The pipe valve only plays the role of sending and receiving the pig when pigging the pipeline, and the pig is responsible for pigging and cleaning the pipeline.
The structural feature of the pigging valve is a new type of valve innovatively designed according to the structural principle of the T-type three-way fixed ball valve after modification and function increase.
The working principle of the pigging valve is to put the pig into the inner cavity of the pigging valve ball, and rotate 90% through the ball in the three-way valve perpendicular to each other. When the spherical channel and the pipeline channel are on the same axis, the pig is activated by the pig valve under the action of the fluid pressure in the pipeline.
According to different purposes, pigging valves can be divided into three categories:
1: Standard type (PC type)
The bore diameter of the sphere is approximately 25% larger than the inner diameter of the connecting tubing. One end of the aperture is equipped with a stop bar that allows media to pass but prevents pigs. When the pig is taken out and loaded, the liquid will be shut off for a short time.
2: Bypass type (Pb type)
When the transmission medium is not allowed to be cut off for a short time, the bypass pigging valve should be used. The ball is larger than the standard pigging valve, and the hole diameter and structure are the same as the standard pigging valve, but the total flow section of the two bypass channels in the vertical direction of the hole axis is about 25% of the valve hole diameter section. During the entire process of pig launching and receiving, fluid flow is not interrupted.
3: Isolation type (PS type)
The sphere's bore diameter is only about 3% larger than the inner diameter of the connecting tube. To minimize mixing of media upstream and downstream of the spacer ball, an additional seal is installed on the upstream side of the aperture baffle.
The pigging valve is actually a T-type three-way fixed ball valve, which is installed and used in long-distance oil and gas pipelines. Therefore, the design specification of the pigging valve complies with GB/T 19672-2005 "Technical Conditions for Pipeline Valves", GB/T 20173-2006 "Pipeline Inversion of Belt Conveyor System in Oil and Gas Industry" and API 6D-2008 "Pipeline Valves" Regulation. The design calculation method of the pigging valve is the same as that of the conventional fixed ball valve.
The pigging valve is a new type of valve designed and innovated on the basis of the structural principle of the fixed ball valve after improvement and function addition. It realizes the opening and closing of the valve through the 90°rotation of the ball, uses the double piston effect to realize the sealing, and is designed with double locking and discharge functions according to the characteristics of the ball valve, so that when the valve is fully opened or fully closed, the medium in the body cavity can be discharged . It inherits all the advantages of the trunnion ball valve and has the same adaptability as the trunnion ball valve. The side of the valve body is provided with a branch pipe perpendicular to the center line of the flow channel, and the branch pipe is provided with a quick-opening blind plate and a discharge valve, which is convenient for the pig to enter and exit the pig valve. One end of the spherical channel is provided with a stop strip, which can block the channel of the pig and allow the medium to flow.