The general objective of the present investigation was: determining the relation of equivalent length in different kinds of valves and accessories, the one that it was used for the following: gate valve 100 % open, gate valve 75 % open, gate valve 50 % open, valve horizontal check, globe valve and elbow of 90°. For that matter, in every one of the mentioned valves and in 90° elbow, it came true previously the measurement of the flow and the evaluation of the pressure drop. The results indicated that, the minimal and maximum value of the pressure drop are: 10 mbar and 48 mbar, which correspond to the globe valve and to the gate valve 50 % open, respectively. In the same way, results indicated that, the minimal and maximum value of the relation of equivalent length are: 11 and 51.2, which correspond to the globe valve and to the gate valve 50 % open, respectively. This tried that as he i...