Slow-Closing Check Valves: Guardians of Pipeline System Safety

In modern industrial and building water supply and drainage systems, pipelines act as "arteries," constantly transporting vital media such as water, steam, and oil. However, with the potential for pressure fluctuations and backflow risks during fluid operation, pipeline systems face hidden dangers. To prevent media backflow, reduce water hammer impact, and enhance system stability, a key automatic valve has emerged: the slow-closing check valve. It not only plays the role of a "safety guardian" in pump rooms and various pipeline systems but also effectively improves operational efficiency, providing a solid guarantee for the long-term stability of industrial and civil facilities.

A slow-closing check valve, also known as a non-return valve, is an automatic valve primarily used to prevent backflow of media in pipelines. Its opening and closing elements rely on the flow and force of the media to open or close automatically, allowing media to flow in only one direction to prevent accidents. These valves are typically installed on horizontal pipelines and are suitable for various pipelines with nominal pressures ranging from PN1.0MPa to 42.0MPa and nominal diameters from DN15 to 1200mm. They can be used for water, steam, oil, and other types of media.

The most fundamental function of a slow-closing check valve is to prevent media backflow. During the operation of a water pump, if the water flow stops or reverses, the slow-closing check valve will quickly close to prevent the media from flowing back into the pump system, thereby protecting the pump from damage caused by backflow. This function is crucial for preventing contamination, system failures, or equipment damage, especially in systems handling hazardous or sensitive materials.

The water hammer phenomenon refers to the pressure waves generated by sudden changes in flow velocity as they travel through pipelines, which can cause severe damage to pipelines and equipment. Slow-closing check valves (especially those with rapid closing mechanisms) help mitigate water hammer by preventing backflow. When the water flow stops or reverses, the slow-closing check valve can quickly close, absorb the impact, and protect the system from potential damage. This function is of great significance for ensuring the safe and stable operation of pump room systems.

By ensuring that fluids flow in the correct direction, slow-closing check valves contribute to the overall stability and efficiency of pipelines. They can maintain the required pressure levels, preventing pressure drops and system inefficiencies caused by backflow. Additionally, slow-closing check valves ensure consistent and uninterrupted fluid flow, reducing the likelihood of system failures or downtime and avoiding costly shutdowns.

Safety is paramount in any industrial operation. Slow-closing check valves reduce the risk of accidents and equipment failures by preventing backflow and controlling pressure. Many slow-closing check valves are designed to meet specific industry standards, ensuring compliance with safety regulations and best practices. This function is of great significance for ensuring the safety and compliance of pump room systems.

The working principle of slow-closing check valves is based on the pressure generated by fluid flow to automatically open and close the valve. The specific working process is as follows:

The operation of slow-closing check valves is characterized by a slow-closing mechanism, which reduces the occurrence of water hammer and water impact, thereby achieving a noise-reducing effect. The interior of the valve consists of two water chambers, with the lower chamber beneath the diaphragm having a throttling port that serves as the water passage (the maximum area of the throttling port is close to the pipe diameter area); the upper chamber above the diaphragm acts as a pressure regulation chamber.

When the water pump stops working, the throttling port quickly closes to 90% due to the weight of the valve disc and the pressure in the upper chamber. The remaining 10% is gradually closed as the pressure in the upper chamber increases, with the pressure behind the valve being transmitted to the upper chamber through a conduit. This gradual closure is what allows the check valve to slowly and quietly close.

The closing process of a slow-closing check valve should be divided into two stages: rapid closure and slow closure, with the slow-closing time being adjustable. The slow-closing travel of the check valve disc, i.e., the extension length of the slow-closing piston, should be fully adjustable throughout its range. The damping piston in the slow-closing device must be highly responsive, automatically and quickly extending to the preset working position when the check valve disc (butterfly plate) opens, and effectively performing the slow-closing function when the check valve disc (butterfly plate) closes to the slow-closing position.

Choosing and installing the appropriate slow-closing check valve is crucial for ensuring the safe and efficient operation of the system. The following are key points for selection and installation:

When selecting a slow-closing check valve, factors such as material, working pressure, temperature range, and applicable media should be considered. Ensure that the selected valve meets the specific requirements of the pump room system to enhance the system's reliability and durability. For example, for pipelines transporting hot water, a slow-closing check valve that is heat-resistant should be chosen; for pipelines transporting corrosive media, materials that are corrosion-resistant should be selected.

