031 - Suppressing tunnel fires with water mist with Johny Jessen

Hello and welcome to Fire Science Show session 31 .As usual great to have you here with me. As you may recall some time ago, I visited and very interesting conference on water mist, and I've met quite a lot of interesting people in there and I've been reaching through some of them because they caught my attention. The interesting thing about this water mist, a group of people is that they test everything with huge fires. And as you can imagine, I like large fire experiments.

business Yes So I'm working with infrastructure projects we are looking into a few projects here in Poland

that's fantastic I know there's so much happening around in here especially in the tunnel uh area and that's something I actually wanted to talk with you today. Myself I'm an engineer who works a lot with road tunnels And I've stumbled upon information that you've done some really huge fire experiments in tunnels with with your water mist technology

That is right Yeah So uh in 2018 uh in combination with winning a big project in Uh one of the requirements in the tender was that we had to verify performance criteria as set by the client

Some weeks ago I have been in the watermist conference by IWMA and I've learned that's watermist people test everything by the trial of fire So somehow I am not surprised by the fact that you've burned the tunnel Uh if this technology is is working that has been the most fascinating aspect from connecting with the world of watermist for myself.

So I think to uh Make it most simple So accordingly to a NFPA 750 So the definition between a sprinkler deluge system and the definition when it's becoming a water

Mister that's because

if you are distributing DB 90 meaning It's in your spray pattern meaning that your droplets is above one millimeter thousand microne

units

by definition a dilute system or a sprinkler system If it's below it's a water mist system and then it's correctly as you said there is high pressure There is intermediate pressure and there is low pressure and they of course have different droplet distribution However part of the should we say the droplet this distribution is In a lot of varieties of droplets we're high pressure is very

very

efficient If you have as close compartment the machinery room where you really have high temperatures and Small droplets get into dang They will not be drafted away by ventilation

or Metro

wind then they immediately have an effect on the cool the fire Where on the opposite if you are in a to your application then of course the smaller droplets will be carried away either by a natural wind or by the ventilation system Then meaning that the smaller droplet will not come into action with a fire where you'll have a low pressure with this Should we say a hybrid between what I would call it tend to be a dilute system but at the same time also have the good droplet droplet distribution

So it could be possible to simplify it into a discussion that the bigger the droplet the easier it has to penetrate through hot air or smoke and it can easily reach the fire but the worst its capability to evaporate and take heat away Right

So th that's true We say total fundamental way of say mitigating a fire that is that a dilute system is a wetting Yeah So that's the main although it also a portion of the droplet we'll also a better rate

and

cool. A vice versa we've talked about a watermist system Then the most important and critical is the smaller

correct

droplet variation which will evaporate and cool it And a minor part will then act as a wetting medium As you said penetrates you to

by

effect or the fire flood as well also Yeah

And they've also always love the differences between like sprinkler system or automatic sprinklers and then the deluge systems And this is something that Hollywood wrap their mind around because you always in the movies it's always like someone breaks a sprinkler and then everything on the floor operates there was for me the my favorite scene was from Blade movie where he turned the water in the tank into holy water and then sprinklered vampires And that was absolutely hilarious

That is not totally correct because they have been. Sure You know watermist you say is not a technology which is 50 or 100 years old

So

it's what we call in our terms a relative new technology So in the start so talking about the eighties and nineties so

there

there was no shall we say a

based

or test perform the so-and-so some of the UK projects some of the big projects made in Spain and France Actually also was based on tender requirements where they had to

to

a full-scale test also.

