4 replies to this topic

[ahyong]

Dear friends,

Recently I've been working on a work which is related to LPG jetty and tankfarms. I have referred to certain materials and also friends regarding the pressure surge protection of pipeline during emergency shutdown. Some materials show that in case of ESD activation during loading to cargo ship, surge drum is provided to protect the system. However, I also found out that surge drum is not a mandatory here as some companies does not include surge drum in their system. Hope somebody could kindly explain the related philosophy.

And also, at the truck loading arm, loading rate and thus pressure is controled by the opening of control valve. So, does it mean that loading pressure at truck is way lower than loading pressure encounter at jetty? (This is currently at proposal stage and no FEED data at all)

 

Thank you very much

[AlertO]

Dear Ahyong

 

Surge analysis is a special study which is might excluded in the engineering phase; therefore, any protection equipment is not installed at site. However, the pressure surge can occur during ESD activation as you mentioned.

 

A surge analysis can be performed by using the proven softwares e.g. Pipenet, Flow master etc. In the program you can simulate how much the pressure present from surge scnario and also do the surge reduction in various ways e.g. surge drum/tank installaion, surge PSV or enlarge the pipe size.

 

Comparing to the truck loading, the pipe lenght is more shorter and if there is only flow control valve which be shut slower than the typical shut off valve. these reasons let us less serious in the truck loading system. Anyway, you can try to study or prove it before ignoring.

 

Hope this can help you.

[ahyong]

 

 

Comparing to the truck loading, the pipe lenght is more shorter and if there is only flow control valve which be shut slower than the typical shut off valve. these reasons let us less serious in the truck loading system. Anyway, you can try to study or prove it before ignoring.

 

Hope this can help you.

Dear AlertO

Thank you for your reply. I dont quite get you regarding your statement above. Do you mean that due to the shorter pipeline length comparing to jetty. So a flow control valve is sufficient enough to control the surge pressure in case of ESD activation? Thanks

[AlertO]

Dear Ahyong

 

the pipe length is main parameter to "Critical Time" as shown in the formula below

 

Tc = 2L/a

 

Any actions which is faster than the critical time will cause a strong effect of pressure surge. so if the pipe is short, the critical time will be small leading to have longer action time from any scenario. For this case, less effect of pressure surge is generated.

 

Be noted that the controller presents much slower response than the surge phenomena. It may help (not much), but ignoring it  to have the worst result is sometimes recommended due to time save and the simply model required during surge analysis.

 

Hope this can give you more idea

[ahyong]

Thanks a lot for your explanation