Section 5(3)(a) in The Petroleum and Natural Gas Regulatory Board (Determining Capacity of Petroleum, Petroleum Products and Natural Gas Pipeline) Regulations, 2010
(a)Constant parameters in the unit as specified in the approved flow equation as per sub-clause (v) of this clause.(i)Internal diameter - The internal diameter shall be determined based on weighted average of internal diameters based on different pipe thicknesses, used in different sections in the pipeline system.(ii)Length - The actual length (for already installed pipeline) or proposed length (for yet to be installed pipeline) of the pipe in the pipeline system.(iii)Roughness - This is fixed value for a pipe which determines the unevenness inside a pipe. Depending on the pipe material the below given value for roughness factors, all be used: