Safety must be the top priority for any company in the pipeline industry. If a lapse in safety protocol occurs, the resulting failures in pipeline systems can lead to catastrophic events and severe environmental and public safety ramifications. One of the most intrinsically difficult aspects of ensuring pipeline safety is the fact that most are installed underground. As a result, the verification process is significantly more cumbersome as it is not possible to visually inspect the pipe without excavation.
Companies utilize integrity digs to give pipeline operators an up-close view of the pipeline to determine if a repair or replacement is required. This process ensures a pipeline is operating in a safe, reliable and sustainable manner and begins when a routine inspection detects something out of the ordinary . As integrity digs require pipeline exposure, it is critical to determine the exact location of the defective section of pipe before beginning repair.
Why Integrity Digs are Required:
- Monitoring and Leak detection
- Ensuring adequate construction and design
- Verification of coating and structural integrity
How to Determine Where an Integrity Dig is Required:
Typically, integrity digs are completed after an in-line inspection (ILI) tool has passed through the internals of a pipeline. These ILI’s are equipped with complex and highly sensitive sensors that can detect and provide precise locations of imperfections and fluctuations in the pipe wall thickness. Upon review of the ILI tool findings, the imperfections will either be noted as an area of concern and monitored for propagation or action will be taken to initiate an integrity dig.
How are Integrity Digs Performed:
- Perform a pipeline inspection via ILI tool.
- Determine where along the pipeline the area of concern is and coordinate with landowners to ensure access.
- Where possible, in keeping with good ground disturbance practice, verify precise location of the pipeline using “daylighting” technique, typically with hydrovac machinery.
- Strip the topsoil nd subsequent layers of earth using machinery. It is important to ensure these layers are preserved and kept separated as they will be reused upon completion of the integrity dig to refill the hole created, and permit viable establishment and regrowth of natural vegetation.
- After the top layers of earth have been removed, the pipeline is exposed carefully using hand tools to ensure no damage is done to the pipeline or coating by the larger machines.
- Once the pipeline has been exposed, the outer protective coating is removed to visually inspect the metal piping.
- Finding the imperfection may not be possible visually, therefore additional methods are used, such as (but not limited too); water and magnets, ultrasonic tools and other means of non-destructive examination.
- Once the imperfection is found, the pipeline can be repaired. The most common type of repair involves a “sleeve” to be placed over the section and welded to the pipe. The sleeve acts as a reinforcement over the area to prevent leakage. Many new products have evolved in recent years in addition to weld on sleeves for “in service” repair of operating pipeline, giving owners a significant range of choice depending on their needs. If the pipe has been seriously damaged, the entire section may be cut out and replaced with new piping.
- After the welding has been completed, the pipe section will be pressure tested and inspected for quality to ensure the issue has been mitigated.
- Once the pipe has been fixed, the protective coating is reapplied.
- After the repairs have been completed, the exposed pipeline is backfilled with the same material and in the same order as in the exposure stage, and the dig site is revegetated to its natural state, completing the process.