IPE-TM-510 Hydraulics
Hydraulics for Fractionation Overhead Systems
IPE-TM-510-10
1. Purpose
This Procedure demonstrates the proper method of setting up the hydraulic circuits for a fractionation column equipped with a total condensing system, an elevated condenser, and a hot vapor bypass. See the example hydraulic tabulations and Figure 1, “Fractionator Overhead Schematic”.
2. General
When a fractionation column is equipped with a total condensing system, an elevated condenser, and a hot vapor bypass control valve, the overhead pressure of the column is controlled by adjusting the opening of the control valve at the condenser inlet. The differential pressure through the hot vapor bypass is controlled by adjusting the opening of the hot vapor bypass control valve. The differential pressure shall be determined by the Design Engineer after reviewing the technology specific design manual if applicable, and Procedure Section 6.2. The receiver pressure varies slightly with flow through the hot vapor bypass. The flow rate through the hot vapor bypass is based on the estimated vapor rate required to makeup for the condensation of overhead material in the receiver due to heat loss.
3. P9.8 Hydraulics Program
To properly model this scenario with the P9.8 hydraulics program, a dummy circuit shall run first. In the dummy circuit, the hot vapor bypass control valve shall be modeled as a miscellaneous piece of equipment with a constant differential pressure. Despite the gas phase application, the differential pressure shall be entered as static head; otherwise, the P9.8 Hydraulics program will vary the differential pressure with the flow rate of each process simulation case. This circuit calculates and stores the receiver pressures at the normal, design, and alternate condition of each process simulation case.
The dummy circuit shall not be included in the Engineering Design Information (EDI) that is given to the customer.
Please note that the flow through the hot vapor bypass control valve is based on six mass percent of the total overhead vapor at the outlet nozzle of the fractionation column. To avoid adding extra margin to the already conservative ‘six mass percent’ basis, the design condition of the hot vapor bypass circuits shall be set to 100%.
Next, the dummy circuit shall be copied. The word ‘dummy’ in the new circuit title shall be deleted. The miscellaneous piece of equipment shall be replaced with a control valve equipment number. The instrument engineer shall use this equipment number to size and specify the hot vapor bypass control valve. The new circuit shall run second. This circuit shall be included in the Engineering Design Information (EDI) that is given to the customer.
The column overhead circuit through the condenser shall run last. Because the receiver pressures were calculated and stored when the hot vapor bypass circuit ran, the P9.8 hydraulics program is now able to accurately calculate the pressure downstream of the pressure control valve at the condenser inlet. Confirm that the receiver hydraulic pressures are greater than the vapor pressure.
Example 1 and Figure 1 shall be used as a guide when setting up the hydraulic circuits.
4. New Hydraulics Program
To properly model this scenario with the new hydraulics program, the hot vapor bypass circuit shall run first. This circuit calculates and stores the receiver pressures at the normal, design, and alternate condition of each process simulation case.
The column overhead circuit through the condenser shall run last. Because the receiver pressures were calculated and stored when the hot vapor bypass circuit ran, the new hydraulics program is now able to accurately calculate the pressure downstream of the pressure control valve (hydraulic balance) at the condenser inlet.
Example 2 and Figure 1 shall be used as a guide when setting up the hydraulic circuits.
Setting Up the Control Valve In the Hot Vapor Bypass Circuit
- The hot vapor bypass control valve shall be assigned a control valve equipment number
- Open the PDIC control valve form
- Under “Valve Hydraulic function”, select “Fixed CV”.
- Click on the “Pressure Drop” tab.
- Enter the controlled differential pressure across the hot vapor bypass control valve in the “Maximum Allowable Pressure Drop” field. It will be the same value for all process cases and flow scenarios.
- In the “Design” subsection, under “Pressure Drop Calc Method for normal flow scenario”, select “Constant P”.
- In the “Rating” subsection, under “Pressure Drop Calc Method for other flow scenarios”, select “Constant P”.
- In the “Rating” subsection, under “Pressure Drop Calc Method for normal flow scenario”, select “Constant P”.
- Select “OK”.
Additional Information for Hot Vapor Bypass Circuit
- Start the circuit with the fractionator since it has a controlled pressure
- Note that the flow through the hot vapor bypass control valve is based on six mass percent of the total overhead vapor at the outlet nozzle of the fractionation column. You need to reference the overhead stream and enter a simulation stream factor of 6% or the hot vapor bypass stream may already be included in the simulation with the flow rates already adjusted.
- To avoid adding extra margin to the already conservative ‘six mass percent’ basis, set the Normal and Design flow factors to 100% for the circuit.
- The Alternate factor shall be set to the project turndown percent
- The line between the fractionator and overhead split shall maintain the project design flow factor (typically 110%)
- Set the overhead splitter at an elevation of 5 feet below the top of the fractionator.
