Malfunction Analysis：
The faults of Marine valves generally include valve body cover faults, packing faults and gasket faults.
Common faults of valve body and valve cover and cause analysis
Valve body and valve cover common faults are nothing more than damage, trachoma and aging or corrosion damage. There are several possible reasons for these problems.
(1)The valve body and bonnet damage is mainly due to small safety factor, unreasonable structure, concentration of internal stress and other poor design factors; Or because of poor manufacturing quality, such as uneven thickness, uneven material; Or because the weld is too brittle, internal stress is too large and other poor welding quality; Or due to improper installation, the position is skewed and twisted; Or due to improper valve selection, and the working condition is not suitable; Or because the water hammer pressure is too high; Or due to poor maintenance, winter insulation is not good freeze crack; Or destroyed by a powerful force.
(2)Trachoma is mainly caused by poor manufacturing quality.
(3)Corrosion or aging is mainly due to poor manufacturing quality, or due to poor anticorrosion and maintenance, replacement and maintenance is not timely.
Common faults and cause analysis of packing
The common faults of packing mainly include too small preload on packing, fastener failure, valve stem sealing surface damage and packing failure. The possible causes of these failures are as follows.
(1)The pretightening force on the packing is too small for the following reasons: insufficient packing, or due to insufficient filling quantity, or due to wear, aging and improper filling; Or because there is no preload clearance; Or because of the pressure sleeve skew, large diameter pressure on the stuffing box; Or because the thread buckle, rust, mixed with impurities, so that the thread tightening blocked.
(2)The reason for the failure of fasteners is that the gland, nut, bolt, ear and other parts are broken; Or relaxed by vibration; Or corroded; Or improper operation of fasteners is damaged due to uneven force or excessive force; Or because of poor maintenance.
The maintenance method：
Repair method of valve body and valve cover failure
On the valve body, valve cover faults common faults can also take the following repair methods: valve body and valve cover damage, trachoma, corrosion aging fault, according to the scientific plugging method plugging; Repair or replace damaged parts or replace valves as required.
Repair method for packing failure
(1)The repair method of preload is too small: after closing the valve or starting the seal, repair the parts, add filler, adjust the preload and preload gap; If the valve can not be closed, on the case of seal failure can be used valve mechanical plugging method or adhesive plugging method or injection agent plugging method for plugging; When the pressure sleeve grounding, should find out the cause of grounding, appropriate medicine, if the pressure sleeve burr or diameter is too large caused by the application of file force dressing to normal so far; If the thread is resistant to entry, it can be cleaned with rust remover or kerosene, and then the thread is repaired with a smooth file until its tightness is appropriate.
(2)The repair method of fastener failure is: after closing the valve, confirm that the packing will not move outward due to internal pressure, repair the fastener according to the normal method; If the valve can not be closed, can be used to replace the sealing method or with pressure bonding repair fasteners; If common fasteners are loose and damaged, they can be repaired and tightened directly.
(3)The repair method of valve stem sealing surface damage is: if it is slight damage can be eliminated by polishing method; If the sealing surface is damaged to leakage, it is necessary to close the valve or enable the upper seal, grinding or local coating repair; If the sealing surface is damaged and difficult to repair, it can be solved by replacing the valve with pressure.
(4)The repair method of packing failure is: after closing the valve or opening the seal, replace the packing or plug the leak with the appropriate valve plugging method, or replace the packing or replace the valve with other methods
