Intrusive Welding Pig Signaller

EMT’s range of intrusive pig signallers are detector instruments mounted on pig launcher and receiver stations to confirm the launch or arrival of a pig. They can also be mounted at any location on a pipeline and will detect the passage of all types of pipeline pigs. 



Intrusive Welding Pig Signaller is intrusive and has a bidirectional trigger. It can be used to monitor the passage of pigs. It can be equipped with a, B, C, D, and other displays. When the pig passes through, the two-way trigger in the pipeline triggers the action of each display:
A: Magnetic lock type pop-up flag;
B: The indicator flag changes from a horizontal state to a vertical state;
C: The indicator flag changes from horizontal to vertical. SPDT or DPDT electric switch acts and maintains;
D: The digital time display starts counting. Is the actual time when the storage is triggered? The SPDT or DPDT electric switch acts and remains until the timing time set at the factory. The display returns to the standby state.
Media compatibility:
Applicable media of sn2-tqz sealing material: compressed air, cold water, and seawater. There are also oil, natural gas, aliphatic hydrocarbon, and oil.
Unsuitable medium for sealing material: oxidizing solid medium and chlorinated hydrocarbon. There are also aromatic hydrocarbons, basic hydrocarbons, ketones, and esters.

Intrusive Welding Pig Signaller

Working principle

Taking sn2-tqz as an example, the end of the movement mounted on the base has a bidirectional trigger striker. The striker penetrates into the inside of the pipe near the pipe wall. When the pig passes through, the striker is pulled and the connecting rod is pulled to make the flag cap pop up. After the flag cap pops up, it will remain in the ejected state before the manual reset. This indicates that the pig has passed.
After the pig passes, the striker will automatically return. At this time, press the flag cap forcibly to reset it and enter the standby state.
If the flag cap fails to reset after being pressed. This indicates that the pig is here. And the striker does not return

Main technical indicators

1. Working pressure: 0 ~ 5MPa and 0 ~ 16MPa. (or designed according to user requirements);
2. Operating ambient temperature: – 20 ~ 120 ℃. (comprehensive value, which may vary for specific media)
3. Base material: Q235A or 20 # (standard configuration)
4. Media compatibility: see overview

Installation method

1. According to the model of the instrument and the wall thickness of the pipe, the hole shall be opened above the pipe at the installation position.

The base pair diameter of sn2-tqz is φ 114 and above.
Opening size:
When the wall thickness of sn2-tqz is 4 ~ 15mm. Opening size ≥ φ 51mm. When the wall thickness is 16 ~ 25mm, the opening size ≥ φ 56mm

2. Installation and inspection

First, determine the extension length of the striker.

Rotate the movement according to the pipe wall thickness to adjust the extension length of the striker. This makes the space position of the shaft center of the striker shaft between 0 ~ 3mm above the inner wall of the pipe after installation. Note the relative position B between the movement and the base (the distance from the upper mouth of the movement display base to the upper mouth of the base).

Secondly, the welding and installation process is completed in four steps.

a) Insert the through Intrusive Welding Pig Signaller with the extended length adjusted into the pipe opening and rotate the movement to make the straight line formed by the flat mouth of the movement parallel to the pipe direction. Weld, a point at the weld junction to position it. When the steps on the base cannot complete the self-positioning of the insertion depth, manual positioning is required during welding.
b) Unscrew the movement from the base and put it in a clean packing box.
c) The base shall be firmly welded to the pipeline according to the welding requirements.
d) After the base is cooled, apply lubricating oil on the sealing surface of the unit and the base, and then install the unit back on the base. B should basically conform to the recorded dimensions. The straight line formed by the flat mouth is parallel to the pipeline direction. Then, tighten the lock nut to make it sealed externally and prevent the movement from rotating.

