Strange CFL Failure Mode

[Arfa Daily]

"Boris Mohar" <borism_void_@sympatico.ca> wrote in message
news:9dsh65djn7tnalepgrbj5m5sehg8a4cog0@4ax.com...

On Tue, 21 Jul 2009 19:40:49 +0100, "Arfa Daily" <arfa.daily@ntlworld.com
wrote:


"Nicholas Bodley" <n_bod_ley@speakeasy.net> wrote in message
newsan.2009.07.21.09.00.40@speakeasy.net...
On Thu, 16 Jul 2009 17:38:16 +0100, Arfa Daily wrote:

I don't think I have ever had a domestic incandescent light bulb [...]

This commentary reminded me of a quite-unpleasant experience in late
boyhood. Apparently, an incandescent bulb in the cellar had a film of
moisture on it (it had just been turned on). When I touched the glass, I
got a nasty shock; damp concrete floor, etc. The socket must have been
wired with its threaded shell to the hot side of the line.

Not the bulb's fault, of course.

Btw, hot glass is conductive, just about certain.

Regards,
--
Nicabod =+= Waltham, Mass.

Well, if it is, and I rather suspect it's not, the amount of conductivity
is
very small. I work a lot with power valves (tubes) which run hot enough to
take your fingerprints off in decimals of a second, and these often have
as
much as 800 volts on the anode pins. Some years back, I used to work with
high power audio distribution amplifiers on a community radio network. The
(foot high internally assembled with nuts and bolts) tubes on these 7 foot
tall amplifier cabinets, often used to run so hot that the glass was
actually glowing dull red. I have seen dents in the glass where the vacuum
has started sucking on areas that have got *so* hot that they have
softened.
The HT supply on these beasts was about 2.5Kv as I recall, derived from
mercury vapour rectifier tubes.

Given these facts, if the glass had much conductivity when hot, you would
pretty soon be into having leakage paths between the pins, and to the
grounded retainer metalwork, that holds the devices into their sockets,
wouldn't you ?

Arfa

Any links to these giants?
--
Boris

Friend of mine still has a couple I believe. I'll get him to check the
numbers on them (it's been a long while ago, and I can't remember any more).
I'll also see if I can get a coupla piccies of them. The amps in question
fed a radio relay network around large areas of the town. They were located
in the cellar of a house in the centre of town. Above them on the ground
floor, was our workshop, which was always lovely and warm in the winter

On the first floor, above that, was the control room. The radio receivers
were located there, and a large patchboard, where the distribution lines
were routed, using the big old three pin Bulgin plugs and sockets. There was
also a desk console, with an array of meters, which measured 'load'. They
were actually measuring audio current going out on the lines.

We used to have fun on a slow Saturday afternoon, when there was no no
bosses about, by waiting for an important set of sports results, and then
either pulling the plug on a whole area, or switching in the spare receiver,
which we had pre-tuned to an offshore pirate radio station. Then wait for
the phone to start ringing off the hook down in the office, where some poor
part time lady would be located to take any service calls ... )

Arfa

 

[Andrew Gabriel]

In article <1r5e65da3od5r3rvmaldbdlslfm5tdabr5@4ax.com>,
Victor Roberts <xxx@lighting-research.com> writes:

Ordinary incandescent lamps are made from soda lime glass,
which has enough conductivity at 100C to maintain a low
frequency (DC or 60Hz) discharge in T12 fluorescent lamps
using electrodes on the outside of the bulb. The place
where the wires are sealed in an incandescent lamp (the
pinch seal) is made from lead glass, that has much lower
conductivity than soda lime glass. Vacuum tubes are usually
made from borosilicate glass (Pyrex(R)) that has even lower
conductivity than lead glass, and much lower than soda lime
glass.

Thanks, interesting.

However note that Pyrex(R) no longer implies any particular
glass type, and in particular, it's no longer borosilicate
glass in the US.

