1. Introduction
Check valve is a one-way fluid control valve. Its main function is to prevent the backflow of media and ensure the safety and stability of the pipeline system. According to the different structures and opening methods, types of check valve can be divided into three types:
a. Lift check valve
b. Swing check valve
c. Dual plate check valve
d. Butterfly check valve
In practical applications, lift check valves, swing check valves, dual plate check valves and butterfly check valves are the four most common types. Although all four have the function of preventing the backflow of media, there are great differences in structural design, working principle, applicable scenarios, installation and maintenance methods.
This article will conduct an in-depth comparative analysis of the characteristics, advantages and disadvantages, and applications of these three check valves to help users better choose the appropriate valve type.
2. Structure and features of swing check valve
2.1 Structure and working principle
The core component of the swing check valve is a disc that rotates around a pin, and its structure is similar to a freely swinging door. The working principle of the valve is as follows:
- Forward flow: When the medium flows in the set direction, the pressure of the fluid pushes the disc to open, allowing the medium to pass smoothly.
- Reverse flow: When the medium tries to flow back, gravity or reverse pressure will automatically close the disc, thereby preventing the medium from flowing back.
2.2 Main features
- Low fluid resistance:
o Since the channel of the swing check valve is relatively spacious, the medium can flow through the valve more freely in the open state, so its pressure loss is small.
- General sealing performance:
-Since the disc of the swing check valve relies on its own weight or reverse fluid pressure to close, the sealing surface may be impacted by the medium, causing wear.
- Flexible installation:
-It can be installed on horizontal, vertical or inclined pipes.
-If installed on a vertical pipe, there will be requirements for the installation direction. The medium must flow from bottom to top to ensure that the valve disc can work properly.
- Applicable to large-diameter pipes:
-Swing check valves are usually used in large-diameter pipes because their design allows large flow rates and can adapt to large pressure fluctuations.
2.3 Applicable scenarios
- Water treatment system: widely used in water supply, sewage treatment plants, pumping stations, etc.
- Oil and gas industry: suitable for conveying high-temperature and high-pressure media.
- Power industry: used in boiler feed water systems to prevent water hammer.
- Chemical industry: suitable for corrosive or high-viscosity fluids.
3. Structure and characteristics of lift check valve
3.1 Structure and working principle
The main components of the lift check valve include the valve disc and the valve seat. Its working principle is similar to that of the globe valve:
- Forward flow: When the pressure of the medium is high enough, the valve disc is pushed up by the fluid to allow the medium to pass.
- Reverse flow: When the fluid stops or flows in the reverse direction, the valve disc will fall back to the valve seat under the action of its own weight and the backflow pressure to prevent backflow.
3.2 Main features
- Good sealing performance:
-Since the valve disc moves in the vertical direction and can closely contact the valve seat, the sealing performance is usually better than that of the swing check valve.
- Large fluid resistance:
-Since the fluid needs to change the flow direction in the valve cavity, the fluid resistance of the lift check valve is larger and the pressure loss is higher than that of the swing check valve.
- Limited installation method:
-Horizontal lift check valves must be installed on horizontal pipes.
-Vertical lift check valves must be installed on vertical pipes and ensure that the medium flows from bottom to top.
- Suitable for small-diameter pipes:
-Since the lifting and lowering movement of the valve disc requires a large pressure, lift check valves are usually used in small-diameter, high-pressure occasions.
3.3 Applicable scenarios
- Steam pipelines: Suitable for high-temperature and high-pressure steam systems to ensure safe operation.
- Hydraulic system: Used to prevent liquid backflow and improve system stability.
- Chemical and pharmaceutical industries: suitable for high-purity or corrosive fluids.
4. Structure and features of double plates check valve
4.1 Structure and working principle
The dual plate check valve consists of two symmetrical semicircular discs, usually installed between pipe flanges. Its working principle is as follows:
- Forward flow: When the medium flows forward, the disc opens to both sides under the action of fluid pressure to allow the medium to pass.
- Reverse flow: When the medium flows back, the spring force and the reverse pressure of the medium cause the disc to close quickly to prevent backflow.
4.2 Main features
- Compact structure and light weight
- Low fluid resistance and low pressure loss
- Spring-assisted closing to reduce water hammer effect
- Flexible installation method, can be installed horizontally or vertically
- Suitable for large-diameter and high-flow rate applications
4.3 Applicable scenarios
- Municipal water supply system
- Seawater desalination equipment
- Oil and natural gas pipelines
- Boiler water supply system
- Chemical and metallurgical industries
5. Structure and characteristics of butterfly check valve
5.1 Structure and working principle
Butterfly check valve generally refers to a micro-resistance slow-closing butterfly check valve. It adopts a butterfly structure, and the valve disc controls the closing speed through a spring and a buffer mechanism. Its working principle is as follows:
- Forward flow: When the medium flows forward, the valve disc opens under the action of the fluid pressure, and the medium passes smoothly.
