1 FLANGE LEAKAGE TEST AS PERASME BOILER & PRESSURE VESSEL CODE Checkingflangesforfailureisoneofthe mostimportantactivitiesofastressengineer.It is alsoconsidered as acomplexactivitybecause oflargeamountofcomputation.Inpastfew decadesflangetestmoduleisaddedinalmost allpipestressprogrammes.However,thereis alwaysaneedtounderstandthe procedure/calculationsinvolvedinstress computations in flanges.Theflangetestorselectionisaddressedin variousASMEcodes.Thesecodesarelisted below: 1. ASME BPVC Section VIII, Division 12. ASME BPVC Section VIII, Division 23. ASME BPVC Section VIII, Division 34. ASME BPVC Section I5. ASME BPVC Section III6. ASME B31.3 (Process Piping) 7. ASME B31.1 (Power Piping) 8. ASME B31.8 (Gas transmission lines) 9. ASME B31.4 (Liquid transmission lines) FlangedesigninASMEBPVCSectionVIII, Division1,isbasedonthedesignbyformula approach. TheallowablestressesusedareasperASME B31.3(ProcessPiping).Itrecommends consideration of thermal insulation and external loads in design.In ASME BPVC Section VIII, Division 2, is based onbothdesignbyformulaanddesignby analysis. It permit higher allowable then Section VIII, Division 1.ASMEBPVCSectionVIII,Division3,is generallyusedfordesignpressuregreaterthan 10,000 psi.ASMEBPVCSectionI,providesrulesonlyfor flangesasperlistedstandards.Norules provided for non standard flanges. ASME BPVC Section III provides rules for class1, 2 and 3 piping. This write-up describes the procedure for flange test as per ASME BPVC Section VIII, Division 1, Appendix 2. The formulas shown are applicable to only weld neck flange (integral type).A step bystepprocedureisprovidedforstress engineerstoquicklyrecapitulatethedifferent parametersrequiredforflangetest.Flangetest forexternalloadsisalsoadded.Attheend different parameters as per ASME BPVC Section VIII,Division1,AppendixSarediscussed. TablesfromASMEBPVCSectionVIII,Division 1 are attached for ready reference. Notations A=outside diameter of flange, in. (mm) Ab = cross-sectional area of the bolts usingthe root diameter of the thread or least diameter of unthreaded position, in2. (mm2) Am= total required cross-sectional area ofbolts, taken as the greater of Am1 and Am2, in2 (mm2) AP= area to outside of gasket contact, in2 Am1 = total cross-sectional area of bolts at rootof thread or section of least diameter under stress, required for the operating conditions, in2 (mm2) Am2 = total cross-sectional area of bolts at rootof thread or section of least diameter under stress, required for gasket seating, in2 (mm2) B = inside diameter of flange, in. (mm).When B is less than 20g1, it will be optional for the designer to substitute B1 for B in the formula for longitudinal stress SH b = effective gasket or joint-contact-surfaceseating width in. (mm) bo= basic gasket seating width (mm) C = bolt-circle diameter, in. (mm)D= nominal bolt diameterd = factor, in3 (mm3) E = modulus of elasticity for the material ofthe flange at the design temperature (operating condition) or atmospheric temperature (gasket seating), as may apply, psi e = factor, in1 (mm1) F = factor for integral type flanges(see Table 2-7.2) FA= applied force Feq= equivalent axial force

2 FL = factor for loose type flanges (see Table 2-7.4) f = hub stress correction factor for integralflanges (see Table 2-7.6) G = diameter, in. (mm), at location of gasketload reaction go = thickness of hub at small end, in. (mm) g1 = thickness of hub at back of flange, in.(mm) H = total hydrostatic end force, lb (kN) HD= hydrostatic end force on area inside offlange, lb (kN) HG= gasket load (difference between flangedesign bolt load and total hydrostatic end force), lb (kN) Hp = total joint-contact surface compressionload, lb (kN) HT= difference between total hydrostatic endforce and the hydrostatic end force on area inside of flange, lb (kN) h = hub length, in. (mm) hD = radial distance from the bolt circle, tothe circle on which HD acts, in. (mm) (see Table 2-6) hG = radial distance from gasket loadreaction to the bolt circle, in. (mm) (see Table 2-6) ho = factor, in. (mm) hT = radial distance from the bolt circle to the circle on which HT acts, in. (mm) (see Table 2-6) J = rigidity index