HI All
The glassworking studio here is a 24ft x 12ft timber shed -
full of glass, cardboard packing boxes, and a couple of glassworking
kilns (operating temperature up to 800c).

As the glass-fusing process typically takes ten hours or so - I've been
in the habit of running the kilns overnight...

Acquired a 'new' (2nd-hand) kiln during the week, and on the first
electronically-controlled firing it became clear that the temperature
sensing was faulty, and the kiln intended to fire, full-on, until
forever.....

Luckily I caught it in time - but was a bit surprised that the inbuilt
micro-controller didn't have a 'sanity check' - along the lines of 'I've
had the elements 'on' for the past hour and the temperature only seems
to have gone up by 20c - so maybe I'd better stop & flag an error!'

Anyway - suitably scared by the experience, what's the recommendation
for a smoke/fire alarm to be installed in the studio - to warn me when
things get a bit too hot....?

Other activities in the room include soldering (fumes), and it can get
'naturally' warm in there at times - so what type of alarm is best at
differentiating between normal activities and 's**T - it's on fire!'.

Thanks
Adrian

In article ,
Adrian Brentnall writes:
HI All
The glassworking studio here is a 24ft x 12ft timber shed -
full of glass, cardboard packing boxes, and a couple of glassworking
kilns (operating temperature up to 800c).

As the glass-fusing process typically takes ten hours or so - I've been
in the habit of running the kilns overnight...

Acquired a 'new' (2nd-hand) kiln during the week, and on the first
electronically-controlled firing it became clear that the temperature
sensing was faulty, and the kiln intended to fire, full-on, until
forever.....

Luckily I caught it in time - but was a bit surprised that the inbuilt
micro-controller didn't have a 'sanity check' - along the lines of 'I've
had the elements 'on' for the past hour and the temperature only seems
to have gone up by 20c - so maybe I'd better stop & flag an error!'

Anyway - suitably scared by the experience, what's the recommendation
for a smoke/fire alarm to be installed in the studio - to warn me when
things get a bit too hot....?

Other activities in the room include soldering (fumes), and it can get
'naturally' warm in there at times - so what type of alarm is best at
differentiating between normal activities and 's**T - it's on fire!'.

Seems like you need a smoke sensor/fire alarm which operates only when
you aren't in there. I could easily program the smokes on my burglar
alarm to work that way, but I don't know if there's a simpler solution.
Might also be nice to have them automatically cut the power (except
lighting). Such systems are used in computer rooms and doubtless other
industrial premises. The power cutting can have a delay so that someone
can acknowledge they're acting on the alarm and hold-off the automatic
cut, if cutting the power might have significant impact in the case of
a false alarm.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

On Oct 15, 3:22*pm, Adrian Brentnall wrote:
HI All
The glassworking studio here is a 24ft x 12ft timber shed -
full of glass, cardboard packing boxes, and a couple of glassworking
kilns (operating temperature up to 800c).

As the glass-fusing process typically takes ten hours or so - I've been
in the habit of running the kilns overnight...

Acquired a 'new' (2nd-hand) kiln during the week, and on the first
electronically-controlled firing it became clear that the temperature
sensing was faulty, and the kiln intended to fire, full-on, until
forever.....

Luckily I caught it in time - but was a bit surprised that the inbuilt
micro-controller didn't have a 'sanity check' - along the lines of 'I've
had the elements 'on' for the past hour and the temperature only seems
to have gone up by 20c - so maybe I'd better stop & flag an error!'

Anyway - suitably scared by the experience, what's the recommendation
for a smoke/fire alarm to be installed in the studio - to warn me when
things get a bit too hot....?

Other activities in the room include soldering (fumes), and it can get
'naturally' warm in there at times - so what type of alarm is best at
differentiating between normal activities and 's**T - it's on fire!'.

Thanks
Adrian

I would really expect a kiln to have a thermal fuse.

http://en.wikipedia.org/wiki/Thermal_fuse

Check some lunatic hasn't bridged it out.

On 15/10/2011 16:47, wrote:
On Oct 15, 3:22 pm, Adrian wrote:
HI All
The glassworking studio here is a 24ft x 12ft timber shed -
full of glass, cardboard packing boxes, and a couple of glassworking
kilns (operating temperature up to 800c).

As the glass-fusing process typically takes ten hours or so - I've been
in the habit of running the kilns overnight...

Acquired a 'new' (2nd-hand) kiln during the week, and on the first
electronically-controlled firing it became clear that the temperature
sensing was faulty, and the kiln intended to fire, full-on, until
forever.....

Luckily I caught it in time - but was a bit surprised that the inbuilt
micro-controller didn't have a 'sanity check' - along the lines of 'I've
had the elements 'on' for the past hour and the temperature only seems
to have gone up by 20c - so maybe I'd better stop& flag an error!'

Anyway - suitably scared by the experience, what's the recommendation
for a smoke/fire alarm to be installed in the studio - to warn me when
things get a bit too hot....?

Other activities in the room include soldering (fumes), and it can get
'naturally' warm in there at times - so what type of alarm is best at
differentiating between normal activities and 's**T - it's on fire!'.

Thanks
Adrian

I would really expect a kiln to have a thermal fuse.

http://en.wikipedia.org/wiki/Thermal_fuse

Check some lunatic hasn't bridged it out.

g - according to the manual

http://www.skutt.com/pdf/HotStart/Ho...anual_08-1.pdf

- next to last page....

the only input to the controller is the thermocouple. No thermal fuse
(it's a bit different to a kettle or a washing machine

The connections at the top of the diagram (as in 's', 'op' etc), are
connections into the microcontroller board. There's an output to the
safety relay from the controller board, but it's not clear what the
logic is that drives that output.

