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FIRE SERVICE AND GENERAL FIRE SAFETY TOPICS => Fire Safety => Topic started by: xan on September 29, 2009, 01:36:05 PM
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I would value your views on this:
Proposal to convert an old water tower into flats (it is a tall and skinny building).
Main staircase to entrance of topmost flat entrance door is 17.5m high (Just below the 18m threshold requirement for a FF shaft.).
However it is over the 11m threshold which I believe (I admit I am not sure-guidance in ADB/BS9999 is a bit vague,but does appear to be so in the old BS5588-5 table 4 )requires a dry riser.
The uppermost flat has an additional 3 internal stories,uppermost floor at 26.5m.However the furthest point from fire service access to furthest point in flat is approx 48m (only just over 45m threshold).Because of limited space,they are finding it difficult to install a riser,and have proposed a Residential sprinkler system,mains fed.
Should they be able to provide a sprinkler system (and there are water supply requirements to be overcome yet), would you accept sprinklers in lieu of the dry mains,despite the height that equipment will have to be carried upstairs by FF,even though the actual distance is just over 45m?There does not appear to be any relaxations given for the provision of sprinklers (Sprinklers would be compulsory at 30m)
thanks,Xan
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Sounds fair enough to me.
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You can only do what you can to make an existing structure fit the guides, the stumbling block may be convincing that the fire authority that the provision of sprinklers (that have been proven in tests to suppress rather than extinguish a fire- especially a shielded fire) will control a fire sufficiently such that they do not need to carry as much equipment up those stairs. The mains supply to the sprinklers will give confidence in this respect- much better than a tank supply that will run out after 10 minutes.
The 45m bit helps because with sprinklers a hosereel is more than likely to be their weapon of choice- its lighter, easier to manouvre, better knock down, quicker to get to work, more controllable, better protection for firefighters etc. Can you reach all areas from the appliance parking position within 60m- the standard hosereel length?
Now just be sure that mains pressure will give you the necessary 0.5 Bar at the highest sprinkler and the necessary flow (allow for 200l/min forget the 168 l/min in BS9251) I bet you will need a pump.If you have a problem with water pressure you could look at water mist.
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What you are proposing sounds, as presented, perfectly reasonable. Kurnal explains the fire fighting logistical arguments well.
You might struggle with the mains supply. You will need over 3 bar at the main sprinkler valve and this may not be supported by the normal mains supply (24/7 requirement). The water suppliers may be reluctant to allow a pump to boost your supply as this reduces pressure in the main and can lead to contamination of the water supply through leaky mains. You will only find out what is feasible by approaching the water supplier.
You mention a "residential" sprinkler system. Be clear of what you want, "residential" is different to "domestic." A "residential" system has a much higher requirement for the water supply than a "domestic" system. You probably want a "domestic" system which requires, as kurnal states, ten minutes of water supply. Also, if it is a "domestic" system you're after, then the flow requirements (at the 3+ bar that is required at the control valve) will actually be much less than the 200l/min kurnal suggests - his figure is for a "residential" system - the actual requirement is likely to be around half of that. If a tank is required for the supply then you are likely to need a tank of between one and two cubic metres. This can be located anywhere in the building but you will also need a pump. The pump has some demands for its electrical supply but these are not too demanding.
As kurnal states, your biggest issue is not going to be in the technology, but in the act of putting a convincing argument to building control and the fire service. Kurnal's comments about fire-fighting give you an idea of how to put your argument together. You should bear in mind, if you go for the domestic system, that the system will only last ten minutes and if the building is located somewhere where the fire service will take 20 minutes to get to the building then the ten minute supply is unlikely to seem like an attractive option for them. If, however, they are likely to get an appliance there within ten minutes then they might be happy that they will be faced with a smaller fire when they attend.
As for water mist, there's no BS and the NFPA standard won't really give you precise guidance on the design of the required system. Remember that you are intending to install the system as a life safety compensatory feature. The NFPA life safety system requires 30 minutes supply and this is infrequently proposed in this country. You may find it hard to present a rigorous argument to building control and the fire service if you propose water mist as compensation for the lack of internal fire fighting facilities.
Stu
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Thanks Stu yes I was getting my domestic sprinkler standard mixed up round the residential standard. The domestic standard provides for two heads to operate for 10 minutes. The residential system provides for up to 4 heads to operate for 30 minutes.
A very significant difference if you are relying on stored water from a tank. But if able to use the towns mains- (and there is a national protocol allegedly the whole of the Water Industry is signed up to though it appears a bit patchy) then a residential sprinkler system over the domestic may be one to keep up your sleeve and could sway the argument ( but pipes need to be a lot bigger of course)
Stu is also right about the reluctance of many brigades to accept water mist- there are high and low pressure systems. There are only International Maritime Organisation standards to work to as far as I am aware but to me if you are on a ship in the middle of the ocean and you have a fire any help will be a long time coming. If the IMO is prepared to rely on water mist for ships its good enough for me.
