Oven brazed Evaps

After some months of experimenting (and a lot of tossed away evaps), I managed to braze two evaps in an oven. They came out very nice and needed no further cleaning. I always hated having to clean the much oxidized copper only to hope that there will be no leaks. Also I did not like the idea of leaving corrosive flux behind inside the evap when brazing with silver rods.

Now I dont need any flux at all...

Regards,

Philipp

http://www.abload.de/img/verdampfer001w5c.jpg

http://www.abload.de/img/verdampfer002sjd.jpg

Great, any pics how did you do that?

Regards

Wow, those look great. What kind of oven did you use?

The oven is normally used for ceramics and makes up to 1100C. I use mainly CO2 as protective gas with water-free ethanol vapor below 450C and CO2 + hydrogen above 450C.

Regards,

Philipp

How do you apply the brazing rod though? Use the oven to heat the evap, pull it out and then apply the rod? Or do you set the rod on the joint, put it in the oven, and then let it self braze?

It looks really good:up: Tell us more..

Have you hooked one up yet and pressure tested it?

As it would bring in oxygen you can not open the oven during brazing, so the brazing rods have to be in place before. So I start the oven, when reaching 450C, I switch from CO2+Ethanol to CO2+hydrogen and at cooldown, at 450C I switch back to CO2+Ethanol for saving purposes (hydrogen is expensive here, I experimented with an elecrolytic hydrogen generator but the gas was much to damp).

Both evaps had no leaks on the first try now :)

Good idea. :up:

Seems like a hassle though to deal with the changing of purging gasses, but the end result is clean. If you can get a good rate of return with very few leaky evaps, you have yourself a winning process.

Mad skills.
Well done Philip

I am very confident now (after a lot of errors) that now the evaps will come out without a leak, but even if, I can put them into the oven again as I dont have any tinder on them after brazing...

Oh man, I have experimented since November to perfect the process and now it finally works perfect :)

A oven will work just fine ,but if you wanted to produce evaps,I would make a Induction heating element/system for them. You would be able to complete the braze measured in seconds.

You sure are right, but this is still my hobby and I am not going to mass produce evaps. An induction heater goes into the 1000s of $ and I would still have the problem with protective gas. This is just to produce some nice looking and tight evaps for my builds (and perhaps for some other people, if needed).

Regards,

Philipp

Nice job PhilippF, I've had the same idea and I'm using a vacuum oven for my prototype evaps. It's not my original idea really, I'm an automotive engineer and all production automotive evaps are either controlled atmosphere or vacuum brazed. Cleaning evaps after they are brazed is just such a drag... Wonderful to have them ready to go when they cool :up:

I started out with making brazing rings from sil-phos-copper alloys, but now I'm using a paste that let's me control the alloy placement much better. What are you using?

You copied Ssilencer!!!

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Originally Posted by DetroitAC

I'm an automotive engineer and all production automotive evaps are either controlled atmosphere or vacuum brazed.

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What's the trick you guys use to get the evaps to not leak just until the the vehicle's warranty runs out ? :shrug:

If its a dodge truck they will leak bofore the warranty is up. :up:

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Originally Posted by [XC] 2long4u

If its a dodge truck they will leak bofore the warranty is up. :up:

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My roommate owned a Dodge truck. Everything died on that truck before the warranty was up. Piece of garbage.

Depends what year. Anyway you look at it they are easier to fix then a Ford.

What would you use to heat an evap in a vacuum? A large inductor? Wonder if I could build a small vacuum oven for evaps for a decent price. Does anyone know of a nice informative website on this concept? Can't find anything but food ovens or product listings.

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Originally Posted by [XC] 2long4u

You copied Ssilencer!!!

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God I hope this is a joke from the last thread about the acrylic mounts? :rolleyes:

STFU 2long! You are doing nothing but spamming this thread. It's people like you that spoil this place.
Polizei, you're not helping either.

If you're seriously keen gomler, I'm sure Philip will give a few pointers.

Hey Philip, how come there is a tiny bit of oxidation at the top? Mostly noticeable on the 1/4" tube cap connecting on the left evap. Is the entire oven not purged? I'm not nit picking, that oxidation is nothing, you have done an awesome job. They look very professional. :up:

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Originally Posted by {.bLanK} GoD

STFU 2long! You are doing nothing but spamming this thread. It's people like you that spoil this place.
Polizei, you're not helping either.

If you're seriously keen gomler, I'm sure Philip will give a few pointers.

Hey Philip, how come there is a tiny bit of oxidation at the top? Mostly noticeable on the 1/4" tube cap connecting on the left evap. Is the entire oven not purged? I'm not nit picking, that oxidation is nothing, yo have done an awesome job. They look very professional. :up:

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It sounds like Phillip is using a kiln mean for ceramics. I was more interested in what DetroitAC and Walt were talking about. I did a short google search and it turned up either cooking ovens or component/vacuum oven sales. Then I got side-tracked into algae farming :D

I'd like to see one prepped before it goes in the oven. Phillip, if you do another, take a before pic will ya?:)

What are you using for braze material?

