Replacing or annealing copper washer

LittleSister

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Drained my diesel tank today. I was concentrating on the diesel rather than anything else, but thinking about it now maybe I should be replacing or annealing the drain plug washer.

The drain plug (this is in a stainless steel tank) appeared to be brass, with an 11mm nut (or at least it fitted an 11mm socket), thicker shaft than a standard metric steel bolt of that size head, and (I think I remember) a shallower thread (more t.p.i.). There was a dark coloured washer on it, but I wasn't paying attention to that at the time.

I now vaguely recall reading somewhere that such plugs will usually have a copper (?) washer that must be replaced or annealed to be sure of a good seal (and I don't want 45 litres of diesel in the bilge!). Is this right?

I seem to remember that you can anneal the washer (if it is copper) to re-soften (?) it, by heating. Is this true, and if so how hot, and do I let it cool naturally, or plunge it into water to cool rapidly?

Thanks in anticipation of the forum's collective wisdom.
 
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Bilgediver

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I seem to remember that you can anneal the washer (if it is copper) to re-soften (?) it, by heating. Is this true, and if so how hot, and do I let it cool naturally, or plunge it into water to cool rapidly?

Thanks in anticipation of the forum's collective wisdom.

Heat to cherry red and plunge into cold water .
 

steadyeddy

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Replacing or annealing a copper washer

If the copper washer is damaged a new one can be purchased from car accessory shops
 

trapezeartist

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Definitely don't quench it. Get it to cool as slowly as possible. Strictly speaking, air-cooling is termed normalising. Annealing should involve control of the temperature to enable it to be cooled more slowly.

I've no idea about temperature, but I suspect it would fall somewhere in that middle ground which is difficult to judge. Hotter than boiling water, but cooler than red hot.
 

VicS

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Heat to cherry red and plunge into cold water
No, just a dull red ... no more.
Quenching is unnecessary just allowing it to cool naturally is all that is necessary.
 

VicS

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make sure you do not heat above 1082°C. :D

I take it that 1082C is the melting point.

I looked all this up a few weeks ago. when someone was asking about bending copper tube.
If it is heated to too high a temperature, or even held at the correct temperature for too long, it becomes coarsely granular and brittle.

Hence the limit being "dull red"

(A bit of Googling suggests that the annealing is best done at a much lower temperature but for a prolonged period. Grain growth then is not a problem. I will try a bit in the oven when cooking lunch one day)
 
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VicS

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Nope, 1083°C is the melting point and copper turns a pinkish colour not red or dull red. :)

How do I know, I am a member of the Royal Navy "1083 Club" as one part of my final Trade Test piece (made of copper) melted. :confused:

:)

If you are going to be pedantic .

the Mpt of copper is 1084.62C and is one of the fixed points on the 1990 International practical temperature scale. :p

Perhaps you were unlucky to be doing your test piece before they defined the 1990 scale :D
 

Poignard

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Just a point:-

Annealing will soften it but it won't restore its original shape. It's very common to find copper joint washers have been badly crushed following over-enthusistic tightening. In this case replace it - they don't cost much.
 

Norman_E

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To quench or not to quench?

Firstly I agree with the last post, if the washer is at all crushed or distorted, get a new one.

As for annealing, there is some misunderstanding about the process, which may be due to the way different metals react. For example to anneal a high carbon tool steel, you heat it red, then allow it to cool as slowly as possible. If you quench it you will harden it. What happens is that on heating to a critical temperature (visually, bright cherry red) the carbon content forms austenite, which is hard, and if cooled slowly the austenite breaks down into ferrite and cementite, resulting in softening, however if rapidly quenched, martensite is formed, which results in a hard and brittle steel, which then needs further heat treatment (tempering) to produce a useable tool.

Copper is different, if you heat it just to the point where it begins to glow pinkish red in a not too brightly lit indoor workshop its grain structure alters and it becomes softer, rapid cooling does not alter it much if at all. When I built a miniature steam locomotive boiler the copper plates needed to be flanged by bending them over a former with a rawhide mallet. A few blows all round the edge and the part needed annealing because copper work hardens rapidly. The advice was to heat, quench, and get on with the job.

The choice is yours, cool it slowly, or quench it, it will make little difference to copper, as for practical purposes you cannot achieve any degree of hardening by quenching.
 

Poignard

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Copper is different, if you heat it just to the point where it begins to glow pinkish red in a not too brightly lit indoor workshop its grain structure alters and it becomes softer, rapid cooling does not alter it much if at all. When I built a miniature steam locomotive boiler the copper plates needed to be flanged by bending them over a former with a rawhide mallet. A few blows all round the edge and the part needed annealing because copper work hardens rapidly. The advice was to heat, quench, and get on with the job.

The choice is yours, cool it slowly, or quench it, it will make little difference to copper, as for practical purposes you cannot achieve any degree of hardening by quenching.

Absolutely right. If coppersmiths had to wait for their work to cool naturally between annealings they would never get anything done.
 

doug748

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I must add my slender weight behind Norman E and Parsival's practical points here. Quenching in acid* also de-scales the thing giving an instant rosy pink finish ready for further work.
However, check out any new washer and if it does not bend easily, give it the treatment. Take off any black scale using fine emery or scouring powder.

* Dilute, H&S, Do not do this at home etc, etc.
 

Heckler

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Drained my diesel tank today. I was concentrating on the diesel rather than anything else, but thinking about it now maybe I should be replacing or annealing the drain plug washer.

The drain plug (this is in a stainless steel tank) appeared to be brass, with an 11mm nut (or at least it fitted an 11mm socket), thicker shaft than a standard metric steel bolt of that size head, and (I think I remember) a shallower thread (more t.p.i.). There was a dark coloured washer on it, but I wasn't paying attention to that at the time.

I now vaguely recall reading somewhere that such plugs will usually have a copper (?) washer that must be replaced or annealed to be sure of a good seal (and I don't want 45 litres of diesel in the bilge!). Is this right?

I seem to remember that you can anneal the washer (if it is copper) to re-soften (?) it, by heating. Is this true, and if so how hot, and do I let it cool naturally, or plunge it into water to cool rapidly?

Thanks in anticipation of the forum's collective wisdom.
Take no notice of the pedants, pair of old pliers, gas stove, heat it up, wont take long, a bit pink, drop it in a cup of water. pisshhhhh, job done, will be nice and soft.
Stu
 

misterg

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...There was a dark coloured washer on it, but I wasn't paying attention to that at the time. ...

It could also be a fibre washer which won't take well to attempts at annealing it!

(They're usually red-ish, but go darker when soaked with diesel).

As to replace or re-use, that depends on how far you have to swim to get to get replacement (a decent motor factor). If you don't have to swim then replace it - cost is peanuts. You will only find out if it's leaking when you fill the tank with diesel. :)

(Nothing wrong with annealing a copper washer if you *have to* - hang it on piece of wire, heat until it goes a nice even pinkish colour - a few seconds - then drop into water. Dropping it into water only helps from the point of view of speeding the process up and shocking the oxide film off - metallurgically, it does nothing for copper.)

Andy
 
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