Process in Pipeline Construction
The pipeline construction process is divided into three phases: pre-construction, construction and post-construction. It is a highly-coordinated, well-planned operation by a large team of experienced professionals.
1.1. Engaging landowners
Teams are in contact with landowners and other stakeholders for months, or even years, in advance of construction, to keep them informed. Communication continues throughout the construction and post-construction process. Construction is planned in such a way to create the least disruption for landowners and wildlife.
1.2. Surveying and staking
Survey teams travel the pipeline route to stake the right-of-way and temporary workspaces. The right-of-way is the area where the pipeline will be buried, as well as where construction activities occur. It can be up to 40 metres wide.
1.3. Preparing the right-of-way
Clearing crews enter the right-of-way to limit the amount of vegetation and structures in the area. In cultivated areas, the top soil (the top 15 to 25 cm containing the organic material that supports vegetation) is carefully removed and set aside, as it will be replaced during reclamation. The depth and type of top soil is identified and recorded during the environmental assessment by the survey crew. All soil layers are segregated so they can be replaced in the same order.
1.4. Digging the trench
Machines create a trench precisely the width and depth necessary for the type of pipeline being built to minimize the disturbance. The equipment used to dig the trench varies depending on both the type of soil and trench required. The trench digging crews move quickly, sometimes covering several kilometres in a day.
1.5. Stringing the pipe
Teams re-stake the center of the trench area and lay out individual lengths of pipe, which have been brought in from nearby storage areas and carefully placed end-to-end along the right-of-way. To maximizing strength and safety, every element is focused on, including the type of steel used, the thickness of the pipe and the corrosion-resistant coatings. The pipe is precisely designed for the conditions it will be exposed to.
2.1. Welding the pipe
The pipe sections will be joined together through welding. Welding shelters are sometimes placed over pipe segments so welders can fuse the segments together while protected from wind or weather. Welders use techniques to make the points where the pipes connect even stronger than the steel in the pipe. Each and every weld is inspected using an X-ray or ultrasound, and is 100% certified.
2.2. Bending the pipe
Pipe-bending machine may be used to match the contours of the land. It’s a gentle and gradual process that retains the strength and shape of the pipe, but allows the operator to follow the safest, most responsible route.
2.3. Pipeline Coating
Special coatings are applied to the pipe during the manufacturing process to prevent corrosion. The coatings are formulated to actually bond to the molecules in the steel, creating a powerful shield. The protective coatings are precisely designed for the conditions outside the pipeline. In cases where internal coating is needed to reduce friction, the lining is adhered to the pipe during manufacturing and the welded joints are coated at the site.
2.4. Pipeline Positioning
The welded pipeline is then gently lowered into the prepared foundation of the trench. Bulldozers using cranes called side booms carefully place the pipeline into the prepared trench bed. The side booms are designed to prevent damage to the pipe and its exterior coating.
2.5. Installing valves and fittings
The shutoff valves and remote sensors are installed at this stage. The sensors will send information to the master control room on flow rate, pressure and temperature. This allows technicians to closely monitor the line. Special valves can quickly shut off the pipeline in case of emergency.
2.6. Restoring the site
Once the pipeline is in place in the trench, the topsoil is replaced in the sequence in which it was removed and the land is returned to its original shape. The process from staking the right-of-way to beginning restoration of the site can take place in as little as 10 days.
3. Post construction
3.1. Testing under pressure
The pipeline the undergoes a series of tests including pressure testing for a minimum of eight hours using nitrogen, air, water or a mixture of water and methanol. Results are analyzed and shared with the regulator prior to approval to open the line.
3.2. Remediating the land
Environmental experts like biologists and agrologists remediate the land with indigenous vegetation. Wildlife experts ensure no long-term impacts to animals have occurred. The operator begins a monitoring and remediation period of no less than three years immediately following the completion of initial right-of-way restoration. The three-year period ensures any impacts from construction can be identified and corrected.
3.3. Regulating every metre of the pipeline
Pipelines must follow rules detailing how pipelines will be built, operated and even retired – while always putting the environment and safety as their primary considerations. Pipeline operators follow high standards for pipeline materials and methods that are set by third-party organizations.
The content of this article is taken from web open source. The blogs are intended only to give technical knowledge to young engineers. Any engineering calculators, technical equations and write ups are only for reference and educational purpose.