USCG Exam PracticeVessel stability — metacentric height, free surface
When calculating free surface effects under 46 CFR §28.540, how must tanks fitted with cross-connection piping be treated?
- A. Each tank must be calculated individually using the inertia method
- ✓ The tanks must be assumed to be one common tank, unless valves kept closed to prevent liquid transfer during heel are installedCorrect
- C. The tanks may be ignored if the total combined volume is less than 3 percent of vessel displacement
- D. The free surface effect must be calculated using the moment of transference method exclusively
Why B is correct
46 CFR §28.540(b) requires that tanks fitted with cross-connection piping be calculated as one common tank unless valves that will be kept closed to prevent transfer of liquids as the vessel heels are installed in the piping. Option D is incorrect because §28.540(c) states the moment of transference method may be used in lieu of the inertia method, not exclusively.
Cited:46 CFR §28.540