Dear All .

I am performing Stress Analysis for a 36 " Offshore line carrying oil Sp. Gravity nearly 1. Pipe Thickness is 25.4. Feasible Supporting span is 30m.

My Sustain Stress is 65%.
Expansion Stress is 50%
Max Sustain Displacment is 40mm.

I would like to know , whether the Sustain deflection of 40mm is acceptable .Any thing to be cinsidered when sustain displacements are big .

Kindly advise me ..

I have restricted my Previous Systems to a max Sustain Dispalcement of 15mm

Regards
Bala

Hi Bala,

The rule of thumb is :
For process units max vertical deflection at the centre of a pipe span should not exceed 16mm.

For offsites max vertical deflection at the centre of a pipe span should not exceed 38mm.

Ofcourse you have to decide which is the worst criteria, maximum deflection or maximum stress.

With regards to span deflections, keep one eye on liquid pockets as it may result in slugging in certain cases, hence the limitation on deflection above, however if there are no pockets, and nothing is overloaded I cant see anything wrong with 40mm of deflction.

Regards
A

Hi Bala,

I overlooked your first point...30m span!!! no!!
Even though this pipe can span 30m it isnt prudent to have such large spans as the structural loadsat the supports will be very high. It is important from an engineering point of view to spead the loads e.g. I am at the moment working with a 30" line full of liquid which is spanned at every six metres, this keeps the structural group happy and the pipe stresses are reasonable too.
Thats all

A

Hi Aaron .

Thanks veymuch for your reply .


Regards
Bala