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Old 21st May 2017, 7:19 pm   #1
TonyDuell
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Default Asbestos heat insulation

Some valved devices contain heat insulating parts that are almost certainly asbestos. What do people here do about them?

Leave it and hope?

Remove it (how, what precautions, etc) and replace it (what with)?
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Old 21st May 2017, 7:59 pm   #2
Bazz4CQJ
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Default Re: Asbestos heat insulation

Well, quite a lot of us live in houses containing asbestos (mine), or maybe work in buildings with asbestos. The hazard, as I understand it, is entirely that of inhalation of fine particles/fibres of certain grades of asbestos. Especially in old equipment, that is really most likely to occur if you start messing about with it - especially cutting it.

Avoid that and I believe the problem is managed.

B
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Old 21st May 2017, 11:32 pm   #3
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Default Re: Asbestos heat insulation

This crossed my mind when looking inside an old battery charger, c/w asbestos lining within the super-coiled current regulator bobbin. I attempted to find out whether PVA would be heat resistant enough to use as a stabilising solution, but my research was inconclusive.

The appearance of the material helps to tell you whether it is starting to fragment, and in this case it does look a bit 'hairy' in places.

The main concern is inhalation, however in certain cases ingestion can cause serious liver damage; it's a double whammy.

Serpentine asbestos types such as Chrysotile (white) asbestos tend to have a lung half-clearance time of the order of days or weeks, meaning they are less likely to cause the most serious malady associated with asbestos, Mesothelioma. Blue or Brown asbestos has shorter, stiffer fibres, and in some cases these simply will not cough up from the lungs, hence the importance of testing on (for example) demolition sites as to which type of material is being dealt with, serpentine or amphibole.

Test kits are available online but are expensive; a cynical tax on health in my opinion. You have to return the sample to the lab for results.

Your first choice i would think (as a hobbyist) is to stabilise suspect material rather than dispose of it- but i haven't yet found out whether a PVA solution is the comprehensive answer.

Anyone....?
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Old 22nd May 2017, 12:11 am   #4
Damien VK3RX
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Default Re: Asbestos heat insulation

I had some vintage radios with asbestos insulation which was fraying along the edge (see pix). I subsequently used a small paintbrush to coat the edge with PVA glue.

It seemed to do the job and no smoke/flames

However I would have looked for another solution if the face of the panel had been fraying, because clearly in this situation that would be copping most of the heat from the valve.

That said, the radios weren't the type to have running for hours on end, being largely for display.
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Old 22nd May 2017, 12:23 am   #5
Bazz4CQJ
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Default Re: Asbestos heat insulation

Quote:
Originally Posted by The Philpott View Post
Test kits are available online but are expensive; a cynical tax on health in my opinion. You have to return the sample to the lab for results.
IIRC, the only way to identify the most dangerous kinds is by optical microscopy and a trained technician. You are probably paying for the priviledge of using an "accredited" lab.

As you say, a stabiliser would be useful and if PVA won't cope with the temp, I'm sure there must be other materials which would.

I once heard the R&D Director of huge, worldwide minerals company tell an interesting story about asbestos. In the days before ground-glass joints became the norm for connecting glass apparatus in chemistry labs, they apparently used asbestos string covered in bees' wax as an "over-wrap" between sections. Someone noticed that the string took up the wax more readily if it was slight wet. The standard means that was developed for achieving slight wetness was to draw the string between your teeth. Ignorance was bliss.

B
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Old 22nd May 2017, 9:14 am   #6
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Default Re: Asbestos heat insulation

In a General Radio 783A 100W audio power meter, circa 1940's, I painted VHT calliper high temp black paint on a thick asbestos sheet to immobilise all surfaces and edges - the sheet had been lovingly drilled by some poor factory worker to pass many heat resistance cabling from the load resistors to switching control parts. The paint permeated the sheet well, and then hardened nicely.

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Old 22nd May 2017, 4:08 pm   #7
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Default Re: Asbestos heat insulation

I have a couple of vintage bakelite hairdryers and the heating elements are wrapped around an asbestos former Therefore, for show only and not for use !!
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Old 22nd May 2017, 6:48 pm   #8
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Default Re: Asbestos heat insulation

I don't think sucking asbestos string would be a problem, it is pretty inert stuff. Though I shan't be trying it. I only have one body...

The danger is in breathing in the fibres.

The only asbestos that I know of in my radios is in the heat shielding around the mains dropper in my DAC90. At some point, I shall be spending time on this radio - with due care and attention. But really, apart from the health issues, it's ideal stuff for this purpose. The best alternative I can think of is dense glass mat. If I have to trim the asbestos or whatever, my plan is to soak the pieces and bench sweepings in epoxy, which should stabilise them.
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Old 22nd May 2017, 7:24 pm   #9
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Default Re: Asbestos heat insulation

Anyone who went to school as late as the 1970s probably remembers being given an 'Asbestos mat', as I was, to stand their Bunsen burner on in the Chemistry/Physics lab.