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

 

[Victor Roberts]

On 24 Jul 2009 08:43:43 GMT, andrew@cucumber.demon.co.uk
(Andrew Gabriel) wrote:

In article <1r5e65da3od5r3rvmaldbdlslfm5tdabr5@4ax.com>,
Victor Roberts <xxx@lighting-research.com> writes:

Ordinary incandescent lamps are made from soda lime glass,
which has enough conductivity at 100C to maintain a low
frequency (DC or 60Hz) discharge in T12 fluorescent lamps
using electrodes on the outside of the bulb. The place
where the wires are sealed in an incandescent lamp (the
pinch seal) is made from lead glass, that has much lower
conductivity than soda lime glass. Vacuum tubes are usually
made from borosilicate glass (Pyrex(R)) that has even lower
conductivity than lead glass, and much lower than soda lime
glass.

Thanks, interesting.

However note that Pyrex(R) no longer implies any particular
glass type, and in particular, it's no longer borosilicate
glass in the US.

Pyrex seems to still be a registered trademark of Corning,
at least in the US, though I do see that the use of the
Pyrex name has expanded well beyond borosilicate glass, for
example, to metal cookware.


--
Vic Roberts
http://www.RobertsResearchInc.com
To reply via e-mail:
replace xxx with vdr in the Reply to: address
or use e-mail address listed at the Web site.

This information is provided for educational purposes only.
It may not be used in any publication or posted on any Web
site without written permission.

 

[TKM]

"Victor Roberts" <xxx@lighting-research.com> wrote in message
news:34ph65hoe8686fams98uo5ac4j63mts5j2@4ax.com...

On Thu, 23 Jul 2009 22:14:05 +0000 (UTC), don@manx.misty.com
(Don Klipstein) wrote:

In <TYn9m.81487$ay4.71863@newsfe27.ams2>, Arfa Daily wrote in part:

The (foot high internally assembled with nuts and bolts) tubes on these
7 foot tall amplifier cabinets, often used to run so hot that the glass
was
actually glowing dull red. I have seen dents in the glass where the
vacuum
has started sucking on areas that have got *so* hot that they have
softened.
The HT supply on these beasts was about 2.5Kv as I recall, derived from
mercury vapour rectifier tubes.

Given these facts, if the glass had much conductivity when hot, you would
pretty soon be into having leakage paths between the pins, and to the
grounded retainer metalwork, that holds the devices into their sockets,
wouldn't you ?

The glass around the pins is not as hot as the glass on the sides and
the top.

Meanwhile, even soda lime glass is not that much of a conductor at
200-300 degrees C.

I have heard of HID lamps requiring any metal supports to be isolated,
to avoid problems with electrolysis of the glass bulb. I imagine this
problem involves amounts of current low enough to not be a shock hazard.

On the other hand, I have seen glass heated to the point of being soft
conduct impressive amounts of current (several milliamps, possibly more)
at a few kilovolts. I do not know what kind of glass was involved -
either soda lime or a cheaper flint glass, probably soda lime.

- Don Klipstein (don@misty.com)

There's an interesting demonstration that can be done with a
rod of soda lime glass. If it is connected to a source with
the appropriate voltage output and current capability, and
then heated, it will conduct enough current to sustain the
temperature required for conduction when the external
heating supply is removed. I'm sorry to say I don't know
how much voltage is required to do this on any particular
size rod of soda lime glass.


--
Vic Roberts
http://www.RobertsResearchInc.com
To reply via e-mail:
replace xxx with vdr in the Reply to: address
or use e-mail address listed at the Web site.

This information is provided for educational purposes only.
It may not be used in any publication or posted on any Web
site without written permission.

Fascinating. I wonder if there are glass furnaces that switch from gas to
electrical glass-conductive heating once the glass is molten.

