PIPE MAINTENANCE
Since oil and gas pipelines are an important asset of the economic development of almost any country, it has been required either by government regulations or internal policies to ensure the safety of the assets, and the population and environment where these pipelines run.
Since oil and gas pipelines are an important asset of the economic development of almost any country, it has been required either by government regulations or internal policies to ensure the safety of the assets, and the population and environment where these pipelines run. Pipeline companies face government regulation, environmental constraints and social situations. Government regulations may define minimum staff to run the operation, operator training requirements, pipeline facilities, technology and applications required to ensure operational safety.
For example, in the State of Washington it is mandatory for pipeline operators to be able to detect and locate leaks of 8 percent of maximum flow within fifteen minutes or less. Social factors also affect the operation of pipelines. Product theft is sometimes also a problem for pipeline companies. In this case, the detection levels should be under two percent of maximum flow, with a high expectation for location accuracy.
Various technologies and strategies have been implemented for monitoring pipelines, from physically walking the lines to satellite surveillance.The most common technology to protect pipelines from occasional leaks is Computational Pipeline Monitoring or CPM. CPM takes information from the field related to pressures, flows, and temperatures to estimate the hydraulic behavior of the product being transported. Once the estimation is completed, the results are compared to other field references to detect the presence of an anomaly or unexpected situation, which may be related to a leak.
The American Petroleum Institute has published several articles related to the performance of CPM in liquids pipelines. The API Publications are:
- RAM 1130 – Computational pipeline monitoring for liquids pipelines
- API 1149 – Pipeline variable uncertainties & their effects on leak detectability
Where a pipeline containing passes under a road or railway, it is usually enclosed in a protective casing. This casing is vented to the atmosphere to prevent the build-up of flammable gases or corrosive substances, and to allow the air inside the casing to be sampled to detect leaks. The casing vent, a pipe protruding from the ground, often doubles as a warning marker called a casing vent marker.
Implementation
Pipelines are generally laid underground because temperature is less variable. Because pipelines are usually metal, this helps to reduce the expansion and shrinkage that can occur with weather changes. However, in some cases it is necessary to cross a valley or a river on a pipeline bridge. Pipelines for centralized heating systems are often laid on the ground or overhead. Pipelines for petroleum running through permafrost areas as Trans-Alaska-Pipeline are often run overhead in order to avoid melting the frozen ground by hot petroleum which would result in sinking the pipeline in the ground.
Maintenance
Maintenance of pipelines includes checking cathodic protection levels for the proper range, surveillance for construction, erosion, or leaks by foot, land vehicle, boat, or air, and running cleaning pigs, when there is anything carried in the pipeline that is corrosive.
