Inspecting Internal Leakages of Buried Ball Valves

Buried ball valves are a type of valve used in various industries to control the flow of fluids. They are called "buried" because they are typically installed underground, making them ideal for applications where space is limited, or aesthetics are important. These valves consist of a hollow ball with a hole in the center, which acts as the flow control mechanism.
 
One of the main advantages of buried ball valves is their durability. Since they are installed underground, they are protected from external elements such as weather conditions and physical damage. This makes them suitable for long-term use without requiring frequent maintenance or replacement. Furthermore, buried ball valves offer excellent sealing capabilities. The ball rotates within the valve body to open or close the flow path, creating a tight seal that prevents leakage. This ensures efficient operation and minimizes any potential environmental hazards.
 
In conclusion, buried ball valves provide numerous advantages in terms of durability, versatility, and sealing capabilities. Their ability to withstand harsh conditions and offer precise control over fluid flow makes them an essential component in various industries. Whether it is controlling water supply systems or managing industrial processes, buried ball valves play a crucial role in ensuring efficient operations while maintaining safety standards.
 
Since the valve cavity discharge pipeline of the buried globe valve of the natural gas pipeline has been led to the ground, and the discharge control is carried out through the cut-off valve or the drain nozzle; the flow meter can be connected to the cut-off valve outlet (Figure 2) or a special fixture can be connected to the drain nozzle through the special fixture.
 

Figure 2 The schematic diagram of the discharged pipeline of the ball valve cavity

1.1 Before daily pipeline hot work
(1) According to the operation plan, carry out the internal leakage detection of the main pipeline ball valve.
(2) Open the bypass pipeline of the main pipeline ball valve and close all the main pipeline ball valves.
(3) Open the vent valve of the ball valve cavity; perform manual venting and preliminarily judge the internal leakage.
The gas in the valve cavity can be emptied to normal pressure through the venting pipeline (drainage pipeline) of the valve cavity, and can be maintained for a long time, which means that the upstream and downstream valve seats of the valve don’t internally leak; if the gas in the valve cavity can be discharged. After a short time, if there is gas in the valve cavity after holding the pressure for a long time, it means that the valve internally leaks; if the gas in the valve cavity cannot be released all the time, it means that the valve internally leaks greatly.
(4) Close the vent valve of the valve cavity; install a joint and a flow meter at the outlet of the vent pipeline, and connect the outlet of the flow meter to the atmosphere.
(5) Slowly open the vent valve in the valve chamber to allow the gas in the valve chamber to flow into the flowmeter, and the flowmeter will measure the inflowing gas and control the opening of the vent valve so that the gas flow does not exceed the flow meter range. If the gas flow exceeds the trend of the flowmeter range, the flowmeter with a larger range should be replaced.
(6) After the flow reading of the flowmeter is stable or the vent valve is fully opened, record the data, that is, the total internal leakage rate of the upstream and downstream valve seats of the valve, as the first measurement result.
(7) Close the cavity vent valve and disassemble the flowmeter.
(8) Open the ball valve; close the bypass pipeline, and restore the process flow.
 
1.2 Pipeline hot work
(1) After the downstream (or upstream) pipe section of the valve is emptied, check to confirm that the main pipeline ball valve is closed and the pressure of the downstream (or upstream) pipe section of the ball valve is zero.
(2) Check and make sure that the vent valve of the valve cavity is closed; install a joint and a flow meter at the outlet of the vent pipeline, and connect the outlet of the flow meter to the atmosphere.
(3) Slowly open the vent valve in the valve chamber to allow the gas in the valve chamber to flow into the flowmeter, and the flowmeter will measure the inflowing gas; control the opening of the vent valve so that the gas flow does not exceed the flow meter range. If the gas flow exceeds the trend of the flowmeter range, the flowmeter with a greater range should be replaced.
(4) After the flow reading of the flow meter is stable or the vent valve is fully opened, record the data, which is the total leakage rate of the valve seat upstream and downstream, as the second measurement result.
(5) Compare the first measurement with the second measurement result. If the value remains unchanged, it means that there is only internal leakage of the valve seat upstream. The second measurement result is the leakage rate of the valve upstream seat. If the value decreases, it means that both the upstream and downstream valve seats internally leak. The second measurement result is the leakage rate of the valve upstream seat, and the difference between the first measurement result and the second measurement result is the valve downstream seat leakage rate.
(6) During the hot work of the pipeline, continuous measurements can be carried out on the drainage gas of the valve cavity to know the change of the gas pressure in the valve cavity in a timely manner.
(7) After the pipeline hot work is completed, close the vent valve of the valve cavity and disassemble the flowmeter.
(8) Restore the process flow of the valve chamber according to the gas supply plan of the pipeline. Restore the process flow.