I'm probably expecting too much - but when I worked in process control
there was an emaphasis on fail-safe, and checking for 'potential fault'
conditions (like 'we've had the mains on this element for the last hour
and the temp's only gone up by 20c')....

On Sat, 15 Oct 2011 15:22:38 +0100, Adrian Brentnall
wrote:


Anyway - suitably scared by the experience, what's the recommendation
for a smoke/fire alarm to be installed in the studio - to warn me when
things get a bit too hot....?

Other activities in the room include soldering (fumes), and it can get
'naturally' warm in there at times - so what type of alarm is best at
differentiating between normal activities and 's**T - it's on fire!'.

Ionisation and optical sensors are probably of little use as I suspect
the kiln can give off sufficient fumes (not a lot are needed) to
trigger them both during overnight firing.

The usual solution where hot equipment is involved (big commercial
deep fat friers for example) would be to string a wire along the shed
roof with fusible links in the wire

http://fusible-links.co.uk/fireprotection.v2.html

above likely problem areas such as the kiln. The wire is spring
tensioned with a standing load of 10 - 40lbs so when the link breaks
they open a water valve to an overhead sprinkler system or similar.
Their great advantage is they don't depend on electricity so if the
kiln malfunction trips the workshop power the fire protection still
works.

On 15/10/2011 17:46, Peter Parry wrote:
On Sat, 15 Oct 2011 15:22:38 +0100, Adrian Brentnall
wrote:


Anyway - suitably scared by the experience, what's the recommendation
for a smoke/fire alarm to be installed in the studio - to warn me when
things get a bit too hot....?

Other activities in the room include soldering (fumes), and it can get
'naturally' warm in there at times - so what type of alarm is best at
differentiating between normal activities and 's**T - it's on fire!'.

Ionisation and optical sensors are probably of little use as I suspect
the kiln can give off sufficient fumes (not a lot are needed) to
trigger them both during overnight firing.

The usual solution where hot equipment is involved (big commercial
deep fat friers for example) would be to string a wire along the shed
roof with fusible links in the wire

http://fusible-links.co.uk/fireprotection.v2.html

above likely problem areas such as the kiln. The wire is spring
tensioned with a standing load of 10 - 40lbs so when the link breaks
they open a water valve to an overhead sprinkler system or similar.
Their great advantage is they don't depend on electricity so if the
kiln malfunction trips the workshop power the fire protection still
works.


I suppose that's a solution - certainly fits the 'fail-safe' criterion...

Not a lot of fumes from this process - but point taken about the
sensitivity of conventional sensors...

Starting to wonder if an alternative solution would be another layer of
electronics control - simulating a thermal fuse and killing (& latching
off) the power to the kiln in the event of over-temperature...

'Twould mean drilling an extra hole in the kiln for the additional
thermocouple - and a box with transformer / contactor / some electronics
installed between the kiln and the wall-socket.

The controller checks for thermocouple o/c, and reversed, but not
(apparently) for 'illogical' conditions....

Again, probably overkill, but the process control gear I worked on had
electromechanical 'watchdog' circuitry in case the uP went awol....

....I'm sorely tempted to reverse-engineer the controller & do it right! g

Adrian

On Oct 15, 6:00*pm, Adrian Brentnall wrote:
On 15/10/2011 17:46, Peter Parry wrote:



On Sat, 15 Oct 2011 15:22:38 +0100, Adrian Brentnall
*wrote:

Anyway - suitably scared by the experience, what's the recommendation
for a smoke/fire alarm to be installed in the studio - to warn me when
things get a bit too hot....?

Other activities in the room include soldering (fumes), and it can get
'naturally' warm in there at times - so what type of alarm is best at
differentiating between normal activities and 's**T - it's on fire!'.

Ionisation and optical sensors are probably of little use as I suspect
the kiln can give off sufficient fumes (not a lot are needed) *to
trigger them both *during overnight firing.

The usual solution where hot equipment is involved (big commercial
deep fat friers for example) would be to string a wire along the shed
roof with fusible links in the wire

*http://fusible-links.co.uk/fireprotection.v2.html

above likely problem areas such as the kiln. *The wire is spring
tensioned with a standing load of 10 - 40lbs so when the link breaks
they open a water valve to an overhead sprinkler system or similar.
Their great advantage is they don't depend on electricity so if the
kiln malfunction trips the workshop power the fire protection still
works.

I suppose that's a solution - certainly fits the 'fail-safe' criterion...

Not a lot of fumes from this process - but point taken about the
sensitivity of conventional sensors...

Starting to wonder if an alternative solution would be another layer of
electronics control - simulating a thermal fuse and killing (& latching
off) the power to the kiln in the event of over-temperature...

'Twould mean drilling an extra hole in the kiln for the additional
thermocouple - and a box with transformer / contactor / some electronics
installed between the kiln and the wall-socket.

The controller checks for thermocouple o/c, and reversed, but not
(apparently) for 'illogical' conditions....

Again, probably overkill, but the process control gear I worked on had
electromechanical 'watchdog' circuitry in case the uP went awol....

