Pipelines are cleaned by pushing through them a close-fitting cylinder called a pig. The name

comes from the squealing noise it makes sliding along. Ref. 50 describes a new non-toxic pig.

driven by compressed air, for cleaning cosmetic and beverage pipes. Suppose the pig

diameter is 5-15/16 in and its length 26 in. It cleans a 6-in-diameter pipe at a speed of 1.2 m/s.

If the clearance is filled with glycerin at 20°C, what pressure difference, in pascals, is needed

to drive the pig? Assume a linear velocity profile in the oil and neglect air drag.