Description

A cleaning pig is an instrument that uses fluid pressure to push through a pipeline for pigging, measuring, probing, or other purposes. The cleaning pig is originally a leather disc piston, which can scrape the wax on the wall of the running pipe and significantly improve the flow of the pipeline without increasing the power. The cleaning pig can also be used to remove debris and water in the new pipeline and improve the reliability of the pipeline operation. Therefore, the pigging technology and its tools have been attached to importance by the petrochemical infrastructure and pipeline production departments.

Cleaning and maintenance of pipes are very important. The role of pigging includes increasing flow, improving production efficiency, reducing internal corrosion, safe production, reducing maintenance costs, extending the service life of the pipeline, etc., and its purpose is to reduce costs and improve earnings. The specific functions of ordinary pig mainly have 4 aspects: pipeline sweeping, rust removal, drying, plugging, and replacement; Wax removal, scale removal, water removal, and dust removal of pipelines in the production process of oil fields; Isolation of different media; Anti-corrosion coating in the pipeline.

Pipe cleaning by pig relies on the pressure of the fluid in the pipe to be cleaned or the water pressure or air pressure provided by other equipment as a power to push the pig forward in the pipe, scrape the dirt on the pipe wall, and push the dirt and debris accumulated in the pipe out of the pipe. The cleaning pig in the pipeline forward is driven by the front and back pressure difference, there are two specific driving methods. One is to use the back pressure of the fluid as the driving force for the pig to travel and remove dirt in the pipeline in front of the pig during propulsion. This method is suitable for cleaning shorter pipes. The other is to use the pressure generated by the fluid leaking from the perimeter of the pig so that the dirt attached to the wall of the pipe is powdered and expelled. This method is more suitable for the cleaning of long pipes.

Pipeline pigging operations are mainly divided into new pipeline production pigging and operating pipeline pigging. For the new pipeline put into operation, the pig can be used to remove the burrs, iron filings, welding rods, stones, and other debris left in the channel. After the pipeline pressure test with water, the pig can be used for drainage and drying. The pigging operation of the running pipeline can remove the water and wax in the channel, improve the quality of the medium transported by the pipeline, and reduce the pressure consumption between stations. Intelligent pigs can be used to detect pipelines, including measuring pipeline corrosion, pipe wall cracks, pipe deformation, etc., to provide guidance for pipeline maintenance and repair so that the pipeline can operate safely and efficiently.

Working principle and advantages of cleaning pig

The working principle of the cleaning pig is to put the cleaning pig into the pipe to form a seal and use the pipe transport medium to push the pig (ball) forward, and then achieve the purpose of removing the sediment in the pipe, scale, and wax on the pipe wall. The cleaning pig can carry out the pigging operation of large pipe diameter, long distance, and solvent-insoluble dirt pipelines. It has the advantages of convenient operation, simple equipment, short time consumption, no pollution, and no stopping production.

Cup pig

The main structure of the cleaning pig consists of a steel shaft and a rubber bowl. In order to achieve different pigging purposes, other components can be added to the steel skeleton, such as wire brushes, strong magnets, etc. Features of the cup pig: It is not easy to stall when passing the 90° elbow with a curvature radius greater than 2D or 2.5D and the orthogonal reducing tee of the stop bar (D is the curvature radius of the pipe elbow); Can carry out the long-distance pigging operation, can continue to use after replacing the cup; Good sealing performance, the cup pig can not only clear the liquid in the pipeline but also clear the solid impurities; Easy to operate and maintain.

The ordinary cup-cleaning pig is composed of a cup, a measuring disc, and a steel skeleton. The cup is made of polyurethane material with an interference volume of 3% ~5%. It is divided into a straight plate type cup and dish-shaped cup, and divided into a guiding bowl, sealing bowl, and isolating bowl in function.

The steel brush bowl pig is a steel brush or nylon brush installed on the steel skeleton, using its toughness to exert shear force on the inner wall of the pipe, which can remove hard dirt on the pipe wall, such as rust and calcium deposits.

The bidirectional pig is composed of a metal tubular skeleton that is connected by a skin bowl and a skin bowl and can place the transmitter, and its shape is a column. Due to the high elasticity of polyurethane rubber, good wear resistance, moderate hardness of the leather bowl, and the steel skeleton connection between the two leather bowls, its hardness, wear resistance, and sealing are better than the pig ball and foam pig. Therefore, when encountering blocky or flat solid objects, it can push the objects forward together under a certain pressure difference and can maintain a more uniform speed.

The principle of bidirectional pig-pushing pollution is: that the interference amount is not large (about 4%), and the pressure difference between upstream and downstream makes the leather bowl open and scrape away the dirt. When the current back pressure difference is about 40kPa, the leather bowl can be pushed forward. The number of leather bowls is generally at least two, that is, double-layer sealing, not easy to gas, two sections of leather bowls form two sealing rings, each section of the leather bowl is supported by the pressure plate flange and fixed on the skeleton, increasing the pressure resistance of pushing dirt. When the skirt is damaged, it can be automatically compensated; When the cup is damaged, it can be removed and replaced. Under normal circumstances, the pig can be replaced once.

cleaning pig