Shell and tube HE tube rupture scenario
Shell and tube HE tube rupture scenario
(OP)
Dear Engineers
I have encountered a scenario study for tube rupture inside the shell and tube heat exchanger.
tube side : LNG 8 barg, -157 C in, and 25 C gaseous out
shell side: water/glycol, 2.5 barg, 55 C in and 35 out.
I assume the possible rupture will be on the back side of the tube sheet, so my question is : how big the rupture crack, hole can be ? (better to have a reference, in case of somebody may question me)
Since I need to determine the rupture disk's required flow rate, which is protecting the low pressure side.
Thanks
I have encountered a scenario study for tube rupture inside the shell and tube heat exchanger.
tube side : LNG 8 barg, -157 C in, and 25 C gaseous out
shell side: water/glycol, 2.5 barg, 55 C in and 35 out.
I assume the possible rupture will be on the back side of the tube sheet, so my question is : how big the rupture crack, hole can be ? (better to have a reference, in case of somebody may question me)
Since I need to determine the rupture disk's required flow rate, which is protecting the low pressure side.
Thanks





RE: Shell and tube HE tube rupture scenario
There was a good discussion at http://www.eng-tips.com/viewthread.cfm?qid=195018
Dejan IVANOVIC
Process Engineer, MSChE
RE: Shell and tube HE tube rupture scenario
Thanks for this. And which revision of API 521 do you have? The one I have is only a table with text, and in paragraph 5.19 there is nothing related to number or size calculation.
I don't have that Crane TP 420, so could you specify a bit detail where this "twice the cross-sectional area" comes ?
RE: Shell and tube HE tube rupture scenario
Dejan IVANOVIC
Process Engineer, MSChE
RE: Shell and tube HE tube rupture scenario
RE: Shell and tube HE tube rupture scenario
"Nobody expects the Spanish Inquisition!"
RE: Shell and tube HE tube rupture scenario
I understand this.
Just curious, can I also apply the API sizing equations for determining the flow through a rupture hole or creep/crack ?
I did a simple check between API PSV sizing equation and nozzle injection flow equation Q=uA rqrt (2*deltaP*rho), u = 0.6 for liquid flow. the answers from both methods only have a difference about 2%
RE: Shell and tube HE tube rupture scenario
Dejan IVANOVIC
Process Engineer, MSChE
RE: Shell and tube HE tube rupture scenario
What is the freeze temp for this glycol / water mix - is it not much higher than -157degC? If so, if you develop a pinhole leak on a tube, solids will grow on the LP shellside during a shutdown and the RD inlet could get blocked ??
Better to have the entire HX to be specified with design pressure of LNG side, add a TSLL on the shellside to trip the LNG feed (in case of low MEG flow), and install the RD or PSV on the expansion drum side of the closed loop MEG / water loop.
RE: Shell and tube HE tube rupture scenario
RE: Shell and tube HE tube rupture scenario
Yes, we have the TSLL on the LP side, which can control the automated valve to close the LNG flow to the tube, therefore only small amount of LNG is trapped in the tube, while the Water/Glycol is recirculating, so frozen is protected.
But personally concerned, I will put the RD horizontally, so the percussive shock wave in water will open the RD immediately, better than having air under the RD , as a buffering , is it better ?
RE: Shell and tube HE tube rupture scenario
RE: Shell and tube HE tube rupture scenario
Dejan IVANOVIC
Process Engineer, MSChE
RE: Shell and tube HE tube rupture scenario
The other thing that needs to be checked from a heat transfer point of view is that the tube OD skin temp must be maintained at several degC higher than freeze point of MEG - water, for the design case duty, else solids will build up on the tube skin OD , and the HX will fail on thermal duty.
RE: Shell and tube HE tube rupture scenario
I did the calculation and suppose the LNG is leaking at a constant speed, it will freeze the shell side, sure.
But there is only few LNG trapped in the tube, and the automatic valve will stop coming LNG in 5 sec. Even though, the LNG in the tube remains only in the beginning , which close to the tube inlet, then it should be vapor after half way travelling through the tube bundles .
If everything is calculated in rate, seems very big, but considering the total tube volume is 37L, and 1/4 is LNG, (but I can have a vaporization speed round to 6000L/min) how should I deal with the high rate?
RE: Shell and tube HE tube rupture scenario
RE: Shell and tube HE tube rupture scenario
This makes me think
Suppose we have a heating fluid that never freezes, and LNG keeps leaking to the shell side and being vaporized into gas. The turbulent vaporization will be so dreadful that I got a required discharge flow rate of that heating fluid equals 1480.1 m3/h (since the rupture disk is on the outlet pipe, instead of the shell side). This lead to a 6 inch diameter disk that we only have a 2 inch pipe. If I have a result like this, it shows there is something wrong with the design and maybe I should re-consider the location of the disk, like on top of the HE shell side.
Is this thinking correct ?
Thanks !
RE: Shell and tube HE tube rupture scenario
The RD can then be installed on the connected piping if still necessary.