Description
A Pipeline Gauging Pig is a type of pipeline inspection tool used primarily to assess the internal condition of a pipeline before more advanced inspection or cleaning procedures are performed. Below is a detailed explanation of what it is, how it works, and its purpose.
What is a Pipeline Gauging Pig?
A Gauging Pig is a mechanical device inserted into a pipeline to verify the internal diameter and detect obstructions, deformations, or foreign objects. It is typically run before inline inspection (ILI) tools, like smart pigs, to ensure the pipeline is free of serious restrictions that could damage high-value tools.
- Foam Pig – for initial cleaning
- Gauging Pig – to verify integrity and clearance
- Cleaning Pig – to remove debris
- Smart Pig – for detailed inspection (e.g., corrosion, geometry, cracks)
Key Features
- Simple Construction: Often consists of a steel or aluminum body with sealing discs or cups.
- Gauging Plate: A thin aluminum or other soft metal plate attached to the pig deforms when it encounters a restriction.
- No Electronics: Unlike smart pigs, gauging pigs are mechanical and passive.
Primary Purpose
- Check for Obstructions: Ensures there are no blockages that may hinder subsequent pig runs.
- Confirm Bore Size: Verifies that the pipeline bore is uniform and within tolerance.
- Pre-Inspection Safety: Protects more expensive tools from damage by identifying problem areas first.
How It Works
- Inserted into the pipeline using a pig launcher.
- Propelled through the pipeline by product flow or compressed air.
- Gauging Plate bends or deforms if it encounters dents, weld protrusions, or other anomalies.
- Retrieved at a pig receiver and inspected for deformations.
Gauging Plate Types
| Type | Material | Use |
|---|---|---|
| Flat Plate | Aluminum | Most common; bends to show restrictions |
| Slotted Plate | Aluminum/Plastic | For more flexible or sensitive pipelines |
| Spring-Loaded | Steel/Plastic | Can maintain contact with wall for greater sensitivity |
Advantages of Pipeline Gauging Pig
- Inexpensive and simple
- Protects more valuable inspection tools
- Early indicator of pipeline issues
Limitations of Pipeline Gauging Pig
- Cannot give detailed data or measurements
- Only indicates that a restriction exists, not its exact type or location
Common Applications
- Pre-inspection for smart pigging
- Commissioning of new pipelines
- Routine maintenance checks
- Pipeline reactivation after shutdown
