Title and Link to Calc:

Incompressible Fluid Flow : Balanced Bellows Relief Valves [3.8], Flow Output : IFF-RP520-0027-1

Description:

Determines volumetric flow rate in a balanced bellows liquid relief valve of a given flow area per section 3.8 of the reference. Equations 3.9 (US units) is used in the calc. The equation is rearranged to solve for flow rate instead of area.

Alternative Descriptors:

Preliminary Sizing of Pressure Relief Valves Requiring Capacity Certification for balanced bellows liquid relief valves

Calc Number:

IFF-RP520-0027-1

Calc Status:

Beta

Reference:

Sizing, Selection, and Installation of Pressure-Relieving Devices in Refineries, API Recommended Practice 520 seventh edition, January 2000, 3.8, pgs. 52-53

Reference Example(s) Modeled/Generalized:

Example 3.8.2.1 of the reference

Calc Origination Date:

03/27/2006

Calc Originator:

RBC

Calc Revision History:

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

Variables:

Variable Description - Description of the variable
Variable Label Description - The description of the variable as it appears in the calc.
Variable Calc Name - The calc internal variable name
Variable Units - The units for the variable
Variable Calc Upper Limit - The highest allowed value in the calc.
Variable Calc Lower Limit - The lowest allowed value in the calc.
Variable Type - Either "Output" or "Input"
Variable Format - Real Number, Text, or Integer
Variable Notes - Other comments about the variable

Variable Description: Volumetric Flow Rate through Relief Valve
Variable Label Description: Flow Rate
Variable Calc Name: VFR
Variable Units: GPM
Variable Calc Upper Limit: 100000000
Variable Calc Lower Limit: 0.001
Variable Type: Output
Variable Format: REAL
Variable Notes:

Variable Description: Reynolds Number
Variable Label Description: Reynolds Number
Variable Calc Name: REY
Variable Units:
Variable Calc Upper Limit: 50000000
Variable Calc Lower Limit: 30
Variable Type: Output
Variable Format: REAL
Variable Notes:

Variable Description: Viscosity Correction Factor
Variable Label Description: Viscosity Correction Factor
Variable Calc Name: KV
Variable Units:
Variable Calc Upper Limit: 3
Variable Calc Lower Limit: 0.001
Variable Type: Output
Variable Format: REAL
Variable Notes:

Variable Description: Backpressure Correction Factor
Variable Label Description: Backpressure Correction Factor
Variable Calc Name: BCF
Variable Units:
Variable Calc Upper Limit: 1
Variable Calc Lower Limit: 0.5
Variable Type: Output
Variable Format: REAL
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). If Reynolds number is below limit then "Reynolds number below lower limit. " is displayed and no output is generated. If backpressure is greater than 50% of set pressure then "Back Pressure greater than 50% of set pressure. " is displayed and no output is generated.

Variable Description: Effective Discharge Area
Variable Label Description: Effective Discharge Area
Variable Calc Name: REDA
Variable Units: SQIN
Variable Calc Upper Limit: 50000
Variable Calc Lower Limit: 0
Variable Type: Input
Variable Format: REAL
Variable Notes:

Variable Description: Pressure at the pressure relief valve inlet (Relieving Pressure)
Variable Label Description: Pressure at PRV Inlet
Variable Calc Name: PIP
Variable Units: PSIG
Variable Calc Upper Limit: 100000
Variable Calc Lower Limit: 0.001
Variable Type: Input
Variable Format: REAL
Variable Notes:

Variable Description: Set pressure of relief valve
Variable Label Description: Set Pressure of PRV
Variable Calc Name: SIP
Variable Units: PSIG
Variable Calc Upper Limit: 100000
Variable Calc Lower Limit: 0.001
Variable Type: Input
Variable Format: REAL
Variable Notes:

Variable Description: Downstream Back Pressure
Variable Label Description: Downstream Back Pressure
Variable Calc Name: DBP
Variable Units: PSIG
Variable Calc Upper Limit: 100000
Variable Calc Lower Limit: 0.001
Variable Type: Input
Variable Format: REAL
Variable Notes:

Variable Description: Combination Correction Factor
Variable Label Description: Combination Correction Factor
Variable Calc Name: RDC
Variable Units:
Variable Calc Upper Limit: 3
Variable Calc Lower Limit: 0.001
Variable Type: Input
Variable Format: REAL
Variable Notes:

Variable Description: Rated Coefficient of Discharge
Variable Label Description: Coefficient of Discharge
Variable Calc Name: KD
Variable Units:
Variable Calc Upper Limit: 3
Variable Calc Lower Limit: 0.001
Variable Type: Input
Variable Format: REAL
Variable Notes:

Variable Description: Specific Gravity of Liquid Relative to Water at flowing conditions
Variable Label Description: Specific Gravity (to water)
Variable Calc Name: SG
Variable Units:
Variable Calc Upper Limit: 3
Variable Calc Lower Limit: 0.01
Variable Type: Input
Variable Format: REAL
Variable Notes:

Variable Description: Viscosity of Liquid in Saybolt Universal Seconds
Variable Label Description: Liquid Viscosity
Variable Calc Name: VS
Variable Units: SSU
Variable Calc Upper Limit: 100000
Variable Calc Lower Limit: 100
Variable Type: Input
Variable Format: REAL
Variable Notes:

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