blowdown calculation final rev b1.pdf

8/10/2019 Blowdown Calculation final Rev B1.pdf

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PT.PERUSAHAAN GAS NEGARA

(Persero) TbkPT. CONNUSA ENERGINDO PT.BINARASANO ENGINEERING

BLOWDOWN ANALYSIS REPORTDocument No. Rev. Date

Page 1 of 13CP19-BRE-3514-PS-CA-002 B 14/10/2014

PT. Perusahaan Gas Negara (Persero) Tbk.

EPC OTSUKA -PURWOSARI GAS DISTRIBUTION PIPELINE PROJECT CP-19

BLOWDOWN ANALISYS REPORT

Contract No.

079800.PK/HK.02/PROYEK/2014

B Issued for review 14-10-14 ARD ILM DVD

A Issued for review 12-09-14 ARD ILM DVD

REV DESCRIPTION DATEPRPD CHKD APVD

PMC PGNPT. BRE


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REVISION CONTROL SHEET

Rev No Date Page Description

A 12-09-14 All Issued for review

B 14-10-14 All Issued for review


3/23





TABLE OF CONTENT

REVISION CONTROL SHEET ______________________________________________________ 2

1. INTRODUCTION _____________________________________________________________ 41.1. General ______________________________________________________________ 4

1.2. Objection _____________________________________________________________ 4

2. REFERENCES ______________________________________________________________ 4

3. DATA SOURCE ______________________________________________________________ 53.1. Process Data __________________________________________________________ 53.2. Blowdown Design_______________________________________________________ 6

4. CALCULATION METHODS _____________________________________________________ 74.1. Upstream Restriction Orifice Calculation _____________________________________ 74.2. Downstream Restriction Orifice Calculation ___________________________________ 9

5. RESULT __________________________________________________________________ 10

6. CONCLUSION______________________________________________________________ 11

Figure 1. Blowdown scheme _________________________________________________________ 6Figure 2. Hysys Depressuring Utilities _________________________________________________ 7

ATTACHEMENT 1 : HYSYS SIMULATION REPORT ____________________________________ 12

ATTACHEMENT 2 : LINE SIZING CALCULATION ______________________________________ 13


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1. INTRODUCTION

1.1. General

Perusahaan Gas Negara (persero) Tbk. (PGN) is the largest natural gas transmission and

distribution company intens to distribute gas from Otsuka to Purwosari with distance about 15

km. Sectional Valve will be installed at KP 8. The Sectional Valve is composed of a manually

operated 10 Block Valve for Otsuka Purwosari Pipeline and a vent nozzle with connections

for temporary blowdown facility. The blowdown facilities optimized for 3 5 hours of blowdown

duration. For normal condition, 5 MMSCFD of gas will deliver to consummer and it will be

increase to 17 MMSCFD as future. 48 km gas pipeline distribution to Malang shall install as a

future plan

1.2. Objection

This document is provided for size calculation from upstream and downstream of restriction

orifice on the OTSUKA PURWOSARI GAS DISTRIBUTION PIPELINE, East Java. Optimum

Restriction orifice will be determined too for 8 km lenght of pipe.

2. REFERENCES

API RP 521 Guide for Pressure Relieving Depressuring System

API 14E Recommended Practice for Design and Installation of Offshore

Production Platform Piping Systems

API RP 520 Sizing, Selection, and Installation of Pressure-Relieving Devices in

Refineries

GPSA Section 17 Fluid Flow and Piping

Kepmen LH No.48/1996 Baku Tingkat Kebisingan

Permen Naker

No. PER.13/MEN/X/2011 Nilai Ambang Batas Faktor Fisika dan Faktor Kimia di Tempat Kerja


5/23





3. DATA SOURCE

3.1. Process Data

The parameters will be use for calculating hydraulic are showed below:

Table 1. Standard Parameters

Gas composition is refer to Heat & Material Balances Table (CP19-BRE -3514-PS-BD-004)COMPOSITION Mole

