Installation Methods of Fully Welded Ball Valves
There is a buried fully welded ball valve among fully welded
ball valves. Here is a detailed introduction to the installation method of buried fully welded ball valves.
1. The valve body of the buried fully welded
ball valve is buried underground. It usually uses an extended rod method to place the opening method on the ground. Strict pressure testing should be carried out before installation.
1.1 Pipeline valves should undergo a pressure test before installation to ensure the tightness and safety of the valve itself.
1.2 Strength test. The strength test uses water as the medium. Weld high-pressure caps on the sleeves on both sides of the valve. After opening the valve to 45 degrees Celsius, inject water into the ball valve through the pressure-testing valve on the sleeve. Increase the pressure to 1.5 times the nominal pressure of the ball valve and maintain it for 15 minutes. No leakage is considered as qualified.
1.3 Tightness test. The rigorous test uses nitrogen as the medium. Close the ball valve. Inject nitrogen gas into the ball valve through the pressure test valve on the sleeve. Increase the pressure to 1.1 times the nominal pressure of the ball valve, and connect the pressure relief valve in the middle chamber to a water container for testing. The insertion depth is 1cm. If there are no bubbles generated within 5 minutes, it is considered as qualified.
2. Installation of fully welded ball valves
2.1 Lift the valve. The valve should be lifted in the correct way. To protect the valve stem, do not tie the lifting chain to the hand-wheel, gearbox, or actuator. Do not remove the protective caps on both ends of the valve sleeve before welding.
2.2 Valve welding process
The connection between the directly buried fully welded ball valve and the main pipeline shall be welded. The quality of the weld seam must comply with the Class II film standard of "Radiography of Disc Bend Melt Welding Joint" (GB3323-2005). Usually, one welding cannot fully guarantee the qualification. Therefore, when ordering the valve, the manufacturer should be required to add 1.0m long sleeve pipes at both ends of the valve. If the weld seam is unqualified, there is enough length to cut off the unqualified weld seam and re-weld it to the ball valve and pipeline. The valve should be in the 100% fully open position to avoid damage by splashing welding slag on the valve ball. At the same time, ensure that the temperature of the internal sealing parts of the valve does not exceed 140 degrees Celsius. If necessary, appropriate cooling measures can be taken.
2.3 Install valve wells for pouring
The directly buried fully welded ball valve adopts a special structural design with maintenance free characteristics. Before burial, Pu special anti-corrosion coating is coated on the outside of the valve. At the same time, three injection pipes are used for emergency grease injection on the valve seat and valve stem, and the middle cavity vent pipe and valve stem are appropriately extended according to the depth of the ground, so that workers can complete various operations on the ground. After achieving direct burial, a small valve hand well can be built, but for conventional non-fully welded ball valves, direct burial is not allowed, and a large valve well needs to be built, resulting in a dangerous enclosed space that is not conducive to safe operation. At the same time, the valve body itself and the bolt connection between the valve body and the pipeline may be corroded, affecting the service life of the valve.
3. Daily operation and maintenance
In order to extend the service life of the valve, the following procedures should be followed for valve operation and maintenance.
3.1 Buried fully welded ball valve operation
Frequent operation of the valve can prevent impurities from accumulating on the valve seat or ball surface. It also avoids excessive wear of the embedded body in the valve seat.
(1) Requirements for opening and closing time. Opening and closing the valve too quickly can cause excessive twisting and load on the valve, resulting in damage to the valve stem. Slow switching can cause the surface of the valve seat to be eroded and worn by the medium for a long time. Therefore, the operating time should be kept within an appropriate range. Based on experience, the range of valve opening and closing time (seconds) can be controlled, with a lower limit of half the nominal size of the valve (inches) and an upper limit of 5 times the nominal size of the valve (inches).
(2) When the valve is in operation, the valve ball should be in a fully open or fully closed position. It is not in a semi-open or semi-closed position, to avoid damage to the valve seat.
2. Daily maintenance
The valve seat chamber is the area where pipeline valves are most susceptible to contamination. To ensure free movement of the valve seat, it should be cleaned once a year and the sealing of the valve should be regularly checked through the drain nozzle. The valve of the auxiliary gas main line is often rarely adjusted, and it should be opened and closed at least once a year and injected with an appropriate amount of lubricating grease to prevent adhesion between the ball and the valve seat, as well as grinding between the ball and the valve seat. The excellent technical characteristics of buried fully welded ball valves enable the entire gas transmission pipeline to be welded together, enhancing the overall stress resistance and geological disaster resistance (such as geological collapse) of the pipeline (including valves), reducing the possibility of air leakage, improving valve reliability, prolonging service life, and making installation and maintenance very convenient.
