1. Main Types  

   - Spring-loaded Safety Valve: Most common type; opening pressure is set by adjusting spring preload.  

   - Lever and Weight-loaded Valve: Uses a lever and counterweight to balance pressure, suitable for low-pressure systems.  

   - Pilot-operated Safety Valve: Consists of a main valve and pilot valve, offering high precision and suitable for high-pressure, large-flow applications.  

2. Installation and Maintenance  

   - Installation Guidelines:  

     ✓ Mount vertically at the highest point of the pressure vessel or pipeline.  

     ✓ Discharge piping must be directed to a safe area to prevent harm.  

     ✓ No shut-off valve should be installed between the safety valve and equipment (unless in parallel and locked).  

   - Maintenance Requirements:  

     ✓ Conduct regular manual testing (monthly) to prevent valve disc sticking.  

     ✓ Inspect sealing performance (no leakage), spring condition, and corrosion.  

     ✓ Calibrate opening pressure annually by a certified agency.  

3. Common Failures and Solutions  

   - Leakage: Caused by disc wear or debris clogging → Lap sealing surface or clean.  

   - Failure to Open: Due to overtightened or corroded spring → Adjust or replace spring.  

   - Chattering (Rapid Cycling): Insufficient discharge capacity or excessive backpressure → Replace with a higher-capacity valve or reduce backpressure.  

4. Selection Considerations  

   - Choose type and material based on medium (steam, oil, water, etc.), temperature, pressure, and flow rate.  

   - Consider special requirements for vessel types (e.g., cargo ships, oil tankers, LNG carriers), such as explosion-proof design.