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So-called general-purpose valves include: ball valves, gate valves, globe valves, butterfly valves, and other valves that serve a switching function. General-purpose ball valves include floating ball valves, fixed ball valves, flanged ball valves, socketed ball valves, welded ball valves, ANSI standard ball valves, high-pressure ball valves, high-temperature ball valves, electric ball valves, pneumatic ball valves, brass ball valves, stainless steel ball valves, gas ball valves, manual gate valves, pneumatic gate valves, electric gate valves, forged steel gate valves, ANSI standard gate valves, knife gate valves, gas gate valves, visible stem gate valves, hidden stem gate valves, stainless steel gate valves, bellows gate valves, electric globe valves, pneumatic globe valves, vacuum globe valves, forged steel globe valves, high-pressure globe valves, angle-type globe valves, steam globe valves, ANSI standard globe valves, German standard globe valves, bellows globe valves, stainless steel globe valves, pressure gauge globe valves, pneumatic butterfly valves, electric butterfly valves, flanged butterfly valves, eccentric butterfly valves, control butterfly valves, ANSI standard butterfly valves, vacuum butterfly valves, signal butterfly valves, high-temperature butterfly valves, ventilation butterfly valves, stainless steel butterfly valves, wafer-type butterfly valves, hard-seal butterfly valves, and soft-seal butterfly valves, among others. Under normal circumstances, if the valve doesn’t close properly, first check whether it has been closed fully. If it is already closed fully yet there is still leakage and it cannot be sealed, then examine the condition of the sealing surfaces. For some valves, the sealing pairs are removable; in that case, they should be taken out and ground before testing again. If it still cannot be sealed properly, then it is necessary to return it to the factory for repair or replace the valve, in order to prevent issues such as impaired normal operation of the valve and operational accidents. If the valve does not close properly, the first step is to identify where the problem lies, and then address it using the appropriate methods. The common reasons why a valve does not close properly are as follows: (1) Impurities get stuck on the sealing surface; debris accumulates at the bottom of the valve or gets trapped between the valve disc and the seat ； (2) The valve stem threads are rusted, preventing the valve from rotating ； (3) The valve sealing surface is damaged, resulting in leakage of the medium ； (4) The valve stem is not properly connected to the valve disc, causing the valve disc to be misaligned and fail to make tight contact with the valve seat. Solutions for valves that don’t close properly: 1. Impurities stuck in the valve’s sealing surface: Sometimes a valve stops closing properly suddenly, possibly because of impurities stuck between its sealing surfaces. In such cases, one should not try to close it forcefully; instead, the valve should be opened slightly before attempting to close it again. Repeating this process usually resolves the issue; if not, further inspection is required. The quality and cleanliness of the medium should also be maintained. II. Rust on the valve stem threads: In the case of valves that are usually in the open position, they may not close properly when closed occasionally, due to rust on the valve stem threads. In such cases, the valve can be opened and closed several times, while simultaneously tapping the bottom of the valve body with a small hammer; this will ensure that the valve closes properly, without the need for any grinding or repair of the valve. III. Damage to the valve sealing surface: If the valve cannot be closed properly even after attempting to open and close it several times, it means that the sealing surface is damaged – either due to corrosion or scratches caused by particles in the medium. In such cases, it is necessary to seek repair. IV. Poor connection between the valve stem and the valve disc: In this case, it is necessary to apply lubricant to the valve stem and the valve stem nut to ensure smooth operation of the valve. A proper maintenance plan should be in place to enhance the maintenance of valves.