Expert: Ray Wilkinson - 2/1/2007

Question
Hi Ray.
What's the difference between a PIPE, a TUBE and a DUCT. I already have a leaning, but would like other opinions. We are trying to create a rule so that a "vessel" from one engineer, doesn't have a different nomenclature from one from another engineer.

Thanks Ian

Answer
Sorry if you get a decline for this, I clicked and scrolled at the same time.

Anyway, I would think you might get almost as many different answers as the number of people you ask. However, my take on it would be:

A pipe is a conduit for fluids (which may be air, but if so at high pressure).

A tube is a geometric shape (a cylinder), although it may be curved. It is typically a structural member in an engineering context, rather than a passage for any fluid.

A duct is a conduit, normally larger than a pipe but not necessarily, that carries low-pressure gas, usually air.

In an aircraft context, I would call all conduits with cabin air, deicing air and starter air 'ducts'. I would call pneumatic conduits (i.e. air pressures of many bar) and all those carrying liquids 'pipes'. Tubes I would only apply to cylindrical objects not carrying any fluids, such as structural items. To add another term, any vessel holding static fluid or air I would call a tank, although this term could apply to vessels of any shape.

I hope this helps rather than hinders. We all think we know what we mean, we probably all mean more or less the same, and we all assume everyone else means the same thing. Teaching students quickly gets over these assumptions!

Regards

Ray