How to Model Support on the Bend in START-PROF

Stanchion, Trunnion, Dummy leg, Lug

Read about START-PROF pipe stress analysis software

How to Model Stanchion in START-PROF (Simple Model)

Insert a node on the bend edge and insert a resting support

To take into account the support thermal expansion, just add the upward displacement of the resting support equal to the value of thermal expansion. To improve accuracy, add rigid element (with temperature expansion) with length equal to the radius of the bend, and after it add trunnion pipe.

 

How to Model Stanchion in START-PROF (Advanced Model)

Insert a node in the middle of the bend

Change the bend property "Flange on the bend" to One flange. It will approximately consider the flexibility factor of the bend with attached trunnion connection.

Measure the horizontal distance between the pipe axis and the node in the center of the bend

Insert the rigid element at 45 degrees into node 33. The horizontal distance should be the same as measured before. Insert vertical pipe element into node 35. It will be "trunnion". Add the support into the node 36.

1 - rigid element, 2 - Joint element (SIF), 3 - Pipe element, 4 - Support, 5 - Node in the middle of the bend

And add the Joint element into the node 35 to take into account the stress intensification factors for trunnion connection

Stress intensification and flexibility factors for trunnion, stanchion, and dummy leg can be obtained from PASS/Nozzle-FEM Software. Also detailed stress analysis from the applied loads can be done.

 

Also stress intensification factors can be calculated manually, for example using equations form EPRI report [EPRI, 1998, Stress Indices for Elbows with Trunnion Attachments, Report TR-107453, Electric Power Research Institute, Palo Alto, CA].

Where K2 index can be taken as K2=1.35

 

Or Kellogg "Design of pipe attachments" method can be used. The loads can be found in the internal forces table of START-PROF

Trunnion Pipe (Dummy Leg) Support Model in START-PROF

To model a trunnion - insert a node on the bend edge

Insert a pipe (trunnion) in this node with zero pressure and zero fluid weight. Don't insert a tee into intersection point. And insert a support at the trunnion's end. To improve accuracy, add a rigid element with length equal to band radius and add trunnion next to it.

The approximate temperature drop per length of trunnion is

Sometimes used 1/3 of operating temperature for trunnion

How to Model the Bend with a Lug and Hanger in START-PROF

It could be modeled the same as shown at example 1. Here we will show the another way of modeling.

Insert a node on any point along the bend axis curve.

 

Additional node is created and bend splitted into two parts. The angle on each part should be set as 90 degree. It means that these two bends are parts of single 90 degree bend. This angle is used for flexibility k-factor calculation.

 

After that the rigid element should be added with a hanger on it's end. The weight of rigid element should be a zero. Don't insert a tee.