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Vessel in ocean-episode II

Vessel in ocean-episode II

Vessel in ocean-episode II

(OP)
There is an interesting thread posted 6 months ago in COMPRESS forum, but no clear answer. Let me re-phrase here:
A slender (100' long) pressure vessel for gas processing unit with half full of liquid mounted on a giant ocean platform which is not stationary. It yaws, pitches and rolls with the ocean wave.
The author has the following questions:
1. How can supplier design this vessel per Div. 1?
2. Is this vessel to be considered in fatigue service due to cyclic stress caused by waving?
(the author got several bids with significant difference in thickness)

Anyone has two cents ?

RE: Vessel in ocean-episode II

The vessel is obviously designed for compliance with ASME VIII-1, including all the external loads. The external loads do include typical maritime transport loads, all trivial to this point.
The described condition is calling for dynamic loads due to the sloshing effects of the partially filled vessel with a particular liquid. The effects of liquid waves due to transport ship motion can be estimated / calculated, but that exceeds by far the competency of a B&PV engineer. I have to confess I have never designed road tankers, or maritime fuel tanks, but the sloshing effects on these vessels are considered significant issue.
However, in your case you'll find the sloshing effects will be minimal loads on vessel, but rather significant on the anchoring attachments, causing some local effects on the shell / lug junction (WRC / PD 5500 calculation). Keep the vessel empty for maritime transport!
My two cents (I'm also sure this is all too trivial for you).
Cheers,
gr2vessels

RE: Vessel in ocean-episode II

1. Yes.
2. Maybe - not enough information provided. However, if the purchaser were to fill out Appendix KK, sufficient information might be provided to make that determination. Certainly, a fatigue screening, such as provided in Division 2, Part 5, Article 5.5.2, would assist in answering that question.

RE: Vessel in ocean-episode II

I have been involved in the design of vessels for use on FPSO's. My experience was to install a series of internal perforated anti-wave baffles to reduce the momentum of the internal liquid generated by the ships pitch etc and therefore reducing additional stress on the vessel proper.

RE: Vessel in ocean-episode II

Motion loads are a standard item for most vessels going onto offshore platforms, floaters.

A fabricator that has not developed a way to calculate these loads, specified by the purchaser, will throw thickness at it to make sure they are covered, thereby a large inconsistency in thickness and pricing.

At the bid tab phase, the purchaser should evaluate each thickness offered and ask each fabricator how they arrived at that thickness.

Proof is in the puddin'

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