Smashing WRTL Arc 90s
Quite a common view back in 2013. Many Arc 90 optics were smashing when they were converted to 150w CDO TT / GE Streetwise lamps! Some of the crew put this down to the optic were over tighten, putting presume on the glass, while one maintenance guy thought the lanterns were being closed to hard! 

These have all since been replaced for LED lanterns.

Smashing WRTL Arc 90s

Quite a common view back in 2013. Many Arc 90 optics were smashing when they were converted to 150w CDO TT / GE Streetwise lamps! Some of the crew put this down to the optic were over tighten, putting presume on the glass, while one maintenance guy thought the lanterns were being closed to hard!

These have all since been replaced for LED lanterns.

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lampy   [20 Jan, 2021 at 08:34 PM]
its toughened glass, more likely someones shot at it with an air rifle, these take some smashing, but if you catch them on the wrong angle they explode
FrontSideBus   [21 Jan, 2021 at 04:16 PM]
Could be a batch of bad glass being found out by the increased temperature of the CDO lamps? The stress that toughened glass is under is mega... something like 30,000 PSI iirc! I've had an oven proof pyrex casserole dish go hand grenade on me for no apparent reason when I took it out of the oven! I was finding bits of glass around the kitchen for weeks!
Mrstreetlight   [21 Jan, 2021 at 08:59 PM]
They definitely were down to the CDO lamps or something from the change to white light, as a good amount of these (talking 100 or so) went smash after a week of running CDO!
AngryHorse   [22 Jan, 2021 at 11:14 AM]
That’s some weird X-files shit right there!, I wonder if their focusing some sort of heat spot in a specific place?
FrontSideBus   [22 Jan, 2021 at 05:25 PM]
Well the reflector is bonded directly to the corners of the glass which is where the tensile stress on toughened glass is the highest, expansion and contraction of the metal reflector will act on the corners of the glass... but I can't see that alone being responsible... maybe just a bad batch of glass where the stress was a bit too high and was tipped over the edge by the new lamp??
Ash   [23 Jan, 2021 at 09:08 AM]
I'd go with the focussing of IR on a spot on the glass - as the arc tube of the new lamp is a point source vs a SON. Maybe the spot is somewhere near the edge where it hits inside the lanten, on a place that touches the glass (the housing edge or seal) and isn't just transmitted out. The reflectors have little flexibility that's probably sufficient to handle normal thermal expansion/contraction, and being Aluminum they conduct the heat throughout so distribute it more evenly

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