I'm a novice in mechanical engineering and I'm having some troubles to find a pipe that change from one section to other. In this case I want to connect a circle section to a rectangular section. I google it but only found the second Figure. Water is going to be used with a pump of 4 HP. The diameter of the circular part is $d_{int}=90 mm.$ and the dimensions of the rectangular side are less than the $d_{int}$. So basically, I want to know how to search them or are there any mechanism that can replace what I'm trying to do?



  • $\begingroup$ I'm curious to know what this application is, I've never seen rectangular piping/tubing only rectangular ductwork for HVAC applications. $\endgroup$
    – J. Ari
    Oct 15, 2020 at 15:35

1 Answer 1


Your three choices are to either change the proposed piping system to have the same cross sectional shape. Circular cross sections are usually the most easily sourced. With pipes of circular cross section it should be easier to find a reducer to act as a joiner for the two different sized pipes.

The second option is to find a circular to rectangular reducer. They are made, but usually for down pipes (or downspouts). Finding one with the cross sectional dimensions you require may be difficult. Also finding one made to withstand the pressures required in your application may also be difficult.

The other option is to have circular to rectangular reducer specially made for your circumstance. This may be difficult to acquire and possibly expensive.


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