Old Heat Detectors

[jakespop]

I have come across a number of old heat detctors in the maintenance buildings of a large hospital. These are metal, about the size of a stapler, and look similar.I seem to remember from my past that they operate on fusible link principle. They must be 50 years old. They are still connected to the general fire alarm system but never tested because test facilities are not available. Is there not a life span for these detectors similar to smoke?

[Galeon]

Yep , but the firm who made them wont be around to tell you so.
I think they worked open going closed , just hope all the resistors in place.

[AnthonyB]

If you are using old heats of that type how old is the fire alarm system!

Part of a hospital trust's site we assessed still had these as part of a non panel 240V Gents system that spread across 4 smallish buildings - rather than worry about testing we went for replacement.

I think at the very least new detectors are required if not a new system - is the area more suited to smokes (When installed heat will have been the most available type of detector whereas now smoke would often be used)

[Wiz]

I have come across a number of old heat detctors in the maintenance buildings of a large hospital. These are metal, about the size of a stapler, and look similar.I seem to remember from my past that they operate on fusible link principle. They must be 50 years old. They are still connected to the general fire alarm system but never tested because test facilities are not available. Is there not a life span for these detectors similar to smoke?

The bit about 'the size of a stapler' comment made me think of an old type of heat detector that used the bi-metal principle rather than a fusible link as suggested. The type I am thinking of released an 'arm' that dropped down when operated. The falling down of this arm caused a switch to operate which was used to signal the fire aalrm system. The 'arm' had to be manually pushed back into place to reset it. The 'arm' could only drop down when it curved from being otherwise straight when enough heat was detected. The arm would bend because it was made of two joined layers of metals each with different expansion rates. When one layer expanded more than the other the arm would bend and be released from the latch that was holding it up. The arm was hinged at the other end from the latch. Gravity would cause the arm to drop down. I think this heat detector was manufactured by GENT and they were certainly quite common when I first got into fire alarms over 30 years ago.

[jakespop]

I think you are quite correct Wiz. It is all coming back to me now. It seems then that the only way of testing these is to physically pull the arm down and push up to reset. I can still not find the bit in BS where it talks about replacing after so many years.

[Tom Sutton]

I can still not find the bit in BS where it talks about replacing after so many years.

The consensus of opinion in a previous thread said it’s not in the BS its the manufacturer who decides. Check out http://www.kingfell.com/~forum/index.php?topic=4587.0

The type of detector Wiz described May Otway rings a bell.

[Chris Houston]

Part of a hospital trust's site we assessed still had these as part of a non panel 240V Gents system that spread across 4 smallish buildings - rather than worry about testing we went for replacement.

Anthony, I know that you'll know this, but for the information of anyone else reading, signs and signals regulations apply to fire alarm systems too and require battery backup for safety signals, thus making most 240v systems illegal (not a breach of a standard,  but an actual breach of legislation).

[Wiz]

I can still not find the bit in BS where it talks about replacing after so many years.

The consensus of opinion in a previous thread said it’s not in the BS its the manufacturer who decides. Check out http://www.kingfell.com/~forum/index.php?topic=4587.0

The type of detector Wiz described May Otway rings a bell.

I agree with TW that BS does not provide specific recommended lifespans for any equipment other than 'manufacturer's advice should be followed.

I also believe;

If any equipment manufacturer's recommendations state a specific lifespan, it would surely be foolish to ignore it.

If no lifespan recommendations exist, then if it still operates at manufacturer's recommended service intervals it is still o.k to continue using it.

If no manufacturer's recommended service intervals exist, then BS recommended service intervals apply.

In saying all of the above, there must come a time when equipment being used for 'life safety' purposes reaches the end of its useful life even though it still seems to be working o.k. At the very least, it will have been superseded by newer and better technology. This is certainly the case with bi-metallic strip heat detectors. Their sensitivity to heat detection is far inferior to modern thermistor/electronic circuitry used in current heat detection devices.

I would say that the fire detection coverage provided by 30+ year old bi-metallic style heat detectors is way past the point of when they should have been replaced with more modern versions.

[Davo]

Gents

Article 10 Principles of Prevention


(d) adapt to technical progress



davo

[Allen Higginson]

I can still not find the bit in BS where it talks about replacing after so many years.

The consensus of opinion in a previous thread said it’s not in the BS its the manufacturer who decides. Check out http://www.kingfell.com/~forum/index.php?topic=4587.0

The type of detector Wiz described May Otway rings a bell.

Nowt wrong with the old principles Wiz - http://www.fenwalcontrols.com/utcfs/ws-375/Assets/12_01_9%20rev.pdf

I agree with TW that BS does not provide specific recommended lifespans for any equipment other than 'manufacturer's advice should be followed.

I also believe;

If any equipment manufacturer's recommendations state a specific lifespan, it would surely be foolish to ignore it.

If no lifespan recommendations exist, then if it still operates at manufacturer's recommended service intervals it is still o.k to continue using it.

If no manufacturer's recommended service intervals exist, then BS recommended service intervals apply.

In saying all of the above, there must come a time when equipment being used for 'life safety' purposes reaches the end of its useful life even though it still seems to be working o.k. At the very least, it will have been superseded by newer and better technology. This is certainly the case with bi-metallic strip heat detectors. Their sensitivity to heat detection is far inferior to modern thermistor/electronic circuitry used in current heat detection devices.

I would say that the fire detection coverage provided by 30+ year old bi-metallic style heat detectors is way past the point of when they should have been replaced with more modern versions.