Oil for a leaking Tinsley standard resistor

[Magnificent Bastard]

Just as well that you included the USA bit, I was just going to make a crack about buying it in blocks in Antarctica. We know where to find you now. 

McMurdo Station

You are welcome to come and visit!

-MB

[tggzzz]

Thanks to everybody that has replied.

I've tried finding mineral/paraffin oil in more than half a dozen pharmacists and traditional hardware shops, completely without success. Most reactions are bafflement or "no". The better reactions include "oh yes, we have some paraffin here" and "I should have some here, oh no it is gone"

Hence it looks like the most probable source would be online, which is a bit of a shame.

However, Real Life has intervened and so this is now on the back burner.

Currently (ho ho) I'm only likely to use the resistor to calibrate DMMs. In most cases they would pass 1mA, which equates to a 10uW dissipation; the worst case is 10mA / 1mW.

Given the size and surface area of the resistance wire, I doubt (without doing calculations!) that would result in a large temperature rise. In that case the principal value of any oil would be to stabilise the temperature and allow the temperature to be measured with a mercury thermometer inserted into the top hole. Hence I may just call it a day and use it without oil.

Nonetheless, the discussion has been interesting and I have learned a lot; thanks.

[Freerthy]

Do you know correct oil level?

[tggzzz]

Do you know correct oil level?

Not explicitly, but there is no point in a partially submerged resistance wire.

Why do you ask?

[GigaJoe]

does anyone knows if it will work ?  I'm about in the same state for resistor ....

https://www.rona.ca/en/paraffin-oil

UPD:  On the other hand, Paraffin oil, known as kerosene in Australia and the United States and stove oil in Canada, is an flammable liquid hydrocarbon burned as fuel.
seems it not ....

[Gyro]

No, that says lamp oil, ie. Kerosene. It will contain quite a lot of water and be acidic.

You want medical grade Liquid Paraffin BP, for internal use.

[GigaJoe]

will that thing work ? :
https://www.amazon.ca/Swan-Mineral-Oil-16-oz/dp/B001B2RG1C

[Gyro]

Yes, that looks like the stuff.

I notice that it contains 0.1% 'mixed tocopherols' as a non active ingredient stabilizer. You might just want to read up on those, but I suppose you want the oil to be stable anyway... https://en.wikipedia.org/wiki/Tocopherol. I suspect that they all might all contain some.

[drussell]

will that thing work ? :
https://www.amazon.ca/Swan-Mineral-Oil-16-oz/dp/B001B2RG1C

That looks rather expensive...

You can get a larger container (591 mL) of the Equate brand (Wal-mart's house brand) stuff at any Wal-Mart for $3.97 Canadian...

[tggzzz]

ManateeMafia noted in https://www.eevblog.com/forum/metrology/precision-resistors-general-thread/msg3624927/#msg3624927

"I came across this document from IET in regards to the oil filled SR-1030 series. Chapter 6 talks about their recommended oil and how to test if it is contaminated enough to warrant doing an oil change. https://www.ietlabs.com/pdf/Manuals/SR1030_im.pdf "

[Gyro]

That section reads just like a Haynes manual (DIY auto manual for non UK), including glossing over the messy bit. 

[leighcorrigall]

FYI, the topic of resistance standard oil has been briefly discussed in the General Precision Resistor thread too.

https://www.eevblog.com/forum/metrology/precision-resistors-general-thread/msg3623623/#msg3623623

[CalMachine]

Food-grade white mineral oil is the way to go

[pico61]

On Ebay Italy 20 liter can!

https://www.ebay.it/itm/255002905357?var=0&mkevt=1&mkcid=1&mkrid=724-53478-19255-0&campid=5338822678&toolid=10029

Agip ITE 600 is an excellent transformers and rheostats oil.

[TimFox]

For a different application (insulating the high-voltage power supply for 450 kV x-ray tubes), we used "Diala" oil from Shell, which is a "transformer oil", mostly used in power-distribution transformers.
It is basically a purified "motor oil" (I used to know the SAE number) without the usual detergent additives, etc. designed for car engines.
It contains a small amount of "anti oxidation" agent, which I remember being either BHA or BHT, common preservatives found in food or cosmetic products.

[Gyro]

Just a note that tggzzz necroposted his own thread yesterday. The discussions on pharmaceutical mineral oil etc, happened a couple of years ago (and I suspect he already topped it up, or decided that he didn't need to).

[tggzzz]

Just a note that tggzzz necroposted his own thread yesterday. The discussions on pharmaceutical mineral oil etc, happened a couple of years ago (and I suspect he already topped it up, or decided that he didn't need to).

The latter; see reply #26.

I added the cross reference for the benefit of any reader that comes along in the future with a similar question.

