Marine valves play a crucial role in the ship's pipeline system, and their sealing technology requirements are strict, which is related to the safe navigation of the ship. The following elaborates on the sealing technology requirements for marine valves from multiple aspects:
Requirements for sealing materials
Material selection: Suitable sealing materials should be selected based on the operating conditions of marine valves, such as temperature, pressure, medium, etc. There are two common types of valve sealing ring materials: metal and non-metal. For example, synthetic rubber is generally used at a temperature of t ≤ 150 ℃, while natural rubber is used at a temperature of t ≤ 60 ℃, suitable for diaphragm valves, pinch valves, etc. with a nominal pressure PN ≤ 1MPa; Polytetrafluoroethylene is commonly used for globe valves, gate valves, ball valves, etc. with a temperature of t ≤ 232 ℃ and a nominal pressure of PN ≤ 6.4MPa; The commonly used grade of chromium nickel titanium stainless steel is 1Cr18Ni9ti, which has good corrosion resistance, erosion resistance, and heat resistance. It is suitable for shut-off valves, ball valves, etc. in steam, nitric acid and other media with temperature t ≤ 600 ℃ and nominal pressure PN ≤ 6.4MPa.
Performance requirements: sealing materials shall have good corrosion resistance, wear resistance, elasticity and aging resistance to ensure stable sealing performance during long-term use. For example, rubber seals used for marine valves should be able to resist corrosion from seawater and have sufficient elasticity to ensure sealing effectiveness.
Structural design requirements
Accurate design: Reasonably design the structural parameters of the valve, including the shape of the sealing surface, the number of sealing pairs, etc., to ensure uniform distribution of contact pressure on the sealing surface and reduce the possibility of leakage. For example, when designing a marine ball valve, it is necessary to ensure that the sealing surface between the ball and the valve seat is tightly adhered and the contact pressure is uniform.
Double sealing design: Some marine valves adopt a double sealing structure to improve sealing reliability. A double sealed marine valve, including a main pipeline, a secondary pipeline, a first control valve, and a second control valve, reduces the risk of pressure loss and improves safety through reasonable structural design.
Manufacturing process requirements
Processing accuracy: The processing accuracy of the valve sealing surface is crucial to the sealing performance. During the manufacturing process, it is necessary to ensure that the surface roughness, flatness, and concentricity of the sealing surface meet the requirements to ensure a good fit between the sealing surfaces.
Assembly quality: During the valve assembly process, it is necessary to strictly follow the assembly process requirements to ensure that all components are installed correctly and tightly, and that the seals are installed in place to avoid seal failure caused by improper assembly.
Sealing test requirements
Testing standard: Ship valves should undergo strength and sealing tests before installation. According to relevant standards, medium and high pressure valves should be inspected 100%, and the pressure should gradually increase during testing. Sudden and abrupt pressure increases are not allowed. The duration of strength test and sealing test is generally 2-3 minutes, and important and special valves should last for 5 minutes. During the sealing test, general valves are only tested once, while important valves such as safety valves and high-pressure valves need to be tested twice. During the experiment, the requirements for leakage should be implemented in accordance with relevant regulations.
Testing methods: Common sealing testing methods include air tightness testing, liquid tightness testing, etc. During the testing process, it is necessary to strictly follow the testing procedures to ensure accurate and reliable test results. For example, when conducting air tightness testing on marine valves, professional air tightness testing equipment should be used to detect the leakage of the valve under specified pressure.
Usage and maintenance requirements
Reasonable use: During use, attention should be paid to avoiding excessive pressure difference and flow rate, avoiding the impact and corrosion of materials on the valve, in order to reduce the possibility of wear and leakage of the sealing surface. For example, during the navigation of a ship, the valve opening should be adjusted reasonably according to the actual working conditions to avoid excessive pressure and flow rate on the valve.
Regular maintenance: Regularly maintain and inspect the valve, clean the inside of the valve, replace severely worn seals, and ensure that the sealing performance of the valve remains good at all times. For example, regularly inspect the seals of marine valves for wear, aging, and other issues, and replace them promptly if there are any problems.
