The ball valve, because its core component is spherical, realizes the switch of the valve by rotating the direction of the through hole of the ball, and has a wide range of uses.
1. Classification of ball valves
According to the structure: one-piece, two-piece, three-piece, the more pieces, the more convenient the maintenance and the higher the price.
According to the connection: flange, thread (screw), welding (butt welding, socket welding), clamp (quick assembly, mostly used for sanitary valves), by order (plastic ball valve).
① Flanges include RF flange (raised face flange), M face flange (convex face flange, used in high pressure environment), FM face flange (concave face flange, used in high pressure environment), FF face flange (full face flange) Flat flange, generally used below PN1.6Mpa). There is a waterline on the edge of the flange, and the waterline can be divided into three lines and multiple lines.
②The thread connection is generally smaller than DN100 caliber, and the threads include G thread (also known as PF thread, national standard), PF thread (American standard thread), NPT thread (American standard high temperature thread), R thread, RC thread, etc.
According to the position of the ball: side-mounted, top-mounted.
According to the channel: two-way, three-way (T-way, L-way), four-way.
According to working conditions: sanitary (half-inclusive, all-inclusive), non-sanitary.
According to the driving mode: manual, electric, pneumatic, gas-hydraulic linkage, electro-hydraulic linkage.
According to the fixing method of the ball: floating type, fixed type.
According to the valve manufacturing method: forging (forging molding, used for high-pressure ball valves), casting (silicone melt casting, composite casting)
By platform: high platform (ISO5211 platform), low platform.
According to standards: National Standard/GB, American Standard/ANSI, Japanese Standard/JIS, German Standard/DIN.
The main components of the ball valve:
Valve body: As the body of the valve, its volume and weight account for a large part of the entire ball valve. During pipeline transportation, the inner wall of the valve body will partly contact the medium. Therefore, when selecting the material, it is necessary to consider whether the valve body is used for the medium. The valve body has carbon steel (WCB), stainless steel 304 (SUS304, CF8), stainless steel 316 (SUS316, CF8M), duplex steel (2520) alloy steel and other materials to choose from.
2. Valve core: It is also the core of the valve, mainly including the valve ball and the valve stem. The valve ball is in direct contact with the medium most, so the selection of its material and the precision of processing directly affect the service life of the ball valve. Most of the valve balls are polished with high precision to reduce the damage to the sealing ring when it is rubbed against the sealing ring during the switch process, and it can be highly fitted when it is closed for complete sealing. The reason why the valve stem is called the core is because of its strength and precision, which directly determine whether the valve can be opened and closed. In addition, the valve stem will also contact a small amount of medium. The influence of The medium on the valve stem must be considered. The material of the valve core is equal to or higher than that of the valve. body.
Valve seat: In the ball valve, the valve seat is mostly called a sealing ring, and one is placed on the left and right sides of the ball. The quality of the sealing ring plays a decisive role in the sealing effect of the valve.
Can be divided into: ① soft seal (PTFE, RPTFE, PPL, PEEK)
②Hard seal (304, tungsten carbide alloy, ceramic)
3. The pressure of the ball valve:
Flange ball valve: national standard/GB, German standard/DIN, unit: Mpa (MPa), kilogram/KG (PN16/25/40/64/100);
American Standard/ANSI, unit: lb/LB (class150/300/600/900);
Japanese standard/JIS, unit: K (10K/20K)
Threaded/welded/clamp ball valve: 1000WOG/2000WOG (water, oil, gas)
4. The caliber of the ball valve: the flanged ball valve is generally from DN10-DN400, the threaded ball valve is generally from DN8-DN100, and it is rarely used if it is larger than DN50.