PIPE PROTECTION FROM CORROSION UNDER THERMAL INSULATION

Abstract

Oil in the northern regions has a positive solidification temperature, so it needs to be heated to ensure pumping. Oil must have a high positive temperature along the entire pipeline length, which leads to a number of issues related to maintaining a positive temperature of oil in the pipeline along its entire length. Taking into account all the geological and climatic features of the Far North, for reliable and safe operation of the oil pipeline it is necessary to ensure the required temperature of the transported product, preventing pumping stops and preventing energy consumption overruns. During the operation of pipelines with thermal insulation, moisture is formed in the thermal insulation layer for a number of reasons. Water gets under thermal insulation in two ways: as a result of condensation or comes from the outside. In addition, the thermal insulation itself can absorb and retain water, which subsequently turns out to be under insulation. Condensation may occur when the operating temperature of the surface changes. Prolonged exposure to leaked or condensed moisture on the outer wall of the pipeline is the cause of corrosion under thermal insulation. The development of the process is quite complex, and has a number of features that distinguish it from conventional corrosion. The nature, speed and degree of damage to the surface are strongly influenced not only by the characteristics of the aquatic environment (hydrogen index, composition and concentration of dissolved electrolytes, etc.), but also by the ability of the insulating layer to release corrosive agents – chlorides and sulfates under the influence of water. Chlorides and sulfates are water-soluble substances, their aqueous solutions have high electrical conductivity, which increases the corrosion intensity. Also the features of moisture accumulation of thermal insulation, which directly depends on the microstructure of the material are important. During operation, the outer surface of the insulated pipelines is inaccessible for visual inspection without opening the insulation, and the beginning of corrosion in this case is difficult to determine, as a result, severe corrosion may occur with subsequent loss of integrity of the pipeline wall. The aggressiveness of the environment under thermal insulation is due to several factors: high temperature, the presence of moisture and chemicals. The problem of metal corrosion is considered to be one of the most significant in safe operation of industrial facilities, as well as reducing the damage to the economics and the environment. Corrosion protection under thermal insulation is a serious problem requiring special attention.