Influence of connection stub parameters and valve closure time on transient measurement accuracy of a pressure transducer

Consider that a transient pressure measurement occurs at the end of the connection stub attached to a pipeline. The question arises as to whether the pressure being recorded at the end of the stub is an accurate representation of pressure in the pipeline. In this study, the influence of three parameters, including pressure transducer connection stub length, stub diameter and valve closure time, on the measurement accuracy of transient pressure is investigated through numerical simulation on a reservoir-pipe-valve-reservoir system. The results show that the larger the diameter of stub, the larger its influence both on the transient in the pipe and on measurement error; the measurement accuracy increases with an increase of the length of the stub only when the closure time of the end valve is less than the time for the water hammer wave to travel back and forth between the measurement point and the end point of stub. In contrast, when the closure time of the end valve is greater than the water hammer wave return time, the measurement accuracy will decrease with an increase of the stub length; the measurement accuracy is improved as the closure time of the end valve increases. As a result, in practice, diameter and length of connection stub for the pressure-transducer should both be selected to be as small as possible.