A dangerous hazard

[Murphyv310]

Hi.
I had a chat with David Boynes a week or so ago and he mentioned about how some round CRTs are mysteriously imploding. This story reminded me of Bill Millars shop in Prestwick who told me of a multiple implosion of old 9 and 12 inch round tubes in his store about 15 years ago.
I've also been told of another collector that had one suddenly implode watching the set it was in!!
We need to be extra careful as these tubes age. I always use goggles, boiler suit and neck protection when handling one. In fact the face shielding plastic used for PPE are a good idea too although they are not a complete answer.

Just be aware that you are holding a bomb with these tubes...... Be careful and don't take chances.

[ppppenguin]

Glass does go though long term changes over time, though the flow of glass to the bottom in old windows is urban myth.

CRTs are under continuous high stress and will accumulate mechanical shocks over time. Scratches and imperfections in the glass can be sites of weakness where a CRT will start to fail.

With the multiple implosions, were they all close enough to each other that debris from one could have damaged another CRT etc?

Trevor is right, never work with a CRT without decent PPE. At the very least good eye protection. Long sleeves and high neck clothing are both a good idea. Going to A&E to have all the bits of glass removed will not be fun.

[Amie]

Dad had a later tube, (cathodeon) in an early Pye PTV implode on him while the sides were off the set, quite shook him up, took out the implosion shield as well, still finding fragments in the workshop three years later.

These things are well past the "sell by date", due to the shape there must be very uneven forces at work, and glass gets more brittle with age....

Thanks Amie

[ppppenguin]

https://en.wikipedia.org/wiki/Embrittlem...d_Ceramics

I'm sure there's plenty more to be found on the subject.

Way back in 1986 when I was shepherding a pre-war EMI 12" CRT through a rebuild we had a choice of several dead ones. We chose on the basis of which glassware had the fewest visible defects and hence lowest implosion risk. Here's that pyrex CRT with Charlie Bradley, the glassblower at Display Electronics in Uxbridge. The gun has been removed and the tube temporarily sealed off. The gun is on the bench between the 2 CRTs.

[Murphyv310]

Im not sure if I am correct and please enlighten me if I am wrong. Are the old Pyrex tubes less likely to implode and if they do there is less small fragments?

RE Bill Millars multiple implosions. Some were boxed and others not, how close they were I've no idea. Bill died a few years ago so I'll never know now but there was over half a dozen that went pop.

[ppppenguin]

Pyrex is inherently stronger than ordinary glass, which may be why it was used by EMI for CRTs before WW2. I have no idea if they used the extra strength to make the CRTs of thinner glass.

If a CRT implodes, I don't think there's going to be much difference between Pyrex and soft glass. There will be lots of nasty small, sharp fragments flying. Toughened glass, used for some windows, historically for car windscreens, shatters into relatively blunt edged peices.

[peter scott]

Cathovisor CRTs were also of a "pyrex" type of glass although with a different trade name "Hysil".

Peter.

[ppppenguin]

https://en.wikipedia.org/wiki/Chance_Bro..._ray_tubes

[Richard_FM]

I've heard of some people hearing a bang in the middle of the night & finding the CRT of their set had spontaneously imploded.

I presume this was caused by the CRT contracting as it cooled, after getting hot while running. I guess if there was a weak point in the glass it could eventually crack.

This sort of incident seemed to be more common in the 1950s-60s. There might have been one model of tube that had a rogue batch that was liable to implode.

I've also heard of implosion guards shattering without warning, one collector on Facebook shared a picture of one in his collection, luckily the CRT wasn't damaged. He reckoned it was due to the recent hot weather and direct sunlight.

[`FRANK.C]

I've heard of some people hearing a bang in the middle of the night & finding the CRT of their set had spontaneously imploded.

It still happens only nowadays it is the toughened glass in the oven door the will be found spewed across the kitchen floor.

Frank