Fire fighting system in chemical plant 1

[rika kose]

The city fire fighting department requested us to modify the fire fighting system.
one of the requirements is to stop fire spreading and transporting.

We have gutters to collect the chemical spills and drain water to the chemical wastes treatment system.
To satisfy the fire department, we need to do something to stop fire spreading in the gutter/sewer.
My opinion: if we can flush the gutter regularly, the chance to have fire in the gutter/sewer is low.

Any suggestions? do we need to cover the gutter or a flame arrestor at some point of the sewer system.
Are there any easy/common solutions?

Thanks in advance,

 

[pierreick]

Hi ,
You need to stick to their request , what are their proposals? The risk is to loose he renewal of your operation permit.
You should talk to the insurance company in charge of your site , they may have requirement .
Company like FMG global and others could help you .
As an example , link from AXA Group :

https://axaxl.com/~/-/media/axaxl/f...lang=en&hash=AF719EEF1FF63FA317B931016545C672

My view :
Siphons (trap manholes) are an effective way to avoid the fire to spread over the drain system .
Regular cleaning of the drainage system is a must to avoid accumulation of chemicals , in particular flammable materials .
Make sure permits and procedure are well applied .

If you cover the trenches make sure someone check the atmosphere before hot work .

My thoughts
Pierre

 

[shvet]

Gutters
In case of large spill of flammable/combustible liquids gutters will provide flame spread. In case of leakage or evaporation from a spill of explosive vapors heavier than air these will accumulate in gutters. The same for gases causing asphyxiation e.g. cold nitrogen. These are the reasons why it is a good industry practice gutters should be minimized or avoided at facilities handling flammable/combustible or explosive fluids. As per my experience gutters are prohibited by local codes and internal instructions of many companies except for drainage of main roads.
Fire spreading is a serious hazard and is controlled by many means. Landscaping of an industrial zone is the most important of those.

Sewer
Hydraulic seals provide sufficient barrier for explosive/flammable vapors migration through sewer system. Sectioning of sewer system by hydraulic seals is mandatory in many countries.

 

[rika kose]

Many thanks Pierre, the document is very helpful
@Shvet, if gutters are prohibited, what do you do to collect the spills or leakage?

 

[shvet]

Concrete paving and toe-walls no less 150 mm height for retaining a spill. Paving is sloped to an open pit. A pit is drained to a sewer system. A sewer well downstream of a pit is equipped with hydraulic seal and normally closed gate valve (and carsealed in some companies). Open pits and sewer wells are provided with means for pumping out by a self-priming pump (hand operated or mounted on truck). Sewer wells more ~6 meters depth are prohibited (depends on vapor pressure of process liquid), otherwise self-priming pump is not able to pump it out.

Because of slope limits equipment zone is sectioned by toe-walls so way one open pit collects spills from 3-5 items of eqipment and surrounding pipeworks.

Access roads and paving outside of toe-walls (where spill/leakage is unlikely) are sloped to rain receivers equipped with hydraulic seals. Roads and pavings are drained to grass only at safe areas otherwise they are equipped with curb.

Sewer system is sectioned so way each group of equipment and building is separated by a hydraulic seal. The same for sewer main - each process unit is separated from others by hydraulic seal. Rain water sewer system (draining areas where leaks are unlikely) is segregated from oily water sewer system (draining areas where leaks are likely). Vent pipes of sewer system are routed to firesafe areas and elevated at a couple of meters above ground. Hatches of sewer wells have no holes and are elevated above ground. In many companies I have met hatches are constantly covered with layer of sand no less 200 mm height.

This design are rather expensive and complicated (e.g. try to calculate # of ramps for maintenance handcart pathway or total elevation of sewer required). Also this design does not allow nearground piping routing as toe-walls crossing are not allowed. But this kind of landscaping provides enough protection against leaks and minor spills. Containment for major spills is provided for critical areas (e.g. tank farms) and is governed by dedicated logic.