Sizing - Fiorentini · Sizing the Pressure Regulators Sizing of regulators is usually made on the...

SizingPressure Regulators &Control Valves

Sizing the Pressure Regulators

Sizing of regulators is usually made on the basis of Cg valve and KG sizing coefficients. Flow rates at fully open position and various operating conditions are related by the following formulae where:

Q = flow rate in Stm3/hPu = inlet pressure in bar (abs)Pd = outlet pressure in bar (abs).

A > When the Cg and KG values of the regulator are known, as well as Pu and Pd, the flow rate can be calculated as follows:

A-1 in sub critical conditions: (Pu<2xPd)

A-2 in critical conditions: (Pu�≥2xPd)

B > Vice versa, when the values of Pu, Pd and Q are known,the Cg or KG values, and hence the regulator size, may be calculated using:

B-1 in sub-critical conditions: (Pu<2xPd)

B-2 in critical conditions (Pu�≥2xPd)

NOTE: The sin val is understood to be DEG.

KsinPuCgQ xxxx= 1526.0)( PdPuPdKG -xx

PuKG

Q x=

Q =

2PuCgQ xx= 526.0

)( PdPuPd

QKG

-x

=

sinPu

QCg

xx

=

526.0

Pu

QKG

x=

2

0,526 x Pu

QCg =

Pu

PdPu - ((

K1xPu

PdPu - ((

REGULATOR INTEGRAL SLAM SHUT

INTEGRAL MONITOR

INTEGRALSILENCER

APERFLUX 851 -5% -5% -5%

REFLUX 819 -7% -7% -5%

REFLUX 819/FO -7% -7% -5%

APERVAL SA-10%

SB-5% -5% -5%

REVAL 182 SA-10%

SB-7% -7% -5%

DIXI -3% Not applicable Not applicable

DIVAL 600 0% Not applicable 0%

NORVAL -7% Not applicable Not applicable

NORVAL 608 -7% Not applicable -10%

CAPACITY REDUCTION TABLE:

The above formulae are applicable to natural gas having a relative density of 0.61 w.r.t. air and a regulator inlet temperature of 15°C. For gases having a different relative density d and temperature tu in �°C, the value of the flow rate, calculated as above, must be multiplied by a correction factor Fc, as follows:

175.8

S x ( 273.15 + tu )Fc =

in order to get optimal performance, to avoid premature erosion phenomena and to limit noise emissions, it is recommended to check gas speed at the outlet flange does not exceed the values of the graph below.

Fc Factor0.780.630.550.790.730.63

Relative density1.01.532.00.971.141.52

Type of gasAirPropaneButaneNitrogenOxygenCarbon dioxide

Correction factors FC

Lists the correction factors Fc for anumber of gases at 15°C.

CAUTION:

where:V = gas speed in m/secQ = gas flow rate in Stm3/hDN = nominal size of regulator in mmPd = outlet pressure in barg.

140

150

160

170

180

190

200

210

220

230

240

250260

0 1 2 3 4 5 6 7 8 9 10 11

Outlet pressure [bar]

Gas

pre

ssur

e at

the

outle

t fla

nge

[m/s

ec]

The gas speed at the outlet flange may be calculated by means of the following formula:

Pd

Pd

DN

QV

+

x-xx=

1

002.0192.345

2

TablesCg and Kg valve coefficient

Nominal diameter (mm)Size (inches) Cg flow coefficientKG flow coefficientK1 body shape factor

Reflux 819/FO

251"

575605

106,78

2008"

2593327282106,78

1506"

1660717471106,78

803"

49375194

106,78

502"

22202335

106,78

1004"

80008416

106,78

25010"

3652538425106,78


Reflux 819

251"

575605

106,78

2008"

2593327282106,78

1506"

1660717471106,78

803"

49375194

106,78

502"

22202335

106,78

1004"

80008416

106,78

25010"

3652538425106,78


Aperflux 851

1506"

1111211678113,9

251"

480505

113,9

2008"

1731618199113,9

803"

37903979113,9

502"

15501627113,9

1004"

55545837113,9

25010"

2454825850113,9


50 2”

16821768103

80 3”

42004414108

Aperflux 101


Staflux 185

251"

439462

106,78

803"

37643960

106,78

502"

16811768

106,78

Staflux 187

251"

130136

106,78


251"

15916799,5

Dixi AP


251"

17017993,5

Dival 160 AP



Aperval 101

50 2”

