Flanges

there are square and elliptical flanges, normally,you'd find square flanges in hydraulic systems. Basically, it has to do with pressure ratings.

Most flanges in piping design engineering are round for torquing purposes. You can get a secure, constant seal all around equally on a round flange. There are probably lots more reasons, but this was the first one to come to mind.

Another reason to make process plant piping flanges round is cost. If you try to make a square pipe flange for a 24" pipe you are talking about a very big piece of steel. This big piece of steel would need to be very thick to exert the proper sealing of the gasket as noted by "alegvold". This added size due to the square shape and the added thickness will increase the weight of the flange. You will now also have to have square flanges on all valves and all the equipment that piping connects to. You then add the extra weight to all of these items. The added weight now requires a stronger foundation. And it goes on and on.
Trust me (and "alegvold") round flanges are better.

round pipe and flanges make for much better flow characteristics and calcs are easier, etc. it goes on and on

any round object is simpler to machine, easier to bring to closer tolerances, easier to adapt to carrier vessels (pipe, tubing, etc.). Components are better able to take high pressure (the arch effect). Plus all of the good reasons previously stated.

In addition to all mentioned and reasonable reasons for making round flanges instead of square flanges, the stress analysis shows a uniform stresses around the circumferential & gasket seating in case of using round flanges. And all international piping codes appreciate round flanges, except in special cases, square flanges can be used subjected to full stress analysis.

Egypt

Because pipe is round? Hmmm....Maybe.

Yes !

All above information M&E technique good and logic.

ZY

last but the best comment - non engg side - pipes are round and we wins the space area when we are going with round flange instead of square flange and vise- versa for square pipe too.

Draw a square flange for round pipe ? You will come to know , why round flange is suitable for round pipe and not the square, and do same for square pipe too