Patent ID: 7818092
Filing Date: 2010-10-19
Classification: G01F,Y10T

Abstract:
1. A process for determining a quantity of a fluid expended to operate a process control device of a control system comprising: providing a control system operating with a normal instrument fluid supply, the control system having a process control instrument and at least one process control device; providing a controlled fluid source in the form of a tank of a predetermined volume containing a gaseous fluid in selective communication with at least one of the process control instrument or the process control device; providing a non-bleeding pressure regulator through which the gaseous fluid flows, the non-bleeding pressure regulator being upstream of the process control instrument, in series with and downstream of the controlled fluid source; providing a means for measuring pressure at an outlet of the process control instrument or of the process control device while the process control instrument is operating and communicating a measured pressure signal corresponding to the measured outlet pressure; determining an initial pressure of the controlled fluid source; supplying the fluid from the controlled fluid source to at least one of the process control instrument or the process control device; operating the control system for a predetermined length of time; determining a pressure of the fluid supplied from the controlled fluid source after the predetermined length of time; communicating to a processor at least one of a signal corresponding to a difference between the pressure of the fluid supplied from the controlled fluid source after the predetermined length of time and the initial pressure, and a first signal corresponding to the initial pressure and a second signal corresponding to the pressure of the fluid supplied from the controlled fluid source after the predetermined length of time; communicating a pressure transmitter signal corresponding to the measured outlet pressure to the processor; and calculating a difference between a value corresponding to a pressure of the fluid supplied from the controlled fluid source during the predetermined length of time and a value corresponding to the outlet pressure from the process control instrument or the process control device measured by the means for measuring pressure at the outlet of the process control instrument or the process control device.