China’s Valve Industry Accelerates Upgrade as Pressure Control Technologies and High-End Manufacturing Demand Continue to Rise

After China's accession to the WTO, alongside the wave of global economic integration, the accelerated shift of worldwide manufacturing to the Chinese mainland has become an irreversible trend. China is gradually evolving into a world-class manufacturing base. Industry experts predict that Guangdong, particularly the Pearl River Delta region with its prominent advantages, will develop into a global ball valve production center within the next decade. Furthermore, as China has been importing nearly $1 billion worth of molds annually in recent years—mostly precision, large-scale, complex, and long-life molds—the market share of such high-end molds is expected to increase steadily from the perspective of reducing imports.

Pressure reducing valves, safety valves, pressure stabilizing valves, and relief valves all belong to the category of pressure valves, primarily distinguished by their functions.

A pressure reducing valve is a device that reduces the pressure of a medium from a higher inlet pressure to a lower outlet pressure. Its key characteristic is maintaining the outlet pressure and temperature within a certain range despite fluctuations in inlet pressure.

A safety valve is used to prevent equipment or pipelines such as boilers and pressure vessels from being damaged due to overpressure. It opens automatically when the pressure slightly exceeds the normal working pressure, allowing the pressure to decrease. It closes automatically when the pressure falls slightly below the normal working pressure, stopping fluid discharge and maintaining a seal.

A relief valve is mainly used in situations where pressure is excessive. When the pressure exceeds the set value, the valve disc is pushed open to promptly release pressure. It returns to its original position once the pressure decreases. It differs little from a safety valve, but relief valves are typically used for liquids, while safety valves are generally for gases and steam.

A pressure stabilizing valve is a device that maintains the medium within a specific area at a relatively constant pressure. The difference from a pressure reducing valve is:

Pressure reducing valve: Reduces the outlet pressure to a rated value regardless of changes in inlet pressure, serving a减压function.

Pressure stabilizing valve: Maintains a constant upstream pressure regardless of changes in downstream pressure and demand.

Safety valves and pressure reducing valves are two types of specialized valves. Among them, safety valves belong to safety relief devices. They are specialized valves that activate only when the working pressure exceeds the allowable range, protecting the system. Pressure reducing valves belong to process valves. They reduce the pressure of high-pressure fluid streams to meet the pressure requirements of downstream systems, and their operation is continuous.

Selection criteria for pressure reducing valves:

For pressure reducing valves with a soft seal, there shall be no leakage within a specified period; for those with a metal seal, the leakage shall not exceed 0.5% of the maximum flow rate.

Within the given spring pressure range, the outlet pressure should be continuously adjustable between the maximum and minimum values without sticking or abnormal vibration.

When the outlet flow changes, the outlet pressure deviation for direct-acting types shall not exceed 20%, and for pilot-operated types, it shall not exceed 10%.

When the inlet pressure changes, the outlet pressure deviation for direct-acting types shall not exceed 10%, and for pilot-operated types, it shall not exceed 5%.

Direct-acting bellows pressure reducing valves are suitable for low-pressure, small and medium-diameter steam media.

Pressure reducing valves have a wide range of applications and can be used in equipment and pipelines for steam, compressed air, industrial gas, water, oil, and many other liquid media. The amount of medium flowing through the outlet of a pressure reducing valve is generally expressed as mass flow or volumetric flow.

Typically, the post-valve pressure should be less than 0.5 times the pre-valve pressure.

Direct-acting diaphragm pressure reducing valves are suitable for low to medium pressure, small and medium-diameter air and water media.

Pilot-operated piston pressure reducing valves are suitable for steam, air, and water media of various pressures, diameters, and temperatures. If made from stainless acid-resistant steel, they can be used for various corrosive media.

Pilot-operated bellows pressure reducing valves are suitable for low-pressure, small and medium-diameter steam, air, and other media.

Fluctuations in the inlet pressure of a pressure reducing valve should be controlled within 80% to 105% of the given inlet pressure value. Performance may be affected if this range is exceeded.

Pilot-operated diaphragm pressure reducing valves are suitable for low to medium pressure, small and medium-diameter steam or water media.

Typically, the post-valve pressure should be less than 0.5 times the pre-valve pressure.

Each spring grade for a pressure reducing valve is only applicable within a certain outlet pressure range. The spring should be replaced if the range is exceeded.

For media such as air or water (liquid), direct-acting diaphragm or pilot-operated diaphragm pressure reducing valves are generally preferred.

For applications with relatively high media working temperatures, pilot-operated piston or pilot-operated bellows pressure reducing valves are generally selected.

For steam media, pilot-operated piston or pilot-operated bellows pressure reducing valves are preferred.

For ease of operation, adjustment, and maintenance, pressure reducing valves should generally be installed on horizontal pipelines.