...I'm sorely tempted to reverse-engineer the controller & do it right! g

Adrian


I suspect you could do it very simply by nothing more than hanging up
a £3 battery ionisation alarm. I'd expect you're only gonig to get
bother from it if you have quite a lot of combustible junk get into
the kiln, which shoudlnt ever happen. I'm no expert on kilns though.


NT

Peter Parry wrote:

The wire is spring
tensioned with a standing load of 10 - 40lbs so when the link breaks
they open a water valve to an overhead sprinkler system or similar.
Their great advantage is they don't depend on electricity so if the
kiln malfunction trips the workshop power the fire protection still
works.

We had a dry powder or aff ( memory fade) extinguisher in the forwarder with
a plastic hose running around the engine compartment. The idea was that the
hose ruptured at the hottest point and the chemical emptied through the
hole.

AJH

On Oct 15, 3:22*pm, Adrian Brentnall wrote:

Anyway - suitably scared by the experience, what's the recommendation
for a smoke/fire alarm to be installed in the studio - to warn me when
things get a bit too hot....?

Arduino, and learn to program it

(Or wait for me to finish mine)

On 15/10/2011 19:54, Andy Dingley wrote:
On Oct 15, 3:22 pm, Adrian wrote:

Anyway - suitably scared by the experience, what's the recommendation
for a smoke/fire alarm to be installed in the studio - to warn me when
things get a bit too hot....?

Arduino, and learn to program it

(Or wait for me to finish mine)

g
I've got a Pic-Axe development board somewhere about the place -
seems there's a stand-alone chip (or maybe two) that translates from
thermocouple-to-analog.....

Having got that far - there's a great temptation to turn it all into a
controller g

Adrian

On 15/10/2011 18:29, NT wrote:
On Oct 15, 6:00 pm, Adrian wrote:
On 15/10/2011 17:46, Peter Parry wrote:



On Sat, 15 Oct 2011 15:22:38 +0100, Adrian Brentnall
wrote:

Anyway - suitably scared by the experience, what's the recommendation
for a smoke/fire alarm to be installed in the studio - to warn me when
things get a bit too hot....?

Other activities in the room include soldering (fumes), and it can get
'naturally' warm in there at times - so what type of alarm is best at
differentiating between normal activities and 's**T - it's on fire!'.

Ionisation and optical sensors are probably of little use as I suspect
the kiln can give off sufficient fumes (not a lot are needed) to
trigger them both during overnight firing.

The usual solution where hot equipment is involved (big commercial
deep fat friers for example) would be to string a wire along the shed
roof with fusible links in the wire

http://fusible-links.co.uk/fireprotection.v2.html

above likely problem areas such as the kiln. The wire is spring
tensioned with a standing load of 10 - 40lbs so when the link breaks
they open a water valve to an overhead sprinkler system or similar.
Their great advantage is they don't depend on electricity so if the
kiln malfunction trips the workshop power the fire protection still
works.

I suppose that's a solution - certainly fits the 'fail-safe' criterion...

Not a lot of fumes from this process - but point taken about the
sensitivity of conventional sensors...

Starting to wonder if an alternative solution would be another layer of
electronics control - simulating a thermal fuse and killing (& latching
off) the power to the kiln in the event of over-temperature...

'Twould mean drilling an extra hole in the kiln for the additional
thermocouple - and a box with transformer / contactor / some electronics
installed between the kiln and the wall-socket.

The controller checks for thermocouple o/c, and reversed, but not
(apparently) for 'illogical' conditions....

Again, probably overkill, but the process control gear I worked on had
electromechanical 'watchdog' circuitry in case the uP went awol....

...I'm sorely tempted to reverse-engineer the controller& do it right!g

Adrian


I suspect you could do it very simply by nothing more than hanging up
a £3 battery ionisation alarm. I'd expect you're only gonig to get
bother from it if you have quite a lot of combustible junk get into
the kiln, which shoudlnt ever happen. I'm no expert on kilns though.


NT

I _think_ I'd want it to link into the house alarms.....
(but I can see ructions if 'something in the kiln' sets the house
noisemakers off at 2am!)

Generally, there's not a lot in the way of fumes - I tend to fire on
some stuff called Kiln Paper, which produces a slight smell as it fires
- but I guess the answer is to try it & see....

Thanks
Adrian

On 15/10/2011 16:47, wrote:
On Oct 15, 3:22 pm, Adrian wrote:
HI All
The glassworking studio here is a 24ft x 12ft timber shed -
full of glass, cardboard packing boxes, and a couple of glassworking
kilns (operating temperature up to 800c).

As the glass-fusing process typically takes ten hours or so - I've been
in the habit of running the kilns overnight...

Acquired a 'new' (2nd-hand) kiln during the week, and on the first
electronically-controlled firing it became clear that the temperature
sensing was faulty, and the kiln intended to fire, full-on, until
forever.....

Luckily I caught it in time - but was a bit surprised that the inbuilt
micro-controller didn't have a 'sanity check' - along the lines of 'I've
had the elements 'on' for the past hour and the temperature only seems
to have gone up by 20c - so maybe I'd better stop& flag an error!'

Anyway - suitably scared by the experience, what's the recommendation
for a smoke/fire alarm to be installed in the studio - to warn me when
things get a bit too hot....?

Other activities in the room include soldering (fumes), and it can get
'naturally' warm in there at times - so what type of alarm is best at
differentiating between normal activities and 's**T - it's on fire!'.

