Overview of butterfly valve products:

With the development of China's infrastructure and the implementation of national large-scale projects, the number of valves in power, petroleum, chemical, and urban water supply and drainage systems is increasing, especially butterfly valves. Domestically produced metal hard seal butterfly valves can be divided into two types in terms of sealing structure, one is elastic hard seal structure, and the other is multi-level hard seal butterfly valves. The elastic production diameter in hard sealed butterfly valves is generally below DN500, and multi-stage structures are mostly used for large diameters. Butterfly valves below DN500 are the most commonly used, so users also encounter more problems when using them. Here is a summary of common problems and guidance for proper installation and use.

2、 Analysis and Problems of Elastic Structures

The structural hard sealing butterfly valve is composed of main components such as valve body, valve plate, valve stem, elastic valve seat, pressure ring, etc.

The structure and function of the pressure ring: The side of the pressure ring is the sealing surface of the valve body and pipeline flange as a sealing pair, and there are bolt holes on the side. The stainless steel butterfly valve pressure ring is fixed on the valve seat by bolts and connected to the valve body to form the total structural length of the valve.

Therefore, the diameter of the effective sealing surface will decrease due to the screw holes on the side of the pressure ring. From the perspective of the flanges used by users, they are mostly flat welded flanges, with an inner diameter and nominal diameter of 10-20mm larger. In this way, the effective sealing surface will be reduced. If the valve and pipeline flanges are not concentric during installation, they will be pressed against the bolt holes in a staggered manner. At this point, the bolt holes will be exposed on the inside of the pipeline flange.

The diameter causes water leakage here. The characteristic of leakage is that the medium flows out from the back of the pressure ring.

III. At present, there is no corresponding special standard for elastic hard sealing butterfly valve flanges in China. According to current national standards, the standard dimensions of flanges are the same, and socket type is used. The inner diameter of the flange is basically the same as the nominal diameter to increase the effective sealing surface, provide good convenience for installation, and ensure the normal use of the valve.

This reminds users that when using elastic hard seal butterfly valves, the matching mating flange must be a special flange, especially the pipeline flange that matches the pressure ring surface of the valve body.

IV. The arrow direction on the valve body refers to the pressure direction of the medium.