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Find the cause and take appropriate action! 01 Leakage in the valve body and valve cover. Causes: ① Poor quality of cast iron casting; defects such as sand holes, loose structures, and slag inclusions in the valve body and valve cover ； ②Heavenly freezing rupture ； ③Poor welding quality, with defects such as slag inclusions, unwelded areas, and stress cracks ； ④The cast iron valve was damaged after being struck by a heavy object. Maintenance methods: ① Improve casting quality; conduct strength tests strictly in accordance with regulations before installation ； ②Valves with temperatures at 0°C or below should be insulated or kept warm; valves that are no longer in use should have any accumulated water removed ； ③The welds between the valve body and the valve cover, which are formed by welding, shall be carried out in accordance with the relevant welding procedures; after welding, flaw detection and strength testing shall also be conducted ； ④It is prohibited to push or place heavy objects on valves; it is not allowed to strike cast-iron and non-metallic valves with a hammer. Large-diameter valves should be installed on supports. 02 Leaks at the packing – External leaks of valves are most commonly caused by problems at the packing area. Reason: ① The wrong type of packing was selected; it cannot withstand corrosion by the medium, nor can it handle high pressures or vacuums, as well as high or low temperatures ； ②The filler is not installed correctly; there are defects such as using a part of smaller size instead of one that’s appropriate, poor spiral winding of the joints, and uneven tightening ； ③The filler has exceeded its useful life, has aged, and lost its elasticity ； ④The valve stem lacks precision and has defects such as bending, corrosion, and wear ； ⑤Insufficient number of packing rings; the gland is not tightened properly ； ⑥The gland, bolts, and other components are damaged, preventing the gland from being compressed properly ； ⑦Improper operation, excessive force, etc ； ⑧The gland is skewed, and the gap between the gland and the valve stem is either too small or too large, resulting in wear of the valve stem and damage to the packing. Maintenance method: ① The material and type of filler should be selected based on the operating conditions ； ②Install the packing in accordance with relevant regulations; the packing rings should be placed and compressed one by one, and the joints should be at an angle of 30° or 45°℃ ； ③Fillers that have been in use for too long, have aged, or are damaged should be replaced promptly ； ④If the valve stem is bent or worn, it should be straightened and repaired; in cases of severe damage, it should be replaced promptly ； ⑤The packing should be installed in the specified number of turns; the gland should be tightened symmetrically and evenly, and there should be a pre-tightening clearance of more than 5 mm in the compression sleeve ； ⑥Damaged gland covers, bolts, and other components should be repaired or replaced promptly ； ⑦The operating procedures must be followed; except for impact-type handwheels, the operation should be carried out at a steady speed with normal force ； ⑧The gland bolts should be tightened evenly and symmetrically; if the gap between the gland and the valve stem is too small, this gap should be increased appropriately ； The gap between the gland and the valve stem is too large; it should be replaced. 03 Leakage at the sealing surface. Causes: ① The sealing surface is not properly ground, preventing the formation of a tight seal ； ②The tip at the connection between the valve stem and the closing element is suspended, misaligned, or worn ； ③The valve stem is bent or not properly assembled, causing the closing element to be misaligned or out of center ； ④The quality of the sealing surface material was improperly selected, or the valve was not chosen according to the operating conditions. Maintenance method: ① Select the material and type of shock pad correctly according to the operating conditions ； ②Carefully adjusted for smooth operation ； ③The bolts should be tightened in a uniform and symmetrical manner; a torque wrench should be used if necessary. The preload must meet the specified requirements, neither too high nor too low. There should be a certain pre-tightening clearance at the flange and threaded connections ； ④The gaskets should be aligned properly when assembled to ensure even distribution of stress; overlapping gaskets or the use of multiple gaskets is not allowed ； ⑤If the static seal surface is corroded, damaged, or of poor quality due to inadequate machining, it should be repaired and ground, and a coloring inspection should be carried out to ensure that the static seal surface meets the relevant requirements ； ⑥Care should be taken to keep the gaskets clean when installing them; the sealing surfaces should be cleaned with kerosene, and the gaskets must not touch the ground. 04 Leakage at the seal ring connection Cause: ① Inadequate pressing of the seal ring ； ②The sealing ring is welded to the main body, and the surfacing quality is poor ； ③Loose threads, screws, or washers connecting the sealing ring ； ④The seal ring connection is corroded. Maintenance method: ① For leaks at the sealed rolling area, apply adhesive and then roll to secure it ； ②The sealing ring should be rewelded in accordance with the welding specifications. When it is not possible to weld repairs at the surfacing area, the original surfacing and the machined portion must be removed ； ③Remove the screws and retaining rings for cleaning, replace the damaged components, grind the mating surfaces of the seal and the mounting seat, and reassemble. For components that have suffered significant corrosion damage, they can be repaired using methods such as welding or bonding ； ④If the mating surface of the seal ring is corroded, it can be repaired by methods such as grinding or bonding; if repair is not possible, the seal ring should be replaced. 05 Leakage caused by the detachment of the closing element. Reasons: ① Improper operation, which causes the closing element to get stuck or go beyond the top dead center, resulting in damage and breakage at the connection points ； ②The closing element is not securely connected; it becomes loose and falls off ； ③The wrong material was chosen for the connectors, which cannot withstand corrosion from the medium and mechanical wear. Maintenance method: ① Operate correctly – do not use excessive force when closing the valve, and do not open it beyond its upper dead center; after the valve is fully open, turn the handwheel slightly in the opposite direction ； ②The closing element should be firmly connected to the valve stem, and a backstop should be provided at the threaded connection ； ③The fasteners used to connect the closing element to the valve stem must be resistant to corrosion by the medium, and possess sufficient mechanical strength and wear resistance.