Thanks
Adrian

I would really expect a kiln to have a thermal fuse.

http://en.wikipedia.org/wiki/Thermal_fuse

Check some lunatic hasn't bridged it out.

g - according to the manual

http://www.skutt.com/pdf/HotStart/Ho...anual_08-1.pdf

- next to last page....

the only input to the controller is the thermocouple. No thermal fuse
(it's a bit different to a kettle or a washing machine - the 'switch'
temperature would need to be somewhere around 900c....)

The connections at the top of the diagram (as in 's', 'op' etc), are
connections into the microcontroller board. There's an output to the
safety relay from the controller board, but it's not clear what the
logic is that drives that output.

I'm probably expecting too much - but when I worked in process control
there was an emaphasis on fail-safe, and checking for 'potential fault'
conditions (like 'we've had the mains on this element for the last hour
and the temp's only gone up by 20c')....

On Sat, 15 Oct 2011 15:22:38 +0100, Adrian Brentnall wrote:

Luckily I caught it in time - but was a bit surprised that the inbuilt
micro-controller didn't have a 'sanity check' - along the lines of 'I've
had the elements 'on' for the past hour and the temperature only seems
to have gone up by 20c - so maybe I'd better stop & flag an error!'

Does seem a bit odd that something with a micro-controller doesn't
have a watch dog.

Anyway - suitably scared by the experience, what's the recommendation
for a smoke/fire alarm to be installed in the studio - to warn me when
things get a bit too hot....?

I think a fixed temperature alarm, mounted where it isn't going to
get a blast of hot air when you open one of the kilns... They trigger
when the "ambient temperature" gets into the high 50's C. I don't
know how long the temperature has to be above the trigger point
before they trigger. This sort of alarm is the type that building
regs now require in some kitchens. An oven is a low temperature kiln
so one assumes that these fixed temp alarms can cope with the blast
of hot air from an oven at 250C being opened. OK 800C is considerably
higher but do you open them when that hot?

--
Cheers
Dave.

On Sat, 15 Oct 2011 18:00:03 +0100, Adrian Brentnall
wrote:


Starting to wonder if an alternative solution would be another layer of
electronics control - simulating a thermal fuse and killing (& latching
off) the power to the kiln in the event of over-temperature...

Well if you want the high tech solution get a computer and webcam,
remove the webcam IR filter and run the free ISpy software which
includes a flame sense motion detection option :-)

On Oct 15, 8:53*pm, Adrian Brentnall wrote:
seems there's a stand-alone chip (or maybe two) that translates from
thermocouple-to-analog.....

Dead easy for kilns, as you don't care about cold junction
compensation.

On Oct 15, 8:56*pm, Adrian Brentnall wrote:

I _think_ I'd want it to link into the house alarms.....

House alarms are for other people, outside the house. For this, you
probably want something independent, with a (smaller) sounder inside
the house. Control panels are cheap, but then so are Arduineaux.

On Oct 15, 11:09*pm, Peter Parry wrote:

Well if you want the high tech solution get a computer and webcam,
remove the webcam IR filter and run the free ISpy software which
includes a flame sense motion detection option :-)


Doesn't work though if your ignition source is an IR laser. I'm
trying to emulate the Violet Fire system from Concorde, and I'm
looking in the UV.

On 15/10/2011 22:03, Dave Liquorice wrote:
On Sat, 15 Oct 2011 15:22:38 +0100, Adrian Brentnall wrote:

Luckily I caught it in time - but was a bit surprised that the inbuilt
micro-controller didn't have a 'sanity check' - along the lines of 'I've
had the elements 'on' for the past hour and the temperature only seems
to have gone up by 20c - so maybe I'd better stop& flag an error!'

Does seem a bit odd that something with a micro-controller doesn't
have a watch dog.

There may be some kind of inbuilt safety-circuit - there's something on
the controller board that lives-up the 'safety relay' - but I don't know
what the logic is behind it..
Not a watchdog in the 'uP's out to lunch - better stop everything' sense...



Anyway - suitably scared by the experience, what's the recommendation
for a smoke/fire alarm to be installed in the studio - to warn me when
things get a bit too hot....?

I think a fixed temperature alarm, mounted where it isn't going to
get a blast of hot air when you open one of the kilns... They trigger
when the "ambient temperature" gets into the high 50's C. I don't
know how long the temperature has to be above the trigger point
before they trigger. This sort of alarm is the type that building
regs now require in some kitchens. An oven is a low temperature kiln
so one assumes that these fixed temp alarms can cope with the blast
of hot air from an oven at 250C being opened. OK 800C is considerably
higher but do you open them when that hot?


Sounds like a plan. It gets hot in there in the summer - but 'hot' as in
35c. Sometime open the kiln when it's live, but not for long, and only
to have a quick peek at how it's going...

I guess it depends on what I'm trying to achieve.... whether I want to
know that everything's operating correctly, or that the shed is in
danger of catching fire imminently....
I think I'd prefer the first option, with a built-in 'power-kill' relay,
if things seemed to be going out of spec.

Having said that, I shall install a new controller board and it'll never
fail again, ever ...... g

Adrian

On 15/10/2011 23:09, Peter Parry wrote:
On Sat, 15 Oct 2011 18:00:03 +0100, Adrian Brentnall
wrote:


Starting to wonder if an alternative solution would be another layer of
electronics control - simulating a thermal fuse and killing (& latching
off) the power to the kiln in the event of over-temperature...

