What should be minimum specific gravity of a subsea pipeline so it won't float in water? I know it has to be higher than 1, but is there any recommended number by API, ASME, DNV, or by any Standard Specification? Any reference will be greatly appreciated.
503 The submarine pipeline system shall have a specific gravity sufficient to avoid floatation. If a sufficient
low probability of negative buoyancy is not documented, the following criterion applies:
yw x (b / (Wsub + b)) <= 1.00
Where:
γw = Safety factor on weight, 1.1
b = buoyancy
Wsub = Submerged weight
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It sounds from seeing your references you could very well be dealing with pipelines installed in seawater or saltwater, which of course has a S.G. not 1 but a little greater than 1 (e.g. near 1.03).
In any case as to just "float", the sea and incidentally shore and bottom soils or mucks are of course not a stagnant environment (there are different properties, currents and motions etc.), so there could more to consider in stability installation and service etc., than just "float" per Archimedes in fresh water or seawater etc. Like you I will await more learned or detailed comments.