Repair and Maintenance
Operation and Maintenance
①. Operation
A. When the valve is opened and closed, turn the handle or hand wheel to drive the valve stem and ram to open and close, the force should be uniform during the opening and closing process, and the switching speed should be fast. When manually opening and closing the valve, pay attention to the rotation direction of the valve “clockwise close,counterclockwise open” to avoid unnecessary damage to the valve.The valve must be fully open or fully closed when in use and must not be used to regulate the flow rate.
B. Liquid medium valves operating below 0° C allow the valve to tilt no more than 30°from the vertical direction of the range of switch operation.
C. After the valve is installed, it must be in the fully open position during the pressure test of the system or pipeline. Do not leave the ram partially open.For regulating flow or emergency discharge, the manufacturer shall not be liable for any harm caused by such use.
D. Usually the gate valve has no insulation part, when the high temperature or low temperature fluid,
do not contact the valve surface to prevent burn/frostbite.
E. The surface and moving parts of the valve, such as the valve stem, the sliding part of the support and the gear, are easy to stick and accumulate ash Dust, oil and medium residue, easy to produce wear and corrosion and even friction heat on the valve, which is conducive to combustion. The gas is very dangerous and should be cleaned frequently according to the working condition.
②. Maintenance
The valve is a hybrid structure of the pressure vessel and the operating machinery, and the maintenance requirements for it should consider both the accidental opening and closing of the valve, and the valve is under pressure most of the time.
A. The maneuverability of valves that remain in a certain position for a long time may decrease to some extent due to corrosion or harmfulaccumulation on the surface of moving parts. In some applications, a partial or full cycle plan for the periodic cycle of such valves is finally developed.
B. Pressure boundaries,fixed assembly joints, and effective working seals between the moving stem and body should be inspected,maintained, and verified regularly.
C. The external structure of the valve is generally easy to inspect and maintain. Reasonable methods should be taken to prevent mechanical damage to the valve and to prevent the erosion of the valve by sediment, chemicals or wet gases in the atmosphere. Work interfaces such as threads, bearings or gears should be lubricated regularly.
Precautions
A. The medium passing through the pipeline should not have large hard particles to avoid damage to the sealing surface.
B. Handwheel or driving devices are not allowed to be used for lifting.
C. The valve must be fully open or fully closed when in use and must not be used to regulate the flow rate.
D. The valve shall be inspected and tested one by one according to API 598/BS6364standard before leaving the factory, and shall be delivered after passing. The installation unit must be installed and debugged according to the instructions before it can be used.
Possible Faults,Causes,and Troubleshooting Methods
| Possible Faults | Causes of faults | Troubleshooting Methods |
| Packing leakage |
1 The sealing surface has dirt and debris attached 2 Sealing surface wear,erosion damage 3 The sealing surface of ram is damaged |
1 Remove dirt and goo 2 Repair the sealing surface of the seat or gate 3 Repair the wedge |
| Sealing leakage |
1 The stud nut is not fastened evenly 2 Flange joint sealing surface is damaged 3 The gasket is damaged or invalid |
1 Uniform fastening 2 Re-repair 3 Replace the gasket |
| The drive is not flexible or the closure cannot be opened or closed |
1 A foreign body is stuck between the gate and the valve body 2 The drive mechanism or connector is damaged 3 The stem is bent 4 Debris is trapped in the rotating part 5 The threads on the valve stem and valve stem nut are damaged |
1 Remove foreign bodies and properly repair the two-seal surface 2 Disassemble and repair the drive mechanism or connecting parts. 3 Correct or replace the valve stem 4 Remove debris and grease 5 Trim the threads or replace the stem and stem nut |
| Leakage at valve stem |
1 Packing gland is not pressed tightly 2 The surface of the valve stem is damaged |
1 Tighten the compression nut evenly 2 Trim the stem surface or replace the stem |
| Middle flange of body leakage |
1. The bolts of the middle flange are loose 2. The gasket is faulty |
1. Tighten the nut of the middle flange 2. Replace the gasket |
| The wedge can’t be opened |
1. Wedge is stuck in the valve body 2. After the rod is heated, the wedge is dead |
1. The closing force is appropriate, and the structure can be used twice. The length of the lever,the use of long bars is not recommended Rod wrench; 2. When the closed gate is heating up, the valve stem should be unloaded once at a certain interval, and the handwheel should be reversed a little. |