Well if you want the high tech solution get a computer and webcam,
remove the webcam IR filter and run the free ISpy software which
includes a flame sense motion detection option :-)


May be a bit too 'hi tech' - more stuff to go wrong at the critical
moment.....? Though I do have a spare webcam.....

Thinking about it - the most likely failure mode (if the kiln locked
'on') would be for the elements to burn out. I 'think' the fairly
massive firebrick chamber would likely contain the heat, without getting
hot enough to set fire to anything around it....

The Kiln Manual says

------------quote----
ERROR MESSAGES
The following errors messages may appear in the display of your
controller.
Err 1
Error 1 occurs during a �ring segment programmed to increase the
temperature. When the kiln is maintaining the
�
requires that the kiln maintain a minimum rise of 12°F (4.8°C) per hour.
This usually indicates that the elements or the relay have failed. The
kiln will shut off.
Err F
Error F occurs during a �ring segment programmed to decrease the
temperature. When the kiln is maintaining the
�
requires that the kiln maintain a minimum fall of 12°F (4.8°C) per hour.
This usually indicates that a relay has failed and needs to be replaced.
The kiln will shut off.
Err D
Error D occurs during a �ring segment programmed to increase the
temperature. If the kiln temperature is 100°F
(38°C) or greater above the set point for 15 seconds then the controller
registers an error d situation.
This usually indicates that a relay has failed and needs to be replaced.
The kiln will shut off.
FAIL
This indicates that the thermocouple has failed and needs to be
replaced. The kiln will shut off.
tc--
This indicates that the thermocouple has been installed backwards. The
thermocouple needs to be removed and reinstalled into the thermocouple
block with the red wire inserted in the hole stamped €œ-€�.

-------unquote---


So I'd imagine that Err1 might/should have caught this particular fault.
Something was badly wrong with the temperature sensing. The thermocouple
is good because I've swapped that to the other kiln, and it's working
fine. Wiring to the thermocouple checks out OK.
At process temperature (c. 760c) the temperature display was indicating
46c, at ambient it was showing 23c - so something wasn't right. The kiln
was firing continually, waiting for the indicated temperature to reach
760c....

The fault's now changed, and the controller is showing 'Fail' -
indicating that it can't 'see' the thermocouple.

It would be useful to have the extra capacity of the new (faulty) kiln,
so today I shall swap the controllers between the kilns and see if that
makes the fault one work. If it does then I shall return the duff
controller for replacement under guarantee, and ask the manufacturer a
few pointed questions about kiln safety systems!

Adrian

On 15/10/2011 23:32, Andy Dingley wrote:
On Oct 15, 8:53 pm, Adrian wrote:
seems there's a stand-alone chip (or maybe two) that translates from
thermocouple-to-analog.....

Dead easy for kilns, as you don't care about cold junction
compensation.

I think the chips I was seeing on Google (Max6675) do all of that for
you....?

Adrian

On 15/10/2011 23:40, Andy Dingley wrote:
On Oct 15, 8:56 pm, Adrian wrote:

I _think_ I'd want it to link into the house alarms.....

House alarms are for other people, outside the house. For this, you
probably want something independent, with a (smaller) sounder inside
the house. Control panels are cheap, but then so are Arduineaux.

Sorry - my bad terminology.
'House alarm' = set of existing linked fire alarms fitted inside the
house....
No point in 'outside' alarms here - nobody but the chickens to hear 'em g

On Oct 15, 8:56*pm, Adrian Brentnall wrote:
On 15/10/2011 18:29, NT wrote:



On Oct 15, 6:00 pm, Adrian *wrote:
On 15/10/2011 17:46, Peter Parry wrote:

On Sat, 15 Oct 2011 15:22:38 +0100, Adrian Brentnall
* *wrote:

Anyway - suitably scared by the experience, what's the recommendation
for a smoke/fire alarm to be installed in the studio - to warn me when
things get a bit too hot....?

Other activities in the room include soldering (fumes), and it can get
'naturally' warm in there at times - so what type of alarm is best at
differentiating between normal activities and 's**T - it's on fire!'..

Ionisation and optical sensors are probably of little use as I suspect
the kiln can give off sufficient fumes (not a lot are needed) *to
trigger them both *during overnight firing.

The usual solution where hot equipment is involved (big commercial
deep fat friers for example) would be to string a wire along the shed
roof with fusible links in the wire

*http://fusible-links.co.uk/fireprotection.v2.html

above likely problem areas such as the kiln. *The wire is spring
tensioned with a standing load of 10 - 40lbs so when the link breaks
they open a water valve to an overhead sprinkler system or similar.
Their great advantage is they don't depend on electricity so if the
kiln malfunction trips the workshop power the fire protection still
works.

I suppose that's a solution - certainly fits the 'fail-safe' criterion....

Not a lot of fumes from this process - but point taken about the
sensitivity of conventional sensors...

Starting to wonder if an alternative solution would be another layer of
electronics control - simulating a thermal fuse and killing (& *latching
off) the power to the kiln in the event of over-temperature...

'Twould mean drilling an extra hole in the kiln for the additional
thermocouple - and a box with transformer / contactor / some electronics
installed between the kiln and the wall-socket.

The controller checks for thermocouple o/c, and reversed, but not
(apparently) for 'illogical' conditions....

Again, probably overkill, but the process control gear I worked on had
electromechanical 'watchdog' circuitry in case the uP went awol....

