The length of a hinge pin support bearing or a clapper arm bearing consisting of a material having
strength and corrosion resistance equivalent to cast iron shall be equal to or greater than 70 percent of
the diameter of the hinge pin, but not less than 5/16 inch (7.9 mm). A clapper arm bearing made of
material having strength and corrosion resistance equivalent to Series 300 stainless steel shall have a
minimum length of 0.165 inch (4.2 mm). Equivalency is to be determined by means of comparative
corrosion tests, depending upon material type. When a hinge pin is not used, the clapper support shall
comply with the requirements of 10.3.