Terry McGowan

Terry McGowan
>

 

[Victor Roberts]

On Fri, 24 Jul 2009 12:14:06 -0400, "TKM" <nomail@no.net>
wrote:

"Victor Roberts" <xxx@lighting-research.com> wrote in message
news:34ph65hoe8686fams98uo5ac4j63mts5j2@4ax.com...
On Thu, 23 Jul 2009 22:14:05 +0000 (UTC), don@manx.misty.com
(Don Klipstein) wrote:

In <TYn9m.81487$ay4.71863@newsfe27.ams2>, Arfa Daily wrote in part:

The (foot high internally assembled with nuts and bolts) tubes on these
7 foot tall amplifier cabinets, often used to run so hot that the glass
was
actually glowing dull red. I have seen dents in the glass where the
vacuum
has started sucking on areas that have got *so* hot that they have
softened.
The HT supply on these beasts was about 2.5Kv as I recall, derived from
mercury vapour rectifier tubes.

Given these facts, if the glass had much conductivity when hot, you would
pretty soon be into having leakage paths between the pins, and to the
grounded retainer metalwork, that holds the devices into their sockets,
wouldn't you ?

The glass around the pins is not as hot as the glass on the sides and
the top.

Meanwhile, even soda lime glass is not that much of a conductor at
200-300 degrees C.

I have heard of HID lamps requiring any metal supports to be isolated,
to avoid problems with electrolysis of the glass bulb. I imagine this
problem involves amounts of current low enough to not be a shock hazard.

On the other hand, I have seen glass heated to the point of being soft
conduct impressive amounts of current (several milliamps, possibly more)
at a few kilovolts. I do not know what kind of glass was involved -
either soda lime or a cheaper flint glass, probably soda lime.

- Don Klipstein (don@misty.com)

There's an interesting demonstration that can be done with a
rod of soda lime glass. If it is connected to a source with
the appropriate voltage output and current capability, and
then heated, it will conduct enough current to sustain the
temperature required for conduction when the external
heating supply is removed. I'm sorry to say I don't know
how much voltage is required to do this on any particular
size rod of soda lime glass.


--
Vic Roberts
http://www.RobertsResearchInc.com
To reply via e-mail:
replace xxx with vdr in the Reply to: address
or use e-mail address listed at the Web site.

This information is provided for educational purposes only.
It may not be used in any publication or posted on any Web
site without written permission.

Fascinating. I wonder if there are glass furnaces that switch from gas to
electrical glass-conductive heating once the glass is molten.

Terry McGowan

Terry McGowan

I had forgotten about that, but the answer is yes.
See US 2,280,101, issued April 21, 1942. I've put a copy on
my web site:

http://www.robertsresearchinc.com/Papers/US2280101.pdf


--
Vic Roberts
http://www.RobertsResearchInc.com
To reply via e-mail:
replace xxx with vdr in the Reply to: address
or use e-mail address listed at the Web site.

This information is provided for educational purposes only.
It may not be used in any publication or posted on any Web
site without written permission.

 

[Andrew Gabriel]

In article <slrnh6o0j0.kfq.don@manx.misty.com>,
don@manx.misty.com (Don Klipstein) writes:

In <vmbj65dq8c93i0mo97bkbivvedlo8kklp9@4ax.com>, Victor Roberts wrote:
On 24 Jul 2009 08:43:43 GMT, andrew@cucumber.demon.co.uk
(Andrew Gabriel) wrote:

However note that Pyrex(R) no longer implies any particular
glass type, and in particular, it's no longer borosilicate
glass in the US.

Pyrex seems to still be a registered trademark of Corning,
at least in the US, though I do see that the use of the
Pyrex name has expanded well beyond borosilicate glass, for
example, to metal cookware.

This makes me wonder if the name "Pyrex" "expanded" to glass types other
than borosilicate, as opposed to merely being "expanded" to non-glass
items.

In the US, Pyrex is currently tempered sola lime glass:
http://www.pyrexware.com/thetruthaboutpyrex/manu.htm
A factory in Europe also licenses the name, and apparently
produces borosilicate glass.

Pyrex is now simply used as a respected brand name, still
owned by Corning, but licensed out to whoever wants to use the
name. It doesn't imply glass, or any particular type of glass.
Corning no longer make anything under the Pyrex name themselves.

