Reflux 819 Sizing Calculation

8/10/2019 Reflux 819 Sizing Calculation

1/16

SizingPressure Regulators &

Control Valves


2/16

Sizing the Pressure Regulators

Sizing of regulators is usually made on the basis of Cg valve and KGsizing coefficients. Flow rates at fully open

position and various operating conditions are related by the following formulae where:

Q = flow rate in Stm3/h

Pu = 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-1in sub critical conditions: (Pu 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


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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 15C. For gases having a different relative density d and temperature

tuin 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 Factor

0.78

0.63

0.55

0.79

0.73

0.63

Relative density

1.0

1.53

2.0

0.97

1.14

1.52

Type of gas

Air

Propane

Butane

Nitrogen

Oxygen

Carbon dioxide

Correction factors FC

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

CAUTION:

where:

V = gas speed in m/sec

Q = gas flow rate in Stm3/hDN = nominal size of regulator in mm

Pd = outlet pressure in barg.

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

Outlet pressure [bar]

Gasspeedattheoutletflange[m/sec]

0

50

100

150

200

250

300

350

400

450

0 5 10 15 20 25 30 35 40 45 50 55


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TablesCg and Kg valve coefficient

Nominal diameter (mm)

Size (inches)

Cg flow coefficient

KGflow coefficient

K1 body shape factor

Reflux 819/FO

25

1"

575

605

106,78

200

8"

25933

27282

106,78

150

6"

16607

17471

106,78

80

3"

4937

5194

106,78

50

2"

2220

2335

106,78

100

4"

8000

8416

106,78

250

10"

36525

38425

106,78


Size (inches)

Cg flow coefficient

KGflow coefficient


Reflux 819

25

1"

575

605

106,78

200

8"

25933

27282

106,78

150

6"

16607

17471

106,78

80

3"

4937

5194

106,78

50

2"

2220

2335

106,78

100

4"

8000

8416

106,78

250

10"

36525

38425

106,78


Size (inches)

Cg flow coefficient

KGflow coefficient


Aperflux 851

150

6"

11112

11678

113,9

25

1"

480

505

113,9

200

8"

17316

18199

113,9

80

3"

3790

3979

113,9

50

2"

1550

1627

113,9

100

4"

5554

5837

113,9

250

10"

24548

25850

113,9


Size (inches)

Cg flow coefficient

KGflow coefficient


50

2

1682

1768

103

80

3

4200

4414

108

Aperflux 101


5/16


Size (inches)

Cg flow coefficient

KGflow coefficient


Staflux 185

25

1"

439

462

106,78

80

3"

3764

3960

106,78

50

2"

1681

1768

106,78

Staflux 187

25

1"

130

136

106,78


Size (inches)

Cg flow coefficient

KGflow coefficient


25

1"

159

167

99,5

Dixi AP


Size (inches)

Cg flow coefficient

KGflow coefficient


25

1"

140

147

93,5

Dival 160 AP


Size (inches)

Cg flow coefficient

KGflow coefficient



Size (inches)

Cg flow coefficient

KGflow coefficient


Aperval 101

50

2

2091

2199

108

80

3

4796

5045

108

100

4

7176

7546

108


Size (inches)

Cg flow coefficient

KGflow coefficient


Aperval

25

1"

584

613

90

100

4"

6719

7055

101

65

2"1/2

3530

3706

101

50

2"

1978

2077

101

80

3"

4525

4751

101


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TablesCg and Kg valve coefficient


Size (inches)

Cg flow coefficient

KGflow coefficient


Terval

100

4"

5490

5775

100

65

2"1/2

2731

2875

104

50

2"

1706

1796

108

80

3"

3906

4112

100


Size (inches)

Cg flow coefficient

KGflow coefficient


25

1"

575

605

106,78

150

6"

16607

17471

106,78

100

4"

8000

8416

106,78

65

2"1/2

3320

4197

106,78

50

2"

2220

2335

106,78

80

3"

4937

5194

106,78

200

8"

25933

27282

106,78

250

10"

36525

38425

106,78

Reval 182


Size (inches)

Cg flow coefficient

KGflow coefficient


Terval/R

100

4"

5660

5954

106

65

2"1/2

2793

2940

104

50

2"

1667

1755

104

80

3"

4099

4315

106


Size (inches)

Cg flow coefficient

KGflow coefficient


Dixi

50

2"

1014

1066

96

25

1"

540

567

96

40

1"1/2

983

1034

96


7/16


Size (inches)

Cg flow coefficient

KGflow coefficient


Norval 608

50

2"

1700

1788

106

80

3"

3500

3681

106


Size (inches)

Cg flow coefficient

KGflow coefficient


Norval

25

1"

331

348

106,78

80

3"

3395

3571

106,78

65

2"1/2

2240

2356

106,78

40

1"1/2

848

892

106,78

100

4"

5100

5365

106,78

50

2"

1360

1430

106,78

150

6"

10600

11151

106,78

200

8"

16600

17463

106,78


Size (inches)

Cg flow coefficient

KGflow coefficient


Dival 600

25

1"

269

283

94

40

1"1/2

652

685

94

50

2"

781

821

86

40

1"1/2

692

727

95

50

2"

770

809

97

Head 280 Head 280/TR

25

1"

315

331

97

Dival 700

See the capacity Table


8/16

Cg and Kg valve coefficient

Choise of the valve is usually on the basis of Cg valve and Cg flow rate coefficients.Cg coefficient correspondsnumerically 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 15C.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 15C. 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/H