But that is for watermist technology Yes And how word that the requirements defined in the

Yeah

for this particular project

So I I not into detail but what I can explain is about the big experiment though The last experiment that we did in Spain in 2018 So this is of course we are not typically not involved in the protocols the basic criteria for living up to what the client wants So

that is

totally up to the authorities having jurisdiction and

and

and choose a local stakeholders and in this case it was in Singapore it was civil defense was very much involved in that And how did they then Create the protocol So they of course hire authority fire lab certified fire lab Gala with them to create the protocol

by by protocol you mean a certain experiment to be carried to

Yes

And what what

is the criteria and then

yeah

actually Yeah So in our case so Effectis was hired by the tunnel owner This wasn't that case was LTA which is typically the same as you would have a Polish highways or something like that They wrote to authorities Of course you will try also to find some

global or

requirements which can be used to put into the specification of the fire test And in this case it was important for them was besides through say the engineering part was the tenability requirements and Particular case they was referring to NFPA 5 0 2 which has the tunnel and the bridge specification regarding to the ability So there is certain tenability requirements regarding criteria and downstream temperatures and so on and so on However set up of the fire load the fuel

So you had a certain criteria defined for tenability which were related to visibility, temperature, heat fluxes and so on which were the target to obtain And then to demonstrate the capacity of this technology you had to compare it with an extinguished fire right

yeah Typically to do what we call free fires

it's very very

to be allowed to do in a test tunnel

Yeah

but anyhow I think for the first and last time we were allowed to do with because I will tell you what happened with that

but I think maybe the

actual tests that we did And then I will go back to

the to the

free fire because that's some interesting aspects in that Yeah

Okay So to start with we to test so first before you've mentioned when we discussed this you've mentioned that a deluge system would be commonly applied for such a tunnel in this region

this region

So can you first tell me how it happened that you propose the mist and in place of that And and then tell me about themist tests

So of course as I was mentioning Referring back to the eighties to the nineties a lot of experiments was done with the water mist also in tunnel application So if you go a little bit more back in the history eh countries like Japan like Australia and a few other also the states uh United States actually the last 50 to 75 years actually implemented deluge system into their tunnel systems So for them it's not a new technology So you can say that in those part they've was leaning to what was

20

I never said it was roughly 30 kilometers of tunnels which had to be re refurbished So it was in the past it was not say installed with any kind of active Fire suppression but as we all know that if you have an existing tunnel system you also have a drainage capacity And for that it was a very large problem for the client that if they want to introduce a deluge system into the existing channels yeah Then the drainage capacity could simply not

say

the water consumption that by activation Yeah by the dilute system So that's why to be honest probably watermist also for them was interesting The other aspect is of course that they didn't want a system or technology with Not as efficient as a

new

system And that's why I think coming back to why was the in the specification in the tender specification that demand for doing full-scale test and also actually comparison test with deluge system and a mixed system to see if the efficiency was the same as for a deluge syste,. So I think that was the basis of

why

we

got

into that project

If you compare the deluge systems and water systems usually discussing their economical benefits it's usually comes down to water consumption uh because you need less water

We have to define I'll be talking about a high pressure low pressure or deluge because there is Yeah it is Yeah Yeah So as I mentioned in the in the introduction onto the start that a low pressure water mist system More kind of a hybrid with a dilution system So it

have

for instance the pressure level is in PSI 16 everything is P and 16 mean maximum 16 bar

So

mean we on the same pressure level as a swing lower dilutions them So that means that pipes pumps are very much similar to what you will find in a deluge system

okay And for high pressure you would need a

you'll have high

specific

Yeah

but then also much less water

So also power again the power consumption from a low pressure is very similar to what you would experience with a deluge system However if you have power from a high pressure system it will minimum be double or triple the power consumption from a dilute or a low pressure

system

Yeah Talking about the water consumption So a deluge system So if we take high pressure low pressure is similar density So uh all from 2.5 millimeter PEM per minute to 4.5 millimeter per minute all depending on the application

So there's also like two and a half or four and a half liters per minute per square meter right

Yeah that's correct If you compare that with a deluge system and now you say referring to in the region where what this system or this application was so there's typically deluge which is 10 millimeter per minute to 12 millimeter per minute And I also was the two different systems that we was bound to test as well also affect his was bound to test in in combination Yeah And I

asked that because whenever I have a discussion with a client regarding installment of fixed extinguishing systems in the tunnels

