What type of flange should I use for plate greater than 24" (NPS 24") ?

[miftahazhar]

Hello guys.. so i have homework to design heat exchanger. Inner diameter of the shell is greater than 24" (lets say 27" ) so I can not made of shell from pipe, i have to use plate. How I select type of flange, I mean its dimension and rating ? because ASME B.16.45 only provide flange until NPS 24.

Should I use ASME B.16.47 ? and if I use that code, my plate (outer diameter) must have the same diameter with the flange? lets say flange's diameter is NPS 27" and my plae's outer diameter is 27" ?

Thanks, sorry I really have less experience in this case

 

[racookpe1978]

NPS of 27? (There is no such National Pipe Size - If that is what you think are proposing.)

Show a drawing (or sketch) of what you are thinking - it is NOT clear from your words.

(Homework (for school projects) is not permitted here.)

First, the diameter for a pipe of a certain size is not the same as the diameter OF a flange that fits a certain pipe size. Look up the B16.5 tables again for a 24 inch flange. That is a flange to fit a 24 inch diameter pipe.

 

[SnTMan]

miftahazhar, first, there is no "B16.45" Perhaps you meant B16.5?

Second, you may use a B16.47 flange IF: the hub small end OD and bore ID is dimensionally compatible with the exchanger shell AND if the flange temperature / pressure rating meets the exchanger design conditions.

Most if not all of these flanges will have hub small end dimensions in even-numbered inches, i.e. 26, 28, 30... There will be rules for permitted bore diameters. So, if you can meet these things you can use one of these flanges. Advantage is, you pick one, you don't have to design it. Disadvantage is, a custom designed flange may be less expensive or otherwise more suitable.

If a B16.47 flange is not practical for whatever reason, then a custom design, such as per ASME Sec VIII, Div. 1, Appendix 2 or other pressure vessel Code is needed. How to go about such a design is a complicated subject. Probably the best advice I can give you is to see if you can get hold of a Taylor Forge Bulletin #502. It will have some explanation of the theory behind the subject and useful procedures. it will contain a manual calculation worksheet for these flanges. Learning to design a flange "by hand" is valuable experience. Also search this forum and the ASME Code Issues forum for discussion of the topic.

And yeah, actual school homework is generally frowned upon on this site.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[MJCronin]

First, you just stated that you must design a "heat exchanger" is this your first HX design assignment ?

Second, you seem to be looking for a flange size that will match your shell diameter .... is that true ? This is not necessary if you are designing/selecting a TEMA style S&T HX.

Third, you state: "Inner diameter of the shell is greater than 24" (lets say 27" ) so I can not made of shell from pipe, i have to use plate" No, if you are designing a TEMA style HX you have many options including making a short, stubby HX with a larger diameter and lower pressure drop or a longer, less expensive HX using piping with a higher pressure drop. HX design is a trade off among factors such as cost, size, length and tube side/shell side pressure drop. Computer programs and spreadsheet help the beginning designer iterate among these alternatives

Fourth, if you are designing a TEMA HX, the only time that you need to have a flange that is the same size as the shell is when the tube bundle must be removable. This "body flange" is typical designed and constructed in accordance with the pressure vessel code. Using an "off the shelf" ASME B16.5 or B16.47 is almost never acceptable..

My opinion only

MJCronin
Sr. Process Engineer