1. The basic structure and working principle of butterfly valves
Butterfly valves are a commonly used fluid control valve, mainly composed of valve body, valve seat, valve disc and operating mechanism. The opening and closing parts of butterfly valves are butterfly plates. Its working principle is to control the flow of medium by rotating the valve disc, that is, when the valve disc rotates to a certain angle, the medium can pass through the flow channel between the valve body and the valve seat to achieve the purpose of controlling the flow. Butterfly valves are widely used in gas pipelines and waterways in metallurgy, light industry, electric power, petrochemical systems, etc. According to the different designs of the pin shaft, butterfly valves can be divided into two types: with pins and without pins.
2. The difference between butterfly valves with and without pins
From the appearance, the most essential difference between pinned butterfly valves and pinless butterfly valves is whether there is a conical pin positioning on the valve plate. The connection method of penetrating the valve plate and the valve stem with a pin is a pinned butterfly valve, and vice versa is a pinless butterfly valve.
① Structural differences
The pinless butterfly valve has a relatively simple structure. It combines the valve disc and the valve stem into one, without a pin to connect the valve disc and the operating rod. The pinned butterfly valve connects the valve disc and the operating rod together through a pin. The pin is located in the center of the valve disc, and the rotation of the valve disc can be controlled by rotating the valve stem.
② Comparison of working principles
The working principle of the pinless butterfly valve is to control the medium flow by directly rotating the valve disc. When the operating rod rotates, the valve disc also rotates. The pinned butterfly valve needs to connect the valve disc and the operating rod through a pin. When the operating rod rotates, the pin also rotates the valve disc.
③ Stability comparison
Because the pinned butterfly valve is fixed with a pin, its stability is definitely better than that of the pinless structure. The pinless structure will wear the matching surface of the shaft and the gate after long-term operation, which affects the movement accuracy.
3. Advantages and disadvantages of butterfly valves without pins and with pins
① The advantages of the pinless butterfly valve are simple structure, light weight, convenient operation, low cost, good sealing performance, strong adjustability, etc.
The disadvantage is that its application range is relatively narrow, and it is only suitable for some low pressure, medium and low temperature occasions where precise flow control is not required.
② The advantages of butterfly valve with pin are wide application range, high flow control accuracy, corrosion resistance, good sealing, and suitable for high temperature and high pressure environment, etc.
The disadvantage is that its structure is relatively complex, the operation is complicated, and the price is relatively high.
In summary, for different occasions and requirements, choosing the appropriate type of butterfly valve can better achieve flow control and performance requirements.
