Artikel 8 Pipa Bawah Laut

Pipelines Commissioning and Pre-commissioning

By definition, commission is a request to someone to perform a task (duty or mission).
The pipeline mission is to transport products safely, without failure or leak during the
design life. Commissioning (or startup) is to introducing the first product in the pipeline
system after the new system is installed. Prior to commissioning, the pipeline system
needs to be checked for cleanness, structure strength, leak proof, etc. These actions
are called pre-commissioning which include;

• Debris removing, cleaning, gauging, and flooding (watering)
• Hydrotesting and leak testing
• Dewatering and drying

After installation, pipeline should be checked for internally cleanness and free from
debris such as welding rods, tools, etc. After debris-removal pig runs, a wire-brush
cleaning pig should run to remove more stubborn debris such as mill scale, weld bead
slag, etc. After cleaning the line, the pipeline should be checked for the pipe ID
reduction due to dent or flattening (increased ovality), by using a guage pig. The guage
pigs are fitted with aluminum plate of which diameter is typically 95% of the minimum
pipe ID. Now the pipeline is ready for hydrotesting and should be filled with filtered
water with biocide or corrosion inhibitor (for a long flood time). Prior to water pumping, a
pig is placed in front of the water to ensure removal of all the air in the line. To save
offshore operation cost, the above steps could be performed simultaneously using a
series of pigs (pig train) while flooding the line.
Each pipeline system, such as pipe segments, jumpers and PLETs, are hydrotested at
factory or confirmed by structural integrity test (SIT) or factory acceptance test (FAT).
However, the overall pipeline system, after completion of transportation and
connections, should be checked for its structural integrity (hydrotest) and leak proof (leak
test). The hydrotest pressure is set to be no less than 1.25 times of the maximum
allowable operating pressure (MAOP) or no more than 90% of the pipe SMYS, for at
least 8-hour holding time. The gas riser needs to be hydrotested for at least 1.5 times of
the MAOP. The leak test can be done with 1.1 times of the MAOP, for at least 1-hour
holding time.
After successful hydrotesting or leak testing, pipeline needs to be dewatered before
introducing the oil or gas. Dewatering pigs (or pig train) is used to displace water
efficiently. Air drying or vacuum drying is required for dry gas pipelines, but not required
for wet gas or oil pipelines. If pipeline is dewatered using a nitrogen gas, there is no
need to dry the pipeline.
During commissioning, pigs (pig train) are located in front of the first produced gas or oil,
to remove remaining air in the line and ensure that the line is fully filled with the product.


Source: Lee, Jaeyoung. 2007. Introduction to Offshore Pipeline and Risers.