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FIRE SERVICE AND GENERAL FIRE SAFETY TOPICS => Technical Advice => Topic started by: Goodsparks on September 04, 2007, 12:21:32 PM
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Just a quickie. Got a large room with an ornate ceiling which is to be protected by a vesda. About 1/3 of the way into the room is a large decorative beam, which, in height just exceeds 10% of the room height (like 12 - 15%). Now, if we were using standard point detectors, would treat as two rooms and install two. Is it any different with aspirators ? Have just looked through 5839 and it seems to indicate that theres no difference.
I`m trying to get hold of the BFPSA CoP at the mo, but no joy as yet.
Any help appreciated.
Paul
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It is my understanding that the aspirating sampling points are required to be located as you would locate traditional point detectors, therefore, I would say yes, you need two sampling points fort the room you describe.
I can forward a copy of BFPSA CoP if you send your email address (about 600KB file size)
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Each sampling port is treated in the same way as a point smoke detector and it's coverage is therefore the same.
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Thanks All, They`ll have to rip up some more oak floorboards :-)
Paul
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Yes goodsparks if you want to issue cert to BS5839 with no variations on the commissioning certificate you had better get the saw sharpened.
Lets not forget though that the aspirating detector is a very different beast than a conventional point detector which relies entirely on the convective energy from the fire in order to sample the atmosphere in the room whereas the aspirator does impart some energy to draw the smoke in - response is therefore much faster, even though the analysis is done remotely.
It would not be too difficult to calculate the delay that would arise as a result of not siting a detector beyond the beam, working on a range of fire sizes.
But depending on the reason for the installation of the detection equipment your client may be happy to offset a few seconds in response time in return for less disruption.
I have seen some aspirating systems that use small bore tubing in heritage building in the past. Cant find it on google at the moment but it may be worth digging around.
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The only time I have seen aspirating systems work well is for specific point protection i.e. in electrical kit, computer banks and the like. In these situations the quick pick up of the smallest nasty particle can lead to a quick shut down of effected item saving more expensive down time and cost of equipment/people replacement. Not a good system for open/larger space detection. But, that is my experience, others may put up a good case for this use.
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Mr P
That is a bit of an old fashioned view of asd now. You don't happen to work for an insurance company i am having a arguement with? They are insisting that asd can only be installed in extreemly sterile small rooms as they are super sensitive.
check here
http://www.vision-fs.com/opencms/opencms/system/modules/com.vfsportal/default_bodies/apac/int_en/products_fire_sevenreasons.html
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Graeme, yes that was a long while ago, and I have checked out the site you posted. Noo, no, no, NO - no. Never say never, but, I would not work in that line. Personally I thought the system I was involved with was good. (I was involved with some trials back in 80's.) Due to great controlability and trigger levels, not many false calls, and you could go direct to the affected point even if smoke was still not visible. Engineers were able to isolate in most cases before anything got out of hand. The remaining problems were the gases given off by 'popped/fried' components.
The systems are even better now and can be used to pick up on a variety of substances. I guess there is a whole debate there waiting as to the pros & cons betweeen system types. Again, for large open spaces... but what is being protected and what is being looked for? I keep open minded!
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Guys
Things have move on a lot from the early days. We have protected large open spaces using Vesda with fantastic results.
Just over a year ago we protected an underground/ underbuilding car park. Running fine, no problems. Occasional flow faults on days of very high winds and changing atmospheric pressures but settles down again very quickly. Client loves it, the engineers think it the dogs..... it is the future.
Dave
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I know of a system in a very large warehouse 400mx120mx15m high- no problems most of the time, a huge number of flow faults when the weather is extremely windy - but thats only happened once, it was rather extreme, blew a few of the vents off the roof and stopped all the lifts working they were shaking in their shafts with the wind pressures, various internal fire doors could not be shut- thank goodness we didnt have a fire that day.
Obviously easy access for maintenance to relatively small numbers of sensors is a huge advantage in such a hig shed.
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So, are they still having to use single tubes from det point back to analyst/sample equip?
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The pipe network is still the case but the sampling ports can be extended from the main pipe to small capillary tubing into flat "discs" mounted on the ceiling which are ideal for the likes olde architectured buildings or cells etc. (as long as the little buggers don't block them up with wet tissue paper or sudocream, as I experienced at a local young offenders centre!).
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Guys,
Does somebody has copy of BS5839? This would help me clarify a lot of issues which was long dominated by UL standard.
Thanks
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Further to Graeme's and Thebeardedyorkshireman's posts I can confirm that I have also successfully used aspirating detection to cover rooms rather than just cabinets.
There is also now a very cost-effective Vds approved aspirating product available that allows you to use the automatic fire detectors of your choice in the sensing chamber, and air is sucked in from your protected area and then sampled. I am considering using this in shafts and risers so that no access by engineers is required into the top of the shaft for installation and maintenance.
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Easy access is a big selling point for aspirating detectors. I got involved with a regional shopping centre with sampling points at ceiling level over the two storey mall. The gubbins is accessed by an access walkway. Much better than smoke heads that require a cherry picker to get to them.
