I don't know if you are using max, maya or blender, but the principle works the same.
Create a nurbs curve that follows the flow and direction you want. In this case a L-shape that extends into one direction. (Using the orthographic views usually helps a lot when creating a curve).
Modify the curve to the desired position and tweak it the way you like it. I use maya for the next part but what you do then is select the faces you want to extrude and then select the curve. Go to the extrude option and tell it to extrude and follow the curve. Play with the segment options (the more segments the smoother the extrusion is). That's pretty much it in a nut shell.
Again I don't know what program you are using but the principle is pretty much the same. Hopefully that helps!
I don't think it needs to be all one contiguous piece? It is kind of hard to tell but it looks like a tank is hanging in front of a large pipe or "inline mixing chamber". Similar to the gray tank in the lower right of this pic
Sometimes its important to remember that things are made up of a lot of separate pieces and they are joined together in a lot of different ways. Those seams are opportunities to put material and smoothing breaks, UV seams and separate objects that might look joined but can technically be divided without anyone knowing.
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Create a nurbs curve that follows the flow and direction you want. In this case a L-shape that extends into one direction. (Using the orthographic views usually helps a lot when creating a curve).
Modify the curve to the desired position and tweak it the way you like it. I use maya for the next part but what you do then is select the faces you want to extrude and then select the curve. Go to the extrude option and tell it to extrude and follow the curve. Play with the segment options (the more segments the smoother the extrusion is). That's pretty much it in a nut shell.
Again I don't know what program you are using but the principle is pretty much the same. Hopefully that helps!
Sometimes its important to remember that things are made up of a lot of separate pieces and they are joined together in a lot of different ways. Those seams are opportunities to put material and smoothing breaks, UV seams and separate objects that might look joined but can technically be divided without anyone knowing.
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Oh, and there's a lot more similar stuff here:
http://wiki.polycount.com/wiki/Subdivision_Surface_Modeling