CH4(Methane) 0.9844

CcH6(Ethane) 0.0050

C3H8(Propane) 0.0020

i-C4H10(i-Butane) 0.0006

n-C4H10(n-Butane) 0.0004

i-C5H12 (i-Pentane) 0.0002

n-C5H12(n-Pentane) 0.0001

n-C6H14 (n-Hexane) 0.0001

H2S 0.0000

No Parameters Unit Value

1 Flow Rate (Q) MMSCFD 5

2 Future Flowrate (Qfuture) MMSCFD 17

3 Operating Pressure (P) barg 16

4 Max Allowable Operating Pressure (MAOP) barg 25

5 Design Pressure barg 35.9

6 Operating Temperature (T)oF 80

7 Design TemperatureoF 130

8 Inside Pipe Diameter (D) inch 10

9 Pipe Lenght (L) km 15

10 Spesific Gravity (Sg) 0.565

11 Compresibilty Factor (Z) 0.9634

12 Density () lb/ft3

1.128

13 Molecular Weight (Mw) 16.36

14 Viscosity () cP 0.01182

15 Roughness in 0.001


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COMPOSITION Mole

CO2 0.0027

N2 0.0046

TOTAL 1.0000

Table 2. Gas Composition

3.2. Blowdown Design

Blowdown designed for one section ( Section 1 or section 2 ) with assumed lenght 8 km /

section. The calculation performed to 3, 4 and 5 hours duration at maximum operating

pressure (25 barg) for future connection (17 MMSCFD). Final pressure target is 100 psig.

Table 3. Blowdown Case

Figure 1. Blowdown Scheme

Upstream Pipe of Restriction Orifice Design Criteria

a. Maximum Velocity = 60 ft/s refer to API RP 521

b. P (psi/100ft) = 0.486 psi/100ft

Case Blowdown Duration Flowrate Pressure

1 3 hours 17 MMSCFD 25 barg



SECTION 1SECTION 2

Blowdown Area


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Downstream Restriction Orifice Design Criteria

a. Beta ratio = 0.2 0.75

b. Maximum Velocity = 500 fps refer to API 14E

c. Noise = 55 dB refer to Kepmen LH No.48/1996

85 dB refer to Permen Naker No. PER.13/MEN/X/2011

4. CALCULATION METHODS

This calculation is performed using HYSYS simulation and MS Excel by input data. Methodology

being used for calculation below :

4.1. Upstream Restriction Orifice Calculation

a. Depressurization simulation using HYSYS

Depressurization simulation performed using HYSYS 7.3 with Peng-Robbinson as fluid

package. The stage are belowed:

1. Gas composition and parameters condition input to stream data.

2. Assumed the vessel orientation is horizontal. Pipe lenght and diameter input to vessel

parameters as a diameter and height. The f igure showed below.

Figure 2. Hysys Depresssuring Utilities


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3. Input the ambient data into heat flux and chose adiabatic for operating mode.

4. For valve parameters chose a supersonic in vapour flow equation and assumed discharge

co-efficient is 0.975.

5. Set depressuring time and final pressure at Operating Condition.

6. run the simulation.

b. Determine friction factor (MS. EXCEL) refer to API 14E

- Trial diameter (D) using gas velocity Equation (API 14E )

- Calculate Reynold number (Re)

c. Determine the value of (/D) and Re from the picture below to get (fm)

d. Determine Pressure Drop using Darcy formula

Where:

vg : Gas Velocity (fps)

Z : Gas Compresibility

Q : Molar flowrate (MMSCFD)

v

R


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T : Temperature inlet (oR)

P : Pressure inlet ( psia )

D : Diameter blowdown pipe (in)

: Density (lb/ft3)

: Viscosity (cP)

W : Mass Flowrate (lb/hr)

fm : Frition factor

4.2. Downstream Restriction Orifice Calculation

a. Orifice Diameter Calculation refer to GPSA section 17

- FTPinitial value set = 1

- Determining critical flow ( YCR) by :

- Determining orifice diameter (d) :

b. Estimation noise by Lighthill's Theory :

Where:

OASPL : Overall sound pressure level of regenerated noise (dB)

d : Inside diameter of vent stack (m)

