shipboard piping load cases

Hi everybody,

I have to assess piping onboard a ship.

There are load cases to be adressed such as hogging, sagging, elongation and contraction of hull due to temperature, accelerations due to pitch and roll, ...

So far, accelerations I accounted for in piping stress analysis where classified as occasional (i.e. for static seismic equivalent).

I've tried to look into IGC code (Lloyd's or BV) but did not find any classification into operating or occasional stress types.

Can we consider acceleration as occasional even though it could happen every 10 seconds for the entire life of the ship (maybe 20 years)?

1) Can anyone help me find it in the books or give me advice concerning stress types for shipboard piping?

2) As far as I've seen, increase in stress is not so high; I've seen more increase in forces and moments on the equipment. Does it mean the stress classification is not the first concern?

yours ,

A good topic with little "published" knowledge. Most people ivolved with FPSO use their own derivations from DNV Norske.

The method as I vaguely understand it involves generating a damage curve of sorts for the combinaed loads. I have yet to get much farther than that... unfortuanately.

I would venture that cyclic loads / stresses due to wave action would have to be held toa very low level of stress artound the endurance linit for the metal.

Thats all I can tell you maybe somebody else can add something....