Handling CRT: Protection & Safety

Agree completely with the above.

For the sake of two or three minutes it takes to fit yourself with the safety protection, it has to be better than resembling an explosion at an abattoir or being blind for the rest of your life.

I must have been a bit of a wuss to, always wore face protection and gloves, not worth the risk.

I was taught an early lesson in my working life about the risks posed by imploding CRTs and the respect they required. As an apprentice another engineer was showing me the safest way of letting down a low emission/faulty CRT, they would have been 14, 17 and 21" unprotected types and the like. This was achieved by placing it in a dustbin and giving the nipple on the neck a gentle tap with a hammer letting the air in gradually only then breaking the glass into smaller pieces for disposal, this was done in a covered loading bay under the workshop where the delivery and engineers vans were kept outside of business hours.

The engineer asked me if I had ever seen a CRT implode, I hadn't and neither had he outside of a set, "should we see what happens" he asked? A CRM171 or something similar was placed in the dustbin face down and the engineer lobbed the hammer towards it while we quickly ran for cover behind a door. It wasn't just a bang, it was a BOOM and glass was heard to shower everywhere. Returning there was virtually no glass in the bin, it was strewn over the whole area, some very small, so large thick chunks. Anyone standing there when it was hit would have probably sustained some very serious injuries and it's a good job the bosses Rover 3500 P6 wasn't parked in there at the time as it usually was during the day otherwise I think we both would have been seeking reemployment.

Like myself the engineer was visibly shaken by the results and from then on I always wore at least safety glasses whist handling them. The dangers with rimguard types was much reduced and I've seen and heard several accidents with no flying glass or injuries but in D.E.R. as with Rediffusion it was a requirement to wear eye protection when any CRT was being handled out of a set.

John.

Philips were very strict on this as well and issued safety goggles to everyone expected to handle CRTs. It was a major disciplinary if you were caught without the goggles...it was about the only thing they were strict on. I only heard one tube go off and it was in the packing area being sent back for regunning. Someone had gone to find a box for it and somehow it got whacked by a passing fork-lift. Two workers nearby saw it falling and dived for cover......

One of my physics teachers told us that he had worked at a colour tube manufacturer and that completed new tubes were left arrayed in a secure area for 24 hours to cool and stress-relieve before release- apparently, if they survived this long, they were likely to last a lifetime. Just occasionally, one would let go and leave splinters of glass stuck in the walls.

Another hazard came home to me when helping another physics teacher (yes, they all seemed at least slightly bonkers, this guy was also an ultra-distance runner, apparently 100 clicks across a far-flung desert was a bit of relaxation!)- he kept several part-dismantled '50s TVs in the lab at any one time, occasionally one would be run up do demonstrate how magnets deflected an electron beam or how far an EHT spark would jump. Lots of unruly 14/15 year-olds crowded round an exposed chassis and innards. I think he just liked an excuse to b----er about. Anyway, I was shifting some of his junk out to make way for some more, I picked up a face-down monochrome tube, both palms gripping the edge of the flare and in contact with the aquadag, one thumb strayed onto the ultor dimple..... YEEEE-OUCH! I learned about dielectric relaxation that day. Fortunately, I'd only just started to lift it, and it dropped (harmlessly) the short distance back onto the wooden table. So, discharge gently and preferably leave shorted, or handle with considerable circumspection.

As an apprentice I worked on tube R&D at Ferranti.

We produced the huge tubes used in radar desks for HM Forces.

They were enormous armoured faceplate tubes, some with flat back projection plates, 27" round, scary.

The armoured face plates were resin bonded on. Sometimes there would be a missed air bubble and the plate had to be removed and replaced. The standard practice was to shatter it with a nail punch and a hammer, soak it in paint remover and rebond a fresh plate. All done on a pumped tube by an apprentice in the open lab area with no protection at all.

There were tubes lying around everywhere. There was a test done by dropping a 5kg pointed weight onto a tube. The film showed the immense forces and the flying chunks of glass embedding into the walls only too vividly.

But nobody cared, still no precautions taken.

https://m.youtube.com/watch?v=Qv-Ub7kgm0Y

No words.
The care in handling CRTs cannot be over emphasised.

Not just a gentle breakage....a LETHAL explosion. (Implosion to be exact, but it would be so quick you would never notice the difference).

Anyone after watching that video and still refusing to use protective gear is a fool dicing with death.

Definitely DO NOT TRY THAT AT HOME.

I didn't quite catch the Scandinavian town he mentioned, but as he said, a lot of faecal matter to clean up!

Speaks for itself I think.....

I have about six or seven B&W CRT's (50's & 60s) in the loft which I wish I didn't have, especially as they are thermally cycling all time.

