hazardous liquids and gas % Dent Ovality calculation for API 5L pipe
hazardous liquids and gas % Dent Ovality calculation for API 5L pipe
(OP)
Can anyone tell me the history of a commonly specified formula for determining the combination % dent ovality for natural gas and harzardous liquids pipelines (usually API 5L pipe)? The formula is this: % Dent/Ovality = [((Dmax-Dmin)-(B-A))/Dnom]*100.
I am having trouble understanding the B-A term. A is given as the depth of the dent. B is the distance from a superimposed nominal diameter distance to the bottom of the dent. Typically the Dmin is a field measured value from the top of pipe to the smallest measureable value at the deepest part of the dent. It would seem that the modification to Dmin would be to just add the dept of the dent to obtain the minor axis of the ellipse. Why does the formula subtract the B term? Is that some sort of factor of safety to make the % ovality more conservative because of the dent?
I am having trouble understanding the B-A term. A is given as the depth of the dent. B is the distance from a superimposed nominal diameter distance to the bottom of the dent. Typically the Dmin is a field measured value from the top of pipe to the smallest measureable value at the deepest part of the dent. It would seem that the modification to Dmin would be to just add the dept of the dent to obtain the minor axis of the ellipse. Why does the formula subtract the B term? Is that some sort of factor of safety to make the % ovality more conservative because of the dent?




