The metal hard seal butterfly valve can be divided into two categories from the sealing structure, one is the elastic hard seal structure, and the other is the multi-level hard seal butterfly valve. The production caliber of elastic hard seal butterfly valve is generally below DN500, and the multi-layer structure is adopted for large caliber. The use of butterfly valves below DN500 is large, so users will encounter many problems when using them. Here, we summarize the common problems and guide the correct installation and use.

由于多层软硬叠式密封圈固定在阀板上，当阀板常开状态时介质对其密封面形成正面冲刷，金属片夹层中的软密封带受冲刷后，直接影响密封性能。

Since multi-layer soft and hard laminated seal rings are fixed on the valve plate, when the valve plate is normally open, the medium will cause a positive flushing on its sealing surface, and the sealing performance will be directly affected after the soft seal belt in the metal sandwich is flushed.

受结构条件的限制该结构不适应做通径DN200以下阀门，原因是阀板整体结构太厚，流阻大。

Due to the limitation of structural conditions, this structure is not suitable for valves with a diameter below DN200, because the overall structure of the valve plate is too thick and the flow resistance is large.

硬密封蝶阀阀门不通。原因有：

The hard seal butterfly valve is blocked. The reasons are:

一、控制通道被杂物堵塞(通道细小，容易堵塞)。

1、 The control channel is blocked by sundries (the channel is small and easy to block).

二、活塞因锈渍卡在高位置；虽上部受力，但不能向下移动，打不开主通道。

2、 The piston is stuck at a high position due to rust stains; Although the upper part is stressed, it cannot move downward and cannot open the main channel.

所以，活塞减压阀前须安装过滤器；对于新安装或长期停用的减压阀，一定要拆开检查和清洗。

Therefore, a filter must be installed before the piston pressure reducing valve; The pressure reducing valve newly installed or out of service for a long time must be disassembled for inspection and cleaning.

三、因三偏心结构的原理，阀板的密封面与阀座之间的密封是靠传动装置的力矩使阀板压向阀座。正流状态时，介质压力越高密封挤压越紧。当流道介质逆流时随着介质压力的增加阀板与阀座之间的单位正压力小于介质压强时，密封开始泄漏。

3、 Because of the principle of three eccentric structure, the sealing between the sealing surface of the valve plate and the valve seat is made to press the valve plate to the valve seat by the torque of the transmission device. In the positive flow state, the higher the medium pressure, the tighter the seal extrusion. When the medium in the flow passage is countercurrent, with the increase of medium pressure, the unit positive pressure between the valve plate and the valve seat is less than the medium pressure, and the seal starts to leak.