1. Process Department

2. COMPARATIVE STUDY OF THE USE OF VISUAL FLOW, INPLANT AND OTHER
SSE-06
COMPARATIVE STUDY OF THE USE OF
VISUAL FLOW, INPLANT AND OTHER
SIMULATORS IN THE RELIEF SYSTEM
DESIGN
Prepared by: Pedro Ceballos
Revised by: Edgar Alfonso / Carmelo Trezza / María Pereira / Fernando Azuaje
Invensys User Group Series, Houston, October 15-16
Copyright © Inelectra SACA.- All rights reserved

3. Content Relief Systems Relief System Components
Relief System Hydraulic Evaluations
DA-1/ DA-2/ VDU Relief System Hydraulic Evaluation
Comparison of Simulators
Conclusions

4. Relief Systems Definition: Standards Applicable to Relief Systems:
Installing a pressure relief device, lines and means for transport and disposal of the relief fluid in gaseous phase, liquid or both.
It is used when the presence of liquid, toxic properties or other factors would make it dangerous to discharge into the atmosphere
Standards Applicable to Relief Systems:
API 520 I.
Sizing, Selection, and Installation of Pressure-Relieving Devices in Refineries. Part I—Sizing and Selection
API 520 II.
Sizing, Selection, and Installation of Pressure-Relieving Devices in
Refineries. Part II—Installation
API 521.
Pressure-relieving and Depressuring Systems
API 526.
Flanged Steel Pressure Relief Valves
API 537.
Flare Details for General Refinery and Petrochemical Service
API 576.
Inspection of Pressure-relieving Devices

5. Relief System Components
Relief Valves
Flare
Discharge Lines
Protected
Equipments
Subheaders
Header
KnockOut Drum
KnockOut Drum Pumps

6. Relief System Hydraulic Evaluations
P1= ? psig
(Backpressure)
P2= 0 psig
Criteria to define the relief valve type:
Relief Valve
(Set pressure)
DPtip= 3 psig
BP Backpressure (psig)
SP Set Pressure (psig)
(%) =
Flare
Conventional: BP/SP<10%
Balanced: 10%<BP/SP<30%
Pilot:
30%<BP/SP<75%
DPsello= 2 psig
KnockOut
Drum

7. DA-1/ DA-2/ VDU Relief System Hydraulic Evaluation
Description:
Project:
Deep Conversion
Location:
Puerto La Cruz Refinery
Engineering:
Detail
Units
Involved:
DA-1/DA-2 (Atmospheric Distillation Units)
VDU (Vacio Unit)
Flare Type:
Ground Flare
Darwin LNG; Australia

8. DA-1/ DA-2/ VDU Relief System Hydraulic Evaluation
Main Objective: *
Validate the results obtained during the basic engineering of hydraulic calculations associated with the main header of Ground Flare Relief System and DA-1/DA-2/VDU referred to in the Deep Conversion Project of Puerto La Cruz.
Secondary Objective : *
Compare the use, advantages and disadvantages of simulators available in the Company (INELECTRA) for Relief Systems Analysis (VISUAL FLOW, INPLANT, Aspen Flare and Superchems).

9. DA-1/ DA-2/ VDU Relief System Hydraulic Evaluation
Relief System Design :
Main Contingency:
General Electric Power Failure
Total Relief Load:
lb/h
Size Head:
42’’
Equipment Involved
DA-1: Atmospheric Tower
DA-2: Atmospheric Tower
VDU: Vacuum Tower
Design Basis: *
Pressure of 10 psi at Ground Flare.
In the General Electric Power Failure DA-1, DA-2 and VDU discharge simultaneously.
Maximum speed (Mach): Discharge Line: 0.75 / Header-SubHeader: 0.50.
Backpressure criteria: Conventional: 10% / Balanced: 30% / Pilot: 75%.

10. DA-1/ DA-2/ VDU Relief System Hydraulic Evaluation
Relief System Scheme:
VDU
TRAIN 1 & 2
42’’
DA-1
Ground
Flare
DA-2

11. DA-1/ DA-2/ VDU Relief System Hydraulic Evaluation
VISUAL FLOW Simulation:
VDU Towers
DA-1 Tower
DA-2 Tower

12. DA-1/ DA-2/ VDU Relief System Hydraulic Evaluation
INPLANT Simulation
VDU Towers
DA-1 Tower
DA-2 Tower

13. DA-1/ DA-2/ VDU Relief System Hydraulic Evaluation
Aspen Flare Simulation
DA-2 Tower
DA-1 Tower
VDU Towers

14. DA-1/ DA-2/ VDU Relief System Hydraulic Evaluation
SuperChems Simulation

15. DA-1/ DA-2/ VDU Relief System Hydraulic Evaluation
Results. Cooling Water Failure (DA-1 Tower)
SIMULATOR
PARAMETER
PSV-04416A
PSV-04416B
PSV-04416C
PSV-04416D
PSV-04416E
PSV-04416F
SP=30psig
SP=31.5psig
BASIC ENG.
(SUPERCHEMS)
Outlet Line Mach Nro
0.191
Backpressure (psig)
21.9
Back P / Set P (%)
73.1
69.6
DETAIL ENG.
(VISUAL FLOW)
0.216
0.214
0.313
15.0
15.3
14.7
14.6
49.9
48.6
46.6
46.5
Results. General Power Failure (DA-2 Tower)
SIMULATOR
PARAMETER
PSV A
PSV B
PSV C
SP= 30 psig
SP= 31.5 psig
BASIC ENG.
(SUPERCHEMS)
Outlet Line Mach Nro
0.169
Backpressure (psig)
21.5
Back P / Set P (%)
71.5
68.1
DETAIL ENG.
(VISUAL FLOW)
0.192
15.4
15.7
51.3
48.8
49.8

