Pipeline Integrity and Repair

As pipelines transport valuable and potentially dangerous products, it is essential that measures are taken to ensure the integrity of the infrastructure. One of the main threats to pipelines is corrosion, as soil contains aggressive, caustic elements.

During construction, a cathodic protection system can be installed to prevent corrosion and to maximise the asset’s life. Corrosion monitoring systems can also be put into place to obtain and analyse corrosion data vital for integrity management planning over a pipeline’s lifetime.

An internal corrosion inhibitor is a chemical compound that can be added to the pipeline product to reduce the pipeline’s corrosion rate. Vapour phase corrosion inhibitors are especially effective in the process of mothballing a pipeline, forming an inhibiting layer to protect the pipe until it is ready to be put into operation again.

Regular inspections of the pipeline are necessary to check that it has not incurred any damage over time. A direct current voltage gradient survey can locate coating defects as small as 3 mm in diameter in buried pipeline. The survey is performed by using special probes and electronics while walking along the pipeline’s route.

During the construction phase, holiday detectors can be used to identify any weaknesses in pipeline coating, while gas detectors allow for the safe detection of gas leaks once the pipeline is operational.

In the case that damage to the pipeline is identified, a number of repair solutions are available. Leak sealing clamps or repair sleeves can be attached to repair or reinforce a pipeline without discontinuing service.

With more serious degradation, it may be necessary to temporarily close off product flow in the pipeline, cut out the damaged section and replace it with new pipe, but in some cases, a technique called ‘hot tapping’ can be used to facilitate the repair a pipeline while it is live.

Hot tapping involves a welded or mechanical fitting and valve installed on an in-service pipeline. A section of the pipe wall is then cut out within the area covered by the mechanical fitting. The cut out section (or coupon) is removed via the newly installed valve.