New Method Designed for Ballasting of Subsea Oil and Gas Pipelines

Subsea pipelines require ballasting, and concrete coating of previously insulated pipes is recognized worldwide as the most reliable ballasting method.

Yet, a new technology for pipeline ballasting has been devised by specialists of the Moscow Experimental Pipe Producing Plant (MTZK). 

The Russian Patent Office has already issued a patent for this technology. With the new technology applied, a previously insulated pipe is encased in a polyethylene or melallopolymeric casing, and a space between the pipe insulation and the casing is filled with a concrete grout. That is the main difference between the new method and a coventional ballasting technique (which involves spraying of a concrete grout, weight coating, etc.). The new technology, utilizing both concrete and polyethylene casing, may also be seen as an additional protective coating to enhance the reliability of both subsea pipelines and pipelines laid in water-saturated soil.

The plant has a complete package for coating pipes with all existing anticorrosion coats, as well as the equipment for manufacturing polyethylene casing. It makes easy and efficient pipe ballasting operations possible without heavy capital spending on specialized equipment.

Also noteworthy is that in the event of transverse movements of the pipeline, this ballasting coating has a sufficient design safety margin and streamline smooth surface (due to the polyethylene casing), and is shifted without actually changing its position in relation to the pipe, thus preserving the ballasting properties and preventing the pipeline from floating.

The MTZK-devised method makes it possible to ballast thermally insulated pipes with an installed heating system based on the so-called skin effect - while the conventional ballasting method cannot be used for such pipes. These types of pipes may be widely employed for constructing oil pipelines in the coastal (offshore) zone of the Arctic regions.

This ballasting method can be used for pipelines laid in water-saturated soil (marshland, high water beds, etc.), as well as for subsea pipelines. 
In November 2006, MTZK completed the supply of steel pipes (?– 820 ?… 20.5 mm) with ballasting coating for the construction of a 47.5 km pipeline in the Barents Sea. The execution of this order was supervised by Germanischer Lloyd, which certified the new method in accordance with applicable specifications and the GL Rules for Subsea Pipelines and Risers.

Up to now, MTZK has carried out extensive work to study the properties of pipes with ballasting coating. Presently, it is testing sample pipes to check shear and compression of the ballasting coating in relation to the pipe body and shift of the casing in relation to concrete. The company has also devised several options to seal the joints of pipes with ballasting coating that are curretly being patented.

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