12 replies to this topic

[KoreaGyu]

Hello everyone, nice to meet you. While searching for various things through the search engine Google, I came across this site and am writing this post.

 

Before asking any questions,

Since my English proficiency is not very high, I am writing this with the help of ChatGPT. I appreciate your understanding if the tone or terminology is not perfect.

 

I understand that determining the size of the safety valve (PSV) is based on the largest external fire scenario for discharge capacity.

 

In the process, it has arisen that the PSV capacity is insufficient, necessitating a replacement of the existing design or the PSV that is scheduled for purchase. I am working to resolve this issue.

 

Since fire protection equipment will not be installed, the API Q value as specified will be calculated.

Q=C X F X A^0.82

 

My goal is to fix the F constant value and lower the Aws by applying external insulation to the vessel.

 

Previously, the discharge capacity was determined based on the actual operating and storage height of the liquid inside the vessel, which is hemispherical on the top and bottom (as set by interlocks). However, the issue is that according to the API, when calculating the wetted surface area by combining the areas of the top and bottom hemispheres with the body area, the surface area is larger than initially calculated. This led to the realization that the PSV sizing was incorrect.

 

The company wants to first consider solutions for applying the height below 7.6 meters to address this issue. Since there are limitations to what can be found through Googling and other searches, I am posting this to seek various opinions and suggestions. Thank you in advance for your input.

 

 

[Dacs]

calculating the wetted surface area by combining the areas of the top and bottom hemispheres with the body area

 

Is your vessel horizontal or vertical? What's the liquid level you're using to get the wetted SA?

 

The company wants to first consider solutions for applying the height below 7.6 meters to address this issue. 

 

Have you done it? Can you take credit in minimizing the wetted surface area due to the vessel elevation?

Be aware that this height (25 ft / 7.62 m) is based on the closest platform (and not necessarily at grade!) that a pool fire can form.

Edited by Dacs, 21 August 2024 - 09:03 AM.

[breizh]

Hi,

Consider this document from LESER , It may help you.

Please review the part related to wetted surface.

Breizh 

Attached Files

•  EHB_en_7-Sizing.pdf   4.77MB   3 downloads

[latexman]

I understand that determining the size of the safety valve (PSV) is based on the largest external fire scenario for discharge capacity.

Maybe in your case, yes, but in general, it depends. There may be other scenarios worse than the fire scenario.

My goal is to fix the F constant value and lower the Aws by applying external insulation to the vessel.

External insulation has no impact on Aws.

[shvet1]

Is the pool fire fed with the vessel liquid? or this vessel contains non-combustible liquid?

[fallah]

Hello everyone, nice to meet you. While searching for various things through the search engine Google, I came across this site and am writing this post.

 

Before asking any questions,

Since my English proficiency is not very high, I am writing this with the help of ChatGPT. I appreciate your understanding if the tone or terminology is not perfect.

 

I understand that determining the size of the safety valve (PSV) is based on the largest external fire scenario for discharge capacity.

 

In the process, it has arisen that the PSV capacity is insufficient, necessitating a replacement of the existing design or the PSV that is scheduled for purchase. I am working to resolve this issue.

 

Since fire protection equipment will not be installed, the API Q value as specified will be calculated.

Q=C X F X A^0.82

 

My goal is to fix the F constant value and lower the Aws by applying external insulation to the vessel.

 

Previously, the discharge capacity was determined based on the actual operating and storage height of the liquid inside the vessel, which is hemispherical on the top and bottom (as set by interlocks). However, the issue is that according to the API, when calculating the wetted surface area by combining the areas of the top and bottom hemispheres with the body area, the surface area is larger than initially calculated. This led to the realization that the PSV sizing was incorrect.

 

The company wants to first consider solutions for applying the height below 7.6 meters to address this issue. Since there are limitations to what can be found through Googling and other searches, I am posting this to seek various opinions and suggestions. Thank you in advance for your input.

 

Hi,

 

Please note to the following points:

 

-As latexman well said, fire case isn't always the sizing case of PSV.

 

-If the vessel dimensions are fixed the only ways to reduce the A_ws are high liquid level reduction or elevating the vessel on the structure around 7.6 m height.

 

-Why do you try to reduce A_ws? Actually, because in most fire cases (especially in cases with vessels without wetted area) the PSV cannot protect the vessel against failure, it's preferred having larger wetted surface area to be able to buy the adequate time for the action of firefighting facilities.

Edited by fallah, 21 August 2024 - 09:41 AM.

[KoreaGyu]

Hi,

 

 

 

 

Please note to the following points:

 

-As latexman well said, fire case isn't always the sizing case of PSV.

 

-If the vessel dimensions are fixed the only ways to reduce the A_ws are high liquid level reduction or elevating the vessel on the structure around 7.6 m height.

