Sealing rings

Jeff Blakeslee wrote:

The copper sealing washers are delivered as soft copper (annealed) and they work harden after the first use. They are not crush washers, they are plain flat copper washers that conform to irregularities in the mating surface to create a seal.   Most folks replace them each use, which is what Rotax recommends.  

Of course replacing them is the best, but in a pinch you can reuse one if you anneal it and then clean up the faces with some 600 grit sand paper.  Annealing is simple, just heat the washer to a dull red and then let it cool naturally.  This puts it back in a softer state so it will conform and seal again.  See link below.  

https://motoiq.com/wrench-tips-6-re-using-copper-washers/

Interesting.

Two points:

First there is a difference (at least in my mind) between a copper crush washer & a copper gasket washer. The former, usually domed/folded, with a seam on one side,  actually crushes/distorts with the pressure of the tightening and should never be reused . The gasket washer,  flat both sides, solid copper ring, can be annealed & reused, if you so wish. The number of reuses will be governed by the thickness of the washer, which will get slightly thinner on each reuse and may crack at some stage.

Annealing copper - I stand to be corrected, however I have always cooled the red hot copper in an oil bath. Usually the copper comes out clean, ie not oxidised/black. There will be momentary fumes from the oil bath, so do this in a well ventilated area away from flammable materials.

Hi all

I know these are not folded or domed, they are indeed flat copper.  As such I am sure if you have the time and desire you may be able to anneal them.  I question the need to do so, at the selling price it seems not worth my time.  A check of the part number and then looking at one of the USA web pages reveals a retail price of $1.19 USD.  If you want to search for the part elsewhere they even provide the DIN info for you.  

Cheers

McMaster-Carr sells them in packs of 25 for about $0.45 each.  Search for DIN 7603.

Of course, replacing them is the way to go and a much more cost-effective use of time. That's why I said "in a pinch".  

I agree with you Jeff....many times I have seen these reused and then leak fuel as the surface is marked by the torque on the face.  Fuel under pressure will always find the scratch on the surface and leak.  With the fuel blocks that attach to the compensation tube (the Rotax certified TSO system) the banjos can also displace a bit of the copper and then the fittings make contact inside the block if used ones are put on again.  

Cheers