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

 

[Don Klipstein]

In <34ph65hoe8686fams98uo5ac4j63mts5j2@4ax.com>, Victor Roberts wrote:

On Thu, 23 Jul 2009 22:14:05 +0000 (UTC), don@manx.misty.com
(Don Klipstein) wrote:

SNIP to edit for space

Meanwhile, even soda lime glass is not that much of a conductor at
200-300 degrees C.

I have heard of HID lamps requiring any metal supports to be isolated,
to avoid problems with electrolysis of the glass bulb. I imagine this
problem involves amounts of current low enough to not be a shock hazard.

On the other hand, I have seen glass heated to the point of being soft
conduct impressive amounts of current (several milliamps, possibly more)
at a few kilovolts. I do not know what kind of glass was involved -
either soda lime or a cheaper flint glass, probably soda lime.

- Don Klipstein (don@misty.com)

There's an interesting demonstration that can be done with a
rod of soda lime glass. If it is connected to a source with
the appropriate voltage output and current capability, and
then heated, it will conduct enough current to sustain the
temperature required for conduction when the external
heating supply is removed. I'm sorry to say I don't know
how much voltage is required to do this on any particular
size rod of soda lime glass.

I do remember seeing somewhere on the Web how to melt a soda bottle (or
was it a beer bottle?) in a microwave oven. The glass bottle to be melted
required a hot spot pre-heated with a "blowtorch" / "propane torch" or the
like, to temperature that I visually estimate to be in the 800's degrees C.
It appears to me that soda lime glass that hot achieves conductivity and
resistivity suitable for being sufficiently receptive for heating by a
microwave oven.

=========================

Disclaimer: I sense that this is adventurous usage of a microwave oven,
attempt to do such only at your own risk of damaging your microwave oven or
burning down the real estate that such microwave oven is in/on and
injuring/killing life forms in/on such real estate including loved-ones,
friends and pets by starting a fire.

- Don Klipstein (don@misty.com)

 

[Don Klipstein]

In <vmbj65dq8c93i0mo97bkbivvedlo8kklp9@4ax.com>, Victor Roberts wrote:

On 24 Jul 2009 08:43:43 GMT, andrew@cucumber.demon.co.uk
(Andrew Gabriel) wrote:

In article <1r5e65da3od5r3rvmaldbdlslfm5tdabr5@4ax.com>,
Victor Roberts <xxx@lighting-research.com> writes:

Ordinary incandescent lamps are made from soda lime glass,
which has enough conductivity at 100C to maintain a low
frequency (DC or 60Hz) discharge in T12 fluorescent lamps
using electrodes on the outside of the bulb. The place
where the wires are sealed in an incandescent lamp (the
pinch seal) is made from lead glass, that has much lower
conductivity than soda lime glass. Vacuum tubes are usually
made from borosilicate glass (Pyrex(R)) that has even lower
conductivity than lead glass, and much lower than soda lime
glass.

Thanks, interesting.

However note that Pyrex(R) no longer implies any particular
glass type, and in particular, it's no longer borosilicate
glass in the US.

Pyrex seems to still be a registered trademark of Corning,
at least in the US, though I do see that the use of the
Pyrex name has expanded well beyond borosilicate glass, for
example, to metal cookware.

This makes me wonder if the name "Pyrex" "expanded" to glass types other
than borosilicate, as opposed to merely being "expanded" to non-glass
items.

- Don Klipstein (don@misty.com)

 

[Franc Zabkar]

On Thu, 16 Jul 2009 17:38:16 +0100, "Arfa Daily"
<arfa.daily@ntlworld.com> put finger to keyboard and composed:

During my
many years of shuffling around on this little orb of ours, I don't think I
have ever had a domestic incandescent light bulb start a fire, explode,

I had a bad batch of incandescent light bulbs where the glass
separated from the base and fell, or was ejected, onto the floor.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

 

[Jeff Jonas]

Yep, soon they'll be considered as dangerous as incandescent lamps
that burn fingers, start fires, explode, send molten glass and
tungsten shooting about and electrocute those who try to change the bulb.

