Steps in pipeline contructions

Gas Pipeline Construction Activities

Clearing
Before any work begins and heavy equipment is brought in, the right-of-way have to be prepared by removing any trees, shrubs and vegetation.The width of the right-of-way are generally 50 and 100 feet, depending on the size of the line and terrain.

Grading
Grading is the process of providing a smooth and even working area to facilitate the movement of equipment onto and along a right-of-way. Top soil is removed and stockpiled on the right-of-way so as to minimize mixing of the topsoil with graded or excavated subsoil. Grading entails leveling, cutting, and filling.

Ditching
Ditching is the process of excavating a trench wide enough to contain the pipe and allowing the lowering in and backfiling activities The depth of the ditch varies depending on the amount of activity a location receives and is usually greater at railroad and highway crossings.

Stringing
Stringing is the process of delivering and distributing the line pipe where and when it is needed on the right-of-way. The stringing operation will include the loading of pipes onto stringing trucks at stockpile sites, transportation to the right-of-way, and distributing the pipes end to end along the work side of the trench.

Bending
Pipeline routes crossed a variety of topographical features ranging from flat to hills and mountain ranges. Bending allows the pipelines to conform to the contours of the terrain through wihich it passes, Various pipe bending process can be applied while maintaining roundness in the bending area.

Welding
Welding is the pivotal operation in pipeline construction. Every pipe will undergo various steps of welding process, x-rays and testings. The profiency in which it is accomplished largely determines the quality, safety and operational life of the finished pipeline.

Coating
Pipelines are externally coated to protect the pipes from corrosion. The primary function of coating is to prevent water from coming into contact with the steel of the pipe. The location of the pipeline in relation to buildings, population centers and soil type may require more durable and specialized coating in order to comply with safety regulations. Concrete coating will be in used in swampy areas or soil with high water table.

Lowering-in
Lowering-in of the pipe into the trench will be generally done using side booms working in tandem. Where the trench contains material that may damage the coating, the pipe will be lowered onto a bed of loose soil or sand.

Backfilling
The ditch is backfilled in a manner that provide for firm support around the pipes and that will not damage ither the pipe coatings or the pipes. On steep pipe trench grades, sand bags or foam barriers commonly known as "soft-plugs"acts as an impermearble barrier that will eventually prevent mud slides and wash out of the trench backfill.

Clean-up and Restoration

Restoration will entail compacting the trench backfill material, restoring the original ground contours, constructing water low control banks to limit water velocities across the restored surface to divert water away from the trench, respreading previously stockpiled topsoil, reseeding, and bruch spreading where appropriate. Regrowth of native flora will be promoted where possible. Trees and deep-rooted plants are not allowed. The right-of-way will be revegetated with approved cover crops maintained at acceptable growth rates to ensure adequate plant cover.

Source: http://www.petronasgas.com/Pages/Stepsinpipelineconstructions.aspx. Accessed by 24-1-2014