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Enagas uses air power to clean, test gas pipelines.

A large fleet of Atlas Copco air compressors is being used on Spanish gas pipelines for testing and cleaning purposes by International Testing Pipelines SA (ITP) as Enagas completes its latest sections on more than 10,000 km of mains pipeline.

Enagas, the Spanish national gas company, has laid a main gas pipeline network of 10,000 km during the past 30 years for residential, industrial and power plant users across the nation, with ITP undertaking the pipeline services.

The most recently completed sections include the Huelva-Sevilla-Madrid gas pipeline over a distance of 600 km and the 100-km gas pipeline Tivissa-Arboc, both projects of Enagas, and the Reganosa Gas Pipeline Project Mugardos--As Pontes--Guitiriz.

Based in Tarragona, ITP has been responsible for pressure testing, cleaning drying and inspections during the test phase and support services over large sections of the pipeline.

Performing a critical role in many of these activities, ITP has been relying on its large fleet of Atlas Copco air compressors which includes seven XRVS 466s, two XRVS 455s, four XAS 555 MDs, plus a XAS 36 YD, a XAS 65 DD, a XAS 175, A XAH 175 and a XAS 495.

The high-pressure compressors are used to overcome the hydrostatic pressure during the dewatering phase while the low-pressure units are used to clean the pipeline.


Prior to flooding, the pipeline has to be cleared of contaminates. Air pushes a pig via water through the pipe to remove all unwanted material such as deposit and debris from the pipeline. The magnetic pig is specially designed for pipeline magnetic cleaning, removing particles as screws and bolts, wires, electrodes, etc. The cleaning of the pipes is performed by Atlas Copco compressors operating at 7 bar and 1,000-1,500 liters/sec.

Pressure Testing

All types of pipelines are pressure tested with water or air. ITP uses water at 130 up to 140 bar. Pressure testing can be divided into two parts: a strength test, and a leak test. Each pressure test is based on section details such as minimum and maximum pressure and the yield strength of each point.


As every 10 meters of vertical height increase, 1 extra bar is needed to overcome the hydrostatic pressure, for dewatering compressed air is brought up to 90 bar.

Electronic Geometry Survey

The electronic geometry survey usually requires low-pressure compressed air at a high volume to move the pig at a good speed. The pig mechanically records internal geometry variations such as dents and ovalities.

All parameters are recorded and documented.


After dewatering, any water remaining in the pipeline has to be removed. Otherwise, it could accumulate into pools or spread around the pipe wall. Appropriate pigs and foam pigs are propelled through the pipeline until these are received in a dry state and the required dew point is achieved of the air in the section. During the air-drying operation, dew point readings are recorded.

For the drying phase, air quality is important. It is performed with the use of an after cooler and filters. The dew point is at--70[degrees] Celsius (-94 F).

In addition to operations in Spain, ITP is providing services and equipment for hydrostatic pressure testing, pig survey and drying activities on BP's Azerbaijan-Georgia-Turkey gas pipeline. It has also undertaken pipeline services in Portugal, Algeria, Morocco, Chile, Yemen, Colombia, Brazil, France and Italy.
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Title Annotation:Empresa Nacional del Gas S.A.
Publication:Pipeline & Gas Journal
Date:Jun 1, 2007
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