Jump to content



Featured Articles

Check out the latest featured articles.

File Library

Check out the latest downloads available in the File Library.

New Article

Product Viscosity vs. Shear

Featured File

Vertical Tank Selection

New Blog Entry

Low Flow in Pipes- posted in Ankur's blog

Fire Case For Unwetted Or Wetted Vessel


This topic has been archived. This means that you cannot reply to this topic.
8 replies to this topic
Share this topic:
| More

#1 nivedita12

nivedita12

    Veteran Member

  • Members
  • 46 posts

Posted 12 July 2016 - 01:41 PM

Dear members

I have a Vessel 2ft x 4 ft which is used to prevent the overfilling of a LNG truck when the pump fils in -pump capacity - 200 gpm and dp gr -0.425. 

The vessel is like a stopper to prevent liquid going into a BOG Header line going to BOG heater.

1. psv case -overfilling

2. Fire case

 

Truck overfilling - considered the pump capacity 

 

Fire case - This is where I am confused, 

Is it the BOG coming back/to  BOG heater to the vessel which is a vapor flow

 

or is it  the flash vapor from the truck overfilling liquid to vessel -liquid flow 

 

Please guide 

 

Attached is the sketch

Attached Files



#2 Bobby Strain

Bobby Strain

    Gold Member

  • Members
  • 3,529 posts

Posted 12 July 2016 - 04:56 PM

You don't provide enough information for us to give you comments. It's dangerous to solicit information from others with such limited information. You might get some advice and follow it. Not always good advice.

 

Bobby



#3 Pilesar

Pilesar

    Gold Member

  • Members
  • 1,347 posts

Posted 13 July 2016 - 12:03 AM

Fire case PSV sizing is usually valid only for vessels containing liquid. The boiling liquid keeps the vessel wall cooler. If the vessel is dry and there is an external fire heating the vessel, the vessel wall is likely to fail before the PSV set point pressure is reached.



#4 nivedita12

nivedita12

    Veteran Member

  • Members
  • 46 posts

Posted 13 July 2016 - 08:22 AM

What information would you need Bobby

Thank you pilesar



#5 latexman

latexman

    Gold Member

  • Admin
  • 1,674 posts

Posted 13 July 2016 - 10:24 AM

Go to your PHA or LOPA or safety analysis and see which scenarios took credit for the PSV.  Read those scenarios very carefully.  They should give you a good idea what you have to evaluate.



#6 Pilesar

Pilesar

    Gold Member

  • Members
  • 1,347 posts

Posted 13 July 2016 - 01:10 PM

What I think you will find when you research the PSV sizing basis:

The Fire Case is not the BOG coming back/to  BOG heater to the vessel which is a vapor flow

The Fire Case is not the flash vapor from the truck overfilling liquid to vessel -liquid flow 

The Fire Case is calculated with the vessel completely blocked in and containing the maximum normal liquid level.

 

Consider that the Fire Case will assume a sustained pool fire. What is the realistic scenario for a pool fire? It would be extremely difficult to get a pool of LNG to sustain a flame lasting more than a few minutes. An unconfined LNG spill has never resulted in a vapor detonation. But putting a big PSV on your vessel for a fire case will make some people feel safer and avoid arguments about inherent LNG safety.



#7 latexman

latexman

    Gold Member

  • Admin
  • 1,674 posts

Posted 13 July 2016 - 02:00 PM

Very wise advice Pilesar!



#8 farid.k

farid.k

    Gold Member

  • Members
  • 384 posts

Posted 31 October 2016 - 04:16 AM

 

What I think you will find when you research the PSV sizing basis:

The Fire Case is not the BOG coming back/to  BOG heater to the vessel which is a vapor flow

The Fire Case is not the flash vapor from the truck overfilling liquid to vessel -liquid flow 

The Fire Case is calculated with the vessel completely blocked in and containing the maximum normal liquid level.

 

Consider that the Fire Case will assume a sustained pool fire. What is the realistic scenario for a pool fire? It would be extremely difficult to get a pool of LNG to sustain a flame lasting more than a few minutes. An unconfined LNG spill has never resulted in a vapor detonation. But putting a big PSV on your vessel for a fire case will make some people feel safer and avoid arguments about inherent LNG safety.

 

Dear Sir, 

 

How about I have a vessel (inlet is ethylene gas + other component), and the vessel is to remove alcohol and moisture content by using licensor adsorbent. The process is continues process. However relief valve on the top of the vessel stated that it has been sized based on fire case. That vessel is designed 1995. 

 

The vessel need to be changed to a bigger one and I need to re-evaluate the existing relief valve. But I am not sure to do what case other than fire case.

 

Appreciate your advice.



#9 senthil13

senthil13

    Veteran Member

  • ChE Plus Subscriber
  • 41 posts

Posted 02 November 2016 - 01:39 PM

Ethylene is super critical. Need to be careful selecting the PSV sizing case for this. You have to evaluate the scenario based on the system. You conduct a contingency analysis and list the potential cases for relief sizing and pick the worse case sizing scenario.

 

Even if the vessel is designed for fire case in 1995. I would re evaluate the system to pick the correct sizing case. they might have considered this vessel as a filter hence fire case came into consideration.

 

You might have a control valve upstream of this vessel which might change your sizing basis of the relief valve. 

 

Just my 2 cents..






Similar Topics