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Since it seems to comply with ADB without a riser, I think the FRS will be thrilled with a sprinkler system.
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Nice one civvy! well spotted.
looking in a bit more detail xan am a bit puzzled by this comment:
However it is over the 11m threshold which I believe (I admit I am not sure-guidance in ADB/BS9999 is a bit vague,but does appear to be so in the old BS5588-5 table 4 )requires a dry riser.
There isnt a table 4 in the old 5588 part 5?
The 11 m threshold for small single staircase buildings in ADB is in respect of means of escape, and of course assumes a normal storey height and flats on each storey. It allows a single means of escape. I guess in a water tower there will be very little accommodation opening into the staircase at the lower levels? Is the dry riser an appropriate compensation for this means of escape issue? Or would you be better to focus the integrity of the means of escape? To this end para 36.2.2.1 on page 51 of BS5588 part 1 gave advice on dealing with small sngle stair flats over 11m in height.
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Table 4 in BS5588-5 does suggest that shafts with unvented lobbies but no mains should be supplied in buildings between 11m and 18m.
ADB does say that where fire fighting shafts are provided they should be generally designed in accordance with BS5588-5, but the recommendations in ADB would not have a ff-shaft in the circumstances given here, so I see no reason to reference any part of BS5588-5.
FWIW, BS9999 follows the same lines of BS5588-5, so if you are designing to BS9999 then you might be stuck with it.
I believe the 11m limit was created in relation to the size of the FRS ladders, and IIRC it goes right back to the fire grading of buildings. (i.e 40ft[?] ladder pitched against a wall.)
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Thanks Civvy just found out I have been looking at an outdated version of the outdated standard part 5. :(
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It is nice to know that it happens even to you, Kurnal. :)
The uppermost flat has an additional 3 internal stories,uppermost floor at 26.5m. However the furthest point from fire service access to furthest point in flat is approx 48m
Kinda sneaked that one in there. A floor at 26.5m? You should be supplying a lift, never mind a riser.
You could raise the argument that the lift could only go to the floor at 17.5m anyway, I would point out that ADB makes reference to "Buildings with a floor at more than 18m above fire and rescue service vehicle access level..." which this building clearly has. (I would also suspect that the reason for the topmost flat being 3 storeys high is simply to try get around the 18m threshold anyway, but then again, I am quite a cynical person.)
I would like to see plans where the 45m hose criterion can be reached on a floor 26.5m above access level, taking into account that Mr. Pythagoras tells us there is at least 37.5m worth of steps. I am not saying it is impossible, just 'unlikely'.
I have no sympathy with any constraints on geometry whatsoever. It is an old water tower. If it is not suited for building flats that conform to current standards then don't build flats there.
All that being said, a residential sprinkler system (As Stu's comments) might compensate quite well but the whole B5 package needs looking at carefully and needs discussing with the appropriate FRS properly.
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I believe the 11m limit was created in relation to the size of the FRS ladders, and IIRC it goes right back to the fire grading of buildings. (i.e 40ft[?] ladder pitched against a wall.)
Civvy, quite right! All about the 'size' of your equipment!!! :-X Do you rmember the wheeled escape? ;D
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I believe the 11m limit was created in relation to the size of the FRS ladders, and IIRC it goes right back to the fire grading of buildings. (i.e 40ft[?] ladder pitched against a wall.)
Civvy, quite right! All about the 'size' of your equipment!!! :-X Do you rmember the wheeled escape? ;D
Gosh, the old wheeled escape by george. A he-man's ladder but a little awkward when you needed to get into a roof space from a bathroom.
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I am not old enough to remember them Mr. P. I hear hook ladders were the tool of the brave though. :)
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I am not old enough to remember them Mr. P. I hear hook ladders were the tool of the brave though. :)
The "brave" bit was getting on to the roof of the tower.
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ah yes, hook ladders and wheeled escapes - back from the days when men were men, women were grateful, and sheep were afraid!!!
(Any complaints about the suitability of this post should be addressed to Firenet Admin) ;)
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Faint echoes of 'stand by to slip' .................
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Slip a disk?
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Thanks for all the comments-been out of office fo a few days.
This building is very tall and skinny-so furthest point is ony 48m.
My version of 5588-5:2004 does say in table 4 riser required in building 11-18m, but maybe as that BS is defunct,we should ignore that.
Developer is proposing residential system with water tank.
Take on board comments about not converting an unsuitable build-the existing tower is having a new external staircase being built-but only to the 17.5m mark.Planning won't allow it to go any higher,plus the developer is running out of time.I don't have a lot of sympathy,but I am not the AI,so the decision at this stage is not up to me.There are other constraints as well as this is a Government directed project.I am quite comfortable with the Sprinkler proposal-providing it is a suitable system.
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My version of 5588-5:2004 does say in table 4 riser required in building 11-18m, but maybe as that BS is defunct,we should ignore that.
It does indeed say that in that BS.
