6 replies to this topic

[Beergson]

Hi guys

 

Doing one of mine jobs I've doubts regarding area of fire that can occure at one plant.

Acc. to API 521 fire zone can be confined to app. 232 m² (shell increased this value to 300m²), so relief load in my opininion can be calculated as the most demanding for PSV orifice taking into account this plot area.

 

But what if plant has one common open sewer (rain) system, and fire can be propagated by it to other section causing total fire at plant ? Plant is localized at area 80x80 m so this plot exceed area stated in API.

 

Do you know any other guide for fire zone determination?

 

Thanx in advance for any suggestions.

[Zauberberg]

How is this propagation envisaged? Through underground collection network? I think we need more detailed information and possibly a snapshot of the plant layout and open drain layout.

[Zauberberg]

Also review the chapter from D.Nollan's book "Fire and Explosion Protection Principles" related to drainage facilities (attached).

 

Your company may have specific guidelines on fire breaks and water seals. Waiting for more information from your side.

 

Attached Files

•  Fire & Explosion Protection Principles - Drainage Systems.pdf   519.69KB   71 downloads

[Beergson]

How is this propagation envisaged? Through underground collection network? I think we need more detailed information and possibly a snapshot of the plant layout and open drain layout.

 

Zauberberg,

I find this statement in old work regarding fire header calculation - "due to the open rain system it was calculated that all (6400m2) plot area is included in fire zone". Although i like conservative approach to safety issues, In my opininion total plant fire shall not be considered, however I saw many calculations of relief headers for almost total fire case.

 

 

Replying to yours questions plant is equipped with open rain system - funnels with water seals and underground network and closed slops (drain) and oily water systems.

[fallah]

Beergson,

 

If the open drain system in your plant is such that can propagate a local fire, you have to consider all 6400 m2 plot area as fire zone; then the relief header should be sized based on simultaneous relieving of all safety devices in the plant...

[Zauberberg]

If there are water traps/seals to prevent from burning liquid carryover from one zone to another, what was the basis for establishing the entire plant area as a single fire zone? Unless the recent investigation (design review performed by your team) revealed that the funnels are undersized and there is still a possibility for multiple zones to catch fire consequentially?

 

Open Drain headers are usually designed not to pass through multiple fire zones in the plant. If this is also the case in your plant, you may take additional credit.

 

Are the paved areas with funnels built with a certain slope? I would assume that entire open drain network flows by gravity to the collection point, which means that different plant areas are at different relative elevation. That makes the overflow case less probable.

 

If I were at your place, I'd look for assistance from HSE/Tech Safety department during the review process. Based on limited information available in this thread, we cannot give you any definite recommendation as to whether you should or you should not consider a single fire zone in the plant. Most of the plants worldwide do have open drain and rainwater collection systems, but not all of them are considered as a single fire zone because of various design measures applied. If you can discover what is it that makes your plant different from this point of view, you will probably get a straightforward answer to your original question.

[Teknas]

Hi,

 

Usually in a plant, the rain water/storm water sewer are kept independent from oil spillage which is the most likely reason for pool fire or fire propagation through sewers.

 

Oil spillages will be collected within the curbed areas around equipment and directed towards an underground oily water drain. These underground drains will have water seals to avoid further fire propagation. The storm water sewers will be outside the curbed areas and will not be exposed to oil spillage.

 

Rain and fire is a remote scenario and mostly may not be a credible scenario at all. But assuming such a scenario, the rain water along with the spilled oil within curbed area will go the under ground oily water system, where the water seal will effectively block fire propagation.

 

Request to check the drain system provided within your plant, whether such segregation has been done or not.

 

If the oil spillage in your plant is directly going to the storm water sewer, the you do have a case for considering entire plant as a single fire zone. But that may still be limited to the routing of sewer.