Please don't say that too loud, lest the electrician's union
place a seal and/or lock on every fixture
to assure only a licensed union electrician ever changes a lamp.
Don't laugh. With all the microcontrollers embedded into everything,
it's possible to add lockout codes so only authorized people may restart it,
just like you car's "service required" light and reset code.

It's bad enough my TV, monitor, radio and such all say
"No user servicable parts inside".
Pray, don't let that happen to my home too.

My my, Terry. You do live an interesting and dangerous life ... During my
many years of shuffling around on this little orb of ours, I don't think I
have ever had a domestic incandescent light bulb start a fire, explode ...

I had a night light bulb shatter, fresh from the package.
I'd say that counts as an explosion.
I swore off dollar store bulbs ever since.

As to fires, I refuse to use lamps over 100 watts at home,
thus avoiding the 300-500 watt halogen torchiere fires
that were terribly common for a while.
The closest I came to a lamp induced fire was a plastic figurine
melting and smoking from being too close to a reflector halogen lamp.

 

[JB]

Please don't say that too loud, lest the electrician's union
place a seal and/or lock on every fixture
to assure only a licensed union electrician ever changes a lamp.
Don't laugh. With all the microcontrollers embedded into everything,
it's possible to add lockout codes so only authorized people may restart
it,
just like you car's "service required" light and reset code.

It's bad enough my TV, monitor, radio and such all say
"No user servicable parts inside".
Pray, don't let that happen to my home too.

Nobody else seems to have brought up that scenario with BPL. How about your

refrigerator needing automatic updates and sending usage tracking back to
the server, then crapping out because the most recent update no longer
supports your model.

 

[Nicholas Bodley]

On Tue, 21 Jul 2009 19:40:49 +0100, Arfa Daily wrote:

"Nicholas Bodley" <n_bod_ley@speakeasy.net> wrote in message
newsan.2009.07.21.09.00.40@speakeasy.net...
On Thu, 16 Jul 2009 17:38:16 +0100, Arfa Daily wrote:

I don't think I have ever had a domestic incandescent light bulb
[...]

This commentary reminded me of a quite-unpleasant experience in late
boyhood. Apparently, an incandescent bulb in the cellar had a film of
moisture on it (it had just been turned on). When I touched the glass,
I got a nasty shock; damp concrete floor, etc. The socket must have
been wired with its threaded shell to the hot side of the line.

Not the bulb's fault, of course.

Btw, hot glass is conductive, just about certain.

Regards,
--
Nicabod =+= Waltham, Mass.

Well, if it is, and I rather suspect it's not, the amount of
conductivity is very small. I work a lot with power valves (tubes) which
run hot enough to take your fingerprints off in decimals of a second,
and these often have as much as 800 volts on the anode pins. Some years
back, I used to work with high power audio distribution amplifiers on a
community radio network. The (foot high internally assembled with nuts
and bolts) tubes on these 7 foot tall amplifier cabinets, often used to
run so hot that the glass was actually glowing dull red. I have seen
dents in the glass where the vacuum has started sucking on areas that
have got *so* hot that they have softened. The HT supply on these beasts
was about 2.5Kv as I recall, derived from mercury vapour rectifier
tubes.

Given these facts, if the glass had much conductivity when hot, you
would pretty soon be into having leakage paths between the pins, and to
the grounded retainer metalwork, that holds the devices into their
sockets, wouldn't you ?

Arfa

Sorry for the delayed reply. If the glass is hot enough to soften, it's
probably conductive to some extent. However, if surrounded by cooler
glass, its resistivity would be too high to matter.

Try this, but be aware that you're dealing with lethal voltages, high
enough to jump a short gap (1 cm or so). You, specifically, most likely
know how to protect yourself! If in doubt, others should not try this.

