Pressure Relief Valve Engineering Handbook - Swan …

1 Technical Document No. TP-V300 Effective: May 1997 Crosby Pressure Relief ValveEngineering HandbookCrosby Valve FMC Corporation , 7:56 AM1 Notes: , 7:56 AM2*United States Customary SystemWarning: The information contained in this Handbook is for informational purposes also Crosby's computer sizing program, CROSBY-SIZE. The actual selection of valvesand Valve products is dependent upon numerous factors and should be made only afterconsultation with applicable Crosby personnel. Crosby assumes no responsibility for theactual selection of such products and hereby expressly disclaims liability for any and allclaims and damages which may result from the use or application of this information or fromany consultation with Crosby Pressure Relief ValveENGINEERING HANDBOOKCONTENTSC hapter 1 Introduction to Crosby Engineering HandbookChapter 2 Fundamentals of Pressure Relief Valve DesignChapter 3 TerminologyChapter 4 Codes and Standards - SummaryChapter 5 Valve Sizing and Selection - * UnitsChapter 6 Valve Sizing and Selection - Metric UnitsChapter 7 Engineering Support InformationAppendixASME Section VIII, Division 1.

2 1992 Edition ExerptsOtherInformationOrdering InformationPressure Relief Valve Specification , 7:57 AM3 The Crosby Pressure Relief Valve Engineering Hand-book contains important technical information relatingto Pressure Relief primary purpose of a Pressure Relief Valve is protec-tion of life and property by venting fluid from anoverpressurized vessel. information contained in thishandbook applies to the overpressure protection ofpressure vessels, lines and is made to the ASME Boiler and PressureVessel Code, Section VIII, Pressure Vessels. Theinformation in this Handbook is NOT to be used forthe application of overpressure protection to powerboilers and nuclear power plant components whichare addressed in the ASME Boiler and PressureVessel Code, Section I, Power Boilers, and SectionIII, Nuclear Power Plant Components, sizing, selection, manufacture, assembly, test,installation and maintenance of a Pressure Relief valveare all critical to obtaining maximum Handbook has been designed to provide a serviceto Crosby s customers by presenting reference data andtechnical recommendations based on our many years ofexperience in sizing, selecting, testing, installing andoperating Pressure Relief valves .

3 Sufficient data issupplied so to properly size and select Crosby pressurerelief valves for specific applications. information cov-ering terminology, standards, codes, basic design, siz-ing and selection information , including examples, arepresented in an easy to use of the material in this Handbook is reprinted orexcerpted from publications developed by associationsor committees in which Crosby has participated. Theinformation contained in the manual is offered as aguide. Those who use the information are reminded ofthe limitations of such a publication and that there is nosubstitute for qualified Engineering Pressure Relief valves are manufactured in ac-cordance with a controlled Quality Assurance Programwhich meets or exceeds ASME Code Quality ControlProgram requirements.

4 Capacities are certified by theNational Board of Boiler and Pressure Vessel Inspec-tors. These features are assured by the presence of anASME Code Symbol Stamp and the letters NB on eachvalve nameplate. Crosby's valves are designed, manu-factured and tested in accordance with a quality man-agement system approved to the International Stan-dard Organization's ISO 9000 Quality Standard Seriesrequirements. With proper sizing and selection, theuser can thus be assured that Crosby products are ofthe highest quality and technical standards in the worldof Pressure Relief in doubt as to the proper application of anyparticular data, the user is advised to contact the near-est Crosby Regional Office or Representative.

5 Crosbyhas a large staff of highly trained people strategicallylocated throughout the world who should be contactedwhen a question arises. Refer to Crosby's WorldwideDirectory for an up-to-date contact 's Computer Aided ValveSizing Program - "CROSBY-SIZE"Crosby has designed a computer sizing program,CROSBY-SIZE, to provide maximum service to our cus-tomers by presenting recommendations based onCrosby's many years of experience. Use of this programallows an accurate determination of such parameters asorifice size, maximum flow and predicted sound program is a powerful tool, yet easy to use. Its manyfeatures include quick and accurate calculations, userselected units, selection of Valve size and style, valvedata storage, printed reports, specification sheets anddimensional Engineering HandbookTechnical Publication No.

6 TP-V300 Chapter IIntroduction1 - , 7:41 AM11 - 2 Crosby Engineering HandbookChapter 1 IntroductionProgram control via pop-up windows, function keys,extensive on-line help facilities, easy to read formattedscreens, immediate flagging of errors, easy editing ofdisplayed inputs and other features combine to makethe program easy to understand and is assumed that the user of CROSBY-SIZE has a basicunderstanding of Relief Valve sizing calculations. Theuser is responsible for correct determination of serviceconditions and the suitability of this program for aspecific and Crosby's Engineering Handbookare useful tools in sizing Pressure Relief valves . Shouldadditional clarification be required, contact , 7:41 AM2 IntroductionA Pressure Relief Valve is a safety device designed toprotect a pressurized vessel or system during an over- Pressure event.

7 An overpressure event refers to anycondition which would cause Pressure in a vessel orsystem to increase beyond the specified design pres-sure or maximum allowable working Pressure (MAWP).Since Pressure Relief valves are safety devices, there aremany Codes and Standards written to control theirdesign and application. The purpose of this discussion isto familiarize you with the various parameters involved inthe design of a Pressure Relief Valve and provide a briefintroduction to some of the Codes and Standards whichgovern the design and use of Pressure Relief of various applicable Codes and Standards areincluded in other sections of this electronic, pneumatic and hydraulic systems existtoday to control fluid system variables, such as Pressure ,temperature and flow.

8 Each of these systems requiresa power source of some type, such as electricity orcompressed air in order to operate. A Pressure reliefvalve must be capable of operating at all times, espe-cially during a period of power failure when systemcontrols are nonfunctional. The sole source of power forthe Pressure Relief Valve , therefore, is the process a condition occurs that causes the Pressure in asystem or vessel to increase to a dangerous level, thepressure Relief Valve may be the only device remaining toprevent a catastrophic failure. Since reliability is directlyrelated to the complexity of the device, it is important thatthe design of the Pressure Relief Valve be as simple Pressure Relief Valve must open at a predeterminedset Pressure , flow a rated capacity at a specified over- Pressure , and close when the system Pressure hasreturned to a safe level.

9 Pressure Relief valves must bedesigned with materials compatible with many processfluids from simple air and water to the most corrosiveCrosby Engineering HandbookTechnical Publication No. TP-V300 Chapter 2 Design FundamentalsCrosby Style JOS Spring LoadedPressure Relief ValveFigure F2-12 - 1media. They must also be designed to operate in aconsistently smooth and stable manner on a variety offluids and fluid phases. These design parameters leadto the wide array of Crosby products available in themarket today and provide the challenge for future prod-uct Loaded DesignThe basic spring loaded Pressure Relief Valve has beendeveloped to meet the need for a simple, reliable, systemactuated device to provide overpressure protection.

10 Fig-ure F2-1 shows the construction of a spring loadedpressure Relief Valve . The Valve consists of a Valve inletor nozzle mounted on the pressurized system, a discheld against the nozzle to prevent flow under normalsystem operating conditions, a spring to hold the discclosed, and a body/bonnet to contain the operatingelements. The spring load is adjustable to vary thepressure at which the Valve will , 7:46 AM1 Crosby Engineering Handbook2 - 2 Chapter 2 DesignFundamentalsThe design of the control or huddling chamber involvesa series of design tradeoffs. If the design maximizes lifteffort then blowdown will be long. If the design objectiveis to minimize blowdown, then the lift effort will bediminished.