Although they were definitely still called 'Asbestos' mats, I wonder whether they really were still Asbestos by that time?
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Old 17th Jun 2017, 9:14 pm   #10
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Default Re: Asbestos heat insulation

I've had satisfactory results [e.g. in DAC 90's] using a PVA drench. However, if this stuff is ever replaced or further heat-proofing introduced ...... I recommend getting a plumbers mat [these are non-asbestos and are used in that industry as heat shields whilst soldering copper pipes and lead working etc.].
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Old 17th Jun 2017, 10:03 pm   #11
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Default Re: Asbestos heat insulation

One game at school was to soften the corner of an asbestos (real!) mat and wet the liberated stuff. It was then thrown upwards to stick on the ceiling over the front bench of the chemmy lab, above where the teacher habitually stood.. As the stuff dried, it would eventually fall. The target was the teacher's bald spot.

1) This was a school held in high regard locally!
2) I'm now very glad I never did this with asbestos
3) I've been worried that I was in the same room ever since the risks of asbestos came to light.
4) The chemistry teacher was a really nice chap and vastly under-appreciated.

Them were the days, Eh?

David
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Old 17th Jun 2017, 10:18 pm   #12
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Default Re: Asbestos heat insulation

The general idea must have caught on, we used the inside lining of fag packets, the silver paper stuff that was lined with tissue paper, we shaped the silver paper a like a golf tee...cup, stem but with fins at the bottom of the stem (the guidance system) the tissue paper was chewed in the mouth to a pulp consistency and then placed in the cup end of the projectile, the stem was then hooked between the two forefingers and on command was flicked up to the ceiling, usually ending in a volley of splats!

Anyways back on topic, off cuts of Masterboard can be subbed for small bits of asbestos sheet in radios etc.

Lawrence.
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Old 18th Jun 2017, 7:43 pm   #13
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Default Re: Asbestos heat insulation

Hi Gents, as I remember it the chem lab asbestos mats were used on top of a tripod tp provide a gentler heat to the likes of conical flasks/

There was also a Rawlplug fibre that we used to form Rawlplugs in cavities that had been pre drilled.
The fibre was moistened before being packed into the cavity; a pilot hole was then formed in the fibre with a small nail and the screw wound in.
It seemed to work pretty well.

Ed
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Old 18th Jun 2017, 10:53 pm   #14
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Default Re: Asbestos heat insulation

Nothing to do with insulation, but I remember my Father using that material, a sort of thick string that you packed in the hole.
The hole was made with a Rawldrill, which wasn't rotary but hammered in. We have it easy these days.
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Old 19th Jun 2017, 12:18 pm   #15
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Default Re: Asbestos heat insulation

I well remember the asbestos mats in the school chemistry lab (late 1960s). Some of them were well knocked about and had chunks missing. I also remember pulling old radio sets apart to scavenge parts in a not particularly careful manner. (Yes, I now cringe at the thought in more ways than one.)
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Old 19th Jun 2017, 2:44 pm   #16
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Default Re: Asbestos heat insulation

Perhaps its worth trying a high temperature exhaust paint to stabilise the asbestos.
Possibly one could carefully remove the asbestos intact from the equipment, give it a drenching in the paint, and re-fit whilst the paint is still slightly soft. I note that some of these paints are claimed to withstand 1000ยบ, but it does not state whether fahrenheit or centigrade. I would think it would bind the asbestos fibres together. Tony.
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Old 19th Jun 2017, 4:57 pm   #17
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Default Re: Asbestos heat insulation

I bought some very high temperature silicone sealant designed for solid fuel fire flues, stands 1250 degrees C.
A layer of that instead of the asbestos would work well I should imagine if you are concerned about the health risk.
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Old 20th Jun 2017, 9:13 am   #18
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Default Re: Asbestos heat insulation

I would reckon that quite a few of us have repaired old Morphy-Richards irons, where there was a sheet of asbestos alongside the element, which frequently stuck and had to be scraped off....
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Old 20th Jun 2017, 12:08 pm   #19
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Default Re: Asbestos heat insulation

A thought..... smear it with silicon grease?


That should be heatproof and "sticky" enough to stop any fibre shedding.
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Old 20th Jun 2017, 12:54 pm   #20
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Default Re: Asbestos heat insulation

Wouldn't silicone grease run when warm though, Chris?

I've always wondered about using ceramic wall tiles to replace flat sheets of dubious insulation. Very cheap, easily cut, heat-resistant etc. But would they provide enough heat insulation?

N.
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