When talking about pipeline pigging and how it works, most people think about the traditional way of sending a mechanical device called a pig down a pipe for inspection or cleaning. However, there is now a newer technology called ice pigging that serves the same purpose but uses an ice slurry instead of the solid pigs of its predecessor. But despite achieving the same goals, these two popular pipeline cleaning technologies each have strengths and weaknesses that influence which is the better option for a given cleaning project. Below, we go over these pros and cons to paint a better picture of what each method is best used for.
Traditional hydraulic pigging starts with sending a ‘prover’ pig with a tracking device down the pipes to check for any obstructions, followed by a series of specialised cleaning pigs to remove leftover products throughout the entire pipeline.
Traditional pigging is ideal for cleaning long miles of pipelines of varying diameters (up to 96 inches) and restoring them to their original conditions or close to them. This is where traditional pigging has an edge over ice pigging, as it can clean longer segments without stopping. However, the latter can certainly clean up to three miles of piping, provided they have a smaller diameter.
The use of a foam pig does raise the concern of getting stuck somewhere along the line, but this rarely happens now unless there are severe line obstructions in the pipes. Choosing the correct pig types and materials also helps prevent this problem, as well as using them to navigate only the elbows, tees, and valves they were designed for.
The two shortcomings of traditional pigging revolve around its setup process and water consumption. For one, it requires a launcher and a receiver to be installed at each pipe end to run the pigs. This process adds time to the overall pigging operation, especially when excavation is also necessary to complete the installation.
Lastly, traditional pigging techniques consume more water by up to 50% for a typical operation compared to ice pigging. If the operation uses unidirectional flushing, traditional pigging uses up to five times more water to boot.
Ice pigging is a newer solution that replaces solid pigs for an ice slurry to remove common pipeline issues since ice is far more effective at cleaning pipes than just flushing with water alone.
The almost liquid form of the ice slurry lends to several advantages, namely greater flexibility to different pipe sizes and obstacles, little to no risk of getting stuck, and being faster than traditional pigging when cleaning underground pipes. Ice pigging can navigate a varied topography of pipe sizes, bends, and valves without any risk of getting stuck, as the ‘pig’ will eventually melt even if the slurry does get blocked.
Ice pigging also has a more streamlined physical setup (which does not need any launcher or catcher devices), making it more time efficient as the ice slurry can be injected into a pipe in mere minutes, provided its opening is two inches or greater. Apart from pipe openings, ice pigs can also be introduced into other existing fittings like air release values, manual air bleeds, fire hydrants, and washouts.
Ice pigging is not without its disadvantages, which mainly involve being less effective at removing tough stains, discovering obstructions, and cleaning large-diameter piping (typically anything beyond 24 inches). Unlike solid pigs, ice pigs are less aggressive at removing obstructions like calcified fats, oils, grease, and hard tuberculation. And since ice pigs are untrackable and less likely to get stuck, they have a lower chance of detecting obstructions that may indicate a bigger issue in the piping.
Hydraulic pigging with solid pigs and ice pigging are two of the most well-known pipeline-cleaning technologies used today. Knowing the pros and cons of each allows operators to choose which is best suited to achieve the goals for a given pipeline cleaning project without running the risk of encountering costly issues.
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