What are the respective advantages and disadvantages of rotary ball valves and butterfly valves?

Ball valves present the least resistance to fluids, while butterfly valves have greater resistance than ball valves. Due to structural considerations, ball valves have certain limitations in terms of diameter, while butterfly valves are suitable for larger diameters.

Comparison of performance advantages between butterfly valves and ball valves: First, in terms of flow capacity, ball valves have a better flow capacity than butterfly valves, as the valve disc and valve shaft present in the butterfly valve when it is open occupy part of the flow channel; the smaller the diameter, the greater the proportion of the flow channel that is occupied by these elements. II. In terms of operating temperature, due to the sealing materials and structure, ball valves are not suitable for use with steam media, whereas butterfly valves can be used with conventional saturated steam used in heating applications (below 350 degrees). III. From the perspective of the stress on the pipeline network, due to the structure of the valve, butterfly valves are able to withstand higher stresses. IV. In terms of service life, both ball valves and butterfly valves can achieve a long service life (over 15 years under normal use). However, in the sealing structure of ball valves, non-metallic materials play an important role, whereas butterfly valves utilize a metal-to-metal sealing mechanism; therefore, under normal circumstances, butterfly valves have a slightly longer service life. V. In terms of operating torque, since the butterfly valve is a three-eccentric metal-sealed butterfly valve, its opening and closing torque is very low. In contrast, as the diameter of a ball valve increases, the contact area of its sealing surfaces increases by a factor of two squared; as a result, the opening and closing torque of large-diameter ball valves is very high. VI. From the perspective of volume and weight, as well as ease of installation, valves below DN300 are preferable; valves above DN300 are lighter in weight and smaller in size. VII. In terms of sealing performance, ball valves outperform butterfly valves, as ball valves achieve zero leakage in both directions. The butterfly valve meets the two-way ANSI Class V standard (no visible leakage). Therefore, both are sufficient to meet the demands of the heating pipeline network, and they will not affect the normal maintenance and repair of the network. VIII. From a price perspective, ball valves with a diameter of DN250 and below offer better prices, while butterfly valves with a diameter of DN300 and above provide more favorable pricing. In summary, in conventional centralized heating piping systems, ball valves with a diameter of DN300 or less offer better cost-performance, while butterfly valves with a diameter of DN300 or more provide superior cost-performance. This is also the choice resulting from the many years of experience of most designers and users.

What I’m interested in is that type of rotary ball valve which looks very similar to a butterfly valve, except that the disc is different; it’s not a ball valve{:3_65:}

Is this not called a butterfly valve anymore? I'm sorry.

After observing the actual product, I found that the difference lies in the design of the butterfly plate; there’s also an additional sealing seat. I can’t see any other differences, but the price difference is significant. I think a three-eccentric hard-sealing butterfly valve can fulfill the same functions at a lower cost. So I’d like to know what advantages this rotary ball valve has to justify such a high price{:3_60:}

If there is no special purpose, when choosing a valve, it is better to focus on the manufacturer rather than the type.

I also think this appears to be a butterfly valve; could it be that the sealing surface is a spherical seal?

It didn’t seem like a ball valve; it was more similar to a butterfly valve