Pig Detector and Pig signaller

What Does Pig Detector Mean?

A pig detector is a sensing tool used to detect the movement of a pig in a pipeline during pigging operations. The detector is installed on the exterior of the pipe and consists of an indicator (such as a LED light) that alerts operators to the pig’s proximity.

Pig detectors are usually placed near the launching and receiving stations, and they are useful for confirming the progress of the pig through the pipeline for maintenance operations.

A pig detector may also be known as a pig tracker.

Corrosionpedia Explains Pig Detector

Pig detectors may be classified as either intrusive or non-intrusive. Intrusive pig detectors are permanently mounted to the pipe via a specialized fitting. A probe that protrudes into the pipe is mechanically activated when the pig passes. A non-intrusive detector, on the other hand, does not need to be permanently mounted and usually senses the pig via magnetic detection.

Pig detectors may also be equipped with electrical switches and PLC controllers to automatically initiate subsequent operations such as clean-in-place processes, line venting, pump/compressor initiation, etc.

What Does Pig Signaller Mean?

Pig signaller is an omni trigger operated unit. The principle feature consists of a magnetic link between two packs of rare earth magnets.

The trigger is omni-directional and may also be actuated upwards as a plunger. When the trigger is actuated (very low torque is required) a follower mechanically moves a magnet pack axially in the signaller body. The magnet pack is strongly linked to a second magnet pack and shaft which move axially within an unpressurised housing.

The movement of the shaft operates a visual, manual reset flag or activates a limit-switch (auto-reset), giving a positive indication that a pig or sphere has passed the signaller.

The flag or switch may be set such that it can be seen from any given direction.

Pig signaller guide

• The pig-sig. range is specifically designed, in concept and detail, to overcome the limitations of earlier signalling methods;
• The sensor probe (trigger) is omni-directional: it can neither damage pigs or spheres nor be damaged by their passage;
• Trigger has 100% free movement; therefore positioning of welding boss is unrestricted;
• Indicator flag is rotatable in 90° increments to obtain the most visible vantage;
• Available for use with foam and polly pigs;
• Positive action indicator flag is instantly reset;