Advantages of ball valves:
(1) Has low flow resistance (actually 0);
(2) Because it does not get stuck during operation (in the absence of lubricants), it can be reliably applied to corrosive media and low boiling liquids;
(3) Can achieve complete sealing within a large range of pressure and temperature;
(4) It can achieve fast opening and closing, and the opening and closing time of some structures is only 0.05-0.1s to ensure that it can be used in the automation system of the test bench. When quickly opening and closing the valve, there is no impact during operation.
(5) The spherical closure component can automatically locate at the boundary position;
(6) The working medium is reliably sealed on both sides;
(7) When fully open and fully closed, the sealing surfaces of the ball and valve seat are isolated from the medium, so the medium passing through the valve at high speed will not cause erosion of the sealing surface;
(8) Compact in structure and light in weight, it can be considered a reasonable valve structure for low-temperature medium systems;
(9) The valve body is symmetrical, especially the welded valve body structure, which can withstand the stress from the pipeline well;
(10) The closing component can withstand the high pressure difference when closed.
(11) The ball valve with a fully welded valve body can be directly buried underground, ensuring that the valve components are not corroded. Its service life can reach up to 30 years, making it an ideal valve for oil and natural gas pipelines.
Disadvantages of ball valves:
(1) Because the main seat sealing ring material for ball valves is polytetrafluoroethylene, which is inert to almost all chemicals, and has comprehensive characteristics such as low friction coefficient, stable performance, not easy to age, wide temperature range, and excellent sealing performance.
However, the physical properties of polytetrafluoroethylene, including its high coefficient of expansion, sensitivity to cold flow, and poor thermal conductivity, require the design of valve seat seals to revolve around these characteristics. So, when the sealing material becomes hard, the reliability of the seal is compromised.
Moreover, the temperature resistance level of polytetrafluoroethylene is relatively low and can only be used at temperatures below 180 ℃. Beyond this temperature, the sealing material will age. When considering long-term use, it is generally only used at 120 ℃.
(2) Its regulating performance is relatively inferior to that of a shut-off valve, especially for pneumatic valves (or electric valves).
Scope of application of ball valves:
Due to the fact that ball valves typically use rubber, nylon, and polytetrafluoroethylene as seat sealing ring materials, their usage temperature is limited by the seat sealing ring material. The cut-off function of a ball valve is achieved by pressing the metal ball against the plastic valve seat under the action of the medium (floating ball valve). Under a certain contact pressure, the valve seat sealing ring undergoes elastic-
plastic deformation in local areas. This deformation can compensate for the manufacturing accuracy and surface roughness of the ball, ensuring the sealing performance of the ball valve. Due to the fact that the valve seat sealing ring of a ball valve is usually made of plastic, when selecting the structure and performance of a ball valve, the fire resistance and fire prevention of the ball valve should be considered, especially in departments such as petroleum, chemical, and metallurgy. When using ball valves in equipment and pipeline systems with flammable and explosive media, fire resistance and fire prevention should be given more attention. Usually, in pipeline systems with dual position adjustment, strict sealing performance, mud, wear, contraction channels, rapid opening and closing action (1/4 turn opening and closing), high pressure cutoff (large pressure difference), low noise, air pockets and gasification phenomena, small leakage to the atmosphere, low operating torque, and low fluid resistance, it is recommended to use ball valves.
Ball valves are also suitable for pipeline systems with lightweight structures, low pressure cutoff (small pressure difference), and corrosive media. Ball valves can also be used in low-temperature (cryogenic) equipment and piping systems. In the oxygen pipeline system of the metallurgical industry, ball valves that have undergone strict degreasing treatment are required. When the main pipeline in oil and gas pipelines needs to be buried underground, full bore welded ball valves should be used. When requiring adjustable performance, a specialized ball valve with a V-shaped opening should be selected. In petroleum, petrochemical, chemical, power, and urban construction, metal to metal sealed ball valves can be selected for pipeline systems with operating temperatures above 200 degrees.