Dear experts,

I am new for piping stress analysis with considering the slug force (multi phase flow piping system), here i have calculated the slug forces with basic formula, the formula image is attached with this post, so Kindly advice me this slug force calculations are correct or not and the slug force is applied at elbow points based on the flow direction, the pipe axial force and orthogonal force is applied at all elbow points.

Here i have attached some images for your review and revert back me as soon as passable.

The following simple load ceases are considered for static pipe analysis with slug force.

L1= WW+HP---------------------) HYD
L2= W+P1+T1-------------------) OPE
L3= W+P2+T2-------------------) OPE
L4= W+P2+T2+F1----------------) OPE-----(SLUG FORCE AT VECTOR-1)
L5= W+P2+T2+WIN1--------------) OPE
L6= W+P2+T2+WIN2--------------) OPE
L7= W+P2+T2+WIN3--------------) OPE
L8= W+P2+T2+WIN4--------------) OPE
L9= W+P1----------------------) SUS
L10= W+P2---------------------) SUS
L11= L4-L3--------------------) OCC
L12= L5-L3--------------------) OCC
L13= L6-L3--------------------) OCC
L14= L7-L3--------------------) OCC
L15= L8-L3--------------------) OCC
L16= L11+10-------------------) OCC
L17= L12+10-------------------) OCC
L18= L13+10-------------------) OCC
L19= L14+10-------------------) OCC
L20= L15+10-------------------) OCC
L21= L2-L9--------------------) EXP
L22= L3-L10-------------------) EXP

Kindly confirm the above load cases are correct or not.

regards

rajiv

Hi Rajiv,
As per process (based on the slug length and timing), how is the slug force being applied- sequentially or simultaneously?
Load case which you have presented shows that the slug force is being applied at all the elbow simultaneously as all the elbow is witnessing the impact in load case L4 and accordingly stresses calculated in load case L16.
Its not always true that simultaneous application of impact load gives the conservative result specially when the force vector is input at mid point of the elbow. Chances are there that forces nullify due to configuration.
Also you will have varied result when forces applied are at far point/near point at each of the elbow.
For sequential application of slug load you need to define different force vector at each elbow, and will have to make adjustment in load cases accordingly.
Also, you need to consider the DLF=2 when u define the force vector while performing quasi-static analysis, in impact loading condition.

Dear Dinesh,

How many elbows we can consider for slug force with static pipe stress analysis, here only 9 vectors are available in CAESAR II, so only 9 vectors only we can apply force at 9 elbows.

Load case at operating condition the forces are like F1, F2, F3, F4, F5, F6, F7, F8, F9.

My stress analysis the piping configuration is more than 9 elbow points are coming, here how to consider the load case for more than 9 elbow piping system.

Kindly advice me the load case options with detailed information.

By
Rajiv

Hi Rajiv,

You are correct that there are only 9 vectors available in CAESAR II, so maximum of 9 vectors can be used for force definition. But again you cannot have all the 9 elbows in your system placed very close together.

With basic idea being selecting elbow pairs at least in such a manner that force doesn't nullify or cancels out, you can choose elbow pairs that are distant apart with the same force vector (say F1). With this you will have the report with slug acting two at a time, three at a time depending on the no. of elbows chosen for same force vector.

Dear Dinesh,

Yes Your correct,

Thanks for your advance reply.

By

Rajiv