The Pipeline Drying and Dewatering Technology for Precommissioning Natural Gas Transmission Pipeline

This paper reviews many kinds of pipeline drying and dewatering technologies currently used for pre-commissioning natural gas pipelines, with cases, introduces two kinds of pig trains that can dewater with one pigging operation mode and its technical key points suitable for long distance pipeline as well as the dewatering methods that several pigs are launched with a certain time interval suitable for short distance pipeline or pipeline section. The principles, processes, advantages and shortcomings for the vacuum drying method, dry air pigging/drying method, and methanol pigging drying method that are mostly used at present are described. A suggestion to adopt dry air pigging method to Sebei-Ningxia-Lanzhou gas transmission pipeline are put forward. In the article, drying time required for some pipe section is predicted.