multi apexed warehouse

[Steve_gb]

I am currently looking at a large warehouse that is about 30m width and 150m length.
The apexes run widthways there are around 12 over the 150m length.
the height of the apexes are around 1.5m, but the height from floor to apex is about 20m. In the early days point detection was put in the apexes but it constantly fails and is obviously a problem to maintain.
The roof is supported by a large steel framework and is open space.
My idea is to  put back to back beams lengthways dropping below the 1.5m apex as there is nothing of risk in the roof area. would a variation be granted and approved on this principle? otherwise its a beam set in each apex of around 30m width

[kurnal]

What is the purpose of the detection system? Presumably for property protection? Thats one helluva  high warehouse for point detectors!

Are there any other fire safety installations such as sprinklers, ventilation installed?

What sort of goods are stored there and what is the storage mode? I guess its probably an automated warehouse?

[Steve_gb]

Its a printers so there are people working at night and yes it is high i was suprised myself.

There are sprinklers but no ventilation. there is a high level crane that travises the warehouse and there is machinery operating at night so i suppose a warehouse is a wrong description it is more of a working area as nithing is stored there.
Yes your right there is a lot of automation which will be protected at low level

[Wiz]

Obviously variations might be allowed based on a risk assessment, but BS5839 Part 1 2002 recommends that the optical beam smoke detectors must be installed in the top 600mm of the highest point of the ceiling. The risk assessment may also request, if the space is considered to be high, supplementary detection of a rising smoke plume and the additional optical beam detectors would be subject to different spacing requirements.

[Ashley Wood]

Have you considered VESDA or similar aspirating detection system? Yes, there will undoubtedly be lots of dust, etc. from the process but these can be compensated for as can any ambient fumes. Just an idea as I have seen these installed at print factories across Europe. One of the problems you will have with an area as tall as this is the inability for the smoke to rise to such a height. Yes, it will eventually once the fire is large enough, but initially the smoke may cool and stratify below a beam or point detector. Vesda would be easy to maintain as the sample units could be placed at low level. Even with beam sensors you will still need to get up high to maintain them.

[Kevin Shea]

Steve,

I have emailed you a file detailing the why VESDA asd is beneficial in warehouses and what sort of pipe layouts would be suitable to your project. Any problems or if you want to go through and specifics email me.

Cheers

VESDA Kev
Xtralis Ltd
KShea@xtralis.com

[Kevin Shea]

Hi guys,

I should also mention to everyone who is looking for similar fire protection in warehouses why they should consider VESDA.

1.) Warehouses (like the one Steve is working on) contain very large volumes of air which will result in the dilution of smoke. VESDA due to it's high sensitivity will detect these a lot sooner than point or beam detectors.

2.) Warehouses will often have high ceilings and once VESDA systems are installed with a ground level maintenance test point you don't have to get back up into the roof with a cherry picker. Unless you really like tall heights.

3.) Storage racks in warehouses can trap smoke which means slow smouldering fires can remain undetected for hours becuase the smoke doesn't rise up to the point or beam detectors. Not until the fire itself is very large.

4.) But we have a sprinkler system? - Just think that for the sprinkler to activate the fire will have to be quite large, do you really want all of your stock to suffer from water damage when you could spend the extra cash initially and have piece of mind that VESDA will pick up the fire a lot sooner than to relie on the water system.

5.) With VESDA you won't get any false alarms from machine movement or stock blocking that can set off point or beam detectors.

All in all yes, VESDA will be more expensive initially to install but does give considerable advantages to protective lives and stock in warehouses. It will be up to you to decide what is best!

VESDA Kev
Xtralis Ltd
KShea@xtralis.com

[Steve_gb]

Vesda sounds a good idea but a recent job i was looking at discounted vesda because when servicing, each of the aspirating holes has to be treated as a point detector. Getting access to each individual hole would be a logistical nightmare over such an area..it is envisaged to discard the existing point detection because of these reasons and continual false alarms.

