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In heating, ventilation, and air conditioning water systems, valves are widely used to control water pressure, flow rate, and direction. The valves commonly used in heating and air conditioning water systems can be classified into categories such as gate valves, butterfly valves, globe valves, ball valves, plug valves, check valves, pressure reducing valves, safety valves, steam traps, and balance valves, based on their valve body structure and function. Based on the driving method, they are divided into four types: manual, electric, hydraulic, and pneumatic. Based on nominal pressure, they are classified into high-pressure, medium-pressure, and low-pressure categories. The working principles and characteristics of the commonly used valves in heating and air conditioning water systems are as follows: 1. Gate valve: A gate valve is a type of valve in which the closing element (gate) moves vertically along the axis of the medium flow channel. Its advantages are a low flow resistance coefficient, low torque required for opening and closing, and no restrictions on the flow direction of the medium. The disadvantages are large structural size, long opening and closing time, easy damage to the sealing surfaces, and complex structure. Control valves are classified into different types; the most common ones are parallel-type and wedge-type control valves. Based on the structure of the valve stem, they can also be divided into stem-type control valves. 2. Butterfly valves – their name comes from the butterfly-shaped disc that serves as the moving part. On pipelines, it is primarily used for cutting off flow and throttling. When a butterfly valve is used for cutting off flow, elastic seals are typically employed, with materials such as rubber and plastic being used; whereas when it is used for throttling, metal hard seals are more commonly used. The advantages of butterfly valves are their small size, light weight, simple structure, rapid opening and closing, good regulating and sealing performance, as well as low fluid resistance and operating torque. Based on their structure, butterfly valves can be classified into lever-type (double rocker), centrally symmetric gate type, offset plate type, and inclined plate type. For nominal diameter DN