Olet fittings (weldolets, thredolets, etc.) work vastly different inside spec-driven piping than every other fitting (see more information here). 

  • It is the only fitting type whose inlet and outlet coordinate systems have Z-axes pointing in the same direction, every other fitting code has them pointing in opposite directions.
  • The only required parameters are FITTING_CODE, SIZE, and END_TYPE.
  • Unlike every other fitting, they cannot be directly inserted into a pipeline.


RsysConfig applies the pipeline run size an Olet fitting can be inserted into along with the actual size the Olet is reducing to (Line Size and Branch Size, respectively in the below picture). 

Branch Size gets applied as the SIZE parameter on the inlet coordinate system and Line Size gets applied as an extra PIPELINE_SIZE parameter on the inlet coordinate system. Both parameters get uploaded to RsysConfig and get written into the spec text files to tell Spec-Driven Piping which pipeline sizes allow which weldolet sizes.

Creo Insertion

Olets have a unique way they need to be inserted into a pipeline in spec-driven mode. First, a “Break Point” must be inserted in the initial pipeline where it will meet the intersecting pipeline. Second, either a "Set Start" can be done on the break point and a user can draw the branch pipeline coming directly out of the run pipeline OR the intersecting pipeline must be routed to the newly-created Break Point using the “To Pnt/Port” button - fr standard weldolets, this should be done at a 90° angle.

From there, you must use the “Insert Fitting” GUI on either of the initial pipeline sections – there are two sections now that we’ve added the Break Point. Select your weldolet fitting from the drop-down menus but be sure that the outlet size of the weldolet matches the size of the intersecting pipeline, Creo does not have self-checking logic for this insertion! If applied correctly, the new BRANCH_LET fitting will look similar to the picture below (a 32A sized weldolet inserting into a 40A pipeline).