- Set the control valve at an elevation of 5 feet above the receiver.
- Set the “Piping Configuration” to “Short Run” for lines 1 and 6
- The circuit can end at the receiver with the circuit end pressure set to “Calculated” or continue the circuit through the pump and downstream equipment.
- Confirm that the receiver hydraulic pressures are greater than the vapor pressure. Type the vapor pressure value in the Circuit Notes.
Information for Column Overhead Circuit
- Start the circuit with the overhead splitter
- The overhead control valve will have “Valve Hydraulic function” set to “Hydraulic Balance”
- Set the control valve at an elevation of 5 feet above the condenser.
- Set the “Piping Configuration” to “Short Run” for lines 3 and 4.
- The circuit will end at the receiver with the circuit end pressure set to “Previous”
Example 1: Hydraulics of Column Total Condensing System with Hot Vapor Bypass (P9.8 Hydraulics Program)
ANY CLIENT Note - the information in this document is Page
XXXXXX PROJECT confidential and the property of Inflection Point Engineering, and Date
ANY , STATE must not be disclosed to others or reproduced in Proj
COUNTRY any manner or used for any purpose whatsoever By
CASE 1 without its written permission. EFID
Circuit 1: FRACTIONATION COLUMN VAPOR BYPASS (DUMMY) Case Design Case Alternate
Press 100.0% 100.0% 60.0%
Drop --------------- --------------- ---------------
Line 100 Per Nozl Press Inlet Press Inlet Press Inlet
Size Eq 100ft Elev Drop Press Drop Press Drop Press
Equipment Identification in ft psi ft psi psig psi psig psi psig
FRACTIONATION COLUMN 216 103.0 103.0 103.0
Line 1 (Desgn%=110.0) 24 10 0.14 1.40 103.0 1.69 103.0 0.50 103.0
OVHD VAPOR SPL – VAPOR BYPASS 40 101.6 101.3 102.5
Line 5 (Flow%=6.0) ‡ 12 4.8 0.14 0.67 101.6 0.67 101.3 0.24 102.5
VAPOR BYPASS DUMMY CV(1251) § 100.9 100.6 102.3
Static Head 11.00 100.9 11.00 100.6 11.00 102.3
Line 6 (Flow%=6.0) ‡ 12 1.7 0.14 0.24 89.9 0.24 89.6 0.09 91.3
FRACTIONATION COLUMN RECEIVER 30 89.7 89.4 91.2
Circuit 2: FRACTIONATION COLUMN VAPOR BYPASS Case Design Case Alternate
Press 100.0% 100.0% 60.0%
Drop --------------- --------------- ---------------
Line 100 Per Nozl Press Inlet Press Inlet Press Inlet
Size Eq 100ft Elev Drop Press Drop Press Drop Press
Equipment Identification in ft psi ft psi psig psi psig psi psig
FRACTIONATION COLUMN 216 103.0 103.0 103.0
Line 1 (Desgn%=110.0) 24 10 0.14 1.40 103.0 1.69 103.0 0.50 103.0
OVHD VAPOR SPL – VAPOR BYPASS 40 101.6 101.3 102.5
Line 5 (Flow%=6.0) ‡ 12 4.8 0.14 0.67 101.6 0.67 101.3 0.24 102.5
VAPOR BYPASS CV(1601) 11.00 100.9 11.00 100.6 11.00 102.3
Line 6 (Flow%=6.0) ‡ 12 1.7 0.14 0.24 89.9 0.24 89.6 0.09 91.3
FRACTIONATION COLUMN RECEIVER 30 89.7 89.4 91.2
Circuit 3: FRACTIONATION COLUMN OVERHEAD Case Design Case Alternate
Press 100.0% 110.0% 60.0%
Drop --------------- --------------- ---------------
Line 100 Per Nozl Press Inlet Press Inlet Press Inlet
Size Eq 100ft Elev Drop Press Drop Press Drop Press
Equipment Identification in ft psi ft psi psig psi psig psi psig
OVHD VAPOR SPL – VAPOR BYPASS 40 101.6 101.3 102.5
Line 2 24 3.4 0.14 0.48 101.6 0.58 101.3 0.17 102.5
OVERHEAD PRESSURE CV(1602) 5.68 101.1 4.37 100.7 9.09 102.3
Line 3 24 2.8 0.14 0.39 95.5 0.47 96.4 0.14 93.2
CONDENSER 40 4.84 95.1 5.86 95.9 1.74 93.1
Line 4 12 3.7 0.14 0.52 90.2 0.63 90.0 0.19 91.4
FRACTIONATION COLUMN RECEIVER 30 89.7 89.4 91.2
‡ This piping segment shall reference the stream in the heat and weight balance corresponding to the total overhead vapor from the column.