Yeah

and I think out of like 20 tunnels we've been involved in Poland the fixed were considered or put in the tender I think three of them and you know the discussion rarely goes into kinetic energy of droplets or the capability of them to penetrate things or stuff like that It usually goes okay But how much water how big the tank uh The power of the pumps that we need can we remove the water from there Will it be contaminated How do we clean it You know these are the things

concerned about

because in the end I guess they assumed that the capability of the system to fight fire is It's similar and it's just provided by the technology So so we rarely go into discussions where the one system is capable of extinguishing or not but rather into the functional aspects of what it means to have the systems on the tunnel

Coming back to the tree most common technologies installed in so-and-so low pressure high pressure or deluge So also again there and that is concern is of course you say contamination and all the faces blocked by dirt and so on And they also again there The difference is that as you know the way that high pressure is distributing the droplets is by pressure mainly

by

the high pressure which is then distribute it those variet of droplet sizes wherever a low pressure system it's again a little bit as a as I mentioned the hybrid with the new system accelerating the water before it went out of her What should we say orifice and the orifices that we use in our streets say a tunnel is between Depending on what application and system a model that we are between two and a half to four millimeters And then you have to bear in mind A high-pressure system is between

of

it's a much more vulnurable contamination from the outside but for sure from the inside

So so the maintenance would be a factor as well I'm I'm surprised actually maintenance is not not that often being brought up by the people who will buy and use the tunnel for the next 50 years And actually they probably should ask that as the first question how much I've also um in in sometimes in Poland we had foam systems

yes

Uh we even had a CAFS compressed form a system designed for one tunnel so there's a large group of active systems that fill more or less the same purpose but with completely different ways Okay So your client was interested in refurbishing a tunnel existing tunnel for which they seem that a more let's say cost effective or a different solution as in water mist would be sufficient I don't want to say better than deluge system because all the systems fit different needs Right But but

No So I mean it was a it was not a surprise for the leadership

because

as I told you that in the tender re

requirements

when we made our offer then it was clear to us and we had to

Okay So okay So sorry

it was not a big shock for my boss

Let me rephrase that Okay Okay boss We can apply for this tender but we need to first find the tunnel to burn down So it is more like this decision. So how does one approach that

So uh then of course you should they actually we talk about European The two most common used test tunnels in Europe there is the in Norway

which is

an abandoned road tunnel And then there is the tunnel in this San Pedro the which is in Asturias in Spain with this an abandoned railway tunnel which then is refurbished to be a road on social

So

to speak Yeah 600 meter long term sort of course You go into communication with the with the guys in Spain and then could be borough Actually it costs something Of course

I can imagine

Yeah Eh do you have some way of time in 2018 for the shop and then they will answer how much time do you need Yes we need to do 16 test sprints Yeah So that was the estimation actually that we had to perform tests to go through all the parameters that the client wants to have verified

16

16

Okay And can you briefly tell us the scope of the tests from the report I've received from VID I saw there was a free burn tests There was two water mist tests right Can you tell us uh more in details about uh

there was a lot of combination tests with we cannot go into too today

because

will be to complex But as you say that you said you

realized

that watermist they do a lot of actual tests

practical

test word deluge or spring the system Yeah they have the base behind them so they can typically in a lot of projects and also accordingly to the regulation go directly So they allowed

in many

To do it without doing that she will test So first of all you could say that we had to calibrate for this test tunnel in relation to what we want to achieve Actually pre-test is the complex thing And this is the thing which takes most the majority of the time when you are into a testimony and the actual final test Press the bottom and you

invite the

client to come and see the actual test and performance That's the smallest part Let me put it this way Yeah Yeah

