Pipelines are widely used throughout the world to transport oil, gas and other fluids over long distances, across continents and offshore.
They are frequently subjected to extreme climatic conditions and huge temperature variations that can cause serious damage to the outer shell. This is why companies operating these lines use preventive methods to detect clogging, corrosion or worse, cracks and flaws that can have disastrous consequences.
One of these detection methods is called pipeline ‘pigging’. It uses devices known as ‘pigs’ to perform maintenance operations on a pipeline without stopping the flow of fluid.
Why pigs? Interpretations differ on why these maintenance devices are named pigs. Some allege that pig is an acronym for ‘pipeline inspection gauge’ or ‘pipeline intervention gadget’; others affirm that the original pigs, made of straw wrapped in wire, and used for cleaning, made a noise similar to the squealing of a pig when traveling through the pipe.
There are several types of pigs, from the foam pig, driven through the line to measure its inner diameter, clean it or dry it, to the inline inspection pigs, including smart pigs, that can check various aspects of the pipeline.
Modern smart pigs are highly sophisticated instruments that include electronics and sensors that collect various forms of data during their trip through the pipeline. They vary in technology and complexity depending on their intended use.
The electronics elements within the pig are sealed to prevent leakage of the pipeline fluid, which range from highly basic to highly acidic and can be of extremely high pressure and temperature. Power for the electronics is typically provided by onboard batteries which are also sealed.
As many of these pigs are used in oil or gas pipelines, it is of the utmost importance that they are designed and built in compliance with the very strict requirements enunciated in standards and specifications, most notably in IEC International Standards developed by IEC Technical Committee 31: Equipment for explosive atmospheres.
As part of its IEC 60079 series of international standards on explosive atmospheres, TC 31 has developed several international standards that cover general and testing requirements for several types of pigs, including magnetic or ultrasonic pig signallers, pig tracking systems and pig intelligent systems.
As is the case for any product, designing and building pigs in compliance with IEC International Standards is not enough. To prove that a pig meets all the requirements spelled out in standards and can be used in explosive (Ex) areas, it has to go through testing and certification.
This is where IECEx, the IEC System for Certification to Standards Relating to Equipment for Use in Explosive Atmospheres, intervenes. An IECEx certificate provides clear proof of claimed compliance with international standards andt certifies that the equipment in question has the right level of protection.
Read more about pipeline pigging in the latest edition of e-tech.