...I'm sorely tempted to reverse-engineer the controller& *do it right!g

Adrian

I suspect you could do it very simply by nothing more than hanging up
a £3 battery ionisation alarm. I'd expect you're only gonig to get
bother from it if you have quite a lot of combustible junk get into
the kiln, which shoudlnt ever happen. I'm no expert on kilns though.

NT

I _think_ I'd want it to link into the house alarms.....
(but I can see ructions if 'something in the kiln' sets the house
noisemakers off at 2am!)

Generally, there's not a lot in the way of fumes - I tend to fire on
some stuff called Kiln Paper, which produces a slight smell as it fires
- but I guess the answer is to try it & see....

Thanks
Adrian

The point is it only costs £3 to try an ionisation type, and it may
prove ok. If it does, you can then get one that wires to the house.


NT

On Sun, 16 Oct 2011 07:52:34 +0100, Adrian Brentnall
wrote:

If it does then I shall return the duff
controller for replacement under guarantee, and ask the manufacturer a
few pointed questions about kiln safety systems!

The safety system may well be the simplest and most reliable of all,
the kiln will withstand the elements at full power indefinitely or
until the heater element itself or some other component overheats in a
predicted way and fails.

On Oct 16, 11:22*am, Owain wrote:

If the kiln alarm goes off, you stop to put your trousers on.

Depends on the kiln.

These kilns don't catch fire, because they're made of steel, firebrick
and FIRE already. So their "fault conditions" are probably just that
the temperature is outside prediction (a temperature of zero is
especially bad, because it means the thermocouple broke) and the
appropriate reaction is to just to cut the power and sound a "job
trashed, building OK" alarm.

If the kiln actually has a "fire", more than it does normally, then
you may not have time for the trousers.


I've got a similar problem with laser cutters. A machine that works by
burning material away will tend to make a smoky exhaust. So how do I
tell the difference between "It's working" and "It has set fire to the
whole sheet" ? It's certainly ill-advised at present to leave lasers
cutting on their own without anyone in attendance - several workers
who've done this have lost £10k+ machines from the resultant fires,
and not dealing with the trivial fire quickly enough.

On Oct 16, 9:02*am, Peter Parry wrote:

The safety system may well be the simplest and most reliable of all,
the kiln will withstand the elements at full power indefinitely or
until the heater element itself or some other component overheats in a
predicted way and fails.

For a Skutt Firebox it's an evens bet between element failure, or the
element overheating the bricks and cracking them. They're an unusually
powerful element for the size of kiln.

Andy Dingley wrote:
On Oct 16, 11:22 am, Owain wrote:

If the kiln alarm goes off, you stop to put your trousers on.

Depends on the kiln.

These kilns don't catch fire, because they're made of steel, firebrick
and FIRE already. So their "fault conditions" are probably just that
the temperature is outside prediction (a temperature of zero is
especially bad, because it means the thermocouple broke) and the
appropriate reaction is to just to cut the power and sound a "job
trashed, building OK" alarm.

If the kiln actually has a "fire", more than it does normally, then
you may not have time for the trousers.


I've got a similar problem with laser cutters. A machine that works by
burning material away will tend to make a smoky exhaust. So how do I
tell the difference between "It's working" and "It has set fire to the
whole sheet" ? It's certainly ill-advised at present to leave lasers
cutting on their own without anyone in attendance - several workers
who've done this have lost £10k+ machines from the resultant fires,
and not dealing with the trivial fire quickly enough.

They should have proper smoke extraction as smoke is bad for the laser
beam and bad for the optics.

On 16/10/2011 12:14, Andy Dingley wrote:
On Oct 16, 11:22 am, wrote:

If the kiln alarm goes off, you stop to put your trousers on.

Depends on the kiln.

These kilns don't catch fire, because they're made of steel, firebrick
and FIRE already. So their "fault conditions" are probably just that
the temperature is outside prediction (a temperature of zero is
especially bad, because it means the thermocouple broke) and the
appropriate reaction is to just to cut the power and sound a "job
trashed, building OK" alarm.

Ah - but it didn't g - wouldn't have minded if it had...
The controller's _now_ decided that it can't see the thermocouple
(even when the thermocouple's replaced by a wire 'short' at the
controller terminals - so it looks like it's a 'late controller'...

Still need to swap the controllers, but I suspect that the old
controller in the new kiln will work fine....

Thanks for all the perspectives
A

On 16/10/2011 13:18, Owain wrote:
On Oct 16, 12:14 pm, Andy Dingley wrote:
If the kiln alarm goes off, you stop to put your trousers on.
Depends on the kiln.
If the kiln actually has a "fire", more than it does normally, then
you may not have time for the trousers.

AIUI the kiln is in a timber shed and my assumption was that it was
detached from the house by sufficient distance to give time to put on
trousers before investigating.

It's about 8 feet away from the house back door...
would really rather it didn't catch fire! g

A

On 16/10/2011 08:50, NT wrote:
On Oct 15, 8:56 pm, Adrian wrote:
On 15/10/2011 18:29, NT wrote:



On Oct 15, 6:00 pm, Adrian wrote:
On 15/10/2011 17:46, Peter Parry wrote:

On Sat, 15 Oct 2011 15:22:38 +0100, Adrian Brentnall
wrote:

Anyway - suitably scared by the experience, what's the recommendation
for a smoke/fire alarm to be installed in the studio - to warn me when
things get a bit too hot....?

Other activities in the room include soldering (fumes), and it can get
'naturally' warm in there at times - so what type of alarm is best at
differentiating between normal activities and 's**T - it's on fire!'.