So the pre-test is when you calibrate the fuel source And so stuff like that

not so much the fuel source because that was a given she was

that was for the fine Okay

But there was a lot of other calibration and also instrumentation which had

to be

calibrated and so on Yeah

what was the fuel source

Coming back to if they're those existing channels in Singapore So at the point in 2018 there was not allowed any heavy goods vehicles to go through this tunnel So the maximum fire load allowed to go into the channels was a hundred megabit Yeah So that means a lot of the goods which have to be transported from one end to the other end of the city had to go a very very Deviation to get to the punch So why they want to install or implement a fixed firefighting systems was

bigger

loads can go through those tunnels

yeah In in the technical documentation they see it was a lot of stacks of wood and then plastic pallettes

You can say why are you using plastics and why are using palace actually as the fuel

So you are doing

Those kinds of tests and you also have to be compared with a competitors so to speak

So

whatever you see our competition doing a similar type of test you will see the same fuel So that is a generally accepted fuel mix because it's replicable That means that Euro pallet whatever it's bought in Poland or it's bought in

Denmark

or moved to Singapore whatever it's having the same dimensions the same wood

Mass and stuff like that Exactly Yeah And it's also

identified what is the Fire capacity within one pallet So it's very easy to build up different fire loads with w

Yeah I understand the choice because we usually sought to working with wood cribs as well in in buildings

So I can tell you that if you go 15 20 years ago there was a lot of experiments done with actual vehicles and also with with the heavy goods vehicles But the problem by that is that you cannot replicate so that

if it's a Japanese

car it's a European car You'll

have

the the content of plastic and

And they're also not representative for years So because you would probably purchase an older vehicle not in necessarily a fresh new from the dealership and and stuff like that That's it's also that's also a thing I've discussed with Anja Boelinghaus Hoffman three episodes ago It's a testing buses and and all these things were very important that the age of the vehicle and what the material contents of the vehicle inside is However here we are I think the biggest challenges

if you look some of the experiments which was done in the early 2002 2010 or 12 then you will see a lot of those experiments was done with what you call open file loss That mean there was not shoes had covered with Taplin or with a metal sheet And that means It's much more easier to uh to suppress say an open fire and that's why today you'll see in all new full-scale tests whatever is performed by deluge or by a different watermista windows you will see always it will be trying

From your perspective is opposite You need the top covered because we don't want to have artificial cooling of the fuel inside by by spraying water on top of it But I also remember a talk I think it was professor Ingasson in Austrian Graz at some point who said that The the ventilation conditions on of the fuel have immense effects on on on the size of the fire And you could you could burn two vehicles of that one to 50 megawatts one to few hundred megawatts just by

thing I first I want just to say just a few brief words about the protocol typically when you have a fire in a tunnel you will try to activate your system as soon as possible to attack the fire in this initial stage But again typically if you refer back to more or less all experiments done with whatever it's dilute or water mist systems you will see a delayed activation And it typically should be period before you will activate your system is either when the temperature reads 60 degrees

allowed

to

activate

the system which will typically not be the actual case because if identified fire either bio detection system or your CCTV system of course you will activate your system to attack the fire its initial state But here we let

it grow

actually you can say all those windows which actually performed a full scale testing build into say kind of a safe extra additional safety factor And of course

you also

in some of the fire strategies in the tunnel you will also see that the authorities want to say a kind of a delay also from a fire detected until System is activated allowing people to evacuate out of the tunnel So that could be a timeframe of two to three minutes

it was also carried in a ventilation conditions So it was the ventilation triggered immediately or also delayed together with your system

in this particular case and in Singapore

local

regulation that they all the time whatever you have a fire not a fire all the 24 7 they run with a five meters per second installation

So it's like the initial condition for everything Yeah

So that means during the whole phase we had five meters per meter running all the time

So you've let the fire grow for let's say seven eight minutes I assume

Yeah No you'll you to take the fire detection of

the fire So to speak

can say Yeah And from that

five

minutes before you allow to activate

and what happens upon activation is the effect like immediate does it take you some time how does it look with the moment you use start the system

So uh especially within visualization and smoke a lot of smoke system but of course whatever it's a dilute system or water mist system until you have penetration to say through the toppling sites

of this

heavy goods vehicles until So you only cool the

So

until you have direct access into the fireside yard then uh but you will see a lot of steam You'll see a lot of smoke there Yeah

