- Pipeline companies follow industry standards and best practices when constructing pipelines and applying protective coatings.
- Each stage of the construction process is overseen by regularly-trained and highly-qualified inspectors.
- Before it is placed into service, an assembled pipeline must still undergo pre-operational testing to ensure integrity.
How are pipelines constructed?
Prior to construction, pipeline operators must notify regulators of their plan and obtain all required permits and approvals to build new or expand existing pipelines.
Before the line pipe can be buried, the pipeline right-of-way must be cleared and prepared for construction. Once ready, the pipeline is carefully placed in a pre-dug trench or bored under waterways or roads. Operators work hand-in-hand with communities to minimize disruptions during the construction process.
Welds at the connection of pipe segments along the pipeline must be inspected for quality with x-ray or an ultrasonic scan. Welders and other construction personnel must demonstrate their abilities in field tests for certification before construction. After passing inspection, weld joints receive the same anti-corrosion protective coating as the pipe body received at the pipe mill. Operators further protect the pipe from corrosion by directing an electrical current on buried pipe in a process known as cathodic protection.
An assembled pipeline and its components such as valves, flanges and fittings must undergo pre-operational testing before it can go into service. Operators pump water into the pipeline and hold it at high pressure to demonstrate there are no leaks in the pipe or its weld joints. Requirements for the water testing must comply with federal regulations. Construction issues identified by the testing are repaired before the pipe is operational.
Each stage of this process is overseen by regularly-trained and highly-qualified inspectors who monitor compliance with the engineering plan, codes, permit conditions, landowner and easement agreements, and regulatory requirements.
After construction, the pipeline is covered and topsoil replaced.
The post-construction phase of any project addresses several aspects including restoring the surface of the land affected by any trenching.
Typical Pipeline Construction Sequence
Pipeline operators typically follow an eight-step process when building a new line.
Stage 1: Survey and Pre-Construction
- Crews begin by surveying the potential route.
- Narrow strips of land called rights-of-ways are acquired for installation of the pipeline and to host on-site construction activity.
- Pipeline right-of-ways are typically 25-150 feet wide.
Stage 2: Clearing
- The right-of-way is cleared of trees, brush and rock for construction activities.
- Topsoil is stockpiled for eventual reclamation.
- The right-of-way is leveled and graded to provide access to construction equipment.
Stage 3: Trenching
- A trench is dug with a trencher or backhoe.
- Depending on the terrain, this process may include boring under waterways, roads or railroads.
- Boring under obstacles is a process known as horizontal directional drilling (HDD).
Stage 4: Pipe Stringing and Bending
- Individual pieces of pipe are laid out end to end along the right-of-way.
- The pipe is bent to fit the terrain using a specialized hydraulic bending machine.
Stage 5: Welding and Pipe Inspection
- Welders join the pipes together using both manual and automated welding technologies.
- The welds are then inspected and certified by x-ray.
- Welded joints are coated with anti-corrosion materials.
Stage 6: Lowering Pipe and Backfilling
- The welded pipe is lowered into the trench using sidebooms, when valves and other fittings are installed.
- The pipe is padded using filtered native soil to keep rock from resting along the pipe.
- Topsoil is replaced in the sequence in which was removed and the land is re-contoured.
Stage 7: Testing
- The pipeline is pressure tested using water.
- Inspection tools are sent through the pipeline to ensure integrity.
- Any detected anomalies will be addressed before the pipe is put into service.
Stage 8: Restoration
- Temporary facilities are removed.
- All impacted land is reseeded for restoration.
- Pipeline markers are installed at each public road and railroad crossing and along the remainder of the buried pipeline.