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What are the installation methods of buried all welded ball valve

Release date: September 22, 2020

The valve body of buried all welded ball valve is buried in the ground, and it is usually opened and installed on the ground by pull rod method. Strict pressure testing must be carried out before installation.

1. Before installation, pressure test shall be carried out for pipeline valve to ensure its air tightness and safety.

2. Power experiment. Water is used as a medium for strength testing. High pressure rubber caps are welded to sleeves on both sides of the valve. When the valve is opened to 45 ° C, water is written into the ball valve through the sleeve pressure test valve. The pressure is increased to 1.5 times of the nominal pressure of the ball valve. Keep the pressure for 15 minutes. No leaks were found.

3. Sealing test. Nitrogen was used as the medium for the closed experiment. The ball valve is closed. Nitrogen is written into the ball valve from the pressure test valve on the sleeve. When the pressure rises to 1.1 times of the nominal pressure of the ball valve, the pressure relief valve in the central chamber is connected to the hose through a water container for testing. The penetration depth is 1 cm, and bubbles are not allowed to appear within 5 minutes.

 Buried all welded ball valve

All welded ball valve device:

1. Lift the valve. The valve must be lifted in the correct way. To protect the valve stem, do not attach the lifting chain to the handwheel, gearbox or actuator. Do not remove the protective covers on both ends of the valve sleeve before welding.

2. Valve welding technology. The connection between buried all welded ball valve and main pipe is welded. The weld quality must meet the class II specification of "punk added fusion weld radiography" (gb3323-2005), because generally, one-time welding can not guarantee all certification. When ordering valves, the manufacturer must be required to add 1.0 m long sleeves at both ends of the valve. Welding is not certified and will not be certified if satisfactory lengths are achieved. Joint cutting and re welding. When welding the ball valve to the pipeline, the valve should be in the 100% fully open position to prevent the spatter welding slag from damaging the valve ball and preventing the temperature of the internal seal of the valve from exceeding 140 ℃. By all means. If necessary, appropriate cooling methods can be used.

3. The valve of the equipment has been inverted. The buried all welded ball valve adopts special structure design, which has the characteristics of unprotected structure. Prior to insertion, a special Pu corrosion resistant coating is applied to the outside of the valve, and the valve seat is coated with three writing tubes of the spool and stem that push grease in. The ventilation pipe and valve rod of the central cavity are properly extended according to the depth of the ground, so that the staff can complete various operations on the ground. Once the direct burial is completed, a small valve hand well can be built. Generally, ball valves that are not fully welded cannot be directly buried in the ground and require the construction of large valve wells, which will lead to dangerous confined spaces and will not lead to safe operation. At the same time, the bolt connection between the valve body and the valve body and the pipeline will corrode, which will affect the service life of the valve.

Installation of welded ball valve

The following procedures must be followed for valve operation and protection:

1. A fully welded buried ball valve will be activated. Frequent operation of the valve not only prevents impurities from accumulating on the surface of the seat or ball, but also prevents excessive wear of the seat insert.

(1) Request when opening and closing. If the valve switches too fast, the valve will deform the load too much. The valve stem will be damaged. If the switching is too slow, the valve seat surface will be washed and worn by medium for a long time. Therefore, the operation time should be kept in an appropriate range. Experience has shown that the lower limit of valve switching time can be halved to the nominal valve size (inches) and the upper limit can be estimated to be five times the nominal valve size (inches).

(2) The valve is working. The seat should be fully open or fully closed, not in the half open or half closed position to prevent damage to the seat.

Normal maintenance

The valve seat cavity is the simplest contamination area of the pipeline valve. To ensure free movement of the valve seat, clean it once a year and regularly inspect the valve seal at the hole leakage. Grease the valve seat and the auxiliary valve seat at least once a year, and then apply grease to the valve seat. You need to avoid friction. The outstanding technical features of buried all welded ball valve integrate (all welded) the whole natural gas pipeline, and improve the overall resistance of pipeline (including valve) to stress and geological disasters (such as geological collapse). It is very easy to install and protect the valve.

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