16. DA-1/ DA-2/ VDU Relief System Hydraulic Evaluation
Origin of differences (Basic Eng. – Detail Eng.)
Header Inside Diameter 42’’:
Basic Eng.: Detail Eng. (Piping Classs)
40’’ ’’
Fittings (Basic Eng.):
Elbow 90°
90 deg. 1 Weld. 90 deg angle
Elbow 45°
45 deg. Standard (R/D=1), all types
T branch
Used as elbow. Standard, screwed
T run
Run through tee. Screwed
K(12”)=1.247
Fittings (Detail Eng):
Elbow 90°
Long-Radius (R/D=1.5), all types
Elbow 45°
45 deg. Long radius (R/D=1.5), all types
T branch
Used as elbow. Standard, flanged/welded
T run
Run through tee. Flanged/welded
K(12”)=0.217

17. DA-1/ DA-2/ VDU Relief System Hydraulic Evaluation
Results. Cooling Water Failure (DA-1 Tower)
SIMULATOR
PARAMETER
PSV-04416A
PSV-04416B
PSV-04416C
PSV-04416D
PSV-04416E
PSV-04416F
SP=30psig
SP=31.5psig
VISUAL FLOW
Outlet Line Mach Nro
0.216
0.214
0.313
Backpressure (psig)
15.0
15.3
14.7
14.6
Back P / Set P (%)
49.9
48.6
46.6
46.5
INPLANT
0.209
15.9
52.8
50.3
ASPEN FLARE
0.212
0.211
0.210
16.3
16.1
54.4
50.4
51.0
51.2
51.3
51.1
SUPERCHEMS
50.1
47.7

18. DA-1/ DA-2/ VDU Relief System Hydraulic Evaluation
Results. General Power Failure (DA-2 Tower)
SIMULATOR
PARAMETER
PSV A
PSV B
PSV C
SP= 30 psig
SP= 31.5 psig
VISUAL FLOW
Outlet Line Mach Nro
0.192
Backpressure (psig)
15.4
15.7
Back P / Set P (%)
51.3
48.8
49.8
INPLANT
0.185
16.2
16.1
54.1
51.0
ASPEN FLARE
0.186
16.3
54.3
51.9
51.7
SUPERCHEMS
0.187
15.8
52.6
50.1

19. Comparision of Simulators
Mounting the Model:
VISUAL FLOW
INPLANT
ASPEN FLARE
SUPERCHEMS
Allows change the method of thermodynamic
YES NO
Allows added viscosity experimental data.
Easy to add components and uses them when performing the simulation on other computers
Allows to create pseudocomponentes with PM>1000
Allowsto add over 50 pseudocomponentes in a line
Allows to add pipes to the library
Allows to copy valves and equipments
Allows to enable and disable lines and equipments
Ease of data entry

20. Comparision of Simulators
Simulator Flexibility:
VISUAL FLOW
INPLANT
ASPEN FLARE
SUPERCHEMS
Evaluation of the pressure drop at the entrance of the safety valve
YES NO
Can simulate various scenarios (contingencies) with a single run
Sizing Relief Valves
Sizing Relief Headers
Allows isometric drawings
Dynamic Evaluation of Fire Contingency
Radiation Evaluation
It takes into account energy losses to the environment

21. Comparision of Simulators
Results Report:
VISUAL FLOW
INPLANT
ASPEN FLARE
SUPERCHEMS
Getting quick results (duration of the run)
YES NO
Reports the pressure drop in each segment / fitting
Calculation of relief temperature
Easy to calculate backpressure on PSV

22. Comparision of Simulators
General recommendations for use of simulators according to the case study
Case
Simulator
Simulation of gas relief
VISUALFLOWSuperchems
Simulation of viscous liquid relief
Inplant
Simultaneous evaluation of several cases where contingency is involved one relief valve
VISUALFLOW Aspen Flare
Quick estimate of the backpressure
INPLANT
Evaluation of the pressure drop at the entrance to the relief valve
VISUALFLOW Superchems
Evaluation of Fire event when multiple loads are involved (dynamic simulation)
Superchems
Evaluation of heat loss to the environment
Superchems, AspenFlare

23. Conclusions *
The diameters established for the main header (42"), for DA-1 subheader (42") and DA-2 subheader (30") during basic engineering are according with the design basis. *
It should verify that the fittings on the pipes do not create an excessive pressure drop avoid unnecessary overdesigns. *
According to the system under study, each relief systems simulator offers particular advantages, among them are the INPLANT by the facilities in the model assembly and VISUAL FLOW for flexibility and good results.

24. Thanks for your attention!!