In industrial production, the safe operation of pressure vessels is of vital importance, and the spring safety valve, as a key device to ensure equipment safety, plays an indispensable role. It relies on the elastic pressure of the spring to lock the sealing components such as the valve disc or plunger. Once the pressure in the pressure vessel abnormally rises, the generated high pressure will overcome the spring pressure of the safety valve, push open the locking device, form a pressure relief channel, and release the high-pressure gas or liquid, thereby protecting the equipment from damage. However, various faults may occur in the use of spring loaded safety valves, affecting their normal operation. Therefore, understanding the causes of these faults and the solutions is of great significance for ensuring the safe operation of equipment.
During daily use, spring safety valves may encounter various faults, which not only affect the normal operation of equipment but may also bring safety hazards. Therefore, it is crucial to promptly detect and solve these faults. Below is a detailed analysis of the common faults of spring safety valves and their causes.
When under the normal working pressure of the equipment, leakage exceeding the allowable level occurs between the sealing surfaces of the valve disc and the valve seat, this is one of the common faults of spring safety valves. The main causes are as follows:
Dirt attachment: Dirt such as dust and impurities between the sealing surfaces of the valve disc and valve seat will affect sealing performance. This dirt may gradually accumulate during operation, preventing tight contact between the valve disc and valve seat.
Sealing surface damage: The sealing surface may suffer from wear, corrosion, or other damage after long-term use, making the surface uneven and rough, thus failing to achieve good sealing. Different levels of damage require different repair methods.
Valve stem deformation or inclination: If the valve stem bends, tilts, or the lever and fulcrum deviate, the valve core and valve disc may misalign, affecting sealing performance. This may result from improper installation, external force impact, or structural deformation caused by long-term operation.
Spring elasticity issues: If the spring elasticity decreases or is lost, it cannot provide sufficient pressure to maintain tight contact between the valve disc and valve seat, leading to poor sealing. Aging, fatigue, or corrosion of the spring may reduce its elastic performance.
This phenomenon makes the operation of the safety valve unstable and affects its normal function. The main causes are:
Excessive spring stiffness: Improper selection of spring stiffness, especially if too large, will cause the valve disc to chatter or vibrate frequently during opening. Too much stiffness means that under the same pressure change, the spring deformation is small, making the opening and closing actions of the valve disc less smooth.
Improper adjustment ring setting: Incorrect adjustment of the ring position can result in excessive reseating pressure. When reseating pressure is too high, the valve disc encounters greater resistance during closing, which easily causes vibration.
Excessive discharge pipeline resistance: If the discharge pipeline design is unreasonable and resistance is too large, it will create excessive discharge back pressure. This adds extra resistance to the valve disc during opening and closing, resulting in vibration or chattering.
When the pressure reaches the set opening pressure of the safety valve but it fails to open normally, possible causes include:
Incorrect pressure setting: The set pressure of the safety valve is inaccurate, possibly due to improper operation during adjustment or changes in spring elasticity. If the set pressure is too high, the valve may fail to open at the required actual pressure.
Valve disc and seat sticking: Adhesion may occur between the valve disc and seat, caused by long-term inactivity, impurity buildup, or corrosion, making it difficult for the disc to open at the set pressure.
Lever safety valve issues: If the lever is stuck or the counterweight is moved, the safety valve may fail to open normally. Poor lever movement or counterweight position changes alter the force balance, preventing opening at the specified pressure.
If the valve disc cannot reseat promptly after discharge, the safety valve remains open, failing to stop medium leakage. Causes include:
Spring bending or misaligned installation: A bent spring or misaligned valve stem/valve disc prevents smooth reseating. This may result from improper installation or external force impact.
Valve disc sticking: The disc may be stuck by impurities or foreign matter after opening, preventing normal reseating. This is often related to equipment cleanliness and medium properties; media with more impurities or particles can easily cause sticking.