Pd = 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) PdKGQ = 106,78sinPuCvQ 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

KGformulae 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)


Size (inches)

Cg flow coefficient

KGflow coefficient

Cv flow coefficient

Reflux 919 - Syncroflux - VLM

25

1"

575

605

18

200

8"

25933

27282

810

150

6"

16607

17471

519

80

3"

4937

5194

154

50

2"

2200

2335

69

100

4"

8000

8416

250

250

10"

36525

38425

1141

106,78sinPuCgQ xxx= 0,526Pu

Pu - Pd( (

sinPu

QCg

x 106,78xx

=

.0,526Pu

PdPu -((

0,526 x Pu

QCg =


9/16

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)

P (P1+P2)

G TQ = 290 Cv

Q = 355 CvGP (P1+P2)

T

W = 13,55 Cv P (P1+P2)

W = 13,55Cv P (P1+P2)

(1+0,00126 t)

Q =262 F Cv P1

G T

W = 321 F Cv P1G

T

W = 11,73 F Cv P1

W = 11,73F Cv P1

(1+0,00126 t)

B. Critical conditions

(when P 0.5F2P1)

A. Subcritical conditions

(when P < 0.5F2P1)

W = 19,1 Cv P (w1+w2)

W = 27,1 Cv P w1

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

W = 19,1 F Cv P1 w1

w1 =100

Xg (Vg1-Vf) + 100 Vf

w2 =100

Xg (Vg2-Vf) + 100 Vf


(when P 0.5F2P1)

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)


(when P < 0.5F2P1)

GAS, VAPOR AND STEAM BIPHASE FLUIDS


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(when P < F2Pc)

Volume flow rate

Weight flow rate

W = 855 Cv GfP

Qf = Cv P

1.17 Gf

Note:For values of P Pk 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 15C=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

PPc

Pk

t

F

G

Gf

Kc

Xg

P1

P2

Pc

Pk

PvT

t1

ts

Q

Qf

W

W1

W2

Vf

Vg1

Vg2

Glossary


(when P F2Pc)

Volume flow rate

Weight flow rate

Qf =F Cv

1.17 Gf

W = 855 F Cv GfPc

Pc = P1-Pc

Pk = Kc (P1-Pv)

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

Pk

Pc

DeltafluxCg and Kg valve coefficient


11/16

Dn

2"

3"

4"

6"

8"

10"

12"

14"

16"

18"

20"

24"

Cv coefficient

at 100% opening

82

215

405

1080

1750

2860

3980

5000

6800

8400

10600

16100

Liquid trim

Deltaflux

Dn

2"

3"

4"

6"

8"

10"12"

14"

16"

18"

20"

24"

Cv coefficient

at 100% opening

60

150

290

650

1225

19752825

3475

4675

5950

7500

11100

Gas trim

Deltaflux

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

Liquid control application

Gas control application

DeltafluxCv coefficient


12/16

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 fullyopen position:

p = pressure loss in bar

Pu = absolute inlet pressure in bar

Q = flow rate Stm3/h

KG = 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 tC, pressure loss can still be calculated with the above formula, replacing the value of the flow

coefficent in the table with:

p =KG x Pu - (KG2x Pu2) - 4Q2

2 x KG


13/16


Size (inches)

KGflow coefficient

25

1"

510

150

6"

14780

100

4"

7120

65

2"1/2

3550

50

2"

1970

80

3"

4390

200

8"

23080

250

10"

32506

SBC 782


Size (inches)

KGflow coefficient

25

1"

549

80

3"

4086

65

2"1/2

2603

40

1"1/2

1116

50

2"

1788

100

4"

6122

150

6"

13680

SCN

200

8"

21700


Size (inches)

KGflow coefficient

150

6"

14780

100

4"

7120

200

8"

23080

250

10"

32470

HBC 975


Size (inches)

KGflow coefficient

40

1"1/2

860

25

1"

500

50

2"

976

Dilock 108


14/16

Sizing the Safety Relief Valves

Calculation of the safety relief valves

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/h

Q = maximum flow rate (Stm3/h)

A = minimum area (cm2) (see table)

Kc= outflow coefficient

P1= 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

2

k( )k-1k+1

M

Z1T1

q

M


15/16


Size (inches)

Calculation area (cm2)

Outflow coefficient K

PVS 782

25

1"

4,71

0,56

200

8"

259,59

0,56

150

6"

168,56

0,56

80

3"

43,01

0,56

50

2"

20,03

0,56

100

4"

74,66

0,56

Relative density

Carbon dioxide

Hydrogen

Methane

Natural gas*

Nitrogen

Oxigen

Propane

* Medium value

Coefficient of expansion C

0,685

0,668

0,686

0,669

0,669

0,685

0,685

0,635

Molecular mass M

28,97

44,01

2,02

16,04

18,04

28,02

32,00

44,09

Molecular mass and expansion coeff.


Size

2 barg

10 barg

20 barg

30 barg

40 barg

Flow rate (Kg/h)

25

1"

332

1885

2472

5337

7063

50

2"

2144

8016

15357

22697

30038

80

3"

4604

17214

32976

48738

64500

100

4"

7991

29881

57242

84603

111964

150

6"

18043

67462

129235

191008

252781

200

8"

27788

103894

199028

294161

389295Pressure

Capacity table versus pressure


16/16

Pietro Fiorentini S.p.A.via E.Fermi 8/10

I-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

DA SISTEMARE !!!!!!!!

CT-s 570-E June 12

Documents

Reflux 819 Sizing Calculation