Ionisation and optical sensors are probably of little use as I suspect
the kiln can give off sufficient fumes (not a lot are needed) to
trigger them both during overnight firing.

The usual solution where hot equipment is involved (big commercial
deep fat friers for example) would be to string a wire along the shed
roof with fusible links in the wire

http://fusible-links.co.uk/fireprotection.v2.html

above likely problem areas such as the kiln. The wire is spring
tensioned with a standing load of 10 - 40lbs so when the link breaks
they open a water valve to an overhead sprinkler system or similar.
Their great advantage is they don't depend on electricity so if the
kiln malfunction trips the workshop power the fire protection still
works.

I suppose that's a solution - certainly fits the 'fail-safe' criterion...

Not a lot of fumes from this process - but point taken about the
sensitivity of conventional sensors...

Starting to wonder if an alternative solution would be another layer of
electronics control - simulating a thermal fuse and killing (& latching
off) the power to the kiln in the event of over-temperature...

'Twould mean drilling an extra hole in the kiln for the additional
thermocouple - and a box with transformer / contactor / some electronics
installed between the kiln and the wall-socket.

The controller checks for thermocouple o/c, and reversed, but not
(apparently) for 'illogical' conditions....

Again, probably overkill, but the process control gear I worked on had
electromechanical 'watchdog' circuitry in case the uP went awol....

...I'm sorely tempted to reverse-engineer the controller& do it right!g

Adrian

I suspect you could do it very simply by nothing more than hanging up
a £3 battery ionisation alarm. I'd expect you're only gonig to get
bother from it if you have quite a lot of combustible junk get into
the kiln, which shoudlnt ever happen. I'm no expert on kilns though.

NT

I _think_ I'd want it to link into the house alarms.....
(but I can see ructions if 'something in the kiln' sets the house
noisemakers off at 2am!)

Generally, there's not a lot in the way of fumes - I tend to fire on
some stuff called Kiln Paper, which produces a slight smell as it fires
- but I guess the answer is to try it& see....

Thanks
Adrian

The point is it only costs £3 to try an ionisation type, and it may
prove ok. If it does, you can then get one that wires to the house.


NT

Yes - good point.
Of course, I'll never know if it really works unless the the kiln
controller fails again and the shed burns down g...
...but it would prove that the cheapie detector isn't tripped by solder
smoke / flux fumes etc!

Thanks
Adrian

On Oct 16, 2:06*pm, Adrian Brentnall wrote:
On 16/10/2011 08:50, NT wrote:



On Oct 15, 8:56 pm, Adrian *wrote:
On 15/10/2011 18:29, NT wrote:

On Oct 15, 6:00 pm, Adrian * *wrote:
On 15/10/2011 17:46, Peter Parry wrote:

On Sat, 15 Oct 2011 15:22:38 +0100, Adrian Brentnall
* * *wrote:

Anyway - suitably scared by the experience, what's the recommendation
for a smoke/fire alarm to be installed in the studio - to warn me when
things get a bit too hot....?

Other activities in the room include soldering (fumes), and it can get
'naturally' warm in there at times - so what type of alarm is best at
differentiating between normal activities and 's**T - it's on fire!'.

Ionisation and optical sensors are probably of little use as I suspect
the kiln can give off sufficient fumes (not a lot are needed) *to
trigger them both *during overnight firing.

The usual solution where hot equipment is involved (big commercial
deep fat friers for example) would be to string a wire along the shed
roof with fusible links in the wire

*http://fusible-links.co.uk/fireprotection.v2.html

above likely problem areas such as the kiln. *The wire is spring
tensioned with a standing load of 10 - 40lbs so when the link breaks
they open a water valve to an overhead sprinkler system or similar.
Their great advantage is they don't depend on electricity so if the
kiln malfunction trips the workshop power the fire protection still
works.

I suppose that's a solution - certainly fits the 'fail-safe' criterion...

Not a lot of fumes from this process - but point taken about the
sensitivity of conventional sensors...

Starting to wonder if an alternative solution would be another layer of
electronics control - simulating a thermal fuse and killing (& * *latching
off) the power to the kiln in the event of over-temperature...

'Twould mean drilling an extra hole in the kiln for the additional
thermocouple - and a box with transformer / contactor / some electronics
installed between the kiln and the wall-socket.

The controller checks for thermocouple o/c, and reversed, but not
(apparently) for 'illogical' conditions....

Again, probably overkill, but the process control gear I worked on had
electromechanical 'watchdog' circuitry in case the uP went awol....

...I'm sorely tempted to reverse-engineer the controller& * *do it right!g

Adrian

I suspect you could do it very simply by nothing more than hanging up
a £3 battery ionisation alarm. I'd expect you're only gonig to get
bother from it if you have quite a lot of combustible junk get into
the kiln, which shoudlnt ever happen. I'm no expert on kilns though.

NT

I _think_ I'd want it to link into the house alarms.....
(but I can see ructions if 'something in the kiln' sets the house
noisemakers off at 2am!)

Generally, there's not a lot in the way of fumes - I tend to fire on
some stuff called Kiln Paper, which produces a slight smell as it fires
- but I guess the answer is to try it& *see....

Thanks
Adrian

The point is it only costs £3 to try an ionisation type, and it may
prove ok. If it does, you can then get one that wires to the house.

NT

Yes - good point.
Of course, I'll never know if it really works unless the the kiln
controller fails again and the shed burns down g...
..but it would prove that the cheapie detector isn't tripped by solder
smoke / flux fumes etc!

