Ball valve is the most widely used mechanical product in all valve markets. It is mainly composed of valve body, valve seat, ball, valve rod and transmission device. The ball core is driven to rotate by the actuator to achieve the function of switch or adjustment. In chemical industry, environmental protection, water treatment, urban construction, machinery, including food and other industries, it is widely used and very popular!
There are many kinds of ball valves, which can be combined into various products with different functions through different structure, connection, pressure level, driving form, etc. However, from the most basic point of view, there are two kinds of differences between full bore ball valve and reduced bore ball valve. Generally speaking, when the inner diameter of the valve ball is less than or equal to 85% of the inner diameter of the ball valve port, it is called reduced bore ball valve, and when the inner diameter of the ball valve is greater than 95% of the inner diameter of the ball valve port, it is called full bore ball valve. So what are the differences between the two in selection or application?
1). The full bore ball valve is an equal width flow channel, that is to say, the size of the flow channel from the inlet to the outlet is the same, and its size cannot be less than the value specified in the standard, which is roughly equivalent to the nominal diameter of the specification. For example, the flow channel diameter of DN50 full bore ball valve should be about 50;
2). The inlet of the reducing ball valve flow path is wider than the flow path diameter, and the actual flow path diameter is about one specification smaller than this specification. For example, the flow path of DN50 reducing ball valve is about 38, which is about the same as that of Dn40. Shrink one specification within DN250 and two specifications within 250-600, and the above 600 shall be determined according to the actual situation.
2、 Applicable media:
1). The full bore ball valve is generally used for conveying viscous and slagging prone medium pipelines. Because of its small fluid resistance, it can be said that there is basically no flow resistance, and it is convenient for the regular paraffin scraper and blower to pass through.
2). The reducing ball valve is suitable for conveying gas or medium with physical properties similar to water, because its weight is about 30% lighter than the full diameter ball valve, and its flow resistance is only about 1 / 7 of the same diameter globe valve. It is beneficial to reduce pipeline load and cost.
3、 Applicable process:
1). For the pipeline requiring regular pigging, full bore ball valve must be used no matter what medium is transported. When the medium passes through the full bore ball valve, it will not reduce the flow, and the flow resistance is small, which is an ideal product for pipeline control, especially for the strict working condition. In particular, when the main pipelines in oil and gas pipelines need to be buried underground, full bore welded ball valves must be used.
2). The reducing ball valve is suitable for some working conditions with low requirements and small requirements for convection resistance. When the inner diameter of the valve is more than 80% of the inner diameter of the pipe end, there is little effect on the flow capacity of the pipe. Many valves have reducing diameter, which is generally controlled within 0.8. On the one hand, reducing diameter reduces the flow capacity of the valve, that is, the Kv value of the valve, increases the pressure drop at both ends of the valve, resulting in energy loss. For the pipeline, it has no great impact, or increases the flushing of the pipeline.
4、 Comparison of advantages and disadvantages:
1). Installation space: the volume of the reducing ball valve is small, so the requirement of its installation space is smaller. Because its weight is about 30% lighter than the full bore ball valve, it is beneficial to reduce the pipeline load, transportation load and cost.
2). Cost: the price of reducing ball valve is one grade lower than that of full bore ball valve. Considering the cost performance, it is generally defaulted internationally, and the same ball diameter valve body is adopted for the adjacent pipe diameter. For example, DN32 and Dn40, DN50 and DN63, dn90 and dn110, dn160 and DN200, DN250 and dn315 use the same sphere.
Note: due to the small inner diameter of the reducing ball valve and the small torque on the valve stem, it is more suitable to extend the service life of the valve switch. Especially the low torque design of large diameter valve. However, the reduction should not be much, otherwise the system resistance will increase. However, if not reduced, the first is to increase the purchase cost, and the second is generally to reduce the valve control characteristics, so that the adjustment effect is poor. For example, if the regulating valve is always used under small opening, the service life of the valve will be reduced.