Analysis of Factors Affecting the Service Life of Check Valves and Methods for Extending It

　　Check valve is a key component in pipeline systems to prevent medium backflow, and its service life directly affects the safe and stable operation of the entire system. Understanding the factors that affect the lifespan of check valves and methods to extend their lifespan is of great significance for equipment management and maintenance work.

　　1、 Typical service life of check valves

　　Under normal operating conditions and reasonable maintenance conditions, check valves of different materials and types have different expected service lives. Cast iron check valves can generally be used for 8 to 12 years in clean water media, cast steel check valves can usually be used for 10 to 15 years in steam or high-temperature media, stainless steel check valves have a service life of about 10 to 15 years in corrosive media, and bronze check valves can reach 15 to 20 years in seawater or corrosive environments. The lifespan of rubber seals is relatively short, usually experiencing aging and hardening or decreased elasticity after 5 to 8 years, requiring replacement of the seals. Full lined fluorine check valves have a lifespan of approximately 6 to 10 years in highly corrosive media. It should be noted that the above years are reference values, and the actual service life is affected by various factors, with significant differences.

　　2、 The main factors affecting the service life of check valves

　　1. Characteristics of the medium

　　The properties of the medium have a significant impact on the lifespan of check valves. Clean media such as water have less wear on valves and a longer lifespan. Media containing particulate impurities such as sediment, welding slag, and rust can accelerate the wear of valve discs and sealing surfaces, significantly reducing their service life. Corrosive media such as acid, alkali, and salt can corrode the valve body, valve disc, and spring, leading to thinning of the wall thickness and spring fracture. High temperature media can accelerate the aging of sealing and lubricating materials, reducing sealing performance. Low temperature media may cause certain materials to become brittle and prone to cracking.

　　2. Operating conditions

　　In pipelines with frequent pressure fluctuations, check valves need to be opened and closed frequently, which accelerates the wear of moving parts. Water hammer impact is an important cause of damage to check valves, and strong shock waves may cause valve disc deformation, valve body cracking, or loose connecting bolts. The vibration of the pipeline system can also be transmitted to the check valve, causing loose fasteners and uneven wear on the sealing surface.

　　3. Valve selection and quality

　　Improper selection is a common cause of premature failure of check valves. For example, if a regular lift check valve is installed on a vertical pipeline, the valve disc cannot retract normally, resulting in it always being in an open state and quickly failing. Improper selection of spring force can also affect the service life. If the spring is too strong, it will accelerate the impact wear of the valve disc and sealing surface. If the spring is too weak, it will not close tightly and the sealing surface will be damaged by the flushing of the medium. The quality of the valve itself is equally important, as casting defects, insufficient machining accuracy, and poor sealing material quality can all lead to a shortened lifespan.

　　4. Installation quality

　　Improper installation can directly affect the lifespan of the check valve. Reversing the flow direction can cause the valve to remain closed and withstand abnormal pressure, resulting in damage. Uneven tightening of flange bolts can cause deformation of the valve body, resulting in misalignment between the valve disc and seat, accelerating wear. Failure to clean the pipeline before installation, welding slag and other hard debris entering the interior of the valve can directly scratch the sealing surface, causing irreversible damage.

　　5. Maintenance and upkeep

　　Lack of regular maintenance is an important reason for the shortened lifespan of check valves. If the sealing surface is not inspected for a long time, slight leaks will gradually develop into serious leaks. If the rotating part of the valve disc is not lubricated, it will gradually become stuck, resulting in inflexible movement. The elasticity of the spring decreases after long-term use, and failure to replace it in a timely manner can lead to loose closure. Loose fasteners not tightened in a timely manner can cause leakage or increased vibration at the valve body connection.

　　3、 Common failure modes of check valves

　　When a check valve reaches its service life, it usually exhibits the following failure modes. Wear or corrosion of the sealing surface is a common form of failure, manifested as poor valve closure and medium backflow. Common causes include impurity erosion, corrosive medium erosion, and frequent opening and closing impacts. Spring failure is manifested as spring breakage or decreased elasticity, resulting in the valve disc not being able to reset normally or not closing in a timely manner. Valve disc jamming is caused by impurities or rust on the rotating parts, which prevents the valve disc from rotating flexibly and may remain in an open or closed state at all times. Valve body cracking is usually caused by water hammer impact, low-temperature brittle fracture, or casting defects, manifested as cracks in the valve body and leakage of the medium. The aging of rubber seals is manifested by the hardening, cracking, or loss of elasticity of the rubber, leading to seal failure.

　　4、 Measures to extend the service life of check valves

　　1. Correct selection

　　Select the appropriate type and material of check valve based on the characteristics of the medium, working pressure, working temperature, and usage requirements. Ordinary cast iron swing check valves can be used for clean water media. For media containing particles, wear-resistant rubber lined butterfly check valves or slow closing check valves should be selected. Stainless steel or fluorine lined check valves should be selected for corrosive media. High temperature steam should use cast steel lift check valves. Pump outlets that frequently start and stop should use silent check valves or slow closing check valves to reduce water hammer impact.

　　2. Standardized installation

　　Install strictly according to the flow arrow and do not install backwards. The selection of horizontal and vertical pipelines should be clearly distinguished. Before installation, the pipeline must be thoroughly purged to remove welding slag and debris. The flange bolts should be tightened symmetrically and evenly to prevent deformation of the valve body.

　　3. Regular maintenance

　　Establish a regular inspection system to check the working status of check valves every six months to one year. By listening to the sound, determine whether the valve disc is closed firmly and whether there is any abnormal vibration. Observe changes in pipeline pressure to determine if there is internal leakage. Regularly clean the interior of the valve body to remove impurities and deposits. For rotating parts, add lubricant appropriately. When minor wear is found on the sealing surface, it can be repaired by grinding. If severe wear is found, replace the valve disc or seat. When the spring elasticity decreases, it should be replaced in a timely manner. After using rubber seals for 5 to 8 years, it is recommended to replace them preventively even if their condition is still acceptable.

　　4. Operation management

　　When starting and stopping the pump unit, slowly open and close the valve to reduce water hammer impact. When multiple pumps are running in parallel, avoid frequent starting and stopping of a single pump. Regularly monitor the fluctuation of pipeline pressure, promptly analyze the cause of abnormal water hammer and take measures.

　　5、 Basis for determining whether the check valve needs to be replaced

　　When the check valve encounters the following situations, replacement should be considered. One is that the sealing surface is severely worn, and even after grinding and repairing, it still cannot guarantee a tight seal. Secondly, the valve body may have cracks or perforations, making welding repairs difficult or unreliable. The third reason is that the spring is broken or severely deformed, and it still cannot work properly after replacement. The fourth issue is severe wear or rust on the rotating parts of the valve disc, which cannot be repaired. Fifth, reaching the design service life and severe aging of key components. For critical equipment and important pipelines, it is recommended to replace the check valve proactively when it reaches the upper limit of its expected lifespan to avoid greater losses caused by sudden failures.

　　summary

　　The service life of check valves is influenced by various factors such as medium characteristics, operating conditions, selection quality, installation level, and maintenance. Under normal conditions, cast iron check valves can be used for 8 to 12 years, while cast steel and stainless steel check valves can be used for 10 to 15 years. By correctly selecting, standardizing installation, regular maintenance, and reasonable operation management, the service life of check valves can be effectively extended, and equipment failure rates and maintenance costs can be reduced. For check valves that have reached their service life or have suffered serious damage, they should be replaced in a timely manner to ensure the safe and reliable operation of the pipeline system.