Thanks
Adrian

Cheap ionisation detectors are very sensitive. All you need establish
is that it doesnt false trigger. If it does, try an optical one for
less sensitivity.


NT

On 16/10/2011 20:01, NT wrote:
On Oct 16, 2:06 pm, Adrian wrote:
On 16/10/2011 08:50, NT wrote:



On Oct 15, 8:56 pm, Adrian wrote:
On 15/10/2011 18:29, NT wrote:

On Oct 15, 6:00 pm, Adrian wrote:
On 15/10/2011 17:46, Peter Parry wrote:

On Sat, 15 Oct 2011 15:22:38 +0100, Adrian Brentnall
wrote:

Anyway - suitably scared by the experience, what's the recommendation
for a smoke/fire alarm to be installed in the studio - to warn me when
things get a bit too hot....?

Other activities in the room include soldering (fumes), and it can get
'naturally' warm in there at times - so what type of alarm is best at
differentiating between normal activities and 's**T - it's on fire!'.

Ionisation and optical sensors are probably of little use as I suspect
the kiln can give off sufficient fumes (not a lot are needed) to
trigger them both during overnight firing.

The usual solution where hot equipment is involved (big commercial
deep fat friers for example) would be to string a wire along the shed
roof with fusible links in the wire

http://fusible-links.co.uk/fireprotection.v2.html

above likely problem areas such as the kiln. The wire is spring
tensioned with a standing load of 10 - 40lbs so when the link breaks
they open a water valve to an overhead sprinkler system or similar.
Their great advantage is they don't depend on electricity so if the
kiln malfunction trips the workshop power the fire protection still
works.

I suppose that's a solution - certainly fits the 'fail-safe' criterion...

Not a lot of fumes from this process - but point taken about the
sensitivity of conventional sensors...

Starting to wonder if an alternative solution would be another layer of
electronics control - simulating a thermal fuse and killing (& latching
off) the power to the kiln in the event of over-temperature...

'Twould mean drilling an extra hole in the kiln for the additional
thermocouple - and a box with transformer / contactor / some electronics
installed between the kiln and the wall-socket.

The controller checks for thermocouple o/c, and reversed, but not
(apparently) for 'illogical' conditions....

Again, probably overkill, but the process control gear I worked on had
electromechanical 'watchdog' circuitry in case the uP went awol....

...I'm sorely tempted to reverse-engineer the controller& do it right!g

Adrian

I suspect you could do it very simply by nothing more than hanging up
a £3 battery ionisation alarm. I'd expect you're only gonig to get
bother from it if you have quite a lot of combustible junk get into
the kiln, which shoudlnt ever happen. I'm no expert on kilns though.

NT

I _think_ I'd want it to link into the house alarms.....
(but I can see ructions if 'something in the kiln' sets the house
noisemakers off at 2am!)

Generally, there's not a lot in the way of fumes - I tend to fire on
some stuff called Kiln Paper, which produces a slight smell as it fires
- but I guess the answer is to try it& see....

Thanks
Adrian

The point is it only costs £3 to try an ionisation type, and it may
prove ok. If it does, you can then get one that wires to the house.

NT

Yes - good point.
Of course, I'll never know if it really works unless the the kiln
controller fails again and the shed burns downg...
..but it would prove that the cheapie detector isn't tripped by solder
smoke / flux fumes etc!

Thanks
Adrian

Cheap ionisation detectors are very sensitive. All you need establish
is that it doesnt false trigger. If it does, try an optical one for
less sensitivity.


NT

OK - thanks!
Adrian

On Sun, 16 Oct 2011 14:02:07 +0100, Adrian Brentnall wrote:

The controller's _now_ decided that it can't see the thermocouple
(even when the thermocouple's replaced by a wire 'short' at the
controller terminals - so it looks like it's a 'late controller'...

But thermocouples aren't just a simple bit of wire, they produce a
voltage in proportion to the temperature. They produce enough
voltage/current to hold open gas valves. So no wonder your controller
is saying "no thermocouple" when there is a wire short in place, it's
not bust it's telling the truth.

--
Cheers
Dave.

On 16/10/2011 23:47, Dave Liquorice wrote:
On Sun, 16 Oct 2011 14:02:07 +0100, Adrian Brentnall wrote:

The controller's _now_ decided that it can't see the thermocouple
(even when the thermocouple's replaced by a wire 'short' at the
controller terminals - so it looks like it's a 'late controller'...

But thermocouples aren't just a simple bit of wire, they produce a
voltage in proportion to the temperature. They produce enough
voltage/current to hold open gas valves. So no wonder your controller
is saying "no thermocouple" when there is a wire short in place, it's
not bust it's telling the truth.


Hi Dave
Sorry to disagree - but lots of controllers (including the one that I
have) include this feature as a built-in test mode - simply because it
is difficult for the average user to test a thermocouple

http://www.bartinst.com/KILN/V6CF/tr...ge.html#bypass

As I've also got another similar kiln here, I've been able to do various
combinations of controllers, relays and thermocouples - and the only
thing that's consistently bust is the controller...

Good news is that the 'new' big kiln is now running using the older
kiln's controller - so I just need to get the duff controller replaced
under warranty and we're back where we should have been!

Have also asked the controller manufacturer how their 'current on, kiln
not heating up' logic works, in the event of a partial failure of the
temperature-sensing circuitry...

Adrian