Check the installation accuracy by measuring the external dimensions :

1. The straight line formed by the flat mouth of the insert is parallel to the pipeline direction:
2. Opening size φ When the wall thickness is 51 ± 1mm (i.e. 4-15mm), when the pipe wall thickness is 4-5mm, B = 51mm; When the pipe wall thickness increases by 1mm on the basis of 5mm, b decreases by 1mm (for example, when the pipe wall thickness is 8mm, B should be between 48 ± 1mm).
3. Opening size φ When the wall thickness is 56 ± 1mm (i.e. 16 ~ 25mm), when the pipe wall thickness is 16mm, B = 51mm; When the pipe wall thickness increases by 1mm on the basis of 16mm, b decreases by 1mm.

Welding requirements

Welding specification JB / t4709-2000. Product welding test plate JB / t4744-2000.
Types, standards, and grades of welding rods applicable to different base metals.
Base metal grade and welding rod model are standard welding rod grades.
Q235 or 20 # e4323 GB / t5117 J422
304SS E308-16 GB/T983 A102
E308-15 GB/T983 A107

Type a sensitivity inspection and adjustment

The stainless steel cylinder installed on the sealing sleeve is detachable. Its function is to protect and limit the indicator flag. After the Intrusive Welding Pig Signaller is installed. If the operator wants to check whether the device is sensitive and reliable. At this time, he can disassemble the stainless steel cylinder to simulate the downward movement of the connecting rod. When the stainless steel cylinder is unscrewed, the flag cap will pop up. In design, the maximum displacement that can be generated by the connecting rod driven by the striker is 13 mm. (when the striker is moved to generate 90-degree deflection). The distance that the stainless steel cylinder moves out when the flag cap pops up is the required connecting rod displacement.

Rotating the stainless steel cylinder counterclockwise can improve the sensitivity of the ball indicator. However, we should pay attention not to increasing the sensitivity to the point where the displacement of the connecting rod is ≤ 3 mm. (rotate the stainless steel cylinder two times anticlockwise, and the flag cap will pop up.).

Before the ball indicator is used below the freezing point, it must be confirmed that the flag cap of the instrument is not frozen on the stainless steel cylinder. The method is to rotate the stainless steel cylinder counterclockwise. If the flag cap of the instrument can pop up, the instrument is normal. If it does not pop up, the flag cap is stuck. Then we should separate them. Dry the contact surface between the two, then install it back to the original position.

Direction adjustment of type B and type C displays

After completing the installation steps. If we want to adjust the orientation of the display. Then slightly loosen the four nuts under the display method. The operator rotates the meter clockwise. After reaching the proper position, they tightened the four nuts that were loosened.


Sn2-tqz welding the non-metallic sealing ring between the base of the base-type flag ball indicator and the movement. It can seal the pipe medium. After one installation, the sealing surface will automatically match the sealing surface of the movement and the base. When it is necessary to remove the unit for remote maintenance or replacement. Operators should use small levers such as flat screwdrivers. The flat mouth is inserted into the ring groove at the upper part of the sealing ring. The operator carefully takes out the non-metallic sealing ring. Then they numbered it (including parking position and time) and saved it. Wait until the original movement comes back.

When installing a new movement on the original base, we should use a new sealing ring. Once a new sealing ring is used, it can be reused only when it follows the movement that uses it. In other words, a used sealing ring. It can be installed on other compatible bases together with the action using it.

When leakage occurs at the sealing ring, first, check whether the lock nut is tightened. If it has been tightened, it is likely that the sealing surface is not clean during installation and the sealing is not tight. In this case, the pipeline needs to be reinstalled after shutdown and pressure relief. When reinstalling, determine whether a new sealing ring is required according to the situation.
If the ball indicator is contaminated by viscous materials, we should first remove the stainless steel cylinder. Then remove the components of the stainless steel cylinder for cleaning.

Application in the medium of crystallization at room temperature

When the sn2-tqz through ball indicator is used in the medium of crystallization at normal temperature. We must ensure that the medium at the base has melted before the instrument is triggered. Otherwise, the following serious consequences may occur:

1. The dynamic seal ring of the instrument is scratched, causing leakage;
2. The instrument fails, and the striker is damaged;
3. The ball is stuck.

If you have any other questions about Intrusive Welding Pig Signaller, please contact our professionals to answer them for you.


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