prussure change in LNG tank

[mounia]

the pressure suddenly drops in the LNG storage tank and the same in the suction flow of the tank vapor recovery compressors
the operating conditions before the incident:
the load of LNG received at the level of the tanks is heavy compared to the load stored in the tanks it contains less nitrogen
a cargo ship
takes place 5 hours before the pressure drop incident
note: after each ship loading there has been a drop in pressure but in our case the drop takes place just after loading and it reabsorbs a significant value after 5 hours

Is that this pressure drop and the result of the accumulation of the heavy load in the tank more favored by the load or this drop due to another cause knowing that usually we have worked with almost the same load without any pressure drop
thank you in advance for your collaboration

 

[1503-44]

Are you trying to take more vapor then that which can boil off across the LNG liquid surface in the tank? If the liquid surface increases as you draw it down, that might explain it.

 

[0707]

I think a vacuum happen! Can you send us a photo of the tank damage.

luis

 

[mounia]

I just sent you two photos to better explain the incident to you
a photo corspandant in the case of loading under normal conditions
the second photo corsspendant of the event of the incident in wich the pressure has dropped to the level of the storage tank after 05 hours after end of load

 

[georgeverghese]

Suction pressure controller at boil off gas compressors not working well for some reason. Can we see P&I D of compression unit with all controls pls ? And also indicate location of PT which shows sudden dip in suction pressure. What about recycle control valve at BOG compressors - is it working okay ? Is BOG compressor variable speed or fixed speed, and what type of compressor - recip or centrifugal ?