There are about 2 million kilometers pipelines installed worldwide with 10% offshore. Nearly 50% of these are in the USA and Canada, where they are used for transporting gas, crude oil and products. The majority (close to 75%) of pipelines worldwide transport gas.
A pipeline system is mainly composed of:
Other components include:
- Cathodic protection system - Required as a backup to the external pipeline coating to prevent external corrosion of the pipeline
- Overpressure protection system - Required to protect a pipeline when the maximum pressure which may be generated by an upstream facility is such that it results in a pipeline pressure in excess of MAIP (Maximum Allowable Incidental Pressure). May take the form of relief valves or an instrumented high integrity pressure protection system (HIPPS).
- Telemetry system - Required to permit pipeline monitoring and remote operation from a central location.
- Leak detection system - The requirement for and the type of leak detection system should be derived from an evaluation of the criticality of the pipeline with regards to the consequence of a leak. This will depend on the transported fluid, the potential amount released, the sensitivity of the environment and, for onshore pipelines, the location class.
Pipeline cost typically includes:
- Right of Way
Pressure rating is calculated based on Barlow's formula.
All metallic buried pipelines need to be coated externally by a suitable anti-corrosion coating, supplemented by cathodic protection. The type of coating depends on operating temperature. Common coating types are Polyethylene (PE) and Fusion Bonded Epoxy (FBE) which may be used up to 60ºC and 70ºC respectively. Some higher temperature coatings are available but at significantly increased cost . For offshore applications, asphalt enamel corrosion coating is often used, especially in combination with concrete weight coating.
The performance of any particular coating system is directly related to the conditions encountered during the transport and storage of the pipes, their installation and the operational life of the pipeline system, e.g. type of transport (rail, barge, etc.), duration and conditions of storage, pipeline terrain, operational temperatures, backfill and soil conditions. Therefore, before any pipeline coating selection is initiated it is imperative that the environmental and construction conditions of the pipeline are well understood. A coating system, with known and identified characteristics can then be matched to the need of a specific project.