- Internal corrosion and Hydrogen Induced Cracking (HIC)
- Internal erosion
- External corrosion and bi-carbonate stress corrosion cracking
- Mechanical impact, external interference.
- Fatigue. E.g. sudden surges of pressure in the fluid
- Hydrodynamic forces
- Geo-technical forces
- Growth of material defects
- Thermal expansion forces
Environmental Impact Assessments (EIA)
- Survey and route selection
- Securing right of way (ROW)
- Site preparation
- Coating and delivery of pipe pieces at site
- Welding and stringing
- Inspection and Testing
- Laying of Stringed Pipe
- Mechanical Completion
- Site Restoration
Survey and Route SelectionThe selection of the route is done by taking full account of the associated risks, particularly safety and environmental risks, the accessibility for maintenance and inspection, topography, soil data, river crossings, road crossings as lots of surveys and analysis of possible routes based on maps, aerial surveys, satellite imagery, GPS (Global Positioning System) and other techniques.
Securing Right of WayFor the most part, cross country pipelines are not visible because they are located under the street or are buried in rights-of-way (ROW) secured by an easement. Easement implies right held by one person to make use of the land of another person for a limited purpose, right of way, license or permit.
Before a pipeline is constructed, ROW is obtained to secure the land rights necessary to construct, operate and maintain the pipeline. The ROW agreement restricts the landowner’s rights within the ROW corridor to uses that are compatible with the operation and maintenance of the pipeline.
The ROW width is normally 30 meters for construction and 15 meters for operation.
Site PreparationThe route is cleared of trees and plant life, the topsoil removed and all material stockpiled for re-instatement (clear and grade). Pipe is delivered by truck and laid along the route.
Coating of PipelineExterior of pipes is generally coated at the shop or site. But at the time of stringing coating may be partly damaged. The coating is repaired and welded joints are freshly coated for corrosion protection.
StringingThe pipelines themselves are fabricated from 12 metre pipe lengths. They are then welded into 250 metre lengths, known as strings. The pipe is then lowered into the trench. Backfill material is added beneath and around the pipe to secure it in place.
When the pipe is converted to a depth of at least one meter, restoration of the area begins.
If necessary, the pipe is bent to follow the natural contour of the land. Welds are stringently tested to ensure with integrity. This is done while laying the pipeline in a string.