C0 : Sonic Velocity (Velocity of sound in atmosphere) (m/s)

vg : Exit velocity of vented gas (m/s)

0 : Density of atmosphere (kg/m

3

)g : Density of vented gas (kg/m

3)

R : Distance from vent (m)


10/23





5. RESULT

The result of calculations are below :

a. Case 1: 3 Hours Blowdown Duration

Table 4. Blowdown Case 1 Result

b. Case 2 : 4 Hours Blowdown Duration


c. Case 3 : 5 Hours Blowdown Duration

DOWNSTREAM UPSTREAM

Option ID (in) Velocity (fps) Mach Number P (psi/100ft) Noise 1 Noise 2 Status

Option 1 2 43.557 0.767 2.285 92.895 71.556 NOT OK

Option 2 3 19.359 0.341 0.277 68.242 46.904 OK

Option 3 4 10.889 0.192 0.066 50.751 29.412 OK

Option 4 6 4.840 0.085 0.008 26.098 4.759 OK


DOWNSTREAM UPSTREAM


Option 1 2 71.818 1.265 6.213 110.272 88.933 NOT OK

Option 2 3 31.919 0.562 0.769 85.619 64.280 NOT OK

Option 3 4 17.954 0.316 0.176 68.128 46.789 OK

Option 4 6 7.980 0.141 0.022 43.475 22.136 OK

DOWNSTREAM UPSTREAM


Option 1 2 54.391 0.958 3.565 100.625 79.286 NOT OK

Option 2 3 24.174 0.426 0.441 75.972 54.633 OK

Option 3 4 13.598 0.240 0.101 58.480 37.141 OK

Option 4 6 6.043 0.106 0.013 33.828 12.489 OK


11/23





d. Restriction Orifice Calculation Result

Table 7. RO calculation result

6. CONCLUSION

a. Based on calculation, the selected downstream diameters thats suitable of criteria is 4 inch

with 0.176 psi/100ft as maximum pressure drop , 0.316 as mach number and maximum gas

velocity calculated is 17.954 fps.

b. For upstream, diameter selected is 4 inch with maximum noise is 68.128 dB.

c. For diameter 4 inch, RO diameter caclulated is 27.17 mm at 3 hours with beta ratio value is

0.267.

No Calculation steps 3 Hours 4 Hours 5 Hours

1 Relief Load (W) (kg/h) 2885 2185 1749

2 Set Initial Value of FTP 1 1 1

3 Critical Flow Function, YCR 0.701 0.701 0.701

4 Orifice Diameter, d (mm)27.17 23.65 21.16

5 Beta Ratio, 0.267 0.233 0.208

6 FTPCalculated 1.0012 1.0007 1.0004

7 Critical Pressure, (kPa)420.81 420.60 420.50

8 Reynold Number 63442.49 48047.83 38477.69

9 Flow Region Turbulent - OK Turbulent - OK Turbulent - OK

10 Flow Behaviour Critical Flow Critical Flow Critical Flow


12/23





ATTACHEMENT 1 : HYSYS SIMULATION REPORT


13/23

LEGENDS

Burlington, MA

USA

Case Name: BLOWDOWN 3 HOURS 8KM .HSC

Unit Set: NewUser4a113

Date/Time: Sun Sep 14 09:44:31 2014

Depressuring - Dynamics: BD 1

DESIGN

Connections

Inlet

Vessel Volume (ft3)

Liquid Volume (ft3)

FEED-2

1.431e+004

7156

Vessel Orientation

Flat End Vessel Volume (ft3)

Height (m)

Diameter (m)

Metal Mass in Contact with Vapour (lb)

Horizontal

1.431e+004

8000 *

0.2540 *

---

Initial Liquid Volume (ft3)

Cylindrical Area (ft2)

Top Head Area (ft2)

Bottom Head Area (ft2)

Metal Mass in Contact with Liquid (lb)

0.0000

6.870e+004

0.5453

0.5453

---

Heat Flux

Operating Mode : Adiabatic

Heat Loss Model : Simple

Overall U (Btu/hr-ft2-F)

Ambient Temperature (F)

