The objective of the present paper is to examine the effect of tightening procedure on scatter in axial bolt forces and the bolt forces distribution in bolted gasketed pipe flange connections where spiral-wound gaskets and PTFE blended gaskets are used. The scatter in the axial bolt forces was examined by several tightening procedures which are JIS B 2251, ASME PCC-1 legacy, ASME alternative #1, #2, #3 and 3 rounds method procedures in ASME 24“ bolted gasketed pipe flanged connection. The leak rate of the tightened bolted flanged connections was also measured. Furthermore, the assembly efficiency based on both axial bolt forces and the tightness parameters of the bolted pipe flange connections was calculated and compared. The obtained results are as following. First, the leak rate of the connection tightened by JIS procedure is the lowest of all the tightening procedures. Second, the assembly efficiency based on axial bolt forces tightened by JIS procedure is the highest, and the assembly efficiency based on tightness parameters according to JIS procedure is also the highest. Third, the assembly efficiency based on tightness parameters is smaller than that based on the axial bolt forces. As a conclusion, the JIS B 2251 procedure is the most efficient tightening procedure of all the tightening procedures tested in the present study and the assembly efficiency based on the tightness parameters is suggested to design bolted connections for more safety.