StillSmart

@Maker. Dont know where you live in relation to anything, but you might consider trying to locate a supplier of materials for building cow sheds or dairy farms. A lot of what you are using originates with the dairy industry. Maybe cheaper.

Maker wrote:Finally for tonight I have been on a womble and found some old copper pipe, after a good clean it looks fine so tommorow I will try to make a product condensor.

I like the womble reference. Make sure to give the tube a good clean on the inside. After you cut the tube to length run some pot scourers through the tube. Either push or pull through with string. Do that several times as the inside of the tubes are probably oxidised and or dirty.

Your product is in contact with the inside of the tubes so you want to start with them nice and clean.

John, I get the ferrules and bends from China as they are much cheaper than any British supplier and the tube I have found a few places online that are pretty reasonable, great idea though.

Myles, the tubes are now lovely and clean, ready to go.
I used an offcut of the copper tube (15mm) and a piece of stainless to have a practice on, if I get it hot I can get lead free solder to flow nicely but it only sticks to the copper and if I heat the stainless untill it glows red the silver solder I have refuses to run at all, if I add more heat so the silver solder gets some directly it just melts in a blob, this is the flux I'm using https://www.fernox.com/solders-fluxes/powerflow-flux any ideas?
I wonder if the silver solder I have has a too high melting point.

That solder won`t work on stainless.

I solder stainless to copper with this solder flux from cupalloys. stayclean and for ease I use their 2207 4% silver solder. Real easy and nice joints.

The flux is a liquid and is agressive so wash it of fairly soon after soldering.

Not a great picture but this is a stainless ferrule soldered to a flat stainless flange. The joint is supported by the copper tube that is a tight fit inside both the ferrule and the flange.

That 2207 solder does a good job on stainless.



The ferrule was soldered onto the copper tube first then it was forced into the flange and the end of the ferrule soldered to the flange also.

I have to admit that I was taken by surprise by the effect that different fluxes and solders have on metals, not taking chemistry beyond GCE O level.

I am catching up.
Robert.

I'm new to soldering so this is another steep learning curve, Myles has done the leg work and shared the answers, thoroughly knowledgeable chap with some great skills. I read earlier in his reply about 4% silver solder and googled it, Maplins sell it so I went and got some, it's not the same, it dislikes stainless but took a fancy to my screwdriver when I tried to spread it on the stainless.
The decision I now need to make is should I buy the flux and solder or change tact to buying stainless tube so I can tig it, I'll sleep on it.

Soldering stainless is not that hard PROVIDED you have the right flux. It needs to be aggressive because of the oxides on the stainless - which is why you also want to wash it off fairly fast.

The 2207 actually has a flux core for stainless but I still use the liquid flux. I have not tried using normal plumbing solder but I have been told it works. I use the 2207 mostly because it is available from the same online shop where I buy my hard solder brazing rods and they have a good selection of alloys.

I've ordered the flux and solder so will be along soon I hope, do you use the flux from the start or just before you add the solder, also is it best to add solder when its only just hot enought to run or try to get it really hot?
One more question... how much slack do you leave around the tube, the copper pipe is 15mm and I have drilled 15mm so the fit is really tight, is that ok or should I drill bigger to allow solder to flow down the side of the pipe?

@Maker Interesting questions. Soldering and brazing are both capillary joints, unlike welding which adds a fillet of alloy.

The rigidity in this condenser will come from the shell and end plates (stainless and welded) so in this case you just need to create a seal. These tube joints will get tighter when you heat them as you have copper inside stainless. The joint gap should be 0.1 to 0.2 mm at soldering temperatures.

This probably means the tube should slide easily into the hole when everything is cold. If it is too tight when heated there will be no gap for the solder to flow into. If you can go up by 0.5 mm the hole will probably be ok.

Apply solder just before heating and only heat enough to get the solder to flow. You get the joint hot before applying solder and it gets sucked around the joint. You can make rings of solder and pre-position them on the tubes before heating. This might be a good idea if you are new to soldering.

Insert all the tubes, add solder rings, add flux and then heat until each ring melts and the solder flows. It flows towards the heat source so you can steer it around the joint.

Then clean everything and leak test. With solder joints if you get a pinhole just re-flux, add a little solder and locally heat that area till it flows.

Over heating burns the flux and the the materials making subsequent repairs more difficult.

Everything I just said is based on an expectation that you will weld the end plates into the shell before fitting the tubes.

Not sure how things would work if you tried to weld the plates to the shell AFTER soldering in the tubes.

When I braze these condensers, I braze in the end plates and then fit the tubes. Other folks solder the tubes into the plates and then slide the tube bundle into the shell.
They typically take measures to cool the tubes to stop the tube joints melting when they join the plates to the shell. Either by inserting wet cloth into the tubes or by having the other end of the tubes in a water bath.

Joint assembly sequence does need to be considered.

I do not wish to sound fatuitous, but that was a well worded and instructed post.
'Nuff said.

Robert.

Today the flux and solder finally turned up from Cupalloys, should have been a few days ago but there was a cock up, no harm done.
Myles, your tutorial helped no end, I diddn't expect it to go so well, the difference is night and day, the solder flowed in a controlled way and stuck very evenly to both copper and stainless, nothing like my previous efforts.
Here it is with solder rings cut.


And here with it soldered,



I'll leak test in the morning but it all looks really well filleted, I had one area of concirn so I intended to 'touch it up' with some solder so I added a little flux and warmed it ready to solder but it just flowed and fixed it's self.

I have a 54mm copper reducer that reduces down to 15mm arriving soon so I can make the next part, here's what it looks like before that arrives.

Forgot to say, I have sanded down the tubes on the inlet end of the condenser to a couple of mm above flush so there is only a small puddle collected rather than how it looks in the image, I have also today received the heating element from brewuk so I have cut a hole in the same way as before to accept a 2" tri clamp.



Next I will weld a disc inside of a 2" ferrule, add a hole to suit the heating element and weld the nut to the inside of the hole, remove the part of the ferrule not needed, pictures to follow.

The hole for the 2inch heating port.....do you mean chain hole drilled as before ?