20912199108

80 3”

47965045108

1004”

71767546108


Aperval

251"

58461390

1004"

67197055101

652"1/2 35303706101

502"

19782077101

803"

45254751101



Terval

1004"

54905775100

652"1/2

27312875104

502"

17061796108

803"

39064112100


251"

575605

106,78

1506"

1660717471106,78

1004"

80008416

106,78

652"1/2

33204197

106,78

502"

22202335

106,78

803"

49375194

106,78

2008"

2593327282106,78

25010"

3652538425106,78

Reval 182


Terval/R

1004"

56605954106

652"1/2

27932940104

502"

16671755104

803"

40994315106


Dixi

502"

10141066

96

251"

54056796

401"1/2

9831034

96


Norval 608

502"

17001788106

803"

35003681106


Norval

251"

331348

106,78

803"

33953571

106,78

652"1/2 22402356

106,78

401"1/2 848892

106,78

1004"

51005365

106,78

502"

13601430

106,78

1506"

1060011151106,78

2008"

1660017463106,78


Dival 600

251"

26928394

401"1/2 65268594

502"

78182186

401"1/2 69272795

502"

77080997

Head ø 280 Head ø 280/TR251"

31533197

Dival 700 See the capacity Table


Choise of the valve is usually on the basis of Cg valve and Cg flow rate coefficients.Cg coefficient corresponds numerically to the value of air flow in SCF/H in critical conditions with full open valve operating with an upstream pressure of 1 psia at a temperature of 15°C.KG. coefficient corresponds numerically to the value of natural gas flow rate in Stm/h in critical conditions with full open valve operating with an upstream pressure of 2 bar abs at a temperature of 15°C. Flow rates at full open position and various working conditions, are bound by the following formule where:

Pu = inlet pressure in bar (abs) Q = flow rate in Stm/HPd = outlet pressure in bar (abs) KG, Cv, Cg = valve coefficent

1 > When the Cg and KG values of the control valve are known, as well as Pu and Pd, the flow rate can be calculated as follows:

1.1 > in non critical conditions:

1.2 > in critical conditions:

2 > Vice versa, when the values of Pu, Pd and Q are known, calculate the values of Cv, Cg or KG with:

2.2 > in critical conditions: (valid for Pu ≥ 2 x Pd)

Reflux 919 - Syncroflux - VLMSizing the Control Valve

(Pu - Pd) Pd KGQ = 106,78 sinPuCvQ xxx= 16,8Pu

Pu - Pd( (

Pu Q= 16,8 x Cv x Pu Q= 0,526 x Cg x Pu (valid for Pu ≥ 2 x Pd) KG

Q x=2

(valid for Pu < 2 x Pd)

( Pd )PuPd

QKG

-

=

sinPu

QCv

x 106,78xx

=

.16,8Pu

PdPu - ((

Pu

QKG

x=

2

16,8 x Pu

QCv =

A oversizing of 20% on calculated values is raccomanded. Cg formulae give flow rate values more correct while KG formulae give values 5% higher than real ones only in noncritical conditions. In the case of noise limitation level a speed at the outlet flange of 130 m/sec. it is also raccomanded. Above formulae are valid for natural gas with a relative specific gravity of 0,61 compared to air and temperature of 15° C at inlet. For gases with different relative specific gravity (S) and temperature t (in °C) ), value of flow rate calculated as above, must be adjusted multiplying by:

175.8

S x ( 273.15 + tu )Fc =

(valid for Pu < 2 x Pd)

Nominal diameter (mm)Size (inches) Cg flow coefficientKG flow coefficientCv flow coefficient

Reflux 919 - Syncroflux - VLM

251"

57560518

2008"

2593327282

810

1506"

1660717471

519

803"

49375194154

502"

22002335

69

1004"

80008416250

25010"

36525384251141

106,78 sinPuCgQ xxx= 0,526 Pu

Pu - Pd( (

sinPu

QCg

x 106,78xx

=

.0,526Pu

PdPu - ((

0,526 x Pu

QCg =

Choise of the valve is usually on the basis of Cg valve and Cg flow rate coefficients.Cg coefficient corresponds numerically to the value of air flow in SCF/H in critical conditions with full open valve operating with an upstream pressure of 1 psia at a temperature of 15°C.KG. coefficient corresponds numerically to the value of natural gas flow rate in Stm/h in critical conditions with full open valve operating with an upstream pressure of 2 bar abs at a temperature of 15°C. Flow rates at full open position and various working conditions, are bound by the following formule where:

Pu = inlet pressure in bar (abs) Q = flow rate in Stm/HPd = outlet pressure in bar (abs) KG, Cv, Cg = valve coefficent

1 > When the Cg and KG values of the control valve are known, as well as Pu and Pd, the flow rate can be calculated as follows:

1.1 > in non critical conditions:

1.2 > in critical conditions:

2 > Vice versa, when the values of Pu, Pd and Q are known, calculate the values of Cv, Cg or KG with:

2.2 > in critical conditions: (valid for Pu ≥ 2 x Pd)

DeltafluxSizing the Control Valve

Volume flow rate (gas and vapor)

Weight flow rate (gas and vapor)

Weight flow rate (saturated steam)

Weight flow rate (overheated steam)

Volume flow rate (gas and vapor)

Weight flow rate (gas and vapor)

Weight flow rate (saturated steam)

Weight flow rate (overheated steam)

ΔP (P1+P2)G T

Q = 290 Cv

Q = 355 CvGΔP (P1+P2)

T

W = 13,55 Cv ΔP (P1+P2)

W = 13,55Cv ΔP (P1+P2)

(1+0,00126Δ t)

Q =262 F Cv P1

G T

W = 321 F Cv P1GT

W = 11,73 F Cv P1

W = 11,73F Cv P1

(1+0,00126 Δ t)

B. Critical conditions(when ΔP � 0.5F2 P1)

A. Subcritical conditions(when ΔP < 0.5F2 P1)

W = 19,1 Cv ΔP (w1+w2)

W = 27,1 Cv ΔP w1

W = 13,5 F Cv P1 (w1+w2)

W = 19,1 F Cv P1 w1

w1 = 100Xg (Vg1-Vf) + 100 Vf

w2 =100

Xg (Vg2-Vf) + 100 Vf

B. Critical conditions(when ΔP ≥ 0.5F2 P1)

Constant liquid/gas mixture ratio (liquid containing non condensable gas or liquid containing high title vapor)

Variable liquid/vapor mixture ratio (liquid containing low title vapor, less then 0.5)

Variable liquid/vapor mixture ratio (liquid containing low title vapor, less then 0.5)

Constant liquid/gas mixture ratio (liquid containing non condensable gas or liquid containing high title vapor)

A. Subcritical conditions(when ΔP < 0.5F2 P1)

GAS, VAPOR AND STEAM BIPHASE FLUIDS

A. Subcritical conditions(when ΔP < F2 ΔPc)

Volume flow rate

Weight flow rate

W = 855 Cv GfΔP

Qf = Cv ΔP 1.17 Gf

Note:For values of ΔP ≥ ΔPk the valve works under cavitation conditions.

LIQUIDS

= valve flow rate coefficient: US gpm of water with

∆P = 1 psi

= valve pressure drop P1-P2: bar

= maximum dimensioning differential pressure: bar

= cavitation differential pressure: bar

= overheating temperature delta t1 - ts: °C

= valve recovery factor: non dimensional

= gas relative density (air=1): non dimensional

= liquid relative density at operating temperature

(water at 15°C=1)

= valve incipient cavitation factor: non dimensional

= weight percentage of gas or vapor in the mixture at

upstream pressure: %

= valve upstream pressure: bar abs

= valve downstream pressure: bar abs

= vena contracta critical pressure: bar abs

= thermodynamic critical point pressure: bar abs

= vapor pressure at operating temperature: bar abs

= upstream gas absolute temperature (273+°C): °K

= overheated steam upstream temperature: °C

= saturated steam temperature at upstream pressure: °C

= volume flow rate at 15 °C and 1.013 bar abs: Sm3/h

= volume flow rate: m3/h

= weight flow rate: Kg/h

= upstream mixture density: kg/m3

= downstream mixture density: kg/m3

= specific volume of liquid: m3/kg

= specific volume of gas or vapor at upstream pressure: m3/kg

= specific volume of gas or vapor at downstream pressure: m3/kg

Cv

ΔP

ΔPc

ΔPk

Δt

F

G

Gf

Kc

Xg

P1

P2

Pc

Pk

Pv

T

t1

ts

Q

Qf

W

W1

W2

Vf

Vg1

Vg2

Glossary

B. Critical conditions(when ΔP ≥ F2 ΔPc)

Volume flow rate

Weight flow rate

Qf = F Cv 1.17 Gf

W = 855 F Cv Gf Δ Pc

ΔPc = P1-Pc

ΔPk = Kc (P1-Pv)

