A pipeline replacement and repair method for the gas pipelines in the areas with deficient liquid nitrogen resources

When a long-distance gas pipeline is replaced or repaired by means of traditional methods, abundant liquid nitrogen is demanded. In some areas and countries where natural gas pipelines are located, the liquid nitrogen resources are deficient and cannot satisfy the demand of pipeline replacement and repair. To deal with this situation, a new emergency repair method for long-distance gas pipeline was researched and developed in this paper. The methods commonly used for replacing and repairing long-distance gas pipelines were overviewed, and a new pipeline replacement and repair method was proposed, i.e., double-capsule process. This method is the modified version of large-vent nitrogen replacement process by adding the lower capsule process to realize local isolation. This method has been successfully applied to a great number of practical operations and emergency repairs and has good effect. To sum up, this method is completely suitable for the gas pipeline replacement and repair in the areas with deficient liquid nitrogen resources. It plays an instructive role in the emergency repair of pipelines locating in the areas with deficient liquid nitrogen resources so as to save operation time and ensure operation safety.