 

-Why do you try to reduce A_ws? Actually, because in most fire cases (especially in cases with vessels without wetted area) the PSV cannot protect the vessel against failure, it's preferred having larger wetted surface area to be able to buy the adequate time for the action of firefighting facilities.

 

Hello, first of all, I apologize for the late response.

 

To reiterate, there was an oversight in reviewing the PSV size during the design phase, and we have taken steps to address this issue.

 

While I have seen other documents suggesting that the PSV has minimal impact during a fire and recommending the installation of external fire suppression systems instead, I am past the stage where additional measures can be applied. Therefore, I focused on resolving issues specifically related to the PSV size.

 

To address the 25 ft height from the floor, I considered two methods in advance: high liquid level reduction or elevating the vessel on the structure. However, reducing the high liquid level seems difficult due to its impact on production capacity and tank size. Additionally, elevating the vessel on the structure is not feasible in practice due to the need to reassess the size of the secondary containment and the distance between the secondary containment and the tank exterior as a result of raising the tank floor.

 

Thank you for your feedback.

[KoreaGyu]

calculating the wetted surface area by combining the areas of the top and bottom hemispheres with the body area

Is your vessel horizontal or vertical? What's the liquid level you're using to get the wetted SA?

The company wants to first consider solutions for applying the height below 7.6 meters to address this issue.

Have you done it? Can you take credit in minimizing the wetted surface area due to the vessel elevation?
Be aware that this height (25 ft / 7.62 m) is based on the closest platform (and not necessarily at grade!) that a pool fire can form.

Hello, first of all, I apologize for the late response.

This is a vertical type. I am aware that this height (25 ft / 7.62 m) is based on the closest platform (and not necessarily at grade) where a pool fire could occur. However, since it exists within the secondary containment area, it was calculated based on the general ground level (the bottom of the secondary containment).

Currently, I plan to choose the more cost-effective option between increasing the PSV size and adding fire suppression equipment by comparing quotes for both methods.

Thank you for your feedback.

[KoreaGyu]

Hi,

Consider this document from LESER , It may help you.

Please review the part related to wetted surface.

Breizh 

 

Hello, first of all, I apologize for the late response.

 

Thank you for the helpful materials. My English skills are not very strong, so it will take me some time to read through them, but I will go through them carefully.

 

Thank you for your feedback

[KoreaGyu]

 

I understand that determining the size of the safety valve (PSV) is based on the largest external fire scenario for discharge capacity.

Maybe in your case, yes, but in general, it depends. There may be other scenarios worse than the fire scenario.

My goal is to fix the F constant value and lower the Aws by applying external insulation to the vessel.

External insulation has no impact on Aws.

 

Hello, first of all, I apologize for the late response.

 

I acknowledge that there may be other scenarios worse than the fire scenario. However, when determining the PSV size, it is common practice to base calculations on the worst-case scenario. Therefore, I applied the external fire scenario as the standard approach

 

External insulation has no impact on AWS. That's correct. Although there may be some differences in interpretation, the intention behind mentioning external insulation was to fix the F value at its lowest and to reduce AWS.

 

Thank you for your feedback.

[KoreaGyu]

Is the pool fire fed with the vessel liquid? or this vessel contains non-combustible liquid?

Hello, first of all, I apologize for the late response

 

In the event of an external fire causing a hole in the vessel's wall, a pool fire is expected to occur at the bottom with liquid, while gas-phase PSV discharge is anticipated at the top.

 

The contents are flammable liquids. However, in Korea, flammable gases are treated with a flare stack to prevent environmental pollution when released externally. On the other hand, NFPA recommends discharging through the PSV. If flammable gases are actually released into the atmosphere through the PSV during an external fire, there is concern that it could create a larger explosion risk and potentially exacerbate the fire.

 

Please let me know if there are any aspects related to the atmospheric release of flammable gases that I may be overlooking. Thank you.

[breizh]

Hi,

Consider this booklet to support your work

Breizh

Attached Files

•  Yellow book -release of hazardous chemicals-physical-effects.pdf   3.41MB   4 downloads

[shvet1]

Please let me know if there are any aspects related to the atmospheric release of flammable gases that I may be overlooking. Thank you.

 

 

It is industry practice venting gases having specific gravity <0.8 than air directly to atm. 

 

It is outdated practice venting flammable vapors to atmosphere. At the region I am from it was a codified and widely spread practice 20-30 years ago. Older generation of personnel I have been in contact with reported that that such design when those happened was extremely dangerous and sometime it did lead to worse conditions - a severe explosion or a tremendous fire devastating the process site and neighbourhood to metal puddles.

Edited by shvet1, 27 August 2024 - 12:37 AM.