by this minimum measure in light of the fact that the pig can be made for different diameter pipes it is better that the pig be oversized by a measure related to nominal pig i d a convenient minimum relationship is to make the pig disc 18 oversized by an amount of approximately 0 02 34 plug 0 01 times pipe diameter in inches for a 24 inch pipeline an oversized disc has a minimum of 0 26 34 to enable sealing scrapping as a practical matter for pipe above about 4 inches i d the overgage is up to about 0 02 plus 0 02 times nominal pipe i d thus the range of overgage can be defined as 0 02 plus pipe i d times 0 01 to about 0 02 on a large pig say 24 inches the diameter can be up to about 0 02 34 plus about 0 98 34 oversize about 1 00 34 is the reasonable maximum preferably the first and second disc differ by at least about 20 units in durometer hardness it is desirable to manufacture the pig with discs of relatively uniform thickness however the deflectability of the scrapper disc 18 can be changed by modification of its thickness considering variations in durometer and thickness it is preferable to construct the disc 18 so that it deflects between 3 and 7 times further on equal loading that is when a force is applied at the edge of the respective discs on the pig 10 deflection is larger by this amount it is preferable to construct the disc 18 with approximately the same thickness as the disc 14 or perhaps.