- Reverse flow: When the fluid stops or flows in the reverse direction, the spring and the buffer device work together to make the valve disc close slowly, thereby reducing the water hammer effect.
5.2 Main features
- Slow closing design, effectively reducing water hammer impact
Low fluid resistance, improve pipeline transportation efficiency
Compact structure, small space occupation - Applicable to high-frequency opening and closing conditions
5.3 Applicable scenarios
- Water supply network
- Fire protection system
- Industrial circulating water system
- Urban sewage treatment
6. Comparative analysis of swing check valve and lift check valve
| Comparison items | Swing check valve | Lift check valve | Butterfly check valve | Double plate check valve |
| Sealing performance | average | Excellent | average | Good |
| Fluid resistance | Low | High | Low | Low |
| Pressure loss | Small | Large | Small | Small |
| Applicable diameter | Large diameter | Small diameter | Large diameter | Large diameter |
| Installation method | Any direction | Limited (horizontal or vertical) | Any direction | Any direction |
| Applicable media | Water, oil, gas | Steam high pressure liquid | Low pressure water, air | Various fluids |
| Maintenance difficulty | Low | High | Low | Low |
7. Maintenance and maintenance points
| Maintenance items | Maintenance frequency |
| Valve disc movement inspection | Every 3-6 months |
| Sealing performance inspection | Every 6 months |
| Internal cleaning | Every 3-6 months |
| Shaft lubrication | Every 6-12 months |
| Flange bolt inspection | Every 6 months |
| Water hammer impact assessment Inspection | when abnormality occurs |
| Anti-corrosion treatment inspection | Every 12 months |
- Before shutting down for maintenance, ensure that the pipeline pressure has been released and follow the safety operating specifications.
- When disassembling the valve, pay attention to protecting the sealing surface to avoid damage due to bumps.
- When replacing accessories, use spare parts recommended by the original manufacturer to ensure matching and durability.
- After resuming operation, gradually increase the flow rate and observe whether the valve works normally.
7.1 Maintenance of swing check valves
- Regularly check whether the sealing surface of the valve disc and the valve seat is worn or there is accumulation of impurities.
- Replace aging sealing materials such as rubber or synthetic gaskets in time.
- Ensure the flexibility of the pin shaft to avoid the valve disc from being unable to swing normally due to jamming.
7.2 Maintenance of lift check valves
- Regularly clean the deposits between the valve disc and the valve seat to prevent sealing failure.
- Check whether the lifting and lowering movement of the valve disc is smooth to avoid jamming due to dirt.
- Ensure that the spring (if any) is in good condition to maintain the normal movement of the valve disc.
7.3 Maintenance of double-plate check valves
- Regularly check whether the valve disc is flexible in opening and closing, and whether there is any jamming, deformation or damage.
- Observe whether the contact surface between the valve disc and the valve seat is worn, corroded or scaled.
- Ensure that the spring mechanism has not suffered fatigue failure, and replace the spring if necessary.
- Regularly clean the dirt, sediment or impurities inside the valve to prevent the valve disc from being blocked and affecting the operation.
- Use appropriate lubricants to lubricate the shaft and hinge parts to reduce wear and maintain flexibility.
- Ensure that the fastening bolts of the mounting flange are not loose to prevent leakage or vibration from affecting the performance of the valve.
7.4 Maintenance of butterfly check valves
- Regularly check the sealing of the valve to ensure that the valve disc can be fully closed to prevent the backflow of the medium.
- Check whether the valve disc is opened and closed smoothly, and whether there is any jamming or slow movement.
- Check whether the spring is fatigued or damaged, and replace it in time.
- Ensure that there is no leakage at the connection between the valve and the pipeline, and whether the bolts are loose.
8. Conclusion
Swing check valves and lift check valves have their own advantages and disadvantages in terms of structure, performance, and application scenarios. Generally speaking, swing check valves are suitable for large-diameter and low-resistance occasions, lift check valves are more suitable for high-sealing performance, high-pressure and small-diameter pipeline systems, double-plate check valves have low flow resistance, low pressure loss, and flexible installation, and are suitable for large-diameter and high-flow rate applications. Butterfly check valves are suitable for large-diameter systems with high flow, low pressure, and large diameter.
In actual applications, the most suitable type of check valve should be selected according to pipeline conditions, medium characteristics, pressure, and installation conditions to ensure the safety and efficiency of the system.