metal ties

[Wiz]

As the old genteleman says, its nothing to do with firemen getting tangled in cables. We told the world about this donkeys years ago. Sadly, the world did not listen.

The truth will never supplant a good rumour.

What other 'old wives tales' do you enjoy?

I particularly enjoy the one about use of mobile phones causing fires in petrol filling stations.

[GregC]

The one about you going blind is also false in my vast and enjoyable experience 

[Big_Fella]

I think the BS recommendation on this point is clear and perfectly written. I don't think it needs to be elaborated.

A leading manufacturer of fire resistant cables explained to me that a certain amount of movement of a cable during a fire may affect it's continued fire resistance. Hence the need for the fire resistance of the support of a cable being at least equal to the fire resistance of the cable.

The affect of movement was explained to me as follows: If a fire resistant cable is subjected to enough heat, a chemical reaction occurs that causes the otherwise flexible fire resistant cable to become brittle whilst still maintaining it's fire resistant properties. However movement of the cable in it's brittle condition can cause the the brittle layer to crack open and allow flames access to the cable cores and destroy them quickly.

The need for correctly supporting a fire resistant cable is therefore of paramount importance.

However, It is up to each cable manufacturer to confirm at what intervals their particular cable needs to be supported to maintain fire resistance.

If the BS was to include a specific recommendation, say for example, every 600mm, and I invented a cable that only needed to be supported every 1000mm, I would be prevented from using this greater fixing distance intervals as a unique selling point for my cable because of BS!

Wiz, I'm quite interested in this, which manufacturer was this? Either message here or PM me?

Cheers

[Graeme]

As the old genteleman says, its nothing to do with firemen getting tangled in cables. We told the world about this donkeys years ago. Sadly, the world did not listen.

Colin

Your little book mentions that the code ammendment 2008 has drawn attention to the hazzard of falling cables to fire fighters after the death of two fire fighters who were entangled in fire alarm cables.

[Allen Higginson]

The falling fire cable thing has always been a red herring as it's generally the data or power cables etc. that are thrown in like spaghettil!

[Wiz]

I think the BS recommendation on this point is clear and perfectly written. I don't think it needs to be elaborated.

A leading manufacturer of fire resistant cables explained to me that a certain amount of movement of a cable during a fire may affect it's continued fire resistance. Hence the need for the fire resistance of the support of a cable being at least equal to the fire resistance of the cable.

The affect of movement was explained to me as follows: If a fire resistant cable is subjected to enough heat, a chemical reaction occurs that causes the otherwise flexible fire resistant cable to become brittle whilst still maintaining it's fire resistant properties. However movement of the cable in it's brittle condition can cause the the brittle layer to crack open and allow flames access to the cable cores and destroy them quickly.

The need for correctly supporting a fire resistant cable is therefore of paramount importance.

However, It is up to each cable manufacturer to confirm at what intervals their particular cable needs to be supported to maintain fire resistance.

If the BS was to include a specific recommendation, say for example, every 600mm, and I invented a cable that only needed to be supported every 1000mm, I would be prevented from using this greater fixing distance intervals as a unique selling point for my cable because of BS!

Wiz, I'm quite interested in this, which manufacturer was this? Either message here or PM me?

Cheers

BigFella, If we are talking about how the cable becomes brittle with high heat etc., this was someone from Pirelli and it was about 12 years ago.

Further interesting comments about flexible fire resistant cable (for the fire alarm industry) that I was personally told about (a different manufacturer this time) was that the instructions for use of their original version of their fire resisting cable did not make it clear that the fire resistance was only valid when the cable was affixed to a wall or metal tray of substantial construction that could absorb some of the heat being applied to a cable. i.e a cable installed with nothing adjacent to it, to absorb the heat, wouldn't last the 30 minutes required. Evidently, when it was realised that cables were often being installed not against a wall or metal tray they hurriedly had to find a solution and developed an 'improved' version of the cable - but they never widely broadcast the reason why they needed to do this.

[Wiz]

The one about you going blind is also false in my vast and enjoyable experience 

I originally heard it was meant to stunt your growth.

But, obviously this is wrong otherwise they wouldn't keep the porn mags on the top shelf 

[colin todd]

Graeme,  So long as the cable does not fall, it will not be a hazrad to fire-fighters. That IS another reason not to use plastic.  However, the trend of mixing plastic and metal will be fine for that. However, it may not be fine for circuit integrity.

[David Rooney]

So isn't  it down to our wonderful risk assessment then.... if the cable has done its job and raised the alarm in a single stage system ... why does it need to maintain any further integrity??

And does this then mean that even "enhanced" cable is no better than standard if it isn't clipped properly??

[Big_Fella]

So isn't  it down to our wonderful risk assessment then.... if the cable has done its job and raised the alarm in a single stage system ... why does it need to maintain any further integrity??

And does this then mean that even "enhanced" cable is no better than standard if it isn't clipped properly??

Good questions, somethings I have'nt thought about

[GregC]

... if the cable has done its job and raised the alarm in a single stage system ... why does it need to maintain any further integrity??

Because it has to continue to operate for a further 30 minutes ?

ie sounders, or in addressable systems, the fire could be spreading further.

[Wiz]

.........And does this then mean that even "enhanced" cable is no better than standard if it isn't clipped properly??

I would suggest that either cable has the potential not to meet it's specified abilities if it is not installed strictly in accordance with the manufacturer's recommendations.

If the manufacturer's recommendations are to a higher standard than the BS (or any other) recommendation then the manufacturer's recommendation takes precedence.

[GregC]

.........And does this then mean that even "enhanced" cable is no better than standard if it isn't clipped properly??

I would suggest that either cable has the potential not to meet it's specified abilities if it is not installed strictly in accordance with the manufacturer's recommendations.

If the manufacturer's recommendations are to a higher standard than the BS (or any other) recommendation then the manufacturer's recommendation takes precedence.

Ahh, but Wiz, the manufacturers do not call for metal clips, they ask for support at prescribed distances, do they not?

[Goodsparks]

http://www.fpcables.co.uk/page.php/faqs

"Copper "P" clips or steel ties can also be used to install FP200®. Plastic or Aluminium clips should not be used as the sole means of support as these will burn during a fire. Reference numbers are shown in our brochure."

[nearlythere]

.........And does this then mean that even "enhanced" cable is no better than standard if it isn't clipped properly??

I would suggest that either cable has the potential not to meet it's specified abilities if it is not installed strictly in accordance with the manufacturer's recommendations.

If the manufacturer's recommendations are to a higher standard than the BS (or any other) recommendation then the manufacturer's recommendation takes precedence.

Ahh, but Wiz, the manufacturers do not call for metal clips, they ask for support at prescribed distances, do they not?

But plastic ones would not support Gregc.