Test Bench for Process Control Valves.

A test bench was conceived in order to determine experimentally the flow coefficient [C_V] for process control valves, operating with compressible fluids, under established regulations by the standards ANSI/ISA-75.02-1996 and ANSI/ISA-75.01.01-2002. This test bench is used to verify the calibration of valves with continually variable opening, after they have been repaired. The measurements in the test bench allow establishing the C_V of these valves for various opening percentages. It was necessary to review the C_V equation for compressible fluids, to proceed with the flow sensor selection. This equation was obtained under similarity conditions, by the equality of Euler numbers between prototype and model (test specimen). It is also described the electronic instrumentation for measuring flow, temperature and pressure difference, the design and the development of electronic circuits which control the instrumentation, and the algorithms for the operation and acquisition of measurements.