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Hi Dr Wiz
Any chance of a link or more info?
Are we talking about putting a standard point detector in a box and drawing the sampled atmosphere over it or have I gone off on one?
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Hi Dr Wiz
Any chance of a link or more info?
Are we talking about putting a standard point detector in a box and drawing the sampled atmosphere over it or have I gone off on one?
Hi back to you Professor K.
Always happy to help a buddy.
You understood correctly. The product description is as follows:
The ASD1/ASD2 aspiration systems actively draw air from the protected area through a network of 25mm pipes, which is then monitored by an internal conventional or analogue addressable smoke detector (not provided)
This would enable you, for example, keep the detector (of your own choice) out of a lift shaft, with just a pipe going into it.
The cost for an ASD1 is about £540.00.
The manufacturer's contact details can be found at:
www.eurofyre.co.uk
Their website is not up and running yet but they sent me details of the prouduct a few months ago.
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We have a small application of just a system in operation. 25mm pipework draws air from a number of small occupied rooms out to a sealed chamber and over a 'normal' smoke detector within the chamber. The actual installation has a sample pipe to each room, and the sealed chamber box is segregated to contain one detector per room.
The chamber box has a small powered fan which draws the sampled air into the chambers. All the detectors are addressed in the normal way into the system.
Reason for installation was to prevent very high levels of vandalism if the detectors were inside the rooms.
Has worked fine since installation
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It sounds a great solution for some specific problems and I am very keen to find out more.
I feel uneasy about the concept of using it to protect a number of rooms for life safety- even to extend the coverage of the point detector in the box beyond the normal 100m2 but for property protection thats another thing perhaps.
The gut feeling is that if we do cover a large area then the airflow across that detector would probably result in its getting dirty much faster than one used in the conventional manner - and whilst vesda do cover huge areas they are designed for this and the air is filtered of course.
Or am I being over cautious?
The cost of the box being what it is will reduce the risk of it being abused in any case.
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Further to Graeme's and Thebeardedyorkshireman's posts I can confirm that I have also successfully used aspirating detection to cover rooms rather than just cabinets.
There is also now a very cost-effective Vds approved aspirating product available that allows you to use the automatic fire detectors of your choice in the sensing chamber, and air is sucked in from your protected area and then sampled. I am considering using this in shafts and risers so that no access by engineers is required into the top of the shaft for installation and maintenance.
I've seen a Siemens version of this - basically a fan in a box with a detector head mounted inside, with your normal run of pipe etc.
- so in this system is the air flow monitored ?
- what about the affects of dilution or do you up the sensitivity of the detector ?
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I agree with Kurnal that when using this type of device then one normal smoke detector shouldn't cover more than one room to avoid possible smoke dilution. I'm sure that this particular version is only meant to cover one area.
With respect to dust, the literature describes it has having a 'Field Serviceable air filter' and suggests it is suitable for 'harsh and dirty IP65 rated environments......in hospitals....in racing stables'
With respect to air flow monitoring the literature says ' The flow level is adjusted on a 10 element bar graph with adjustments for high and low thresholds. Flow failure is reported as a device fault'.
I must confirm that I have not used this model myself yet, but it caught my eye as being a cost-effective alternative to a traditional aspirating system for suitable single area applications. I was thinking of lift shafts and risers but it would surely be suitable for rooms that would normally be covered by a single smoke detector and where a detector couldn't be installed because of vandalism/asthetics.
I would encourage anyone who is interested, to obtain the product literature from the manufacturers. I am not really in a position to answer in-depth answers to questions regarding a product that I have not even used yet!
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Hi Dr Wiz
Any chance of a link or more info?
Are we talking about putting a standard point detector in a box and drawing the sampled atmosphere over it or have I gone off on one?
Hi back to you Professor K.
Always happy to help a buddy.
You understood correctly. The product description is as follows:
The ASD1/ASD2 aspiration systems actively draw air from the protected area through a network of 25mm pipes, which is then monitored by an internal conventional or analogue addressable smoke detector (not provided)
This would enable you, for example, keep the detector (of your own choice) out of a lift shaft, with just a pipe going into it.
The cost for an ASD1 is about £540.00.
The manufacturer's contact details can be found at:
www.eurofyre.co.uk
Their website is not up and running yet but they sent me details of the prouduct a few months ago.
Blimey, for that money you can buy a real HSSD from Stratos - micra 25 !
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Can anyone give a ballpark for installation of a micra 25 and provision of an interface box for later connection to an existing system- to be connected by others- for a single one of these units in a small room say 12 x4x3m? Just in very roundabout figures or even just a guess at time to install and commission assuming power available and straightforward job- its not an auction I am just curious.
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Kurnal
We have done hundreds of these. The cost of the aspirator,detector, power supply ,batteries and interface including commissioning is around £1k selling each. Say £350 for a days labour to bolt it all together inc pipe and fittings.
Variables are the type of detector, type of interface and its cheaper per room if you use the 2 detector box.
Dave