By Ricardo Pires
Pipeline construction projects include new and expansion plans to mainly transport oil, natural gas and LNG. Operators and the “Majors” usually build pipelines using construction and service companies. Roughly 90% of pipeline jobs occur onshore with just 10% occurring offshore.
In the past, pipeline construction companies generally built pipelines and pipeline service companies provided the cleaning, testing, dewatering, drying, inspection, and coating services. Now those services are provided by either the service companies or the construction companies themselves.
These services require high flow air and can be either low or high pressure depending on the application and elevation of the pipeline. The larger the pipe diameter, the greater the need.
Pipeline projects can have a long sales cycle and may be delayed or even cancelled due to permitting, weather or construction delays. I will not go into detail on explaining the pipeline construction cycle and will jump directly to the 3 most common applications that typically happen during pre-commissioning, inspection and maintenance.
This process consists in removing large portions of water out of the pipeline. Usually a pig is sent through the pipeline driven by air to push the water out. High pressure compressors, boosters and related equipment need to be used. The maximum dewatering speed is defined by the customer and in many cases the customer collects the water for environmental reasons.
Usually after dewatering a pipeline, water still remains in the pipes. Dry air goes under pressure into the pipes to absorb the remaining water in the pipeline. Compressors and dryers with pressure dew points down to – 40 degrees F or even lower are usually provided to insure the shortest possible drying time.
Purging and inerting
These procedures are usually done in new natural gas pipelines. Nitrogen enters the pipeline by injection and the pipes are then safely purged of air. These procedures are essential. Not only do they displace the oxygen, but they also delay oxidation and avoid explosions by not allowing air and natural gas to mix in dangerous concentrations. Nitrogen generators with different flows and purities are matched with compressors and boosters to reach the desired Nitrogen pressure and flow.
If you are interested about reading about an innovative pipeline project and its use of air, please click here: http://www.atlascopco.us/en-us/Rental/news/customized-oil-free-hot-dry-air-solution-for-an-efficient-pipeline-drying-project