2.642

82.00 *

Overall Heat Transfer Area (ft2) 6.870e+004

Valve Parameters

Vapour Flow Equation

Cd

Area (in2)

Vapour Back Pressure (bar_g)

Valve Equation Units

Supersonic

0.9750 *

0.1933 *

0.0000

lb/hr

Liquid Flow Equation

Liquid Back Pressure (bar_g)

(No Flow)

0.0000

Options

PV Work Term Contribution (%) 80.00 *

Operating Conditions

Operating Pressure (bar_g)

Time Step Size

25.00

---

Depressuring Time (seconds) 1.080e+004 *

Vapour Outlet Solving Option

Initial Cv Estimate

Calculate Cv

0.9750 *

Final Pressure (bar_g)

Solved Pressure (bar_g)

6.895 *

---

WORKSHEET

Properties

Name

Vapour Fraction

Temperature (F)

Pressure (bar_g)

Actual Vol. Flow (barrel/day)

Mass Enthalpy (Btu/lb)

Mass Entropy (Btu/lb-F)

Molecular Weight

Molar Density (lbmole/ft3)

Mass Density (lb/ft3)

Std Ideal Liq Mass Density (lb/ft3)

Liq Mass Density @Std Cond ( lb/ ft3)

Molar Heat Capac ity (Btu/lbmole-F)

Mass Heat Capacity (Btu/lb-F)

Thermal Conductivity (Btu/hr-ft-F)

Viscosity (cP)

Surface Tension (dyne/cm)

Specific Heat (Btu/lbmole-F)

Z Factor

Vap. Frac. (molar basis)

FEED-2

1.0000

80.00 *

25.00 *

1.157e+005

-1997

2.281

16.36

6.894e-002

1.128

18.99

4.332e-002

9.324

0.5698

2.073e-002

1.182e-002

---

9.324

0.9450

1.0000

Aspen Technology Inc. Aspen HYSYS Version 7.3 (25.0.0.7336) Page 1 of 2

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14/23

LEGENDS

Burlington, MA

USA

Case Name: BLOWDOWN 3 HOURS 8KM .HSC



Depressuring - Dynamics: BD 1 (continued)

Properties

Vap. Frac. (mass basis)

Vap. Frac. (Volume Basis)

Molar Volume (ft3/lbmole)

Act.Gas Flow (ACFM)

Act.Liq.Flow (USGPM)

Std.Liq.Vol.Flow (barrel/day)

Std.Gas Flow (MMSCFD)

Watson K

Kinematic Viscosity (cSt)

Cp/Cv

Lower Heating Value (Btu/lbmole)

Mass Lower Heating Value (Btu/lb)

Liquid Fraction

Partial Pressure of CO2 (bar_g)

Avg.Liq.Density (lbmole/ft3)

Heat Of Vap. (Btu/lbmole)

Mass Heat Of Vap. (Btu/lb)

1.0000

1.0000

14.51

451.3

---

3.014e+006

16.97

19.27

0.6543

1.381

3.463e+005

2.116e+004

0.0000

-0.9439

1.161

3033

185.3

COMPOSITIONS

Methane

Ethane

Propane

i-Butane

n-Butane

i-Pentane

n-Pentanen-Hexane

H2S

CO2

Nitrogen

FEED-2

0.9844 *

0.0050 *

0.0020 *

0.0006 *

0.0004 *

0.0002 *

0.0001 *0.0001 *

0.0000 *

0.0027 *

0.0046 *

Results

Initial Pressure (bar_g)


Depressuring Time (seconds)

Vapour Cv

Liquid Cv

Vessel Fluid Initial Temperature - Vapour Phase (F)

Vesssel Fluid Final Temperature - Vapour Phase (F)

Vessel Fluid Minimum Temperature - Vapour Phase (F)

Valve Outlet Initial Temperature - Vapour Phase (F)

Valve Outlet Final Temperature - Vapour Phase (F)

Valve Outlet Minimum Temperature - Vapour Phase (F)

Inner Wal l Ini tial Temperature - Vapour Phase (F)

Inner Wal l Final Temperature - Vapour Phase (F)

