Worksheet GL-c3

by M. Fraganza and M. Miccio based on the Examination test of June 10, 2015
rev. 2.5 on 16.04.2021


Objectives

Plotting the possible intrinsic characteristics (given Cvn for each DN).

Sizing the valve as a function of authority: the value chosen for the authority automatically determines the inherent characteristic of the valve.

Plotting the installed characteristic from the values of measurement rangeability and authority.

Verifying the sized valve for another nominal flow rate with a different liquid.

Data:


Select the type of fluid from the list:

the liquid selected from the list is the one with the highest density, which will determine the highest Cv
atm
Pa
psi

Insert P1

Insert P2

Insert Pv
L/s
gal/min

Insert the volumetric flow rate

Calculation of the flow coefficient:

Calculation of the intrinsic characteristic

and

of the flow coefficient Cv* at 70% stroke:

Manufacturer's table for Samson valve Series V2001 Type 3321

Input rangeability:

VA1 type valve, with equal percentage characteristic.

Input Cvn :

VA2 type valve, with linear characteristic.

Input Cvn :

VA3 type valve, with quadratic characteristic.

Input Cvn :

Data entry for the installed characteristic:
atm
Pa
psi
bar

Enter the value e Pu for the utility:

Selection of the most suitable intrinsic characteristic for the valve with the above DN and the above authority:

if V > 0.4,

if V ≤0.25,

if 0.25 < V ≤0.4,

=%
linear
quadratic

Select the intrinsic characteristic:

Calculation of the nominal flow rate

Calculation and plotting of the installed characteristic

Flow calculations through the valve at a given value of opening:

Input h1 (corsa):

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Calculation of the stroke at a given value of the flow rate:

Input flow rate [gal (US)/min]:

h2 it is determined by the intrinsic characteristic chosen by an inverse formula

Check cavitation:

Input FL:

Calculation of the theoretical recovery coefficient:

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Calculation and plotting of the flow characteristic:

OTHER DATA:

see Magnani, Ferretti e Rocco

Calculate relevant points, referring to Cv at 70% of the stroke and to the selected liquid :

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Valve verification problem:


Select the fluid from the list::

Calculate the new nominal flow rate:

Ceck again the flow rate:

Input the verification value for flow rate [gal (US)/min]