Before attempting to explain pipeline pigs, it’s necessary to cover some pipeline basics. Otherwise, we could regale a wide-eyed site visitor with details on hydrostatic testing all day long and end up with nothing but confused stares. It’s best just to remember that pipelines represent a hefty investment, one that has to be tested for initial functionality, and one that must be periodically cleansed in order to keep expensive fluids on the move. In protecting that investment, we need to access the part of a pipeline that can’t be reached by hand, the internal surfaces. Access comes from pipeline pigs, the small cylindrical devices that travel inside pipes. They’re carried by flow pressure and directed through the network of piping in an effort to clean debris out of the system, thus eliminating system congestion.
A crack in a pipe can be disastrous in the petrochemical industry. A blockage in a factory pipe will stop a newly formulated pharmaceutical before it mixes, rendering the process useless. The application of a pigging device allows engineers to enter this long, sealed environment with small devices, the so-called pigs that are driven through the pipeline. A pig launcher sends the device rocketing through the conduits, and it’s the job of an engineering team to direct the pig through each stage, a task they accomplish by opening and closing pipe valves as they corral it into each section. Incidentally, the alleged origins of the “pig” label stems from early versions of the device, a ball of wadded leather that pioneers pushed through pipes. The leather rubbed against the iron pipe and created a squealing noise, a sound that conjured up images of a trapped pig.
The format has changed dramatically since the early days of leather wadding. Solid steel bodies and mandrel assemblies scrape grease and debris from semi-blocked pipes. Special hydrostatic test units integrate electronics into the pipeline pigs, sending instrumentation through boreholes to collect data on the condition of every section of the pipe, including the quality of weld seams. They’re like smart bullets racing through a gun barrel, looking for leaks, and protecting us from pipe-related disasters that could result in a disastrous explosions. From one end of the design spectrum to another, the little pig’s journey through the pipes prove them as proficient cleaners and sentinel inspectors.
It’s impossible to see within a pipe once it’s part of a working system, to make a cleaner that can remove internal debris, but clever engineers have access to tiny, pipe-sized voyagers that can do all of these tasks. They eject unwanted materials that stubbornly cling to interior cylindrical surfaces, use virtual senses to magnetically check the condition of inward-facing surfaces, and work this magic in every industry where pipes are present.