“intelligent” or “smart” pigs
In-line inspection (ILI) tools, sometimes called as “intelligent” or “smart” pigs, are advanced inspection technology that used to inspect pipelines for evidence of internal or external defect such as corrosion, laminations, deformations, cracks, or other defects. Pig is short for Pipeline Inspection Gauge. In addition, the pig also makes loud noises, like a pig, during the process of cleaning the inside of the pipe.
pig functions to clean dirt or unwanted objects that are feared will interfere with the flow of fluid in the pipe. Therefore pigs are equipped with special components, such as magnets and brush to sweep away dirt on the inner walls of the pipe.
Pigging is one of the routine activities carried out in the pipeline world. The goal is to carry out maintenance of the pipeline by inserting a tool called a pig into the pipeline through the pig launcher. This tool will move down the pipe, following the flow of fluid in it, until it reaches the end that has been determined. The pig will be retrieved through the pig receiver.
it is very important to select the correct tool. Pipeline operator will consider the pipeline integrity, pipeline physical condition and operational characteristics. They will evaluate the types of defects the pipe might be subject to and the risk presented to the pipeline section being inspected.
There are the two primary methods for ILI and each have their own advantages and disadvantages i.e. Magnetic Flux Leakage (MFL) and Ultrasonic Testing (UT).
MFL is a metal loss checking technique for pipes using the principle of a magnetic field. If a disturbance in the magnetic field is recorded, it means that there is metal loss at that point in the pipe. The pigs will be equipped with special sensors and memory to record the results (graphs) of the magnetic field emitted along the pig’s passage through the pipe. The data that has been obtained by the pig can be transferred to a computer, and then read the results.
Ultrasonic Testing (UT) tools are well suited for heavy walled pipe. Ultrasonic Testing tools will require couplant to make sure ultrasonic pulses can travel to the pipe wall. If there is any gas between Ultrasonic Testing sensors and the pipe wall, then we will have an interfere with the inspection. Magnetic Flux Leakage (MFL) and Ultrasonic Testing (UT) will require a clean pipeline. maintenance pig or cleaning pig should be carried out until we meet the cleanliness criteria before the smart pig is run through the line.
specifications for intelligent pig inspection of pipelines
The main purpose of pipeline pigging for in-service pipeline is for cleaning and inspection.
For the commissioning stage of new pipeline, pigging is required to:
- Proving that the pipeline is perforated in accordance with the design specifications and construction objectives of the pipeline.
- Clean the pipeline from unwanted material which is the remainder of the construction phase
For the operational reason, maintenance pig is required to reduce / eliminate deposits / accumulations that may affect the production process (pressure drop, roughness, liquid slug, etc.).
During my job assignment in Oil and Gas Company, I have experience with LIN SCAN, ROSEN and DACON technology. Each ILI tool has unique specification. ILI company providers will design the tools to be “fit for purposes” for each pipeline segment.