[Gazzaaa]

Ey Up Steve ...... Have you learnt nothing? aspirating detection solves everything (big FAN of it myself .... oh dear). Give me a call if you need further info.

[Kevin Shea]

Hi Steve,

When you are looking at servicing a VESDA system even in your warehouse environmnet is actually very easy. While you are correct in thinking that each sampling point is considered a point detector I will tell you of a way to get round having to go up and test them all!

During the design and installation you want to make sure that one of the end pipes from the VESDA unit is brought down from the roof and capped off as a ground access test point. So during servicing you can test the flow rate and transport times for the whole pipe system from the ground and not at each point up in the heavens.

The VESDA systems complies with the BS standard of 120 seconds maximum for the transport time, however we as the manufacturer reccomend 60 seconds max. Now if during these test on the access point the times are lagging behind what they should be it will likely mean that some of the pipe sampling holes are pluggin up with dirt from the environment. This can decrease the amount of air being sucked into the VESDA system and will slow down the flow rate etc.

If this happens and you think the sample holes are clogging up you have three stages to follow as our reccomendations.

1.) You can hook up a small air pump to the ground test point and blow/suck air through the pipe system dislodging any dirt around the sampling holes. This should raise your flow rate etc back to the original time.

2.) Once you have bown air through the system and the transport time is still too long you can increase (through a programmer) the speed of the aspirator, which increases the suction of air into the VESDA unit and will compensate for the smaller sampling holes. If you do this we reccomend that you don't increase the aspiration speed to maximum becuase you should always try and leave yourself extra if possible.

3.) Failing the above measures you will have to see about manually cleaning the sample point holes by hand, so out comes the cherry picker. This said however in nearly all cases (unless the environment is extremely dirty) the first two stages will make the servicing of the system a doddle with out you having to get up into the roof and test each hole.

Hope that makes sense.

VESDA KEV
Xtralis Ltd
KShea@xtralis.com

[AnthonyB]

400,000 sq ft 8 bay warehouse, all open plan with no walls, multi use & tenant - paint spraying, shot blasting, steel fabrication, coach depot. 12.1m highest point in apexes

Could you use VESDA here as suggested above? And very roughly what would it cost?

The building needs a very prompt alarm to allow maximum evac time, but with minimal false alarm risk from processes undertaken.

(Don't mention walls or compartment sizes or sprinklers - I know, client clutching at straws to get away with an L1 system only, no alarm fitted at present)

[nearlythere]

If the area is open plan, and assuming there are sufficient exits why need a detection system in the first place? Is it for property protection? Is it not reasonably likely that, being open plan with high ceiling, any fire would be identified fairly quickly to allow quick evacuation? Is the risk such that a fire would develop so quickly that it could adversly effect an evacuation?

[kurnal]

Yes you could use vesda but clearly there are some activities going on that may mean that maintenance is a problem (spraying) and the fabrication side of things may mean that the sensitivity has to be ratcheted down that may defeat the objective.

I presume that you are looking at providing a system for life safety and possibly to justify extended travel distances, using the advantage of early detection to initiate a faster response to a fire? If so it may be worthwhile doing a little fire modelling first and approach it from an RSET / ASET point of view?

A similar large building we were looking at came out at an ASET of 16 minutes so extended travel distances were not a problem

[Davo]

Ripping out some of our VESDAs after less than three years, can't get parts to repair them (so says our nationally known contractor)
You have been warned

IMO agree with nearlythere, the fire would be identified quickly.
Why is the salesman slagging sprinklers???  If the brigade are some way away it may be the only thing to save you.

davo

davo

[afterburner]

We're removing aspirating systems due to very high maintenance / false alarm rates. (most of which are deliberately induced). The aspirating systems do what they say on the tin, but we have found they are too sensitive and too open to abuse in some locations. So we're replacing the system with point detectors.