Distance between rupture disc and PSV

[laliyo]

Hello,

Does anyone know if a rupture disc can be installed at a larger distance from PSV ?

I am thinking of installing a rupture disc on a STHE-2 (see the sketch), which is not in use on shell side and hence empty, but still being used on tube side. So a tube rupture case is valid.Presently, the vapor line from shell is blinded.So the existing psv-1 , can not provide any relief.
The PSV capacity is adequate for relief load.Also, the relief fluid is a 2-phase light hydrocarbons.The distance of blinded vaporline from the PSV is @90 feet.

All the literature /code/standard says about a "closed coupled" rupture disc, that is the disc is just u/s of PSV.

Any help is greatly appreciated.

 

[Chance17]

Question: Would a tube rupture cause the shell side pressure to exceed shell hydrotest pressure??
This is commonly known as the "2/3 Rule".
If the shell hydrotest is not exceeded, it may be argued shell side pressure protection is not needed.

 

[Chance17]

After the elapse of 3 days I looked at the sketch again.
Yes - it is true DISK-PSV combination must be close coupled (1-2 feet).
I do not see the sketch facility as fitting this model.
Instead the sketch looks more like relief devices in series.

 

[Casimo5]

laliyo,

Are you considering using a rupture disk in place of the blinds that are on the vapor line of the exchanger whose shell side is not in service so that in the event of a ruptured tube, the shell side would then be open to the relief path to the PSV?

The problem with relieving from one system into another is with the back pressure. If the pressure of the system you are relieving to can vary, then it can make things more complicated. It would be better to add another relief device to the exchanger shell that is not in service. Otherwise if you install a PSV or rupture disk that relieves to the other system, you have to be sure that you specify a differential pressure between the systems that guarantees you don't exceed your design pressure. Either method is acceptable.

Casimo

 

[laliyo]

Thanks all.

I did move away from this alternative since the RD and PSV are not close coupled.