Install the apparatus so that the b

Install the apparatus so that the bottom part of the pipe is located at the center of a test piece, and set the scale so that the zero is located 16mm above the surface of the test piece. Drop the steel ball specified in 5.2.1 Read the numerical value of the scale at the upper surface of the steel ball when it rebounds to the highest position. Obtain correct values at least three times within 1 min in a test pieces. In the case where the steel ball comes in contact with the pipe when the steel ball drops or rebounds, invalidate the value at that time. Express the median of the mumcrial values so obtained as the result. When a certain measurements deviate from the median by 20% or more, an additional examination is executed twice, and the median is calculated from five measurements.*”Median” is just a value of the center(in case of the odd number piece) or the average of two values in which the center is placed(In case of the even number piece) when measurements are arranged in order of the size.