This indicates that the discharge capacity of the safety valve is insufficient to meet safe relief requirements. Causes include:
Improper discharge capacity selection: If the selected safety valve capacity is smaller than the required relief capacity, excess medium cannot be discharged promptly. As pressure rises, insufficient discharge causes continued pressure increase, failing to protect equipment.
Misaligned stem or rusted spring: A misaligned stem or rusted spring affects the opening height of the valve disc, reducing actual discharge capacity. Rust reduces spring elasticity, preventing sufficient force to push the valve disc to the required opening height.
Insufficient exhaust pipe cross-sectional area: A too-small exhaust pipe cross-section restricts medium discharge speed, causing continued pressure rise. The exhaust pipe design must meet safety discharge area requirements.
When the safety valve opens before reaching the set pressure, possible causes are:
Incorrect pressure setting: Similar to failure to open at specified pressure, inaccurate setting may cause premature opening. This may result from improper adjustment of spring compression or counterweight position.
Spring aging and loss of elasticity: Spring aging reduces elasticity, making it unable to hold the valve closed until the set pressure is reached. Over time, this alters the valve’s opening pressure.
To ensure the proper operation of the spring-loaded safety valve and extend its service life, in addition to promptly eliminating faults, daily maintenance and care are required. The following are key points for routine maintenance and care.
Frequently keep the safety valve clean to prevent the valve body, spring, and other parts from being blocked or corroded by oil stains or dirt. Regularly clean the surface and internal parts of the safety valve, especially the sealing surfaces and moving components, to ensure they are free of impurities. For safety valves installed outdoors, appropriate protective measures should be taken to prevent rain, fog, dust, and other contaminants from entering the valve and discharge pipeline.
Regularly check whether the lead seal of the safety valve is intact to prevent the counterweight of the lever-type safety valve from loosening or being moved, and to avoid the adjusting screw of the spring-loaded safety valve from being tampered with. The integrity of the lead seal is an important guarantee for ensuring the accuracy of the set pressure. If damage is found, the cause should be promptly identified and the lead seal reapplied.
Frequently check whether the safety valve in operation shows abnormal conditions such as leakage, sticking, or spring corrosion. Observe whether the lock nut of the adjusting screw sleeve and the adjusting ring set screw is loose. If problems are found, appropriate corrective measures should be taken promptly. If leakage is detected, the safety valve must be repaired or replaced immediately, eliminating leakage by increasing the load is strictly prohibited.
To prevent the valve disc and valve seat from being stuck by oil or other impurities in the gas, which could prevent normal operation, safety valves used for air, steam, or other gases containing viscous impurities but posing no hazard during discharge should undergo regular manual exhaust tests. By manually opening the safety valve, its opening and closing performance can be checked to ensure reliable operation when needed.
For outdoor-installed safety valves, when the ambient temperature falls below 0 °C, necessary anti-freeze measures should be taken. Thermal insulation materials can be applied to the valve, or heating devices can be installed to prevent the safety valve and discharge pipeline from freezing due to low temperatures, which could hinder proper operation.
The safety valve should be periodically cleaned and calibrated to ensure good performance. Appropriate cleaning agents should be selected to avoid damage to valve components. Calibration must be carried out by qualified organizations, and after adjustment, multiple tests should be performed to verify whether all performance indicators of the safety valve meet the required standards.
As a critical safety device for pressure vessels, the spring safety valve plays an essential role in industrial production. Understanding the causes and solutions of its common faults is significant for ensuring equipment safety. In practice, we must not only troubleshoot faults in time but also strengthen daily maintenance and care to keep safety valves in good working condition. Through regular inspection, cleaning, adjustment, and component replacement, the service life of safety valves can be effectively extended, reliability improved, and smooth industrial production ensured. In short, only by attaching importance to the maintenance and management of spring safety valves can their protective role be fully realized, avoiding equipment damage and safety accidents caused by valve failures.
