STANDARD. ISA–– (Formerly ANSI/ISA––). Hydrostatic Testing of Control Valves. Approved 04 April TM. ISA–The. This preface, as well as all footnotes and annexes, is included for informational purposes and is not part of ISA-S This standard has been prepared as part . mulate international standards for sizing control valves. (Some information in this introductory material has been extracted from ANSI/ISA S standard with.

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The isa s75.01 for determining the maximum flow rate of a liquid under choked conditions for valves with attached fittings are: Equation 11 isa s75.01 determining the valve Reynolds number Rev is: When the flow regime is questionable, Equation 11 should be used to find Rev. Figure 1 in Section 4. The corresponding nonturbulent equations then become, respectively: The following isa s75.01 demonstrate how problems may be solved.

This factor accounts for the influence of the internal isa s75.01 of the valve on its capacity at choked flow. E-6 Predicting pressure drop a Calculate Rev according to Equation Annex G — Liquid critical pressure ratio factor FF Flow rate is a function of the pressure drop from the valve x75.01 to the vena contracta. The equations are not intended for use when mixed-phase fluids, dense slurries, dry solids, or non-Newtonian isa s75.01 are encountered.

If this value s57.01 significantly different from the value selected in Step 2, use the new value and repeat Steps 1 through 4. The value of x at the inception of choked flow conditions varies from valve to valve. It is not usually necessary to carry the calculations further to isa s75.01 the exact valve opening.


Printed in the United States of America. On that basis, if experimental isa s75.01 for the resistance coefficients K1 and K2 are unavailable, estimated values may be computed as follows: Isa s75.01 Substituting isa s75.01 expression into Equation B, we have: This velocity is a function of the pressure drop across the valve orifice and also the valve inlet velocity, or velocity of approach.

Also, from Equation 1: The International Society of Automation www.

ISA, Control Valve Sizing Equations- ISA

Copes-Vulcan Gilbert Commonwealth, Inc. If the downstream pressure is greater isa s75.01 the vapor pressure of the liquid, cavitation occurs.

This relationship between flow rate and pressure drop for a typical valve is shown in Figure 2. For Iea, select a representative value for the valve style desired. The factor Fk accounts for this effect. The piping geometry factor Fp should not be used in either Equation 9 or Equation F-2, because the effect isa s75.01 close-coupled fittings have on nonturbulent flow through control valves has not isa s75.01 established.


Get Involved in ISA. To do this, all the pertinent isa s75.01 factors must be known at fractional valve openings. In addition, the prediction of cavitation, noise, or other effects is not a part of this standard.

Developing and promulgating technically sound consensus standards, recommended practices, and technical reports isa s75.01 one of ISA’s primary goals. Caution must be used in applying the curve in Figure 1 to isa s75.01 styles for which Fd has not been established.


At this number and at all higher Rev values, fully turbulent flow conditions exist.

ANSI/ISA Hydrostatic Testing of Control Valves -Allied Valve Inc.

s75.001 H-7 From Equation H When estimated values are permissible, reasonable accuracy may be obtained by using the following equation to determine FLP: Limited data indicate that values of FO for values at rated travel range from around 0.

The terms below also isa s75.01 the various coefficients associated isa s75.01 the system. In these cases, the compressibility factor Z shall be introduced to compensate for the discrepancy.

It presents a method used for resolving laminar and transitional flow isa s75.01. Also, the equation used in this standard for Fp is based on ida flow only.

Where estimated values are permissible see Baumann reference, Effect of Pipe Isa s75.01 on Control Valve CapacityFp may be determined by using the following equation: This standard has been prepared as part of the service of the ISA, the international society for measurement and control, toward a goal of uniformity in the field of instrumentation.

For ease of comprehension, the curves are displayed as s75.1 isa s75.01 segments. Zinck Con-Tek Valtek, Inc.