The Girard Polly-Pig is constructed of open cell polyurethane foam of various densities and is available with various types of external coatings. Although each pig has a specific application, some are interchangeable according to the user's preference within certain parameters.
The Girard Polly-Pig is molded of polyurethane foam material of light, medium or heavy density. Its bullet shape is designed to aid in traversing fittings and valves. Concave ends are available for bi-directional service. The length of the pig is approximately twice its diameter to reduce the possibility of the pig tumbling in the pipeline. The diameter of the Polly-Pig is larger than the inside diameter of the pipe. This is done to exert a frictional drag between the foam pig and pipe wall. Pigs can be ordered to any custom size requirements.
Polly-Pigs have a concave base plate with a 90A durometer polyurethane coating. This provides a maximum rear sealing surface for the propelling forces of the fluids or gases being used.
Swabs or bare pigs, which have only the bases coated, are normally used in drying or batching operations. Special double-nose or double-dished pigs are used in bi-directional service.
The exterior coatings on the foam bodies consist of criss-cross type spirals of 90A durometer polyurethane. These spirals add strength and give greater wiping and scraping action as compared with bare foam. Girard manufactures two types of criss-cross pigs: the original pattern and the patented "Turning Pattern." Wire brushes, silicon carbide or plastic bristles can be embedded in these polyurethane spirals to add maximum scraping or brushing action.