Inner Wall Minimum Temperature - Vapour Phase (F)

Vessel Fluid Init ial Temperature - Liquid Phase (F)

25.00

6.896

1.080e+004 *

0.9750 *

---

80.42

79.19

79.19

57.19

78.87

57.19

---

---

---

80.42

Vessel Fluid Final Temperature - Liquid Phase (F)

Vessel Fluid Minimum Temperature - Liquid Phase (F)

Valve Outlet Init ial Temperature - Liquid Phase (F)

Valve Outlet Final Temperature - Liquid Phase (F)

Valve Outlet Minimum Temperature - Liquid Phase (F)

Inner Wal l Ini tial Temperature - Liquid Phase (F)

Inner Wal l Final Temperature - Liquid Phase (F)

Inner Wall Minimum Temperature - Liquid Phase (F)

Initial Mass of Vapour (lb)

Final Mass of Vapour (lb)

Peak Vapour Flow Through Valve (lb/hr)

Initial Mass of Liquid (lb)

Final Mass of Liquid (lb)

Peak Liquid Flow Through Valve (lb/hr)

79.19

79.19

57.19

57.65

57.19

---

---

---

1.615e+004

4593

6360

0.0000

0.0000

0.0000


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15/23

LEGENDS

Burlington, MA

USA

Case Name: BLOWDOWN 4 HOURS 8KM.HSC




DESIGN

Connections

Inlet

Vessel Volume (ft3)

Liquid Volume (ft3)

FEED-2

1.431e+004

7156

Vessel Orientation


Height (m)

Diameter (m)


Horizontal

1.431e+004

8000 *

0.2540 *

---



Top Head Area (ft2)



0.0000

6.870e+004

0.5453

0.5453

---

Heat Flux





2.642

82.00 *


Valve Parameters


Cd

Area (in2)



Supersonic

0.9750 *

0.1446 *

0.0000

lb/hr



(No Flow)

0.0000

Options




Time Step Size

25.00

---



Initial Cv Estimate

Calculate Cv

0.9750 *



6.895 *

---

WORKSHEET

Properties

Name

Vapour Fraction

Temperature (F)

Pressure (bar_g)




Molecular Weight








Viscosity (cP)



Z Factor


FEED-2

1.0000

80.00 *

25.00 *

1.157e+005

-1997

2.281

16.36

6.894e-002

1.128

18.99

4.332e-002

9.324

0.5698

2.073e-002

1.182e-002

---

9.324

0.9450

1.0000


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16/23

LEGENDS

Burlington, MA

USA





Properties




Act.Gas Flow (ACFM)




Watson K


Cp/Cv



Liquid Fraction





1.0000

1.0000

14.51

451.3

---

3.014e+006

16.97

19.27

0.6543

1.381

3.463e+005

2.116e+004

0.0000

-0.9439

1.161

3033

185.3

COMPOSITIONS

Methane

Ethane

Propane

i-Butane

n-Butane

i-Pentane

n-Pentanen-Hexane

H2S

CO2

Nitrogen

FEED-2

0.9844 *

0.0050 *

0.0020 *

0.0006 *

0.0004 *

0.0002 *

0.0001 *0.0001 *

0.0000 *

0.0027 *

0.0046 *

Results




Vapour Cv

Liquid Cv











25.00

6.898

1.440e+004 *

0.9750 *

---

80.42

79.08

79.08

57.19

78.80

57.19

---

---

---

80.42















79.08

79.08

57.19

57.65

57.19

---

---

---

1.615e+004

4606

4818

0.0000

0.0000

0.0000


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17/23

LEGENDS

Burlington, MA

USA





DESIGN

Connections

Inlet

Vessel Volume (ft3)

Liquid Volume (ft3)

FEED-2

1.431e+004

7156

Vessel Orientation


Height (m)

Diameter (m)


Horizontal

1.431e+004

8000 *

0.2540 *

---



Top Head Area (ft2)



0.0000

6.870e+004

0.5453

0.5453

---

Heat Flux





2.642

82.00 *


Valve Parameters


Cd

Area (in2)



