Removable Pig Indicators – with Ball Valve

The pig signaller is often used in the descaling process of long-distance pipelines.


Why do you use a pig signaller?

The pig signaller is often used in the descaling process of long-distance pipelines. At present, most of the pig signallers used in the long-distance pipeline are explosion-proof mechanical ball-through indicators, for example, most of the pig signallers used in the long line of Sinopec Instruments are explosion-proof mechanical ball-through indicators. This kind of indicator has the advantages of simple structure, explosion-proof, direct and reliable indication, etc. It can transmit the passage of the pigging body in the pipeline through mechanical positioning, so as to guide the switch of the process. After the ball indicator is used for a long time, the equipment will appear different degrees of corrosion and aging problems and need to be maintained and replaced, Because the through ball indicator is installed on the inlet and outlet pipelines and the receiving cylinder of the oil transmission station, the maintenance and replacement of the through ball indicator can only be carried out after the pipeline is stopped and emptied. Moreover, due to terrain factors, the empty-setting operation time after the shutdown of some oil transmission stations is long and difficult, so the maintenance and replacement of the pig signaller are very difficult, and the shutdown cost is high and the safety risk is greater. In order to solve the problem of maintenance and replacement of the through ball indicator, Pressure disassembly through ball indicator came into being.

pig signaller2

The pig signaller disassembly tool is mainly composed of 9 parts, including movement connecting head, long shaft smooth rod, ball valve, reducing connecting pipe, sealing cylinder, pressure gauge joint, sealing gland, feed device (feed thread pipe, feed sleeve), casing seal and so on. Wherein, the movement connecting head is connected with the long shaft smooth rod through the square head and 1 screw; the DN65 mm ball valve is connected with reducing connecting pipe and sealing cylinder through thread; The pressure gauge joint is welded on the sealing cylinder; The upper part of the sealing cylinder is a sealing part, which is mainly composed of sealing gland, 2 types 0 sealing rings, 2 copper gaskets and U-shaped sealing rings for the piston rod; The feed device is composed of two parts, the feed thread pipe is directly connected with the sealing cylinder, the feed sleeve is connected with the feed thread pipe, combined into a feed device; The sleeve head is connected with the feed sleeve and the upper part of the long shaft rod, and there is a type 0 sealing ring in the sleeve head as the shaft seal to prevent external water, air, and impurities from entering the tool and causing corrosion inside.



Operation method

The disassembly and assembly of the ball indicator mainly include the following 10 steps:

1. Connect the movement connector to the movement with the hex wrench.

2. Connect the reducing connecting pipe to the base of the ball indicator, and wrap raw tape on the thread to enhance the tightness.

3. Slowly rotate the long-axis light rod counterclockwise, and observe the pressure gauge value, When the pressure gauge value changes, stop rotating the long-axis light rod; After the pressure is balanced and stable with the pressure in the pipeline, continue to rotate the long-axis smooth rod counterclockwise under no abnormal condition, and unscrew the movement from the base.

4. Rotate the feed device counterclockwise to completely retract the movement into the sealed cylinder.

5. Close the ball valve and drain the oil in the sealing cylinder until the pressure gauge is 0.

6. Remove the sealing cartridge from the ball valve, take out the old movement, and install the new movement.

7. Connect the sealing cylinder to the ball valve, then slowly open the ball valve, and pay attention to the change in the pressure gauge value.

8. After the pressure gauge value is stable, rotate the feed device clockwise and move the movement to the base position of the pass ball indicator.

9. Rotate the long shaft smooth rod clockwise and tighten the movement on the base of the pass ball indicator.

10. Slowly empty the crude oil in the sealing cylinder, and pay close attention to the change of the pressure gauge value. If there is no change within a period of time after the value of the pressure gauge is 0, it means that the movement has been successfully replaced; If the pressure gauge value is not 0, it indicates that there is leakage between the movement and the base, then remove the movement and replace the movement again.

pig signaller


The practical application shows that the developed tool can solve the problem of maintenance and replacement of the ball indicator under pressure. For the ball-through indicator commonly used in the long-distance pipeline industry, the main structure of the tool remains unchanged for the ball-through indicator of different sizes. By replacing the movement connector of different sizes, most ball-through indicators can be dismantled and assembled with pressure. It can greatly reduce the pipeline outage time, reduce the production cost of enterprises, and has great reference significance for the same industry in the maintenance and replacement of the ball indicator movement.




pig signaller







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