Pc = Pv (0,96-0,28 ) Pv

Pk

ΔPc

DeltafluxCg and Kg valve coefficient

Dn

2"3"4"6"8"10"12"14"16"18"20"24"

Cv coefficient at 100% opening

8221540510801750286039805000680084001060016100

Liquid trim

Deltaflux

Dn

2"3"4"6"8"10"12"14"16"18"20"24"

Cv coefficient at 100% opening

60150290650122519752825347546755950750011100

Gas trim

Deltaflux

Note: To verify the dimensioning and, in detail, for the dimensioning of Deltaflux control valves bigger than 24”, always refer to Pietro Fiorentini S.p.A.

Liquid control application

Gas control application

DeltafluxCv coefficient

Sizing the Slam Shut Valves

Calculation of the pressure drop

The following formula can be used to calculate pressure losses of the slam shut valve in fully open position:

Δp = pressure loss in barPu = absolute inlet pressure in barQ = flow rate Stm3/hKG = flow coefficient

)15.273(

8.175

tSKG1 = KG x

+x

Pressure loss calculated as above is referred to natural gas with specific gravity of 0.61 (air=1) temperature of 15 °C at valve inlet, for gases with different specific gravity S and temperatures t °C, pressure loss can still be calculated with the above formula, replacing the value of the flow coefficent in the table with:

Δp = KG x Pu - (KG2 x Pu2) - 4Q2

2 x KG

Nominal diameter (mm)Size (inches) KG flow coefficient

251"

510

1506"

14780

1004"

7120

652"1/2

3550

502"

1970

803"

4390

2008"

23080

25010"

32506

SBC 782


251"

549

803"

4086

1001"1/2

2603

401"1/2

1116

321"1/4

717

502"

1788

1004"

6122

1506"

13680

SCN

2008"

21700


1506"

14780

1004"

7120

2008"

23080

25010"

32506

HBC 975


401"1/2

860

251"

500

502"

976

Dilock 108

Sizing the Safety Relief Valves

Calculation of the pressure regulator

q = (0.9 Kc) • (394.9 x C) • P1 A • Q = 23.661

The flow rate is calculated by the following formulae:

q = maximum flow rate to be discharged, in Kg/hQ = maximum flow rate (Stm3/h)A = minimum area (cm2) (see table)Kc = outflow coefficientP1= setting pressure plus a 10% overpressure (bar abs)T1= temperature in °K of the fluid at the valve inlet during

the discarge, reported by user or by designer.0,9 = safety coefficient

M = molecular mass of the fluid in Kg/Kmol (see table)Z1 = compressibiliti factor of the fluid under the P1

conditions to be considered approximately equal to one if the actual values is not known.

k=Cp exponent of equation of the isentropic expansion Cv under the P1 and T1 conditions. Cp = specific heat at consistant pressure Cv = specific heat at consistant volume

C = coefficient of expansion = C = (see table) k+1

2k ( ) k-1

k+1

MZ1 T1

qM

Nominal diameter (mm)Size (inches) Calculation area (cm2)Outflow coefficient K

PVS 782

251"

4,710,56

2008"

259,590,56

1506"

168,560,56

803"

43,010,56

502"

20,030,56

1004"

74,660,56

Relative densityCarbon dioxideHydrogenMethaneNatural gas*NitrogenOxigenPropane* Medium value

Coefficient of expansion C0,6850,6680,6860,6690,6690,6850,6850,635

Molecular mass M28,9744,012,0216,0418,0428,0232,0044,09

Molecular mass and expansion coeff.

Nominal diameter (mm) Size 2 barg 10 barg20 barg30 barg40 bargFlow rate (Kg/h)

251"

3321885247253377063

502"

21448016153572269730038

803"

460417214329764873864500

1004"

7991298815724284603111964

1506"

1804367462129235191008252781

2008"

27788103894199028294161389295

Pres

sure

Capacity table versus pressure

Pietro Fiorentini S.p.A.via E.Fermi 8/10I-36057 Arcugnano (VI) Italy

Tel. +39 0444 968.511Fax. +39 0444 960.468

The data are not binding. We reserve theright to make eventual changes withoutprior notice.

www.fiorentini.com

CT-s 570-E June 10

Sizing - Fiorentini · Sizing the Pressure Regulators Sizing of regulators is usually made on the...

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