This is result of boolean difference of box with pipe.
Result failed because of cross intersections inside the pipe.
Is it possible to remove this edges?
Other words i need single solid, not crossed inside.
Merge all edges not useful this case.
Cut your pipe using "Wirecut" into two pipes such that the overlapping sections belong to two different polysurfaces.
You can also use an isocurve ("Extract Isocurve" and toggle the U/V to get the circles going across the pipe) to do this.
Then, if this is laid out flat, go to the top viewport and select the two pipes, and use the "Intersect" command.
You will get a line denoting where the two pipes' surfaces intersect. Use this line to trim away at the surfaces from the two pipes so that they end up not overlapping.
You can also use Isocurves for the pipes to create just the 'cross section' of them (the spot where they intersect) and trim/split/join that part until it is one single part, then boolean difference the three polysurfaces (the two pipes and the joint) from the stock.
On Rhino V4 you cannot just boolean the larger object and the smaller pipes (due to the overlap).
I'm not sure whether this has been update on Rhino V5, so your best bet is to split your pipe into two, using for example, the method above,
Thank you for reply Jorge.
Also i can trim that pieces using curve found by intersections.
But i cannot create solid back after it because of gaps between surfaces.
I looking for simple command like MergeAllFaces