3 Air pipe venting criteria
Clasification Society 2023 - Version 9.38
Statutory Documents - IMO Publications and Documents - Resolutions - Maritime Safety Committee - Resolution MSC.245(83) - Recommendation on a Standard Method for Evaluating Cross-flooding Arrangements - (Adopted on 12 October 2007) - Annex - Recommendation on a Standard Method for Evaluating Cross-flooding Arrangements - 3 Air pipe venting criteria

3 Air pipe venting criteria

  3.1 In arrangements where the total air pipe sectional area is 10% or more of the cross-flooding sectional area, the restrictive effect of any air back pressure may be neglected in the cross-flooding calculations. The air pipe sectional area should be taken as the minimum or the net sectional area of any automatic closing devices, if that is less.

  3.2 In arrangements where the total air pipe sectional area is less than 10% of the cross-flooding sectional area, the restrictive effect of air back pressure should be considered in the cross-flooding calculations. The following method may be used for this purpose:

The k coefficient used in the calculation of cross-flooding time should take into account the drop of head in the air pipe. This can be done using an equivalent coefficient ke , which is calculated according to the following formula:

ke = kw + ka (ρ a/ρ w) (Sw/Sa)2
where:
kw = k coefficient for the cross-flooding arrangement (water)
ka = k coefficient for the air pipe
ρ a = air density
ρ w = water density
Sw = cross-section area of the cross-flooding device (water)
Sa = cross-section of air pipe

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