Supersonic

0.9750 *

0.1155 *

0.0000

lb/hr



(No Flow)

0.0000

Options




Time Step Size

25.00

---



Initial Cv Estimate

Calculate Cv

0.9750 *



6.895 *

---

WORKSHEET

Properties

Name

Vapour Fraction

Temperature (F)

Pressure (bar_g)




Molecular Weight








Viscosity (cP)



Z Factor


FEED-2

1.0000

80.00 *

25.00 *

1.157e+005

-1997

2.281

16.36

6.894e-002

1.128

18.99

4.332e-002

9.324

0.5698

2.073e-002

1.182e-002

---

9.324

0.9450

1.0000


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18/23

LEGENDS

Burlington, MA

USA





Properties




Act.Gas Flow (ACFM)




Watson K


Cp/Cv



Liquid Fraction





1.0000

1.0000

14.51

451.3

---

3.014e+006

16.97

19.27

0.6543

1.381

3.463e+005

2.116e+004

0.0000

-0.9439

1.161

3033

185.3

COMPOSITIONS

Methane

Ethane

Propane

i-Butane

n-Butane

i-Pentane

n-Pentanen-Hexane

H2S

CO2

Nitrogen

FEED-2

0.9844 *

0.0050 *

0.0020 *

0.0006 *

0.0004 *

0.0002 *

0.0001 *0.0001 *

0.0000 *

0.0027 *

0.0046 *

Results




Vapour Cv

Liquid Cv











25.00

6.904

1.800e+004 *

0.9750 *

---

80.42

79.07

79.07

57.19

78.78

57.19

---

---

---

80.42















79.07

79.07

57.19

57.65

57.19

---

---

---

1.615e+004

4615

3857

0.0000

0.0000

0.0000


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19/23





ATTACHEMENT 2 : LINE SIZING CALCULATION


20/23

1. Upstream RO

Design Data Design Criteria

Pressure P = 377.3 psia Max. Velocity = 60 ft/s Refer to API RP 521

Temperature T = 80 F P (psi/100 ft) = 0,486 psi/100 ft

= 540 R

Density = 1.128 lb/ft3

Molecular Weight Mw = 16.36

Viscosity = 0.01182 cP

Compressibility Factor Z = 0.945

Roughness = 0.001 in

Pipe Material = Carbon Steel

Calculation Methode

1. Determine friction factor refer to API 14E

- Trial diameter (D) using gas velocity Equation (API 14E )

- Calculate Reynold number (Re)

2. Determine the value of (/D) and Re from the picture below to get (fm)

3. Determine Pressure Drop using Darcy formula

LINE SIZING

V =

R =

=

0,000336


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Calculation Result

- Depressuring time = 3 hours

- Molar Flowrate (Q) = 3.54 MMSCFD from HYSYS

- Mass Flowrate (W) = 6360 lb/hr from HYSYS

Option (/D) Gas Velocity (fps) Re fm P (psi/100ft) Status

Option 1 0.0005 71.818 1699710.084 0.0165 6.213 NOT OK

Option 2 0.000333333 31.919 1133140.056 0.0155 0.769 NOT OK

Option 3 0.00025 17.954 849855.042 0.015 0.176 OK

Option 4 0.000166667 7.980 566570.028 0.0145 0.022 OK





Option 1 0.0005 54.391 1287266.309 0.0165 3.565 NOT OK

Option 2 0.000333333 24.174 858177.540 0.0155 0.441 OK

Option 3 0.00025 13.598 643633.155 0.015 0.101 OK

Option 4 0.000166667 6.043 429088.770 0.0145 0.013 OK





Option 1 0.0005 43.557 1030869.364 0.0165 2.285 NOT OK

Option 2 0.000333333 19.359 687246.243 0.0152 0.277 OK

Option 3 0.00025 10.889 515434.682 0.0152 0.066 OK

Option 4 0.000166667 4.840 343623.121 0.0145 0.008 OK

Selected Pipe Size

Based on calculation result that suitable of criteria :

D = 4 in

P = 0.176 psi/100ft

Gas Velocity = 17.954 fps

Depressuring time = 3 hours

D(in)

