13 replies to this topic

[Falah]

Hello, can you help me?
I have a closed drain drum, it is connected to LP flare, when l read HAZOP about scenario of overpressurization of this drum, it is mentioned that one of safeguards is that it is floationg with LP flare, l don't understand this.
In another closed drain system, purging by nitrogen or fuel gas for drain drum is not used. My question is when we do not use purging by nitrogen or fuel gas for closed drain drum. In addition to the above, is there any considerations for using fuel gas instead of nitrogen for the purging this drum? put aside economical side

Edited by Falah, 27 January 2024 - 09:44 AM.

[Pilesar]

'Floating with LP flare' means that the vessel in operation has no control valves between the vessel and the flare header. This would make it difficult to overpressure. A continuous nitrogen or fuel gas purge on a vessel is likely for the purpose of keeping the vessel away from an environment that might burn. Some liquids do not readily form vapor which combusts in air so keeping air away would not reduce a hazard. The purge gas must be sent to a safe location. Nitrogen and fuel gas act differently when they arrive at the open flame of a flare. 'Putting economics aside' is not something I recommend. Economics, availability, reliability, existing system design are all involved in choosing the best way to operate safely.

[Falah]

Ok,thank you, Pilesar!
It is mentiond in the operating manual that "To prevent ingress of air during loading operations, whilst emptying the vessel, fuel gas is added automatically to the flare header.''
it means that to avoid the ingress of air to closed drain drum while epmpting it, we add fuel gas to the flare. I don't understand how we avoid ingress of air to the vessel by using purging for the flare. I think that is why we dont use purging for this closed drain drum.
I know the importance of economics for operating safely, but l need a scientific explantion for using fuel gas instead of nitrogen for purging.

Edited by Falah, 27 January 2024 - 05:40 AM.

[fallah]

Ok,thank you, Pilesar!
It is mentiond in the operating manual that "To prevent ingress of air during loading operations, whilst emptying the vessel, fuel gas is added automatically to the flare header.''
it means that to avoid the ingress of air to closed drain drum while epmpting it, we add fuel gas to the flare. I don't understand how we avoid ingress of air to the vessel by using purging for the flare. I think that is why we dont use purging for this closed drain drum.
I know the importance of economics for thi, but l need scientific explantion for using fuel gas instead of nitrogen for purging.

 

Hi,

 

Actually adding fuel gas to the flare while the drum is emptying is to be done avoiding vacuum generation inside the drum hence preventing air ingress to closed drain drum...

 

A simple sketch of the system you described will help to submit a more proper response...

[Falah]

Fallah, You can see closed drain drum attached below
https://easyupload.io/3sar6n

[fallah]

Fallah, You can see closed drain drum attached below
https://easyupload.io/3sar6n

 

The access for me is denied...

[Falah]

Just press on download, Fallah

[fallah]

Just press on download, Fallah

 

No "download" button is appeared to press!

 

Please attach a simple sketch using "More Reply Options" button...

[Falah]

Kindly try this link
https://ibb.co/rbhX9H2

[fallah]

Kindly try this link
https://ibb.co/rbhX9H2

 

Got it...thanks

[fallah]

Hello, can you help me?
I have a closed drain drum, it is connected to LP flare, when l read HAZOP about scenario of overpressurization of this drum, it is mentioned that one of safeguards is that it is floationg with LP flare, l don't understand this.
In another closed drain system, purging by nitrogen or fuel gas for drain drum is not used. My question is when we do not use purging by nitrogen or fuel gas for closed drain drum. In addition to the above, is there any considerations for using fuel gas instead of nitrogen for the purging this drum? put aside economical side

 

Hi,

 

One safeguard against overpressure is "floating with LP flare" due to an permanent open path to the flare , as shown in the PID. This open path prevent any overpressure due to the receiving drains by the drum and is sized for the biggest volume of the receiving drains to be able to transfer the replaced vapor volume to the flare header without drum over pressurization. 

Edited by fallah, 27 January 2024 - 07:14 AM.

[Pilesar]

It is mentiond in the operating manual that "To prevent ingress of air during loading operations, whilst emptying the vessel, fuel gas is added automatically to the flare header.''
it means that to avoid the ingress of air to closed drain drum while epmpting it, we add fuel gas to the flare.

No, I think you have the meaning of the intent of the sentence in the operating manual wrong. It means 'To prevent ingress of air into the flare header... fuel gas is added automatically to the flare header.' You never want a negative pressure in the flare header. There is an open path to the air at the flare tip. Backwards flow in the flare could result in a flammable mix of air and fuel in the header with a fire inside the header piping. A fire in this header will cause trouble. When the drain vessel empties, the liquid volume is displaced by vapor from the flare header. Typically, fuel gas will be automatically added to keep the flare header pressure positive under all conditions, not just for this vessel draining.

[Falah]

Thanks Fallah Pilesar
In the P&ID l shared, we dont use specific line for purge that is why l mentioned it is probable to use fuel gas in flare header also for purging drain drum.
But in another project whose PID l will share below they used a specific one to purge drain drum continously. at the begining nitrogen was used for purging but changed to fuel gas during HAZOP. the question is "is there any relation between purge drain drum and purge flare header? and kindly clarify if there is reason to use fuel gas for purge instead of nitrogen here probably because another line of fuel gas is used to purge flare header, and we need consistency between purging the drain drum and flare header.
https://ibb.co/LvwhSZ5

Edited by Falah, 27 January 2024 - 12:56 PM.

[Falah]

In addition to the above, purging drain drum by fuel gas here is used to pressurize the drain drum during start-up what do we do for the drain drum that l shared previously that does not have a specific line for purging?especially during start-up
Thank you alot for your valuable information.

Edited by Falah, 27 January 2024 - 01:28 PM.