During the installation of a slow-closing check valve, it is essential to strictly follow the manufacturer's instructions. The valve should be installed horizontally on the pipeline, ensuring the correct flow direction of the media. Additionally, attention should be paid to the maintenance and upkeep of the valve, with regular checks on its sealing performance and operational flexibility to ensure long-term stable operation.

Regular maintenance and upkeep are essential to ensure the long-term stable operation of slow-closing check valves. The following are detailed steps for maintenance and upkeep.

Regular inspection is an important aspect of maintaining slow-closing check valves, covering the following areas:

Sealing Performance Inspection: Check for any leakage in the valve. This can be done by observing the sealing parts to see if any media is seeping out. If leakage is detected, the sealing elements should be replaced promptly.

Operational Flexibility Inspection: Check whether the valve operates smoothly without any jamming. This can be assessed by manually operating the valve to feel if the opening and closing processes are smooth. If jamming is detected, it may be due to internal impurities or damaged components, which require further inspection and cleaning.

Damping Piston Action Inspection: Ensure that the damping piston operates sensitively and functions properly. This can be verified by observing the piston's movement to ensure it extends and retracts normally during valve operation. If the action is not sensitive, it may be due to dirt or damage on the piston or piston rod surface, which requires cleaning or replacement.

Regular cleaning of the valve to remove potential impurities and dirt can effectively extend its service life. The specific steps are as follows:

External Cleaning: Use a clean cloth or brush to remove dust and dirt from the exterior of the valve. For hard-to-clean areas, a mild detergent can be used, but care should be taken to avoid corrosive chemicals.

Internal Cleaning: If there are impurities or dirt inside the valve, it may affect its normal operation. The valve can be disassembled to clean the internal impurities. In particular, the damping piston cylinder in the slow-closing device should be regularly inspected for internal blockages to ensure its proper functioning.

If damaged sealing elements or damping pistons are found during inspection, they should be replaced promptly to ensure the valve's performance. The specific steps are as follows:

Sealing Element Replacement: If the sealing elements are worn or damaged, they should be replaced immediately. When replacing, ensure that the new sealing elements meet the required specifications and materials and are correctly installed.

Damping Piston Replacement: If the damping piston or piston rod surface is damaged, it may affect its sensitivity. In such cases, a new damping piston should be installed. When replacing, ensure that the piston and piston rod surfaces are smooth and undamaged and are correctly installed.

Slow-closing check valves are widely used in various industrial and building systems, especially in pump room systems, where their importance is particularly prominent.

In pump room systems, slow-closing check valves are mainly installed at the outlet of water pumps in high-rise building water supply systems and other water supply systems. Their multiple functions make the pump room system safer, more reliable, and more efficient. For example, in high-rise building water supply systems, slow-closing check valves can prevent water backflow, protect water pumps from damage, mitigate water hammer phenomena, and ensure the stable operation of the water supply system.

In addition to pump room systems, slow-closing check valves are also widely used in the following scenarios:

• Industrial Pipeline Systems: In industries such as chemical, oil, and pharmaceutical, slow-closing check valves are used to prevent media backflow, ensuring the safety and stability of the production process.

• Steam Systems: In steam pipelines, slow-closing check valves prevent steam backflow, protecting equipment from damage.

• Oil Transportation Systems: In oil pipelines, slow-closing check valves prevent oil backflow, ensuring the safety and efficiency of the transportation process.

As an important automatic valve, the slow-closing check valve plays a significant role in preventing media backflow, mitigating water hammer phenomena, enhancing pipeline system efficiency, and ensuring system safety. Selecting the appropriate slow-closing check valve and correctly installing and maintaining it can greatly improve the reliability and stability of pipeline systems. In modern industrial and building fields, the safe and stable operation of pipeline systems is crucial. As the guardian of pipeline system safety, the importance of the slow-closing check valve is self-evident. By understanding the working principle, selection key points, installation methods, and maintenance and upkeep of slow-closing check valves, we can better utilize this type of valve to ensure the safe and efficient operation of pipeline systems.