Sag

The reference test element shall be placed in a straight line on a smooth, horizontal table surface in such a way that one end of the duct extends 500 mm beyond the edge of the table. The part of the duct lying on the table shall be restrained on the top along its whole length. The sag is obtained by measuring the angle between the projected line of the support and the line defined by the free end of the duct.

Four measurements shall be performed with the test element by rotating the element 90° after each measurement and a subsequent waiting period of five minutes. The sag is the average value of the four measurements.