Author Topic: Sodium lamp explosion risk?.  (Read 653 times)
Bulbhead500w
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Sodium lamp explosion risk?. « on: October 09, 2018, 12:11:58 PM » Author: Bulbhead500w
HPS And SOX
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dor123
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Re: Sodium lamp explosion risk?. « Reply #1 on: October 09, 2018, 11:33:22 PM » Author: dor123
The internal pressure of HPS and LPS is lower than that of the surrounding air, so there is no risk of explosion.
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Medved
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Re: Sodium lamp explosion risk?. « Reply #2 on: October 10, 2018, 01:19:25 AM » Author: Medved
HPS And SOX

LPS may only implode,because there is just vacuum inside. The only explosion possible is the sodium Coulombic explosion once it get released and happen to meet water.

The HPS has about an atmosphere in the burner, with vacuum outer. So the burner may "explode" (well, the energy there is so low it would be barely a cracks), the vacuum outer then may just implode, nothing else. And with Hg free HPS there could be again some Coulombic explosion once the sodium meets water...
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lights*plus
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Re: Sodium lamp explosion risk?. « Reply #3 on: October 10, 2018, 01:09:16 PM » Author: lights*plus
I have seen a few HPS and 2 SOX lamps crack and fail before my eyes. The worst thing that is heard is a loud cracking with a sudden loss of light followed by pulsating plasma glows outside the arctube inside the bulb - essentially the lamps leak.

On the other hand both CMH and M-H lamps can explode a bit more violently, yet the outer bulb typically contains any projectile.
« Last Edit: October 10, 2018, 01:14:04 PM by lights*plus » Logged
Medved
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Re: Sodium lamp explosion risk?. « Reply #4 on: October 10, 2018, 01:51:56 PM » Author: Medved

On the other hand both CMH and M-H lamps can explode a bit more violently, yet the outer bulb typically contains any projectile.

There the pressure uses to be way above 10 atm (lower wattage means higher pressure), so pretty high amount of energy there to propel the fragments out.
The "typically" does not mean guaranteed (unless expliciteky open rated), so not a good idea to operate such lamps without some containment measure. Mainly during fresh lamp overload (ballast failure,...) the explosions tend to be very violent, because the fresh burner tends to be very tough, so allows such high pressure to build up without leaking, so allow to accumulate really very high energy there.

The HPS may develop higher pressure in case they get overloaded (ballast failure,...), but first this tend to kill the arc due to too high voltage drop so too low OCV marging to sustain the arc, plus because the normal pressure is never supposed to be too high the arctube uses to be rather thin so ruptures/leaks sooner than any significant pressure so energy builds up there, so in a quite effective way prevent the explosion becoming so violent the outer wont be able to contain it.
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BlueHalide
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Re: Sodium lamp explosion risk?. « Reply #5 on: October 10, 2018, 09:40:11 PM » Author: BlueHalide
HPS lamps can explode but it is very rare and almost always due to non-passive ballast failure

Here is an HPS lamp I found on a job that went out with quite the bang

https://www.lighting-gallery.net/gallery/displayimage.php?album=lastup&cat=11470&pos=6&pid=143865
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Medved
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Re: Sodium lamp explosion risk?. « Reply #6 on: October 11, 2018, 12:46:50 AM » Author: Medved
HPS lamps can explode but it is very rare and almost always due to non-passive ballast failure

Here is an HPS lamp I found on a job that went out with quite the bang

https://www.lighting-gallery.net/gallery/displayimage.php?album=lastup&cat=11470&pos=6&pid=143865


These are the reasons, why the lamp makers require even standard HPS and MV lamps to be covered, with the only exception of explicitly open rated types.
There the outer may have failed not directly from the arctube rupture, but by a thermal shock from the arc in the outer after the ceramic leaked. But still it have ruptured and allowed the hot fragments to fly away...
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lights*plus
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Re: Sodium lamp explosion risk?. « Reply #7 on: October 11, 2018, 03:08:12 AM » Author: lights*plus

Here is an HPS lamp I found on a job that went out with quite the bang


I find the ends of the obliterated arc tube very nice, as in - was it a new lamp?
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BlueHalide
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Re: Sodium lamp explosion risk?. « Reply #8 on: October 11, 2018, 09:22:23 PM » Author: BlueHalide
@lightsplus  No, these lamps shouldve all been at least 15K-20K hours used, my company services all the interior and exterior lighting for this client, however the client is cheap and only calls for relamping service by the time a large number of lights are completely burned out. I have a feeling that when this lamp was severely overloaded the blackened ends of the arctube probably cleared up, like what happens sometimes when you overdrive a well used MH lamp. Either that, or the exposure to open air once exploded cleared up the arctube wall
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MissRiaElaine
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Re: Sodium lamp explosion risk?. « Reply #9 on: October 12, 2018, 02:28:00 PM » Author: MissRiaElaine
I have seen a few HPS and 2 SOX lamps crack and fail before my eyes. The worst thing that is heard is a loud cracking with a sudden loss of light followed by pulsating plasma glows outside the arctube inside the bulb - essentially the lamps leak.
Ye gods, what are you doing to them  Shocked I've been running SOX lamps for 40 years and never had one fail yet, well not violently, anyway.
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lights*plus
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Re: Sodium lamp explosion risk?. « Reply #10 on: October 12, 2018, 02:52:13 PM » Author: lights*plus
I often "find" lamps and, not knowing their condition, put them through tests. About 50% of them are nearly always beyond EOL, so it can happen.

@BlueHalide: I see, thanks for the added info!
« Last Edit: October 12, 2018, 02:55:49 PM by lights*plus » Logged
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