Calculating Load Requirements

Two formulas that define the minimum load re-quired to effect a seal on a particular gasket are Wm1and Wm2. When these formulas have been calculated,the larger load of the two is the load necessary to effect a seal.Let:
is greater or less than 1/4", thenfind B
1 :If B
1/4", then B
1 = B
;If B
> 1/4", then B
1 = ( B
)/ 2B
1 =______Using B =3.14P =Maximum internal pressureM =Gasket factor "M" defined on page D-33.(M = 3 for spiral wound gaskets)Y =Seating stress "Y" defined on page D-33.(Y = 10,000 psi for spiral wound gaskets)N =Basic width of a gasket per chart on page D-32.(For raised face flanges see diagram 1a)B
1 , determine G:G =OD - [(B
1 )(2)]Now, insert these values in the final equations todetermine minimum required load: Wm1 = [ (P)(G
2 )/4] + [2(B
1 )( )(G)(M)(P)] Wm2= (B
1 )(G)(Y) When Wm1 and Wm2 have been calculated, thelarger of the two numbers is the minimum load requiredto seat a gasket. In most cases the available bolt load in a connection is greater than the minimum load on thegasket. If not, higher bolt stresses or changes in thegasket design are required for an effective seal.
=Basic seating width of a gasket per charton page D-32. (For raised face flanges, B
= N/2)B Note:
1 =Effective seating width of a gasket; mustbe determined.ID =Inside diameter of gasket OD =Outside diameter of gasketFor gaskets where the raised face is smaller than the OD of the gasket face, the OD isequal to the outer diameter of the raised face.Find:ID =______ OD =______Given the ID and OD, find the value of N. Thendefine B Flange design code suggestions for low pressureapplications calling for minimum seating stress (Yvalue) are sometimes inadequate to seat the gasket because the bolting and flange rigidity are insufficientto effect a proper seal. Care should be taken to ensurethat flange conditions provide a suitable seatingsurface. For internal pressures to be contained, flangerotation and sufficient residual loads must also beconsidered in the flange design.
in terms of N (See page D-32):N =______B
=______ Determine if B
D-34