Take a [neon] sign or oil burner ignition transformer (the latter is
probably better) and arrange temporary electrodes (or use those in a
discarded oil burner) to create a steady arc. That arc is like a flame --
it will melt and ignite materials. place a piece of well-insulated glass
in the arc (safety glasses!), and let the arc heat the glass. When it
starts to glow, or possible a bit sooner, it will become conductive;
you'll see the arc divert so current passes through the glass.

As to your power tubes/valves, you might have been lucky.

Regards,

--
Nicabod =+= Waltham, Mass.

 

[Nicholas Bodley]

On Wed, 22 Jul 2009 09:47:11 -0400, Victor Roberts wrote:

On Tue, 21 Jul 2009 19:40:49 +0100, "Arfa Daily"
arfa.daily@ntlworld.com> wrote:


"Nicholas Bodley" <n_bod_ley@speakeasy.net> wrote in message
newsan.2009.07.21.09.00.40@speakeasy.net...
On Thu, 16 Jul 2009 17:38:16 +0100, Arfa Daily wrote:

I don't think I have ever had a domestic incandescent light bulb
[...]

This commentary reminded me of a quite-unpleasant experience in late
boyhood. Apparently, an incandescent bulb in the cellar had a film of
moisture on it (it had just been turned on). When I touched the glass,
I got a nasty shock; damp concrete floor, etc. The socket must have
been wired with its threaded shell to the hot side of the line.

Not the bulb's fault, of course.

Btw, hot glass is conductive, just about certain.

Regards,
--
Nicabod =+= Waltham, Mass.

Well, if it is, and I rather suspect it's not, the amount of
conductivity is very small. I work a lot with power valves (tubes) which
run hot enough to take your fingerprints off in decimals of a second,
and these often have as much as 800 volts on the anode pins. Some years
back, I used to work with high power audio distribution amplifiers on a
community radio network. The (foot high internally assembled with nuts
and bolts) tubes on these 7 foot tall amplifier cabinets, often used to
run so hot that the glass was actually glowing dull red. I have seen
dents in the glass where the vacuum has started sucking on areas that
have got *so* hot that they have softened. The HT supply on these beasts
was about 2.5Kv as I recall, derived from mercury vapour rectifier
tubes.

Given these facts, if the glass had much conductivity when hot, you
would pretty soon be into having leakage paths between the pins, and to
the grounded retainer metalwork, that holds the devices into their
sockets, wouldn't you ?

Arfa


Ordinary incandescent lamps are made from soda lime glass, which has
enough conductivity at 100C to maintain a low frequency (DC or 60Hz)
discharge in T12 fluorescent lamps using electrodes on the outside of
the bulb. The place where the wires are sealed in an incandescent lamp
(the pinch seal) is made from lead glass, that has much lower
conductivity than soda lime glass. Vacuum tubes are usually made from
borosilicate glass (Pyrex(R)) that has even lower conductivity than lead
glass, and much lower than soda lime glass.

Aha! In the experiment I just posted a message about, I was using a glass
rod, perhaps for stirring mixed drinks. It might well have been soda-lime
glass. While typing, I was wondering about the conductivity of various
kinds of glasses. Thank you, kindly, for the enlightenment.

I s.t.r. reading, a long time ago, that Corning Glass used the
resistivity of molten glass to keep it hot by passing a lot of current
through it. I don't know how it mas heated to begin with, though.

Best regards,

--
Nicabod =+= Waltham, Mass.

 

[Nicholas Bodley]

On Thu, 23 Jul 2009 22:14:05 +0000, Don Klipstein wrote:

On the other hand, I have seen glass heated to the point of being soft
conduct impressive amounts of current (several milliamps, possibly more)
at a few kilovolts. I do not know what kind of glass was involved -
either soda lime or a cheaper flint glass, probably soda lime.

That surely describes the case in the experiment I described in a post a
few minutes ago.

Best regards,

--
Nicabod =+= Waltham, Mass.