I'm asking because from the plots I see the the spike in radiation and uh rapid change in the in the right red it hit flux and it's also something which is my own feeling when I They with with any extinguishing systems that if you if you are actually The source of fire And I assume in your laboratory when you do protocols you feel that as well the moment this device is activated is like someone turned off radiation It's like

yeah And

gone it's amazing How extremely well water is in shielding from radiation And I assume that is the biggest effect that it can have on the life life safety ahead of the fire So I assumed the moment that the water released and the courses of two tests have completely disjoint So so In the free burn test which I see the peak heat release rate reached at 233 megawatts That is a lot of heat release Yeah

The most frightening here I think is the speed within it it res

so that I always what

I'm referring to discussion with consultants

or

owners that as we all know that 95% of all tunnels whatever is in Europe

or

globally is depending on a ventilation system to to do the job so to speak but here you can see that the ventilation system the only thing that it actually Performed was up to the tenability requirement Meaning the upstream

it's an

was done but

All the

parameters and then coming back to why but ever never be allowed more to do a free free burn in a in a test one So actually we destroyed 150 meters of the tunnel there Oh Uh very unfortunately uh so they told us very specifically if ever again B should come there

not actually

to us directly because it was effective Who

on our

behalf was Yeah hiring the on the client's behalf I was hiring the the chance that it will ever never be allowed anymore do a free burn. So probably we will be the last tunnel winner who will be allowed to do a free burn But I mean now

test can be used as reference I assume you would be kind enough if someone wants to

I

I

the Wojciech is very much coming back to what you say that the ventilation velocity have a lot of

effort

on the firewall My thesis there is that if it was been running with the critical velocity for that then you will not have have that gross potential So it will have been delayed much much more also for the test situations where our system was if it was not performed with five meters per second Two or two and a half meters depending on what was the calculated critical velocity you will see a much more critical or dramatic gross fire gross rate as you see on those experiments

I I think it was the clearest it shown it was when experiments carried in Gent for the Flanders government It was experiments run by Xavier Deckers and the university of Gent.

just just one comment to that And I think that is Generally not observed in results And also the aftermath of the result is that when you do your heat release rate in those experiments it's typically is the chemical heat release that you

are seeing So

that means it's consumption of

oxygen

yeah Of oxygen Yeah But this is what I would call telling something about the fire machine I mean

that

in

the

of the fire it's not actually telling anything outside the center of the fire

So

for me in a single source should be for channel owners and stakeholders should be more interesting to look at the convective heat release rate And also if you look at the report that

that

I did there if you look at Temperatures outside what I would call the fire machine so to speak Then you receive they are relatively low I think in this case a 59 megawatt fire temperature

Yeah So so the chemical release was around 50 megawatts in in your in your water sprayed test

look just outside the center of the fire quite low temperatures

which makes sense because you're very effectively even though the heat is released to the

it's not you say reflecting the jet fence or ventilation system which is installed in tunnels that they don't take that aspect fully into consideration

Okay Now I have to ask you two questions related to myths about a water

Yeah

I am often facing when I'm discussing the technologies with stakeholders one is that the combination of water mist and the ventilation that the water mist will be carried away from the fire by the ventilation itself And you had very strong ventilation in here because five meters per second is way above the critical velocities which we would calculate usually so so what's your take Did you observe any uh negative interference between ventilation watermist in your case

From my perspective I would say it's a little bit overrated this deviation aspects You will see I mean if you physically look at the display impact the mutilation on

this you

have a deviation Yeah But it's minor Oh yeah Probably for low pressure dilute system It's definitely a minor deviation but why I think More or less relevant is that typically here in Europe when we when you do fire suppression systems and channel you're

all that

building that on a on a tree So strategy meaning that you have your middle zone but you have your

fire

but you activate upstream and you activate downstream

So you make sure that the fire is more less in the middle of the of the

So that means that even if you have Some effect by high velocities from the ventilation system but that also mean that you will move your fire in the same direction

