34. If the first section of the drill pipe is unable to reach total depth, and higher strength pipe must by used, the previous equation will by modified to account for the variance. What will change is that the air weight of the drill collars multiplied by the length of the drill collars will now by added to the length of the pipe (L) multiplied by the air weight of the pipe (W), This number will then by divided by air weight of the second pipe (W2)