METAL/SPIRAL WOUND GASKETS
Engineering Data/FAQs
Calculating Load Requirements
Two formulas that define the minimum load required to effect a seal on a
particular gasket are Wm1 and Wm2. When these formulas have been calculated, the
larger load of the two is the load necessary to effect a seal.
| Let: |
|
| pi = | 3.14 |
| P = | Maximum internal pressure |
| M = | Gasket factor "M" (M = 3 for spiral wound gaskets) |
| Y = | Seating stress "Y" (Y = 10,000 psi for spiral wound gaskets) |
| N = | Basic width of a gasket per chart (For raised face flanges see diagram 1a on the chart) |
| B0 = | Basic seating width of a gasket per chart (For raised face flanges, B0 = N/2) |
| B1 = | Effective seating width of a gasket; must be determined. |
| ID = | Inside diameter of gasket |
| OD = | Outside diameter of gasket For gaskets where the raised face is smaller than the OD of the gasket face, the OD is equal to the outer diameter of the raised face. |
Find: |
|
| ID = | _______ |
| OD = | _______ |
| Given the ID and OD, find the value of N. Then define B0 in terms of N | |
| N = | _______ |
| B0 = | _______ |
| Determine if B0 is greater or less than 1/4", then find B1: | |
| If B0 < or = 1/4", then B1 = B0 | |
| If B0 > 1/4", then B1 = (sq.root B0) / 2 | |
| B1 = | _______ |
| Using B1, determine G: | |
| G = | OD - [(B1)(2)] |
| Now, insert these values in the final equations to determine minimum required load: | |
When Wm1 and Wm2 have been calculated, the larger of the two numbers is the minimum load required to seat a gasket. In most cases the available bolt load in a connection is greater than the minimum load on the gasket. If not, higher bolt stresses or changes in the gasket design are required for an effective seal.
NOTE:
Flange design code suggestions for low pressure applications calling for minimum
seating stress (Y value) are sometimes inadequate to seat the gasket because the
bolting and flange rigidity are insufficient to effect a proper seal. Care should
be taken to ensure that flange conditions provide a suitable seating surface. For
internal pressures to be contained, flange rotation and sufficient residual loads
must also be considered in the flange design.
WARNING:
Properties/application shown here are typical. Your specific application
should not be undertaken without independent study and evaluation for
suitability. For specific application recommendations consult Garlock.
Failure to select the proper sealing products could result in property
damage and/or serious personal injury.
Performance data published here has been developed from field testing, customer field reports and/or in-house testing.
While the utmost care has been used in compiling this information, we assume no responsibility for errors. Specifications subject to change without notice. This edition cancels all previous issues. Subject to change without notice.