The cleaning of the gas pipeline is an essential pipeline maintenance operation in the pipeline. Its main purpose is four aspects: first, to remove the fluid and sundries in the pipeline, reduce the friction loss and improve the transportation efficiency of the pipeline; second, to avoid stagnant water in low-lying areas; third, to remove the sediment and corrosion products of the pipe wall so that there is no additional corrosion electrode and reduce the loss under the scale; fourth, to carry out the inspection and isolation of liquid in the pipe.

This natural gas pipeline was put into operation in December 2014. As of the beginning of 2020, the pipeline has not been cleaned since it was put into operation, and the pipeline has passed through 1000 m river flow section and across many mountains, with a relative height difference of 300m..

1.Overview of the natural gas pipeline

The total length is 176 km, the whole line has 12 valve chambers. And the maximum height difference is 300 m, which has the characteristics of many crossing, long pipeline distance and large riverbed section.

2.Pig selection

The foam pig is generally made of polyurethane mould, and the surface is bonded with hard polyurethane strip or abrasive to improve wear resistance. The foam pig relies on the extrusion foam to contact the pipe wall to realize the waxing and sealing, and its sealing property is good. It relies on the pressure difference before and after the pipe cleaner to push the pig to run forward. It can pass through the pipe with less diameter change without being stuck or damaged by the pits in the pipe.

The mandrel cleaner is characterized by a mandrel in the middle, usually with two leather bowls at both ends, and a scraper or steel brush in the middle to remove impurities or dirt from the pipe wall. According to the structure of the central axis pipe cleaner can be divided into leather bowl pig, straight plate pig, wire brush pig and so on. Leather bowl pig has the advantages of good sealing, wear resistance and long service life. Straight plate pig can be used in both directions, and the decontamination effect is obvious. Steel wire brush pig can be used to remove thin and hard iron chips, calcium deposits and other pipe dirt.

According to the situation of the pipe, this cleaning operation selected the use of foam pipe cleaner, leather bowl pig, steel brush pig and caliper pig.At the same time, according to the characteristics of long time uncleaned pipe and long distance, a jet hole is processed on the pipe cleaner to help the pipe cleaner run. Its function :1. Through the back-end air flow to disperse the front-end impurity backlog, reduce the risk of block. 2. reducing the pressure difference before and after the pig makes the pig run too fast under the condition of large flow rate. As shown in the figure:

3.Results of clearance

Clear out black ash 20 KG, welding rod 10, wire shelf 1, steel debris 1, construction waste 1, the results of the pigging as shown above.