Russia | External coatings Yarudeiskoye fi eld gas pipeline.


For both buried and overground heat-insulat- ed pipelines, 3LPE is the preferred coating technology together with a factory-applied insulation layer of PU foam. The


insulation is typically protected with an outer layer of zinc galvanized steel (with a 3LPE coating applied to the zinc galvanized steel for underground applications).


<30 years 38.0%


Offshore pipelines are estimated to account for less than 1% of the total Russian oil and gas pipeline sector. The best known are the two 1,200km Nord Stream pipelines under the Baltic Sea, and the 400km section of the Blue Stream and 160km section of the Dzhubga – Lazarevskoye – Sochi pipelines under the Black Sea. 3LPP is the preferred coating solution for offshore applications in Russia.


Field-applied coatings in use in Russia include hot


Heat shrikable 3LPE sleeves are the most common girth weld protection option in use in Russia


and cold applied polymer bituminous coatings (which will be discussed later in this article), butyl rubber tapes (no longer used by either Gazprom or Transneft but still employed by some smaller companies), and liquid coatings such as FBE and PU. With 3LPE coatings dominating the Russian oil and gas pipeline sector, it is little surprise that the main girth weld protection option is heat-shrinkable 3LPE sleeves. A limited, and declining, amount of mastic- backed PE sleeving is also used, while some heat-insu- lated pipe girth protection systems combine 3LPE with a PU layer and coated zinc steel external protection. The greater part of Russia’s oil and gas pipeline


network was constructed during the 1960s, 1970s and 1980s. It is estimated, for example, that one third of the country’s oil trunkline network is between 20 and 30 years old, around one third older than 30 years and only one third is younger than 20 years. In the gas sector, Gazprom’s data shows just 25% of its gas trunkline (by


<21-30 years 36.7%


<10 years 13.2%


<11-20 years 12.1%


Age of Gazprom gas trunklines (%)


Source: Gazprom


length) is less than 20 years old while 38% is more than 30 years old. As a result, both the major network operators are investing considerable sums in pipeline repair and maintenance programmes; in 2012 Gazprom allocated RUB23.6bn (€590m) in upgrading its gas transmission network. Gazprom will replace coatings in the fi eld where the


protective function has been impaired by damage but the underlying steel is in good condition. The pipeline will usually remain in operation during the repair process, although operating pressures are reduced over the repair period. A typical replacement will use a hot applied coating process comprising: excavation of the pipe; removal of the old coating; cleaning of the metal surface, application of bituminous primer; application of hot glass fi bre-containing mastic; application of a top layer of crosslinked PE tape; reburial of the pipe. Hot coating repairs can be made at a rate of between 300m and 700m per shift, depending on the pipe diameter. It is Gazprom’s most commonly used in-fi eld repair method but cannot be applied in all situations - it cannot be used on pipes running at a high inclination, for example. In such cases, slower cold applied methods are used (cold application takes around twice as long per linear metre). Gazprom’s cold application method follows the same


process up to the point of primer application. However, the hot applied mastic is substituted with a cold-applied glass fi bre reinforced mastic tape installed by winding with a 50% overlap and topped with a mastic-coated PE tape.


These in-fi eld coating repair processes are defi ned by the Gazprom’s VNIIGAZ technical institute and have been in use in Russia for around a decade. It is estimat- ed that Gazprom reinsulates around 700km of gas pipeline each year, mostly 48 and 56-inch diameters. Looking specifi cally at Transneft’s oil trunkline


32 PIPELINE COATING | May 2014


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