[Gyro]

I was lucky enough to pick up a 1k Ohm Tinsley 3504D Standard resistor a couple of days ago (photos... https://www.eevblog.com/forum/chat/what-did-you-buy-today-post-your-latest-purchase!/msg5584307/#msg5584307 ), in nice condition.

I was cleaning it up today and took the opportunity to open the filler screw, and found that it was empty. Looking at the rubber seal and inside with an endoscope, it appears that it has never been filled. I can't see the actual winding, all that is visible inside the casting is a brass cylinder.

Now I know that later resistors (as the OP's, presumably) they used Castrol Whitemor WOM14 (aka food grade Liquid Paraffin BP) and presumably the same would be applicable.

My question is, after 50+ years being empty and as far as I can measure, only 10-20ppm low in value, do I fill it at this stage of just leave it empty? I was somewhat thrown by seeing the brass cylinder inside rather than the winding, I have no way of seeing if this assembly is sealed itself, or the winding construction. It forms a double concentric chamber anyway, so nothing like the current model.

I would be grateful for opinions, and particularly any 3504D specific data. All I can find is a couple of listings on ebay and the datasheet for the current 5685 standard resistor (which comes pre-filled).


P.S. I've just found a second, larger, filler port under the identification plate. Initially I wondered if it went into the inner cylinder, but it goes into the same outer space as the other one, odd. It's certainly a heavy casting. Images attached, the edge of the brass cylinder is visible...

[Gyro]

It occurred to me that I hadn't tried the endoscope through the larger filling port. Winding located, it is closely wound around the brass (actually copper) cylinder, all but invisible under the varnish also hampered by the few mm distance from the fixed focus lens. I managed to image the wire terminations to the horns too, extremely short - I would certainly have snapped them if I had succeeded in removing the lid. Maybe the larger port is an access way for specially trained Imps!

So I guess the question remains. To fill or not to fill?

[Overspeed]

Hello

A crucial problem is oil mixing compatibility if you change oil you need to clean the tank several times to remove all possible '' old oil '' and also avoid possible strange chemical reaction with the new

I warm oil to 50 deg C , fill , shake , empty the tank I do that 3 times and let the tank open in a upside down several hours before filling with teh new oil

Regards
OS

[Gyro]

I should have made clear that my Reply #42 was a necro-post of tggzzz's old thread. He is now sorted I think.  In my case, the resistor has never been filled for some reason.

I agree though, mixing of different oils can cause issues, particularly if they are of different composition, eg. mineral and Silicone. [Edit: Or the original oil has decomposed and become acidic.]

Thanks for the heads up - a messy procedure!

[Gyro]

So I guess the question remains. To fill or not to fill?

So, any thoughts before I pour in the Laxative this evening?  (I've even bought human grade rather than veterinary).

[tggzzz]

So I guess the question remains. To fill or not to fill?

So, any thoughts before I pour in the Laxative this evening?  (I've even bought human grade rather than veterinary).

Trouble is, I suspect nobody will be able to give a solid answer for several years.

It sounds as if - whether or not it has the desired effect inside the resistor - it is having the designed effect inside you 

[Gyro]

Haha, I know I got it cheap, but yes, it is tweaking the bowels a bit.

I guess if it is designed to be filled, filler, seals etc then it should be. It's a normal thing for reference resistors (as you know). It's just so damned pristine inside!

I just wish I could find something that says 'fill on receipt'.


EDIT: 200ml brought the level to within 5mm of the top leaving a small expansion volume... for better or worse.

[Gyro]

After leaving to settle for a couple of days, I thought I had better check the insulation resistance of the Liquid Paraffin - now that's something that I really should have done before I poured it in!.

Using my Kewtech KT35 insulation tester, I went up through the voltage ranges, on the highest 2GOhm scale, and am pleased to find that it reads over-range on the maximum 1kV setting, applied between one terminal and outer casing for 30 seconds.

Whilst not a definitive test for moisture content (as the winding itself is lacquered) the terminations to the horns, their mounting nuts etc. are exposed to the liquid. It is certainly enough to establish that the filling will have no measurable shunting effect on the winding resistance. I intend to repeat the insulation test every few months to check that nothing suspicious is happening.


For reference, this is the Liquid Paraffin that I used...  https://www.amazon.co.uk/Bells-LIQUID-PARAFFIN-BELLS-150ML/dp/B00433YP3I

This was the only one I could find that specified for human consumption rather than veterinary use, so purity is hopefully a bit better. The label indicates active ingredients: Liquid Paraffin 100%, which hopefully means no additives, it is clear, colourless and odorless anyway. The manufacturing date on the bottles that I purchased was Mar 23, with expiry date (medicinal presumably) of Mar 28.

The remainder will almost certainly end up being used (sparingly and only!) on kitchen chopping boards.