I certainly don't like to contemplate moving them from the cold loft into a warm bathroom ( loft hatch access is there). It probably needs to be done in summer when there's not such wide temperature variances between the two environments.

I have to admit to contemplating nipping the pip off all of them in the loft, thereby removing the danger altogether. Wish I had dumped them long ago as they are just a PITA. They used to be stored in the workshop but they just made me nervous, took up too much valuable space and there was always the danger they would get clonked.

I have three colour CRT's downstairs (all have intended destinations, just not done them yet) and although these are large and could be equally dangerous, at least the are banded.

Anyone else got CRTs  up in their lofts?

Chris said

Anyone else got CRTs  up in their lofts?  

No, and I wouldn't keep any unless they were individually safely packaged in their shipping cartons (or something similar).

A further danger is if there are several stored and exposed to each other, if one blows, the whole lot will. Domino effect.

I used to have some in the loft at our old house, they were 14" colour ones mostly, from modern TVs and pc monitors. I sent some of the pc monitor tubes to the tip when we moved, but kept the ones from TVs as they will become useful. I also have a Mazda CRM122 in a box under the stairs, it doesn't work, but I'll keep it in case it ever does become possible to re-gun it. It is a scary prospect handling one of those old wine glass thin Mazda's! I do have some safety specs, but I should really get some face protection. I remember removing the tube from the Samsung Slimfit so I could wash the cabinet, that was a scary beast, it weighed a tonne... I'm normally quite ok with handling CRT's, and so far I've never had any implode.

there are quite a few videos on YouTube of people finding ever more creative ways to make CRT's go boom, just watch some of the ones where they cut the rim band then leave a blow torch heating the face, there's not much left after it's gone pop! 

Regards,

lloyd

Does anyone know of a case where a CRT has imploded without the extreme external influence we have seen above?

For instance, how tight does a securing rim-band have to be before the glass is fractured....something that does concern me if re-fitting a tube in a set. I try to get so the tube is only just held securely without slipping, whereas I know that too tight will make the tube more likely to implode if struck by accident.

With a rim band, generally there's a rubber gasket between the CRT and the band to provide grip. Plus, CRTs like this have implosion guards in front of the CRT. You would have to tighten a securing band to some ridiculous force to cause it to go 'pop'.

I recall a school physics teacher picking up a 14" CRT by its neck in a lesson. I dived for cover, but it didn't go bang.

Equally, I recall a schoolmate and I spent ages lobbing bricks at the front of a CRT to no avail in his parents' old mono TV. It was when we lobbed then at the back we got the desired result...

I once remember my granddad grabbing a 17" 70° mono CRT by the neck and waltzing it out into the yard - no gloves nor anything else and the CRT had no band nor anything else. Somehow, it didn't seem to bother him, and I never even thought of the dangers, but then, an 11 year old nipper probably wouldn't realise the danger!

Now me.... I have a 12" roundy in the cabin, wrapped up in a mound of old curtains. but then there's a Mullard AW43-80 just sitting on top of a stack of other stuff - no wrappings. Perhaps that's just my perception of what 'looks' dangerous?

I wonder how my brother disposed of all my G6s, some 30 years ago! - The git!!

PYE625 said
Does anyone know of a case where a CRT has imploded without the extreme external influence we have seen above?

Yes

https://www.vintage-radio.net/forum/showthread.php?t=5505&highlight=crt+imploded

PYE625 said

A further danger is if there are several stored and exposed to each other, if one blows, the whole lot will. Domino effect.

As you can see by following the link, the domino effect as you suggest is not necessarily true. Quite how the other tubes survived is incredible but nonetheless, survive they did!

I have various tubes in the loft. From 12 inch mono from the 50.s to NOS A56-120X. Never had any implosions. Malc.

That implosion can't have been a massive bang - the keyboard on top of that computer hadn't even been lifted, nor the three reams of printer paper damaged. There wasn't a great deal of scatter, and most of the glass was very local to the faceplate's last known location.

I wouldn't want to have been near it when it went, but on face value, it was a relatively low energy implosion. It was very lucky that a flying shard didn't neck the CRT next to the one that went bang.

One TV dealer in York was renown for necking all trade-in sets. The apprentice's job every Saturday morning was to go out into the yard with a big pair pliers and simply 'knock off' the necks of all that week's trade-ins. It was suggested that it would be safer to leave the set-backs in place and just use a big hammer instead! - BOOOSCH-TINKLE-KLINK!

Katie_Bush said

I wouldn't want to have been near it when it went, but on face value, it was a relatively low energy implosion. It was very lucky that a flying shard didn't neck the CRT next to the one that went bang.

It is possible the vacuum was already partially impaired or....

I wonder if the level of implosion is relative to the amount of energy applied, obviously a fast projectile in the video above had much energy, but if the glass failed by itself so to speak, would it be so dramatic?