Worksheet F-1.a
by M. Fraganza and M. Miccio based on the Examination test of January 16, 2008
rev. 1.1 of 30.04.2019

Objectives

• Selection and sizing of a butterfly valve (for adjustment) from the manufacturer's data in table form.
• Calculation and tracing of its flow characteristic in the nominal conditions object of the previous sizing.
• Tracing of the installed characteristic and calculation of a salient point chosen by the user

Data given by the manufacturer: PRATT

Valve size (inches):

Angle (deg):

Flow coefficient

NB:

as is typical of butterfly valves, the intrinsic characteristic is mixed: quadratic in the first section, with rapid closure in the final section.

Data input for valve sizing :

Select the liquid type

from the drop-down list:

upstream pressure P₁

downstream pressure P₂

vapor pressure P_v

mass flow :

nominal valve diameter (inch) :

Calculating Cv at stroke θ=65° and comparing it to the "required" Cv :

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Calculation and tracing of the Flow Curve

by "ISA Annex D"

vedi Magnani, Ferretti e Rocco

OTHER DATA:

They are determined, with ref. to Cv at the angle θ = 65 °, the following salient points:

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Writing the salient vectors, we give an asymptotic representation of the flow curve:

It is:

Data input for the installed characteristic :

pressure drop on the valve in nominal conditions ΔP_n :

pressure drop on the user equipment ΔP_u :

Pressure drop in the circuit:

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NB: This butterfly valve has only one type of intrinsic characteristic

Characteristic graphs:

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Calculation of transit flow rate and pressure drop for a pre-set angle value:

Input the angle value θ (degrees) at which the flow rate is to be calculated :

Calculations made for the value of the angle θ (degrees) that is closest to the chosen value:

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