So the water will meet the fire wherever the ventilation make them go Okay

doesn't have any effect on the capability of the irrespectively if it's a high pressure system or it's a low pressure deluge system Yeah

And the the second one comes I think more from foam industry may be if you have an accident where the fuel is not necessarily on the top of the vehicle but it's sort of spillage what extent this technology would would still work with a pool fire as we are perfectly aware that that it has no way to interfere with the fuel surface at all Right So so

yeah So then we have differentiate between a deluge system attacking a pool fire or is a water mist

Steve checking

a pool fire However talking about a water mist Solution attacking a pool fi is very efficient and even more efficient than the a deluge system

and

as efficient that's you say I came as efficient as a foam Even the pickup the fuel spillage is you more efficient It is You have immediately I mean really immediately

within

activate the system You will have such a proration factor that you you have to see it's totally absorbed And

we

did some in coming back to the test that we did in uh Where we did a fuel spillage pool fires up to 30 or 40 megabits fires And within two minutes it was totally extinguished

Extinguished

extinguished even extinguished Yeah But that means that smaller fuel spillage

you don't get

that big evaporation FX So it take a little bit longer time. Of course we know that a foam it will totally I isolate But I mean if you I have seen some American research I will fight that research for you You will see they try to compare the extinct race time between firm's systems mixed foam water mist systems and bottom is systems

And

it's minor differences I mean really really minor differences

yeah Uh I have one more mythF what about the visibility. Have you observed any effects related to the loss of visibility in the extinguishing green

So also again then you have to lean up to some specifications or requirements Also again here we lean up to all

File I've

up to what she say is accepted in the NFPA 5 0 2 where you have to say firearms or lamp poles within a certain distance have to be visible meaning that

you

see exit signs and so on And we performed very well as you can Probably I don't know if you can see in

that region

but then in not a report you can see that Yeah

is a part of evaluation If

you look When we do videos when we activate the system you can do that for a deluge system You can do that for a water mist system And of course there there is some slight difference between a high pressure and a low

pressure

because of the tents that small droplets will make it a little bit more she would say yeah tends to look into but you will see people downstream 50 meters easily So for sure it will live up to the requirements whatever is within in FPA 5 0 2 for sure

Okay I think it's important too to talk about this you know myths because it's always being dropped in the middle of the discussion as a aha moment Okay But we will not see a the technology is great but you will not see anything so it's cannot be used So

I mean also then also you again you have to look into the practical So how is the fire strategy implemented into channels Typically you would you could of course have people into the channel when you activate the system But what you will try to attend this People who are out of the terms before that you will activate your system That's the typical

with uh

I would say

I usually tell them I would rather be wet and with bad visibility then exposed to 250 megawatts that I I mean if I had the choice I would rather be wet than burn down Yeah Okay Johnny I'm very thankful for sharing your views on this important subject And you also armed me up for better discussions with my local authorities uh uh for the future attended projects because I see immense value in in using active fire systems in tunnels to reduce the risks I'm also very In a way happy

yeah for sure

there was a webinar right

Yeah for sure We that's part of our company policy We have nothing to hide I mean and

all the

research that we do uh we put that public If

go into

our websites or to the LinkedIn website probably is the better one because

I

have released a lot of reports and posts there

regarding

the tissue looking for temperature in LinkedIn then they will find the good material

I will search for that and put that in the show notes So the audience can just go there with one click and share the resources And I'm from what I've saw it's worth spending a few minutes of your time taking a look in into them They were very interesting Johnny Thank you so much for coming to the Fire Science Show in person that I appreciate that a lot and yeah All the best Thank you so much

pleasure to be part of it

And that's it. It was a great experience for me. Not only because I've learned so much watermist systems in tunnels, but also whole process of recording. This episode was fantastic. As Johnny has visited me in my office, and I had a very rare chance to make your life interview. And I prefer it very much over online it's much easier and such a better contact with the guests to, Inside your office and just discuss fire. From the episode itself.