Description

Introduction to Pig Detectors

Pig Detectors, also known as Pig Signallers or Pig Indicators, are devices used in pipeline systems to detect the passage of a pipeline inspection gauge (pig). Operators send pigs through pipelines to clean, inspect, or perform other maintenance tasks. These detectors help operators confirm a pig’s location, which is crucial for operational control, safety, and maintenance scheduling.

1. Trigger Types

This refers to the mechanism by which the detector senses the pig’s passage.

Bi-directional: This type of detector can accurately sense and indicate the passage of a pig traveling in either direction through the pipeline. This is a versatile and essential feature for complex pipeline networks where flow can be reversed or where pigs are launched and received from the same location.

Uni-directional: A simpler mechanical or non-visual trigger that detects the pig only when it passes in one specific direction.

2. Indicator Types

This describes how the device alerts the operator after detection.

Popper: A mechanical flag that physically “pops up” or changes position. It provides a clear, local visual indication.

Manual reset flag: A flag that stays in the signaled position until an operator manually resets it.

Manual reset flag combined with electrical switch output: Offers both a local visual flag and an electrical signal (for remote monitoring/SCADA systems) that can be transmitted to a control room.

Digital display combined with electrical switch output: Provides a local digital readout (e.g., pass count, time) along with a remote electrical signal output.

3. Base Types

This specifies the connection method for installing the detector onto the pipeline.

1. 2″ flange connection: Uses a standard 2-inch flange for bolted connection to a pipeline fitting.
2. 2″ welded nipple: A 2-inch nipple (a short pipe) that is welded directly onto the pipeline.
3. 2″ welded base NPT nipple connection: Features a base with a National Pipe Taper (NPT) threaded connection, which is then welded to the pipeline.

Summary Comparison Table