§ This is a miscellaneous piece of equipment. The differential pressure is determined by the process engineer and shall be identical for all process simulation cases. Despite the gas phase application, the differential pressure shall be modeled as static head.
Example 1: Hydraulics of Column Total Condensing System with Hot Vapor Bypass (P9.8 Hydraulics Program) (cont’d)
ANY CLIENT Note - the information in this document is Page
XXXXXX PROJECT confidential and the property of Inflection Point Engineering, and Date
ANY , STATE must not be disclosed to others or reproduced in Proj
COUNTRY any manner or used for any purpose whatsoever By
CASE 2 without its written permission. EFID
Circuit 1: FRACTIONATION COLUMN VAPOR BYPASS (DUMMY) Case Design Case Alternate
Press 100.0% 100.0% 60.0%
Drop --------------- --------------- ---------------
Line 100 Per Nozl Press Inlet Press Inlet Press Inlet
Size Eq 100ft Elev Drop Press Drop Press Drop Press
Equipment Identification in ft psi ft psi psig psi psig psi psig
FRACTIONATION COLUMN 216 103.0 103.0 103.0
Line 1 (Desgn%=110.0) 24 10 0.15 1.50 103.0 1.82 103.0 0.54 103.0
OVHD VAPOR SPL – VAPOR BYPASS 40 101.5 101.2 102.5
Line 5 (Flow%=6.0) ‡ 12 4.8 0.15 0.72 101.5 0.72 101.2 0.26 102.5
VAPOR BYPASS DUMMY CV(1251) § 100.8 100.5 102.2
Static Head 11.00 100.8 11.00 100.5 11.00 102.2
Line 6 (Flow%=6.0) ‡ 12 1.7 0.15 0.26 89.8 0.26 89.5 0.09 91.2
FRACTIONATION COLUMN RECEIVER 30 89.5 89.2 91.1
Circuit 2: FRACTIONATION COLUMN VAPOR BYPASS Case Design Case Alternate
Press 100.0% 100.0% 60.0%
Drop --------------- --------------- ---------------
Line 100 Per Nozl Press Inlet Press Inlet Press Inlet
Size Eq 100ft Elev Drop Press Drop Press Drop Press
Equipment Identification in ft psi ft psi psig psi psig psi psig
FRACTIONATION COLUMN 216 103.0 103.0 103.0
Line 1 (Desgn%=110.0) 24 10 0.15 1.50 103.0 1.82 103.0 0.54 103.0
OVHD VAPOR SPL – VAPOR BYPASS 40 101.5 101.2 102.5
Line 5 (Flow%=6.0) ‡ 12 4.8 0.15 0.72 101.5 0.72 101.2 0.26 102.5
VAPOR BYPASS CV(1601) 11.00 100.8 11.00 100.5 11.00 102.2
Line 6 (Flow%=6.0) ‡ 12 1.7 0.15 0.26 89.8 0.26 89.5 0.09 91.2
FRACTIONATION COLUMN RECEIVER 30 89.5 89.2 91.1
Circuit 3: FRACTIONATION COLUMN OVERHEAD Case Design Case Alternate
Press 100.0% 110.0% 60.0%
Drop --------------- --------------- ---------------
Line 100 Per Nozl Press Inlet Press Inlet Press Inlet
Size Eq 100ft Elev Drop Press Drop Press Drop Press
Equipment Identification in ft psi ft psi psig psi psig psi psig
OVHD VAPOR SPL – VAPOR BYPASS 40 101.5 101.2 102.5
Line 2 24 3.4 0.15 0.51 101.5 0.62 101.2 0.18 102.5
OVERHEAD PRESSURE CV(1602) 5.49 101.0 4.12 100.6 9.02 102.3
Line 3 24 2.8 0.15 0.42 95.5 0.51 96.4 0.15 93.3
CONDENSER 40 5.00 95.1 6.05 95.9 1.80 93.1
Line 4 12 3.7 0.15 0.56 90.1 0.68 89.9 0.20 91.3
FRACTIONATION COLUMN RECEIVER 30 89.5 89.2 91.1
‡ This piping segment shall reference the stream in the heat and weight balance corresponding to the total overhead vapor from the column.
§ This is a miscellaneous piece of equipment. The differential pressure is determined by the process engineer and shall be identical for all process data cases. Despite the gas phase application, the differential pressure shall be modeled as static head.
