Tube rupture - Tube side protection 2

[Bill3752]

For "normal" tube rupture case (tube side is high pressure, shell low pressure) the standard approach is to assume 2 orifice or 1 orifice / 1 pipe - i.e. from both sides. However, for case where tube side is low pressure, protected side, I am not sure how dual source would apply. Anyone had experience with this?

 

[Latexman]

Won't the high pressure shell side fluid enter into both sides of the broken tube?

Good Luck,
Latexman

 

[Bill3752]

Latexman, that was also my thought, but have never seen both sides of the tubes being protected (i.e. RV on both inlet and outlet of (in this case) cooling water. Thank you

 

[Latexman]

My company's design manual on this also says, "When the high pressure is on the shell side rather than the tube
side, a total failure is much less likely. Tubes will normally collapse rather than split open."

And, that makes it less clear.

Good Luck,
Latexman

 

[Bill3752]

Yep, We normally assume a 1/8" tube leak for this case. However, a Client has opted to take a much more conservative case for situations wherein the upstream pressure exceeds the lower pressure, protected, system MAWP by 2X. That has caused us to look at the full tube rupture case. As you said, murky waters.

 

[Latexman]

I've never seen two reliefs either, a relief on the inlet AND outlet tube side, but if full tube failure is assumed and the shellside MAWP or normal operating pressure > 1.5 X the tubeside MAWP (or 1.3 X after 1999) how do you make two reliefs go away and pass the red face test?

I'm an operating company engineer, so I get to shape our policies, but I guess you have to give the client what he wants, huh?

Good Luck,
Latexman

 

[georgeverghese]

For the case where the LP side is the tubeside, I still see a way for 2 paths (one short path, one longer path) for the HP shellside stream to get to the PSV. This longer path goes in the reverse direction through the split tube, and then through all the unbroken tubes in the forward direction till it gets to the PSV?
In some Companies, tube rupture is to be accounted for when the max normal HP side pressure(either the HP side PSHH setting or the RV setting if there is no PSHH) > the LP side process design pressure.

 

[Bill3752]

George, I had not thought through the possibility of the flow path pack through the tube chamber and back through the tubes. I do think that is valid.
This helped. Thank you both.

 

[georgeverghese]

If it is some flammable or toxic gas that will be leaking into cooling water in this case, this gas will accumulate at the hot return water well at the cooling tower. Suggest a gas tight cover on the hot well and pipe the exhaust to a safe location / safe elevation where flammables cannot get sucked into the fans at the cooling water tower.

 

[pierreick]

Hi,
You may consider this paper.
Pierre