Infrastructure construction remains a core focus of China's economic development. Water supply and drainage systems, particularly large-scale sewage treatment projects, have driven the growth of the water industry, which includes critical components such as pipelines and valves. This has created significant opportunities for the valve manufacturing sector. With China's entry into the WTO, global demand for valves has reached approximately 3 million tons annually. Leveraging the advantages of a labor-intensive industry, relatively low per capita wages, and favorable working conditions compared to developed countries, China has become an attractive destination for global manufacturing. This has enabled the country to actively participate in the global economy. The following sections briefly explore the current status and future development of water supply and drainage valves.
**Current Situation**
There are currently around 3,000 valve manufacturers across China, including 600 in Wenzhou, nearly 200 in Zhengzhou, over 150 in Shanghai, 250 in Liaoning, and more than 200 each in Jiangsu and Fujian. Despite a wide variety of products—over 3,000 types and nearly 30,000 specifications—the quality and performance of these valves have significantly improved. Sealing performance, strength, control functions, and operational efficiency have all seen notable progress. A decade ago, there was a well-known saying among industry professionals: “Ten valves, nine leaks,†which, although exaggerated, reflected real challenges. Today, however, many valves meet high-quality standards, with some even reaching international levels.
Despite this progress, the industry still faces numerous challenges. Rapid market expansion after the reform and opening-up period led to the decline of state-owned enterprises, while township and private enterprises grew quickly but often lacked technical expertise and advanced equipment. Many products were imitations, and market disorder was widespread, especially in low-pressure valves used in water supply and drainage systems. However, in recent years, a few leading companies have driven innovation, achieving remarkable improvements. Some valve types now match global standards, and many firms are pursuing new growth opportunities. Nevertheless, there is still a long way to go, making it crucial to develop technical strategies for 2010 and 2020.
**Commonly Used Valves**
In water supply and drainage projects, medium- and low-pressure valves are widely used, with low-pressure valves (nominal pressure PN ≤ 1.6 MPa) being the most common. Medium-pressure valves (PN 2.5–6.4 MPa) are less frequently used. Gate valves and butterfly valves are the most basic and widely applied types.
**2.1 Status and Development of Gate Valves**
Gate valves have a long history of use and remain dominant in many regions, especially for diameters below DN 300 mm. They operate by using the pressure difference between the upstream and downstream sides to push the gate against the seat, ensuring a tight seal. When fully open, the gate does not obstruct the flow, resulting in minimal pressure loss. They are ideal for cutting off media in pipelines.
However, gate valves have several disadvantages. They require a large operating torque, and the valve body and stem are prone to damage, especially in large-diameter models. For example, a DN 1000 gate valve can be up to 3200 mm tall and requires four people to operate. Therefore, they are typically used in smaller sizes, usually below DN 500.
The flow resistance of a gate valve is minimal when it is partially open, but increases sharply as it approaches full closure. In this range, the flow resistance changes little, but when the valve is nearly closed, the flow rate drops significantly, making it unsuitable for precise flow control. If the valve is opened very slightly, the flow velocity at the opening becomes very high, potentially causing cavitation on the lower side of the gate, leading to vibration and noise. Prolonged throttling can also cause damage to the valve body and gate due to cavitation.
When the gate valve is in the intermediate position, the gate is supported by guide rails on both sides. However, when fully closed, the gate fits tightly against the seat. In the middle position, the gap between the gate and the guide rail may cause vibration. Even in areas with low erosion risk, prolonged throttling can lead to deformation or damage of the guide rails. Additionally, since the seats do not make full contact, the contact surface experiences high pressure, leading to erosion or adhesion. Therefore, gate valves should not be used for flow regulation.
It is also important to note that when a gate valve is operated at a small opening, the flow rate changes dramatically. Sudden opening or closing can cause a sharp increase in pressure or even negative pressure, especially when the valve is closed.
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