O ring advice

CSA should of course be CS - cross section.

I would go to Brammer aka BSL or try Eriks. You can download a catalogue from here to find the nearest standard size. O rings are measured and specced by ID and section.

Simply Bearings have a good range of O Rings

For instance they do 39.5 i/d 2mm cross section.

I have used them a couple of times and they have been prompt.

Roger Woollett

Ideal fit is of little consequence, it's a coffee machine, not a hydraulic ram gland with 3000psi behind it. Any O ring will do the job provided there's a bit of ''nip'' as you tighten it up or assemble it.....

Julian.

Ideal size but they only seem to stock Nitrile o-rings. The existing o-ring is silicon so I think the replacement needs to be the same.

Archie

Why not get the correct part from a Krups dealer?

Good point. I had discounted that route thinking they would not want to o-ring on its own because it wasn't a user serviceable part and want to supply the complete thermoblock. Also, I have ordered user serviceable parts for the machine before and they took 4 weeks to arrive and sourcing an o-ring quickly seemed a good option. It is worth a phone call to find out though.

Nitrile rubber is one of the finest most resilient/resistant rubbers known to man. For instance it's about the only material that'll withstand phosphate ester hydraulic fluids. (nasty stuff) So if it's good enough for hydraulic seals in aircraft systems then it'll suffice for a little coffee maker!

Julian.

It is the temperature rating that causes concern. Nitrile o-rings are rated at up to 120C where silicone o-rings go up to 200C. I know the water coming out of the thermoblock will be less that 100C but as the thermoblock case has the element wound round the outside and I am sure it will reach a higher temperature, especially when producing steam.

I may have told you a load of rubbish regarding nitrile rings, I found this on the www:

which seems to list various material properties. I still think you're looking for problems that don't exists, just throw a seal in and be done with it - you could probably get away with an off-cut of cat gut if push came to shove!

Julian.

The use of silicone rubber may be more to do with its suitability for food use rather than its temperature resistance i.e. there are no poisonous additives in the silicone rubber compound that might leach out. I am not stating this for a fact, but as a chemist I do know that some additives such as phthalates are banned from plastics that are intended for contact with food.

Cliff Coggin.

Cliff Coggin.

Mark.

Thanks for the Brammer suggestion Mark. I found that there is a Brammer office near me in Grangemouth and they can get me the correct seal in a few days. Minimum order Qty of 20 though so if anyone needs any 39x2 silicone o-rings then I will have some spare.

Were the O-rings Black or Orange Silicone??