Double Trunnion Modeling in AutoPipe


I modelled double trunion in AutoPipe by using Cross connected with two rigid elements, and then rigid elements connect to trunnion pipes, SIFs between trunnion pipes and rigid elements had been specified from FE-Pipe.

a warning message show, cross centre point SIF had not been specified, actually, I had specified it.

is my model something wrong?



  • You defined the SIF for the connection points of the trunions, but not the cross itself.  AutoPIPE still sees it as a fabricated fitting and requires a SIF for this connection.  Any time you put a fitting in there, it thinks it is an opening in the pipe.  Unlike your trunions which are not "open" inside the pipe to the flow stream which reduces the strength in the area.

    you could just model it as a cross with a "other" designation and then put the in and out SIF's at 1.00.  if they are load bearing, then you may want to increase that to something else depending on the code you are designing too.  

  • Thanks Samhuff,

    I think we are right, I checked from WIKI, the message shows no SIF in the centre point, this message can be ignored,

  • Hello LZ,

    Samhuff is correct, when modeling a lug start with a Tee or Cross fitting where Type of Tee = other, enter SIF = 1.0, model rigid pipe (no weight added, but considers thermal growth)  from the Center-line out to the surface of the pipe, add a user SIF, and additional piping to support location.

    This modeling approach can be found with Bentley's Knowledge Search utility:

    ____1. Go to the Bentley web site (

    ____2. Select  "Support and Services" from the top


    ____3. Select "Support" hyper link

    ____4. In the multi colored blue/green grid, under

                 Support Tools heading, select

                 "KnowledgeBase" hyperlink

    ____5. Log into the Bentley website. (call Bentley if

                 you have troubles logging into the website)

    ____6. Enter the following into the "Search Text" field

                 "54367" and press "Search" button.

    ____7. The first 100 hits will be displayed.

    ____8. Review the results and select the hyperlink

                 labeled "AutoPIPE modeling: Trunion / Lug



    a. Use the "Advanced search" hyper link can yield more specific results (exact phrase, limited to a product name, etc..)

    b. See training video on using Knowledge Search at:


    Mike Dattilio

    Bentley Technical Support Analyst