D(in)

2

3

4

6

D(in)

2

3

4

6

2

3

4

6


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2. Downstream RO

Design Data Design Criteria

Pressure P = 100 psig Beta ratio 0.2 - 0.75

= 790.8 kPa Max. Velocity 500 fps Refer to API 14E

Pressure Tip = 0 psig Noise 85 dB Refer to Kepmen LH No.48/1996

= 14.7 psia 55 dB Refer to Kepmen Naker No.51/1999

Downstream Pressure Pd = 1 bar

Temperature T = 82.5 F

= 301.2 K

Density = 1.128 lb/ft3

Spesific Gravity SG = 0.565

Molecular Weight Mw = 16.36

Viscosity = 0.01182 cP

Compressibility Factor Z = 0.945

Specific Heat Ratio Cp/Cv = 1.381

Roughness = 0.001 in

Piping Data

Upstream Diameter D = 4 in

101.6 mm

Restriction Orifice Data

Discharge Coeficient Constant = 0.975

Calculation

Estimation noise by Lighthill's Theory :

OASPL = Overall sound pressure level of regenerated noise (dB)

d = Inside diameter of vent stack (m)

C0 = Sonic Velocity (Velocity of sound in atmosphere) (m/s)

Vg = Exit velocity of vented gas (m/s)

0 = Density of atmosphere (kg/m3)

g = Density of vented gas (kg/m3)

R = Distance from vent (m)

No 3 Hours 4 Hours 5 Hours

1 Relief Load (W) (kg/h) 2885 2185 1749

2 Set Initial Value of FTP 1 1 1

3 Critical Flow Function, YCR 0.701 0.701 0.701

4 Orifice Diameter, d (mm) 27.17 23.65 21.16

5 0.267 0.233 0.208

6 1.0012 1.0007 1.0004

7 Critical Pressure, (kPa) 420.81 420.60 420.50

8 63442.49 48047.83 38477.69

9 Turbulent - OK Turbulent - OK Turbulent - OK

10 Critical Flow Critical Flow Critical Flow

Calculation steps

Beta Ratio,

FTPCalculated

Reynold Number

Flow Region

Flow Behaviour

= 61,8 + 10 log

20 log


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Noise

Sonic Velocity = 459.861987 m/s

Wind Velocity = 6 knots

= 3.084 m/s

Air Density = 1.27605002 kg/m3

Vapour Density = 0.70028956 kg/m3

Note :

Noise 1 85 dB Distance 3 m Refer to Kepmen LH No.48/1996

Noise 2 55 dB Distance 35 m Refer to Kepmen Naker No.51/1999

Blowdown Time 3 Hours

Option Mach Number Noise 1 Noise 2

Option 1 1.265 110.272 88.933

Option 2 0.562 85.619 64.280

Option 3 0.316 68.128 46.789

Option 4 0.141 43.475 22.136



Option 1 0.958 100.625 79.286

Option 2 0.426 75.972 54.633

Option 3 0.240 58.480 37.141

Option 4 0.106 33.828 12.489



Option 1 0.767 92.895 71.556

Option 2 0.341 68.242 46.904

Option 3 0.192 50.751 29.412

Option 4 0.085 26.098 4.759

Selected RO Size

Blowdown Time = 3 Hours

ID Downstream = 4 in

Mach Number = 0.316

Beta Ratio = 0.267

Orifice Diameter = 27.17 mm

1.070 in

Reference

1. API RP 521 - "Guide for Pressure Relieving - Depressuring System"

2. API 14E - "Recommended Practice for Design and Installation of Offshore Production Platform Piping Systems"

2. API RP 520 - "Sizing, Selection, and Installation of Pressure-Relieving Devices in Refineries"

4. GPSA Section 17 - " Fluid Flow and Piping"

StatusID Downstream (in)

2 NOT OK

3 NOT OK

4 OK

6 OK

ID Downstream (in) Status

2 NOT OK

3 OK

4 OK

6 OK

4 OK

6 OK

ID Downstream (in) Status

2 NOT OK

3 OK

blowdown calculation final rev b1.pdf

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