A pig is a device inserted into a pipeline which travels freely through it, driven by the product flow to do a specific task within the pipeline. These tasks fall into a number of different areas: (a) Utility pigs which perform a function such as cleaning, separating products in-line or dewatering the line; (b) Inline inspection pigs which are used to provide information on the condition of the pipeline and the extent and location of any problem (such as corrosion for example) and (c) special duty pigs such as plugs for isolating pipelines. During the construction of the line, pigs can be used to remove debris that accumulates. Testing the pipeline involves hydro-testing and pigs are used to fill the line with water and subsequently to dewater the line after the successful test. During operation, pigs can be used to remove liquid hold-up in the line, clean wax off the pipe wall or apply corrosion inhibitors for example. They can work in conjunction with chemicals to clean pipeline from various build-ups. Inspection pigs are used to assess the remaining wall thickness and extent of corrosion in the line, thus providing timely information for the operator regarding the safety and operability of the line. Pigs (or more specifically) plugs can be used to isolate the pipeline during a repair. >