3 replies to this topic

Hi

I have a problem with selection the relief valve for ambient air vaporizer. I dont know what is the best way to recalculate it. If someone have any idea please contact me. Thank you.

[Art Montemayor]

Dorota:

You state you have a problem SELECTING a proper PSV for an ambient vaporizer. You also say you dont know what is the best way to RECALCULATE it.

What do you mean by "recalculate it"? You normally calculate or obtain the maximum vaporization rate available with the vaporizer and specifiy that rate in a specification sheet to a PSV manufacturer.

Why do you want us to "contact" you? Don't you want to make the use of the Forum to get as much professional help from our members as is possible?

What is your basic data? You don't tell us what you are vaporizing, how the vaporizer is configured, the vaporizing load - normal and maximum, relieving temperature and pressure, etc., etc.

Await your reply.

What do you mean by "recalculate it"? You normally calculate or obtain the maximum vaporization rate available with the vaporizer and specifiy that rate in a specification sheet to a PSV manufacturer.

If I would calculate like you just said i wouldn't need any help because I just need to put relief valve with vaporisation rate bigger then ambient air vaporizer.


What is your basic data? You don't tell us what you are vaporizing, how the vaporizer is configured, the vaporizing load - normal and maximum, relieving temperature and pressure, etc., etc.


I am vaporizing LNG, the vaporizing rate is 600Nm3/h, working pressure 5 bar, max. working pressure is 9.5 bar. The safety valve is mountend on the pipeline just after the vaporizer.

I want to send you some information and regulations that we have used to design our installations. So we selected our safety valves in accordance with standard PN-EN 1473 p. 8.1.6 is European Standard so its availability in English is well.
Please find bellow our calculation:
In condition that ambient air vaporizer is shut off by cut valve so is no in inflow and no outflow, inside the vaporizer is max. 80 l of liquid and in pipes between cut valves is max. another 1.5 l. So we checked how many meters of gas we can get from this amount.
m = ρ • V
m – mass [kg]
ρ – density of LNG in our working pressure 5 bar is 388,73kg/m3 – accordance with quality certificate
V – amount of gas in vaporizer plus gas in pipes which is max. 81,5 l
m = 388,73kg/m3 • 0,0815m3 = 31,68 kg
from 1 kg of LNG – is 1,346m3LNG – it’s amount of gas what we can get in regassification process 1 kg LNG - accordance with quality certificate
Therefore max. amount of gas that we can get from the liquid inside the vaporizer is 42,64m3
Nominal capacity of our safety valve is 148m3/h so is much more then amount of gas that we will get in regassification process from 81,5 l of liquid, there is only one last question that I don't know the answer how long it will take to empty the ambient air vaporizer from this gas?

[JoeWong]

"600Nm3/h" is the normally operating flowrate.

The PSV big enough to relieve maximum flow generated by vaporiser under maximum possible heat input. First thing is to find the "maximum possible heat input" then maximum relief can be calculated based on latent heat at relieving pressure.