Q: Butterfly valve structure and working principle? Answer:?
Butterfly valve, also called flap valve, is a kind of regulating valve with simple structure. It can also be used in the switching control mode of low-pressure pipeline medium. Butterfly valve refers to a kind of valve whose closing piece (valve disc or butterfly plate) is a disc and rotates around the valve shaft to open and close. It mainly plays the role of cutting off and throttling in the pipeline. The opening and closing part of butterfly valve is a disc shaped butterfly plate, which rotates around its own axis in the valve body to achieve the purpose of opening and closing or adjustment?

Leakage control technology and knowledge summary of non-metallic compensator
（1） Overview
In order to ensure the characteristics of large temperature variation, strong corrosiveness and irregular shrinkage of the desulfurization flue, non-metallic shrinkage joints are used in the selection of shrinkage joints. The non-metallic shrinkage joints are easy to manufacture, easy to construct on site and extremely low in cost. The non-metallic contraction joint is composed of skeleton and skin. The skeleton is made of 20 # channel steel, and the skin is composed of four to ten layers of fabric, which is then fixed on the channel steel with pressure plates and screws.
（2） Analysis of the cause of leakage
(1) Leakage caused by design defects