ISA 75.01.01

ANSI/ISA-75.01.01 (IEC 60534-2-1 Mod)-2007 includes equationsfor predicting the flow coefficient of compressible andincompressible fluids through control valves.

The equations for incompressible flow are based on standardhydrodynamic equations for Newtonian incompressible fluids. Theyare not intended for use when non-Newtonian fluids, fluid mixtures,slurries, or liquid-solid conveyance systems are encountered.

At very low ratios of pressure differential to absolute inletpressure (P/P₁), compressible fluidsbehave similarly to incompressible fluids. Under such conditions,the sizing equations for compressible flow can be traced to thestandard hydrodynamic equations for Newtonian incompressiblefluids. However, increasing values ofP/P₁ result in compressibility effectsthat require that the basic equations be modified by appropriatecorrection factors. The equations for compressible fluids are foruse with gas or vapor and are not intended for use with multiphasestreams such as gas-liquid, vapor-liquid or gas-solid mixtures.

For compressible fluid applications, this part ofISA-75.01.01-2007 is valid for all valves. However, manufacturersof some valves with x_T greater than or equal to 0.84have reported minor inaccuracies (see Annex G). Caution must alsobe exercised when applying the equations for compressible fluids togaseous mixtures of compounds, particularly near phaseboundaries.

The accuracy of results computed with the equations in thisstandard will be governed by the accuracy of the constituentcoefficients and the process data supplied. Methods of evaluatingthe coefficients used in the equations presented herein are givenin ANSI/ISA-75.02-1996. The stated accuracy associated with thecoefficients in that document is ± 5% when C_v/d² less than 0.047 N₁₈. Reasonable accuracycan only be maintained for control valves if C_v/d² less than 0.047 N₁₈.

Edition:

07

Published:

11/07/2007

ANSI:

ANSI Approved

Number of Pages:

76

File Size:

1 file , 310 KB