Construction steps
The construction of a large gas pipeline is a complex job. Imagine a moving assembly line. Experienced contractors with specialised teams are responsible for building the various pipeline lots / sections.
Here’s a step-by-step guide of how the Trans Adriatic Pipeline is being constructed.
1
Survey
Detailed environmental surveys for possible archaeological findings are conducted to determine the most suitable construction techniques.
2
Clear and grade easement
A 38 meter ROW (Right of Way) is cleared and graded along the pipeline route. The top soil is stored at the edge of the ROW for later reinstatment.
3
Stringing and bending
The 48 inch steel pipes are hauled by truck to the easement. The pipe are laid end-to-end. The pipe can be bent using specialised equipment to match changes in terrain or direction in route.
4
Welding and X-ray / ultrasounds testing
The pipe is welded above ground. All the welds are subject to automatic testing to ensure they meet national and international standards.
5
Weld joint coating
Each weld is grit blasted and covered with a protective coating to prevent corrosion and protect against mechanical impacts.
6
Trenching
A trench is dug for the pipeline. The top soil is placed separately for the reinstatement.
7
Lowering in
Side boom tractors are used to lower the welded pipe into the trench. Generally, up to one kilometre of pipe is lowered into the trench at a time.
8
Tie-ins
A tie-in is carried out when two lowered-in pipe strings are weleded together in the trench.
9
Padding and backfilling
Fine soil is placed around the pipe in the trench to act as padding, protection the pipeline. After padding is completed the trench is backfilled and compacted with the subsoil and original topsoil.
10
Pressure testing
The integrity of the pipeline is further verified using hydrostatic testing. The pipeline is capped with test header and water is pumped to a pressure higher than the maximum allowable operating gas pressure.
11
Reinstatement
The ROW is restored to its original state as much as possible. Where required, erosion control mechanisms are constructed and additional topsoil is spread to encourage soil retention and vegetation growth.
12
Signage
As a safety measure, signs (marker posts) are erected to warn of the location of the buried pipeline. Also cathodic protection wherever is needed.
