TEMA question 3

[mielke]

for baffle tube holes TEMA rcb-4.2 says

"Where the maximum unsupported tube length is 36 inches or less, or for tubes larger in diameter than 1-1/4 inches O.D., standard tube holes are to be 1/32” over the O.D. of the tubes. Where the unsupported tube length exceeds 36 inches for tubes 1-1/4 inches diameter and smaller, standard tube holes are to be 1/64” over the O.D. of the tubes."

seems a little ambigious to me. If i have 3/8" tubes with an unsupported length of 12" i'm assuming that per tema i would over size my holes 1/32" (the first case). am I interpretting this correctly?

thanks

 

[desertfox]

Hi mielke

Yes I agree with you 1/32"

desertfox

 

[TJOrlowski]

Your interpretation is correct, however you can make the baffle holes 1/64" over the tube OD for extra cage stiffness, and consideration for the ligament between tube holes in your baffles. If you are using a 15/32" tube pitch, and you make the baffle holes 13/32". Your ligament between baffle holes is only 1/16". If you make the baffle holes 25/64", your ligament is now 5/64".

Desired shell-side flow characteristics should determine which way you go. As well as RCB-2.32, which can be affected by baffle hole size.

-TJ Orlowski

 

[rmw]

Mielke,

Your assumption is right. Since your unsupported span is only 12 inch, there is not the need to make the baffle holes tighter to try to mitigate the effects of vibration on long unsupported spans.

Making your support baffle holes only 1/64" over will make your bundle more difficult to tube.

rmw

 

[adamp716]

You'd have a tough time convincing me to ever make the holes 1/64" larger than the tube OD. I would not want to have to deal with the shop's complaints.

 

[mielke]

thanks for the help all. one more question about TEMA. tube sheet thickness calculation is based on G. G is defined by the diameter over which the pressure under consideration is actinge. yet they say nothing about a rectangular tube sheet. what is the best way to relate a rectangular flange to a diameter code value?

 

[heathexer]

Possibly, treat longest dimension as diameter. But I didn't look it up. What does ASME require?

 

[heathexer]

Possibly, use the longest dimension as the diameter. But I didn't look it up. What does ASME state?

 

[mielke]

I dont have access to asme