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Vessel Coonected To Flare Directly


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#1 m42364236k

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Posted 19 October 2014 - 09:00 AM

Dear friends
I have one question regarding to instaling the psv .
In our water treatment system we have the vessel that operating in 0.9bar with design pressure of 7bar .
In this vessel designer do not consider the psv .this vessel withi one 4"pipe directly connect to yhe lp flare net work.and design for safety system
My question is:
As my experiance
Is see this situation just in flarw ko drum be cause flare ko drum conbect direvtly to flare stak.
As i know pressire vessel should have psv .do any one one see such this design ?
I think designer increas the design pressure and because of that they do not consider the psv.if the designer decrease the dwsign presdure on that time they should conside the psv

Thanks
Mike

#2 lokeshmiddha

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Posted 19 October 2014 - 11:28 AM

Hi mike
If vessel is directly connected to flare then PSV is not required and
If vessel is fabricated with 4 inch pipe then it will not stamped under ASME sec 8 aandpsv will not be required if fire is the only credible scenario.

#3 flarenuf

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Posted 20 October 2014 - 06:45 AM

Mike

 

some comments for thought

 

it is not clear from your question as to what this drum is actually doing but..

if its a water filled drum then connecting it directly to the LP header will result in HC gases in the drum as there is no PSV or PCV in the line.

 

If the drum is operating at 0.9barg then a 3.5barg design P would have been more than adequate. Increasing this to 7barg is more costly than putting a PSV on the overheads surely.

if the designer has chosen 7barg as a DP because this is the expected bP in the LP header then its not an LP header !!

 

its not clear what has gone on here but it doesn't add up

 

brian



#4 fallah

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Posted 20 October 2014 - 07:25 AM

Mike,

 

1- There are the cases other than KODs might be open to flare network such as sump drums in closed drain systems. The vessel in your case also may be a buried sump drum. Please let's have a simple sketch of the system for more clarification.

 

2- The design pressure of such drums is same as that of the flare network to which it's connected. Then as brian mentioned, because the design pressure of LP flare network can't be around 7 barg, appears the vessel is overdesigned in DP standpoint.

 

Please recheck the a.m. points and let's know the result...



#5 m42364236k

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Posted 20 October 2014 - 09:50 AM

Dear freinds thanks for your reply.
This work as slope oil pump and all oily water gather in this vessel.
On the tip of the vessel. 4"vessel directly connectd to lp flare header.
Design pressure is 7bar and operating is near ATM
Is it possible to increase the design pressure and avoid to considering the psv .is it posible as per api or asme?
If vendor confirne that this 4"can handel the flow rate when fire happen can we accept that or we should aske them to provide the psv

Many thanks
Mike

#6 m42364236k

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Posted 20 October 2014 - 11:20 AM

Dear fallah
Thanks
This vessel is not under ground
It is the slop oil vessel.
All oil and water from.other vessrl come in this vessel.
At the top of the vessel we have
one 4"nozzle which is connected to lp flare without any psv .
Design preddure of this vessel is 7bar and yhe operating is near the ATM.

oes it possible vendor increas the dp for avoiding tje psv . As per api or asmr is it possible ?
Thanks

#7 fallah

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Posted 20 October 2014 - 12:07 PM

Mike,

 

The slop vessel (or tank) acts as a sump drum of a closed drain system floating to flare network with a vent connection...

 

The vent line to LP flare can do the job as relieving device in fire case if it would be applicable to this slop vessel (or tank), but it might such vent line with 4" size can handle the fire relief load only if the relieving pressure adjusted to be 7.7 barg (7*1.1) based on which the vessel DP had to be considered equal to 7 barg...



#8 m42364236k

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Posted 21 October 2014 - 10:08 AM

Dear nasset
I do not inderstand your last answer that you.said..
Design for fire case in 7.7barh
As i know set pressure is aplicable on psv .
In this case when fire happen we have the open vent line to flare header and pressire will not be reach higher than the operating pressur e .
For EX if the operatoon.pressure is 0.5 .pressure can reach to 2nar because of open vent .

Thanks

#9 fallah

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Posted 21 October 2014 - 01:19 PM

Mike,

 

I just guess to be as i mentioned...

 

Anyway, the fire relief load might be so high leading to pressure build up around to 7 barg due to unadequacy of 4" vent line for relieving such high load at lower pressure than 7 barg...



#10 m42364236k

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Posted 25 October 2014 - 08:08 PM

Dear nasser tanks for your rply.
I have other question about RO in dipppresurizing line and write it in new topic. And it is my pkeasure you answer it
Thanks




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