The problem of the valve not closing properly

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Leaky valves are a common problem in industrial fluid control, and their causes are often related to operational, maintenance, or design defects. The following are the main incorrect operating methods that lead to poor valve sealing, along with corresponding analyses: 1. Poor sealing due to improper operation 1. Excessive force or incomplete closure when shutting down the valve – Symptoms: Excessive torque is applied when closing manual valves, or electric/pneumatic valves stop moving before completing the closure process. - Consequences: It may cause misalignment between the valve core and the valve seat, or damage to the fluoropolymer coating (such as PFA, PTFE), resulting in minor scratches or deformation that compromises the sealing performance. - Case: In pipelines for ultra-high-purity chemicals, damage to the fluoropolymer lining can lead to medium leakage, affecting product purity (refer to the material properties of fluoropolymer ball valves). 2. Frequent opening and closing of valves – Error manifestation: Repeatedly opening and closing the valves over a short period of time, especially under high-temperature or high-pressure conditions. - Consequence: It accelerates the wear of the sealing surfaces, leading to a decrease in the fit accuracy between the valve seat and the valve core, and ultimately causing leakage. - Applicable scenarios: In the semiconductor industry, high-purity gas valves need to be used infrequently to extend their lifespan. 3. Operation not in accordance with the flow direction of the medium – Error manifestation: The valve is installed in a direction that does not match the flow direction of the medium, or a two-way valve is used in one direction for an extended period without having its direction changed. - Consequence: Medium erosion leads to increased wear of the unilateral sealing surface, resulting in leakage. - Solution: Install strictly in accordance with the markings on the valve body, and regularly switch the operating direction of the two-way valve. II. Inadequate sealing due to lack of maintenance 1. Failure to clean and lubricate regularly – Symptoms: Failing to remove impurities inside the valve over time (such as particles and crystals), or failing to apply lubricant to the moving parts. - Consequences: Impurities get trapped on the sealing surface, causing sticking; the lubricant dries up, which increases the resistance to opening and closing, preventing the valve core from closing fully. - Industry impact: In the transportation of electronic-grade chemicals, particle contamination can directly lead to a decrease in the yield of semiconductor chips. 2. Failure to replace seals in a timely manner due to aging – Symptoms of the issue: Failure to inspect vulnerable components such as O-rings and gaskets on a regular basis, or using them beyond their recommended lifespan. - Consequence: The seal loses its elasticity or becomes corroded, failing to fill the tiny gaps between the valve core and the valve seat. - Typical case: PTFE seals may accelerate aging in strong oxidizing agents (such as concentrated sulfuric acid). III. Inadequate sealing due to design or installation defects 1. Incorrect valve selection – Manifestation: The appropriate type of valve is not chosen based on the properties of the medium (such as corrosivity or particle content); for example, a fluorocarbon-lined ball valve is not used when a regular carbon steel valve would be more suitable. - Consequence: The medium corrodes the valve body or valve core, resulting in leakage. - Industry standards: Electronic-grade applications must comply with SEMI standards to ensure material purity and sealing performance. 2. Stress transfer from the pipeline to the valve – Symptoms of the problem: Expansion joints are not provided during valve installation, or the pipeline is not fixed properly, resulting in stress concentration. - Consequence: The valve body deforms, preventing the valve core from fitting tightly against the valve seat. - Preventive measures: Use flexible connections or supports to hold the pipes in place, so as to prevent external forces from affecting the valves. IV. Incorrect responses under special operating conditions 1. Failure to account for the effects of temperature changes – Error manifestation: Valves handling high-temperature media are not preheated, or valves handling low-temperature media lack insulation. - Consequence: Sudden temperature changes cause the valve body and the valve core to expand and contract at different rates, resulting in seal failure. - Solution: Gradually increase and decrease the temperature, using valves with radiators or jackets. 2. Operation at excessive pressure or temperature – Error manifestation: The valve operates for an extended period at pressures/temperatures exceeding those specified in its design. - Consequences: material creep, plastic deformation of the sealing surface, and ultimately leakage. - Industry warning: Ultra-pure gas valves in the semiconductor industry must be designed in strict accordance with ASME B31.3 standards. V. Proper Operation and Maintenance Recommendations 1. Operating Procedures – When closing manual valves, apply force slowly; for electric valves, ensure that the feedback signal from the actuator is normal. - Avoid frequent opening and closing, especially in high-risk operating conditions (such as flammable or highly toxic media). 2. Regular maintenance – Clean the interior of the valve quarterly and check for wear on the sealing surfaces. - Replace the seals as recommended by the manufacturer (usually every 1-2 years). 3. Selection and Installation – Choose the appropriate valve type based on the properties of the medium (e.g., ultra-high purity fluorinated rubber ball valves are required for electronic-grade applications). - Ensure that the pipes are stress-free during installation; use expansion joints or flexible connections if necessary. In summary, poor valve sealing is often caused by improper operation, lack of maintenance, or incorrect selection. In the field of ultra-high-purity chemicals (such as in semiconductors and photovoltaics), improper handling can directly lead to product contamination or equipment damage; it is therefore necessary to strictly adhere to industry standards (such as SEMI F57) and manufacturer guidelines. Regularly training operators and establishing preventive maintenance plans are key to reducing the risk of leaks.