ASMEB16.20.Усилиезатяжкидляпрокладок

Calculating Load RequirementsTwo formulas that define the minimum loadDetermine if Bo is greater or less than 1/4",thenrequired to effect a seal on a particular gasket arefind B1:Wm1 and Wm2.When these formulas have beenfBo≤1/4"，then B1=Bo;calculated,the larger load of the two is the loadIf Bo 1/4",then B1=(V Bo)/2necessary to effect a seal.B1=Using B1,determine G:Let:G=OD-[B)(2]π=3.14Now,insert these values in the final equations toP=Maximum internal pressuredetermine minimum required load:M=Gasket factor "M"defined on page 27.Wm1=[π(P)(G2/4+[2(B1)(G(M(P](M=3 for spiral wound gaskets)Wm2=π(B(G))Y=Seating stress "Y"defined on page 27.(Y=10,000 psi for spiral wound gaskets)When Wm1 and Wm2 have been calculated,theN=Basic width of a gasket per chart on page 26.larger of the two numbers is the minimum load(For raised face flanges see diagram 1a)required to seat a gasket.In most cases the avail-Bo=Basic seating width of a gasket per chartable bolt load in a connection is greater than theon page 26.(For raised face flanges,Bo N/2)minimum load on the gasket.If not,higher boltB1=Effective seating width of a gasket;muststresses or changes in the gasket design are re-be determined.quired for an effective seal.ID=Inside diameter of gasketNOTE:OD Outside diameter of gasketFlange design code suggestions for low pressureFor gaskets where the raised face is smallerapplications calling for minimum seating stress (Ythan the OD of the gasket face,the OD isvalue)are sometimes inadequate to seat the gasketequal to the outer diameter of the raised face.because the bolting and flange rigidity are insufficientFind:to effect a proper seal.Care should be taken toID=ensure that flange conditions provide a suitableOD=seating surface.For internal pressures to be con-tained,flange rotation and sufficient residual loadsGiven the ID and OD,find the value of N.Thenmust also be considered in the flange design.define Bo in terms of N (See page 26):N=B0=28