also have clear guidelines on what to look for, including the condition of marker posts, signs of ground movement, and any new developments in the area that could impact the pipeline.
What to Look For During a Line Walk
During a line walking survey, inspectors should focus on identifying any signs of degradation or potential threats to the pipeline. Key areas of concern include:
- Marker Posts and Cathodic Protection (CP) Test Posts: These are critical for maintaining pipeline integrity. Inspectors should ensure that they are intact and, if appropriate, functioning properly.
- Signs of Ground Movement or Shallow Cover: Changes in the landscape, such as soil erosion or ground subsidence, can reduce the cover over the pipeline, increasing the risk of damage.
- New Developments: Construction activities or new buildings near the pipeline can pose a threat if not properly managed. Inspectors should be vigilant for any changes in land use.
- Third-Party Activities: Unauthorized activities near the pipeline, such as excavation or construction, are a significant risk and should be reported immediately.
Responding to Immediate Threats
If an immediate threat to the pipeline is identified during a line walk, the inspector must take prompt action. This could involve contacting the pipeline operator, stopping any nearby construction activities, or marking the area for further investigation. Quick response is crucial to preventing potential accidents or damage.
Post-Survey Actions
After completing a line walk, it is essential to document all findings comprehensively. This includes recording any issues identified, actions taken, and recommendations for further inspection or repair. Proper documentation ensures that all concerns are addressed and provides a record for future reference.
Line walking surveys are a vital component of pipeline integrity management. By allowing for close-up inspection of the pipeline and its environment, they help identify potential threats before they become critical issues. When combined with a risk-based approach, line walking ensures that pipeline operators can maintain their infrastructure’s safety and reliability, protecting both the environment and the communities that rely on these essential services.