Infrastructure construction remains a core focus of China's economic development. Water supply and drainage projects, particularly large-scale sewage treatment initiatives, have significantly driven the growth of the water industry, including the manufacturing of water treatment equipment such as pipelines and valves. These developments have created favorable conditions for the expansion of the valve industry. With China's accession to the WTO, global annual valve demand has reached approximately 3 million tons. Leveraging its labor-intensive nature, relatively low per capita wages, and improved 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 world economy. The following sections briefly discuss the current status and 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. Although product quality varies, there are over 3,000 types of valves with nearly 30,000 specifications available. In terms of performance, sealing capability, strength, regulation functions, and operational efficiency—especially sealing—have seen significant improvements. Ten years ago, a well-known figure from the town water supply association once remarked, “Ten valves, nine leaks,†which, while exaggerated, reflected the reality at the time.
The challenges faced by the valve industry stemmed from rapid market expansion after the reform and opening up, leading to the decline of original state-owned enterprises. Meanwhile, township and village enterprises (private companies) grew quickly, but often started with low technical capabilities, basic equipment, and limited innovation, resulting in many imitations. Market chaos was widespread, especially in low-pressure valves used for water supply and drainage, where problems were serious. However, over the past decade, a few leading companies have made notable progress, with some products reaching international standards. Many firms have also embarked on second ventures. Despite this, there is still a significant gap compared to global leaders, and much work remains to be done. Therefore, developing technical strategies for 2010 and 2020 is of great importance.
**Commonly Used Valves**
In water supply and drainage projects, medium- and low-pressure valves are widely used, with low-pressure valves (nominal pressure PN ≤ 1.6MPa) being the most common, followed by medium-pressure valves (PN 2.5–6.4MPa). Gate valves and butterfly valves are the most fundamental and widely used types.
**2.1 Status and Development of Gate Valves**
Gate valves have a long history of use and remain popular globally, especially for diameters below DN300mm, where they still dominate. They operate by using the pressure difference between the upstream and downstream to push the gate against the seat, providing 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 require significant operating torque, and the valve body and stem are prone to damage, especially in large-diameter models. A DN1000 gate valve can be over 3.2 meters tall and typically requires four people to operate, making them more suitable for smaller sizes, generally below DN500.
The flow resistance of a gate valve is minimal when it is partially open, but increases sharply as it approaches full closure. In the middle range, flow resistance remains relatively stable. However, when the valve is almost closed, even small changes in opening can lead to significant flow variations, making it unsuitable for precise flow control. If the opening is too small, high-speed flow can cause cavitation, leading to vibration, noise, and potential damage to the valve body and gate.
When the gate valve is in a partially open position, the gate is supported by guide rails. At full closure, the gate fits tightly against the seat. However, in the intermediate position, a large gap may exist between the gate and the guide rails, causing 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, high contact pressure can cause erosion or adhesion, so gate valves are not recommended for flow regulation.
It’s also important to note that when a gate valve is operated at a small opening, the flow rate changes rapidly. Sudden opening or closing can cause pressure surges or negative pressure, especially during closure.
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