My point being that if you comply with ADB, you almost certainly comply with Building Regs... Since ADB does not require the fire fighting shaft in a building of that purpose group at the 11-18m height, then there is no reason to go anywhere near BS5588 part 4.
However this building is clearly above the 17.5m that is being mentioned, so some compensation is needed.
FWIW, I personally think that a sprinkler system will do a very good job of compensating. I appreciate that they have a lot of kit to carry up the stairs, and we don't want them knackered before they are even entering the fire compartment. But I believe the real hard work starts when they are entering the heat and smoke, and the sprinkler system should ensure that they are not put under such physical and mental strain as they would be in a compartment with an uncontrolled fire.
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Interseting point about Sprinklers, the determination in June on there use in residential accommodation in different circumstances I agree, leaves it open to debate about their usefulness.
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The determination you mention (if it is the one I am thinking of) is specifically regarding B1 and inner-room bedrooms. The main point of the determination (There have been a few similar determinations btw) was that passing through a fire affected room, even with sprinklers, is simply not as safe as the code-compliant escape corridor/hallway. (I am not saying I agree or disagree with it, but that was the crux of the decision)
Here we are talking about the people who have to walk into the building when the fire has been going for some time and it is untenable for anybody else. Even fully kitted up, the firefighter is under a great deal of physical stress while in the heat. CLG and BDAG have done some published research into this. Something minimising the risk of flashover or even simply lowering the temperature of the room has got to be a great bonus for the firefighters.
I am sure any of the operational or ex-operational people here can explain how long a BA set lasts in good conditions and how long the same set lasts in severe heat. O2 uptake is a good indication of physical stress.
In fact, we could temporarily ignore B5 and simply ask one of the operational guys what they would prefer;
a) A walk up a stair with the high pressure hosereel with a sprinklered fire at the end of it.
or
b) A walk up the same stair, with a dry riser to connect to and an unsprinklered fire.
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This was my earlier point. If the hosereel is in range (usually total of 60m on the drum, though some brigades have shorter these days) then assuming the sprinklers have done their job and suppressed the fire, the hosereel is the best tool to finish it off, hauled aloft.
Having to carry a roll of 25m delivery hose and branchup to that height, unroll and charge the full 25m length in the confined space of the landing before you can safely enter the flat invoved is a nightmare. Normally this would be done at a bridgehead one or two floors below the fire.
Hence my other point. If domestic sprinklers are installed from a tank supply then they will only work for 10 minutes. The water will have run out long before the brigade arrive and if the fire is shielded say under a table it will be up and away. If a residential system is installed from a tank supply at least the system will work for 30 minutes giving the brigade chance to set up and enter.
If the sprinklers are from a mains supply either will be fine.
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I’ve watched this thread with interest and would like to add my thoughts-
We have successfully argued that residential sprinklers should be installed in a development due the excessive distances. However, where there are access problems you need also to consider a fire occurring in the communal areas. Therefore, best practice would dictate that sprinklers are provided in these areas too.
I have heard that some metropolitan brigades have used residential sprinklers where access problems existed up to 90m
Also, 48metres is only 3m in excess of the ADB would I be that worried bearing in mind the length of a hose reel?
All our appliances have shorter hose reels (54/55m) due to an increase in the diameter of the hose.
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NICS also has a say in how firefighters are contolled at a fire in high rise buildings now as well.
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Just another thought- all our discussions about sprinklers, rising mains, hosereels and main jets are irrelevant if the crews arriving at a working job are not aware of the fire strategy for the building.
A riser inlet is obvious on arrival- but how would the message be given to operational crews that sprinklers had been installed in lieu? ................Its a long walk up those stairs - what would you carry to save your legs?
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I totally agree. It is great that we know that the hosereel will reach every part of the flats, and that it should be enough to deal with the expected fire, but if they don't have that information they might simply start laying hose lengths down.
With the influx of mobile data terminals, where accurate information can be given direct to any attending crews from a terminal in the appliance, we should be able to ensure that this information is available.
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Kurnal the answer to the question should be 'firemanship' although I think the PC phrase is 'firecraft' realistically though I feel Civvy is right - MDT. However, my brigade is struggling to put the info we have into the agreed format.
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I totally agree. It is great that we know that the hosereel will reach every part of the flats, and that it should be enough to deal with the expected fire, but if they don't have that information they might simply start laying hose lengths down.
With the influx of mobile data terminals, where accurate information can be given direct to any attending crews from a terminal in the appliance, we should be able to ensure that this information is available.
Yes I have carried hose up 10 floors in B.A. (many moons ago) because there was no lift available and then fought a fire,of course i was much younger and fitter then.If i turned up at this building,with my knowledge,I would probably be thinking wheres the riser?However,most Ops guys would look for one,and if it ain't there just get on with it,and maybe question why afterwards.There should be a sprinkler alarm operating anyway-so that might give them a clue on the action they should take.Yes we can put info on turn out systems-but do they aleways read it all?