Title Page & LocationsIN-HOUSE SOFTWAREProgram:PSVsizeVersion:1Revision:0Rev. date:10/25/99Master Copy Location:s:\Engineering\Process\Calculation Spreadsheets\Approved SoftwareUser Manual Location:NOT REQUIRED - PROGRAM SELF EXPLANATORYTechnical Manual Location:NOT REQUIRED - REFER 'INTRODUCTION PAGE'FOR BASIS AND LIMITATIONSMS WORD Location:

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IntroductionINTRODUCTION TO RELIEF VALVE SIZING PROGRAMProgram NameRelief valve sizingRevision0AuthorMJARev. Date15-Apr-03PurposeThis program is designed to assist with sizing of relief valves for vapour and liquid relief using the guidelines ofAPI 520, Part-I, 7th Edition, January 2000. For two phase relief, the sizing method has not been includedin this revision. Until this method has been included in the next version, the individual orifice areas calculatedseparately for liquid and vapour components would be added together to obtain the total orifice areaInstructions for use1. Copy the protected programme from the 'Approved Software' directory into relevant project directory.2. Go to the desired worksheet (PSV Vapour relief, PSV Liquid relief by clicking on the relevant button atthe bottom of this spreadsheet program. Fill in designated input (sheet is self- explanatory) and press print buttons as required.PSV for vapour relief2a. Input the following process data for sizing of PSV for vapour relief in worksheet "PSV Vapour Relief".- Select the relieving scenario and design code of the vessel protected by the PSV from drop-down list boxes.- Input Mass Flowrate, Molecular Weight, Relief temperature, Compressibility, Cp/Cv, Set pressure and Back pressure.- Input back pressure correction factor 'Kb' if available. This input is optional. The program defaults to a value of 1.- Input % accumulation if it is different from the value selected by program. This input is optional. For vessels designedto ASME section VIII, Div. 1 and 'Fire relief' scenario, the program defaults to 21% accumulation. For all other cases,the program defaults to 10% accumulation.3a. The program calculates the orifice area for the PSV, selects the next higher standard orifice size and gives preliminarysize of the selected PSV. The program also calculates the relieving capacity of the selected relief valve.PSV for liquid relief2b. Input the following process data for sizing of PSV for liquid relief in worksheet "PSV Liquid Relief".- Input the relieving scenario and design code of the vessel protected by the PSV.- Input Mass Flowrate, Density and Viscosity at flowing conditions, Set pressure and Back pressure.- Input % accumulation if it is different from the value selected by program. This input is optional. The program defaults to10% accumulation for all liquid relief cases.3b. The program calculates back pressure correction factor, viscosity correction factor, orifice area for the PSV, selects thenext higher standard orifice size and gives preliminary size of the selected PSV. The program also calculates therelieving capacity of the selected relief valve.PSV for two phase (vapour+liquid) relief2c. The sizing method for two phase relief from PSV is being finalised in API 520. Till the new method is availablecalculate individually the orifice area for the vapour and liquid components using worksheets 'PSV Vapour Relief' andPSV Liquid Relief' respectively and obtain the total orifice area. Select the PSV size manually.Limitations1. No choice of RV type is given. For backpressure higher than 10% of the maximum relieving pressure(set pressure+accumulation), the program automatically selects balanced bellow relief valve and usessizing equation for critical flow in gas service (see also 'Limitation note 2').For backpressure