Title and Link to Calc:
Description:
Calculates output parameters per D.2.1 of AP RP 520 - Sizing for Two-Phase Flashing or NonFlashing Flow Through a Pressure Relief Valve. Calculates omega per equation D.1.
Alternative Descriptors:
Two Phase Flow Through a Relief Valve
Two Phase Compressible Flow
Two Phase Flow Through a Nozzle
Two Phase Flow Through a Relief Valve, Non-flashing Sub-cooled Liquid
Two Phase Flow Through a Relief Valve, Non-flashing Sub-cooled Liquid and Non-condensable Gas
Two Phase Flow Through a Relief Valve, Flashing Saturated Liquid & Vapor
Calc Number:
CFF-RP520-D2111-1
Calc Status:
Beta
Reference:
Sizing, Selection, and Installation of Pressure-Relieving Devices in Refineries, API Recommended Practice 520 seventh edition, January 2000, D.2.1.1, pgs. 69-71
Reference Example(s) Modeled/Generalized:
Example Number(s):
Calc Origination Date:
02/09/2006
Calc Originator:
RBC
Calc Revision History:
None
Calc Guidelines:
User should refer to the specified reference above.
Access:
Activating this calc requires entry of the correct access code. Contact eng-calc@eng-calcs.com to obtain the access code.
Variables:
Variable Description: Required Effective Discharge Area
Variable Label Description: Required Effective Discharge Area
Variable Calc Name: REDA
Variable Units: SQIN
Variable Calc Upper Limit:
Variable Calc Lower Limit:
Variable Type:Output
Variable Format:Real Number
Variable Notes:
Variable Description: Critical Pressure
Variable Label Description: Critical Pressure
Variable Calc Name: CP
Variable Units: PSIA
Variable Calc Upper Limit:
Variable Calc Lower Limit:
Variable Type:Output
Variable Format:Real Number
Variable Notes:Outlet pressure where sonic velocity is achieved.
Variable Description: Critical Pressure Ratio
Variable Label Description: Critical Pressure Ratio
Variable Calc Name: NC
Variable Units:
Variable Calc Upper Limit:0.957
Variable Calc Lower Limit:0.1245
Variable Type:Output
Variable Format:Real Number
Variable Notes:
Variable Description: Omega
Variable Label Description: Omega
Variable Calc Name: OME
Variable Units:
Variable Calc Upper Limit:100
Variable Calc Lower Limit:0.01
Variable Type:Output
Variable Format:Real Number
Variable Notes:
Variable Description: Comments
Variable Label Description: Comments
Variable Calc Name: COM
Variable Units:
Variable Calc Upper Limit:
Variable Calc Lower Limit:
Variable Type:Output
Variable Format:Text
Variable Notes: Displays "Input(s) out of range." if an entered input variable(s) are out of range. Displays "Output(s) out of range." if an output variable exceeds its range. The "out of range" variable(s) are displayed in yellow. The limited range values are used in the calculation, not the "out of range" value(s).
Variable Description: Relief Scenario Description
Variable Label Description:Relief Scenario Description
Variable Calc Name: RSD
Variable Units:
Variable Calc Upper Limit:
Variable Calc Lower Limit:
Variable Type:Input
Variable Format:Text
Variable Notes:User determined description. Has no effect on calculation.
