Butterfly valve installation direction

Under normal circumstances, manual butterfly valves have no orientation requirement; however, if an orientation is indicated on the valve body, it must be installed in accordance with those indications. Manual butterfly valves are divided into single-direction sealing and double-direction sealing types. For those with double-direction sealing, there is no issue regarding the installation direction; therefore, arrows are usually not indicated on the valve ； For manually operated butterfly valves with one-way sealing, there are specific requirements regarding their installation direction. The arrow on the valve body should indicate the direction of pressure; in other words, the direction of the arrow shows the direction that facilitates sealing. For example, on the outlet pipes of multiple water pumps, the arrow on the valve body should point in the opposite direction to the flow of water, toward the pump – only in this way can sealing be improved.

The back side of the valve faces the direction from which the fluid comes; the pressure generated causes it to close more tightly as pressure increases, preventing any leakage. If the smooth surface faces the fluid, it is prone to internal leakage in the absence of external forces. Generally, the direction of the arrow on the valve body follows this rule. You might as well give it a try to find out.

Let’s not discuss the installation direction of butterfly valves for now; I’m referring to how the arrows on the valve bodies manufactured by valve producers are determined – whether there is any theoretical basis or logical explanation for this. Because I found that in our company, for single- and triple-eccentric flow arrows, the direction is from the back side to the smooth surface, but for double-eccentric cases, it is from the smooth surface to the back side.

So for our double-eccentric butterfly valve, the flow direction is from the smooth side to the back side. As you said, wouldn’t that make it difficult to achieve a good seal? How to explain it?

This post was last edited by CHANGBAISHI on 2018-10-6 at 09:30. First, explain to me what your “double-eccentric butterfly valve” looks like; send me a picture and then I’ll explain it to you. Discussion topics should be targeted, and questions should clearly refer to those topics to avoid accusations. Additionally, double-eccentric butterfly valves also have a directionality, which should be determined according to the markings on the valve body. Because the valve core connected to the valve stem shaft is not coaxial, it is offset. The contact surface of the valve port is also asymmetrical and offset. That’s why it’s called double eccentricity. Hehe, answering questions here comes with the risk of being criticized.

It’s not an accusation; I mean, isn’t it a contradiction? We discussed it together; I don’t quite understand it myself. Besides, the flow arrows in our unit may not necessarily be logical. This is a simplified diagram of double eccentricity that I drew – it should be understandable.

But your title is the installation direction itself.....