Example 2: Hydraulics of Column Total Condensing System with Hot Vapor Bypass (New Hydraulics Program)
Circuit 2 : Fractionation Column Hot Vapor Bypass
Normal Design Alternate
PRESS 100.0% 100.0% 50.0%
DROP ------------------- ------------------- -------------------
LINE 100 PER NOZL PRESS INLET PRESS INLET PRESS INLET
SIZE EQ 100ft ELEV DROP PRESS DROP PRESS DROP PRESS
EQUIPMENT IDENTIFICATION IN ft psi ft psi psig psi psig psi psig
Fractionation Column 143.7 256.0 256.0 256.0
LN-XP-655(Des=110%) 24 1.45 0.38 0.55 256.0 0.67 256.0 0.14 256.0
Overhead Vapor - Hot Vapor Bypass Split 138.7 255.4 255.3 255.9
LN-657 8 3.24 0.36 1.17 255.4 1.17 255.3 0.29 255.9
Hot Vapor Bypass PDIC: CV-1644 50.9 8.00 254.3 8.00 254.2 8.00 255.6
LN-658 8 0.63 0.37 0.24 246.3 0.24 246.2 0.06 247.6
Receiver 45.9 246.0 245.9 247.5
Notes:
The receiver vapor pressure = 245 psig
The inlet/outlet streams for the PDIC were already at 6% of overhead stream
Circuit 3 : Fractionation Overhead
Normal Design Alternate
PRESS 100.0% 110.0% 50.0%
DROP ------------------- ------------------- -------------------
LINE 100 PER NOZL PRESS INLET PRESS INLET PRESS INLET
SIZE EQ 100ft ELEV DROP PRESS DROP PRESS DROP PRESS
EQUIPMENT IDENTIFICATION IN ft psi ft psi psig psi psig psi psig
Overhead Vapor - Hot Vapor Bypass Split 138.7 255.4 255.3 255.9
LN-670 24 6.52 0.38 2.51 255.4 3.03 255.3 0.63 255.9
Overhead CV-1648 56.0 3.14 252.9 1.82 252.3 6.78 255.2
LN-670A 24 1.45 0.38 0.56 249.8 0.68 250.5 0.14 248.5
Condenser (Shell) 51.0 3.00 249.2 3.63 249.8 0.75 248.3
LN-XP-656 18 1.13 0.18 0.20 246.2 0.24 246.2 0.05 247.6
Receiver(Des=100%) 45.9 246.0 245.9 247.5
Example 2: Hydraulics of Column Total Condensing System with Hot Vapor Bypass (New Hydraulics Program) (cont’d)
Circuit 2 : Fractionation Column Hot Vapor Bypass
Normal Design Alternate
PRESS 100.0% 100.0% 50.0%
DROP ------------------- ------------------- -------------------
LINE 100 PER NOZL PRESS INLET PRESS INLET PRESS INLET
SIZE EQ 100ft ELEV DROP PRESS DROP PRESS DROP PRESS
EQUIPMENT IDENTIFICATION IN ft psi ft psi psig psi psig psi psig
Fractionation Column 143.7 256.0 256.0 256.0
LN-XP-655(Des=110%) 24 1.45 0.37 0.54 256.0 0.66 256.0 0.14 256.0
Overhead Vapor - Hot Vapor Bypass Split 138.7 255.5 255.3 255.9
LN-657 8 3.24 0.36 1.16 255.5 1.16 255.3 0.29 255.9
Hot Vapor Bypass PDIC: CV-1644 50.9 8.00 254.3 8.00 254.2 8.00 255.6
LN-658 8 0.63 0.37 0.23 246.3 0.23 246.2 0.06 247.6
Receiver 45.9 246.1 245.9 247.5
Notes:
The receiver vapor pressure = 245 psig
The inlet/outlet streams for the PDIC were already at 6% of overhead stream
Circuit 3 : Fractionation Overhead
Normal Design Alternate
PRESS 100.0% 110.0% 50.0%
DROP ------------------- ------------------- -------------------
LINE 100 PER NOZL PRESS INLET PRESS INLET PRESS INLET
SIZE EQ 100ft ELEV DROP PRESS DROP PRESS DROP PRESS
EQUIPMENT IDENTIFICATION IN ft psi ft psi psig psi psig psi psig
Overhead Vapor - Hot Vapor Bypass Split 138.7 255.5 255.3 255.9
LN-670 24 6.52 0.38 2.49 255.5 3.01 255.3 0.62 255.9
Overhead CV-1648 56.0 3.19 253.0 1.89 252.3 6.80 255.2
LN-670A 24 1.45 0.38 0.55 249.8 0.67 250.4 0.14 248.4
Condenser (Shell) 51.0 2.96 249.2 3.58 249.8 0.74 248.3
LN-XP-656 18 1.13 0.17 0.20 246.3 0.24 246.2 0.05 247.6
Receiver(Des=100%) 45.9 246.1 245.9 247.5
Figure 1 Fractionator Overhead Schematic
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