Variable Description: Vapor Mass Fraction at the Pressure Relief Valve Inlet
Variable Label Description: Vapor Mass Frac. @ PRV Inlet
Variable Calc Name: VMF
Variable Units:
Variable Calc Upper Limit:1
Variable Calc Lower Limit:0
Variable Type:Input
Variable Format:Real Number
Variable Notes:
Variable Description: Vapor Specific Volume at Pressure Relief Valve Inlet
Variable Label Description: Vapor S. Vol. @ PRV Inlet
Variable Calc Name: VSV
Variable Units: CF/LB
Variable Calc Upper Limit:15000
Variable Calc Lower Limit:0.01
Variable Type:Input
Variable Format:Real Number
Variable Notes:
Variable Description: Two Phase Specific Volume at Pressure Relief Valve Inlet
Variable Label Description: Two Ph. S. Vol. @ PRV Inlet
Variable Calc Name: TPSV
Variable Units: CF/LB
Variable Calc Upper Limit:15000
Variable Calc Lower Limit:0.01
Variable Type:Input
Variable Format:Real Number
Variable Notes:
Variable Description: Specific Volume Difference at Pressure Relief Valve Inlet
Variable Label Description: S. Vol. Diff. @ PRV Inlet
Variable Calc Name: VLSVD
Variable Units: CF/LB
Variable Calc Upper Limit:15000
Variable Calc Lower Limit:0.01
Variable Type:Input
Variable Format:Real Number
Variable Notes:
Variable Description: Heat of Vaporization at Pressure Relief Valve Inlet
Variable Label Description: Heat of Vap.@ PRV Inlet
Variable Calc Name: LHV
Variable Units: BTU/LB
Variable Calc Upper Limit:15000
Variable Calc Lower Limit:0.01
Variable Type:Input
Variable Format:Real Number
Variable Notes:
Variable Description: Temperature at Pressure Relief Valve Inlet
Variable Label Description:PRV Inlet Temperature
Variable Calc Name: PIT
Variable Units: R
Variable Calc Upper Limit:10000
Variable Calc Lower Limit:1
Variable Type:Input
Variable Format:Real Number
Variable Notes:
Variable Description: Liquid Specific Heat at Pressure Relief Valve Inlet
Variable Label Description:Liquid Specific Heat at Inlet
Variable Calc Name: LSH
Variable Units: BTU/LB/R
Variable Calc Upper Limit:15000
Variable Calc Lower Limit:0.01
Variable Type:Input
Variable Format:Real Number
Variable Notes:
Variable Description: Specific Heat Ratio of Vapor
Variable Label Description:Specific Heat Ratio of Vapor
Variable Calc Name: SHR
Variable Units:
Variable Calc Upper Limit:3
Variable Calc Lower Limit:1
Variable Type:Input
Variable Format:Real Number
Variable Notes:
Variable Description: Pressure Relief Valve Inlet Pressure
Variable Label Description:PRV Inlet Pressure
Variable Calc Name: PIP
Variable Units:PSIA
Variable Calc Upper Limit:15000
Variable Calc Lower Limit:0.01
Variable Type:Input
Variable Format:Real Number
Variable Notes:
Variable Description: Downstream Back Pressure
Variable Label Description:Back Pressure
Variable Calc Name: DBP
Variable Units:PSIA
Variable Calc Upper Limit:15000
Variable Calc Lower Limit:0.01
Variable Type:Input
Variable Format:Real Number
Variable Notes:
Variable Description: Mass Flow Rate
Variable Label Description:Mass Flow Rate
Variable Calc Name: MFR
Variable Units:LB/HR
Variable Calc Upper Limit:100,000,000
Variable Calc Lower Limit:0.01
Variable Type:Input
Variable Format:Real Number
Variable Notes:
Variable Description: Valve Discharge Coeffcient
Variable Label Description:Valve Discharge Coefficient
Variable Calc Name: VDC
Variable Units:
Variable Calc Upper Limit:1
Variable Calc Lower Limit:0.01
Variable Type:Input
Variable Format:Real Number
Variable Notes:
Variable Description: Back Pressure Correction Factor
Variable Label Description:Back Pressure Correction Factor
Variable Calc Name: BPC
Variable Units:
Variable Calc Upper Limit:1
Variable Calc Lower Limit:0.01
Variable Type:Input
Variable Format:Real Number
Variable Notes:
Variable Description: Rupture Disk Correction Factor:
Variable Label Description:Rupture Disk Correction Factor:
Variable Calc Name: RDC
Variable Units:
Variable Calc Upper Limit:1
Variable Calc Lower Limit:0.01
Variable Type:Input
Variable Format:Real Number
Variable Notes:
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