Abstract

Precise determination of the full opening time of ON-OFF pneumatic valves is mandatory especially when they are used as safety elements. This paper proposes a new identification method based on the time at which the tank pressure time derivative is maximum during a charge test. Assuming that the flow is still choked in the valve at least up to this time, it can be shown that this maximum coincides with the full opening. In order to fulfill this condition, a minimal volume for the tank is required according to the valve dynamics and its flow characteristics. Two other conditions have to be verified: first, a constraint on the temperature time derivative during the opening phase and second, a constraint on the temperature itself just after the full opening. It can be shown that these requirements are well met. in adiabatic and isothermal conditions. However, in the general case, i.e. when convective heat exchange is considered, the analytic expression of the admissible range of physical parameters for the experimental setup is not obvious. Simulations for different kinds of opening evolutions, time displacements and valve flow characteristics underline the interest of the method and show that limitations can be reached only in non-realistic conditions. Finally, experimental results consisting in applying the proposed method to charge tests of several volumes with two kind of valves show perspectives in using this new experimental method along reliability tests.

This content is only available via PDF.
You do not currently have access to this content.