How does Gosmeyer do the cryostars?

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Originally Posted by wdrzal

What's the trick you guys use to get the evaps to not leak just until the the vehicle's warranty runs out ? :shrug:

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It's easy, hire substandard engineers like me :yepp:

@2long4u: Yes! I must have copied somehow! The Chrysler Dayton Accustar plant was legendary for it's quality control of evaps. :rolleyes:

@gomeler: They heat by radiation, and just use electric elements (at least mine does)

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Originally Posted by DetroitAC

It's easy, hire substandard engineers like me :yepp:

@2long4u: Yes! I must have copied somehow! The Chrysler Dayton Accustar plant was legendary for it's quality control of evaps. :rolleyes:

@gomeler: They heat by radiation, and just use electric elements (at least mine does)

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So a vacuum chamber and then high-temp electric coils like those found on an electric kitchen stove? Seal it in a steel box, insulate, have a pump-down port. Hrm..

I like it very much. Excellent work, indeed.

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Originally Posted by [XC] gomeler

What would you use to heat an evap in a vacuum? A large inductor? Wonder if I could build a small vacuum oven for evaps for a decent price. Does anyone know of a nice informative website on this concept? Can't find anything but food ovens or product listings.



God I hope this is a joke from the last thread about the acrylic mounts? :rolleyes:

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Just search for ceramic ovens, they go up a little further to 1100C.

The way I put the brazing there is still a bit of a "production secret", as I am still on my way to improve it further, at the moment it is a little pain in the a** to put it there.

As far as I remember Gosmayr used also a ceramic oven, I think I remember a photo posted by him with a lot of evaps on a tray...

Regards,

Philipp

You can get vacuum ovens in all different temperature ranges,the hotter ones have refractory brick lining them like a Kiln.

I seen a guy selling ceramic refractory brick by the case pretty cheap on ebay a while back.

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Originally Posted by [XC] gomeler

So a vacuum chamber and then high-temp electric coils like those found on an electric kitchen stove? Seal it in a steel box, insulate, have a pump-down port. Hrm..

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I don't know if a stove element would do it. I love the idea. Vacuum ovens arn't cheap.
Sorry for the spam I couldn't help myself. :rofl:

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Originally Posted by PhilippF

The way I put the brazing there is still a bit of a "production secret", as I am still on my way to improve it further, at the moment it is a little pain in the a** to put it there .

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The paste DetriotAC mentioned works well, just cut a template where you want the paste applied. You control the amount by the Thickness of the template. You can use a .050 or if more paste is needed increase the template thickness say to .075 until you get the right amount. You just fill in the void and run a scraper over the top to remove the excess.

You may someday want try a CO2 blaster to clean with too . Dry ice pellates work great,they just sublimate away. You can combine the dry ice pellets with supercritical co2. I,m sure you know it's a great solvent.

[B]BTW Super job on what you already done. :up: :up: :up:

Great idea and technique for applying precise amount of solder paste Walt :up:

And very good execution on what you've done thus far Philipp :clap:

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Originally Posted by mytekcontrols

Great idea and technique for applying precise amount of solder paste Walt :up:

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Just to be clear,the paste DetriotAC mentioned is actually flux & powered brazing filler in a paste form. By controlling the width & height by using template slots you don't over or under apply the filler alloy. :)

What about induction heating? Just use a vacuum jar and a coil carrying high frequency current around it.
http://www.richieburnett.co.uk/indheat.html

Star882, Hannah :confused: what happened to Britney? :shrug:

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Originally Posted by wdrzal

Star882, Hannah :confused: what happened to Britney? :shrug:

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That was just a funny quote from a HVAC friend of mine. Way too good to pass up. He has already built a chiller based on R134a (about 1/2 ton capacity) and is planning to build a "pseudo-cascade" using R410a that uses a water cooled condenser and connections to the chiller to reduce condensing pressures. Hannah is the "fridge girl" I have mentioned before, and she is currently in a relationship with the "HVAC guy" I got the quote from. Every once in a while, they would set up a public HVAC/R discussion and allow those interested in HVAC/R to participate. I have actually learned a lot about HVAC/R from them.

As for Britney, it was a nice CPU, although somewhat outdated today. A modern quad core can easily outperform a Britney in almost all real world applications (except those using lots of memory bandwidth), for lots cheaper too.

Don't you guys think that it's a little bit too much OFF TOPIC ?!

To get back on topic, the "AC/R couple" agrees that induction brazing evaporator blocks sounds neat, although the costs are a little high to be justified just to make a few blocks. Maybe an induction kiln can be DIYed using common electronic parts. 400w was enough to get a small nut in air white hot in 45 seconds, so we'll probably want something like 1000w max for an evaporator block in vacuum. Design the power stage with variable power to allow for careful control of the block temperature.

In few months I will finish H-bridge inverter, and, since I'm interested in how induction heating would work for brazing evaporators, I'm going to test. However, I have feeling that it will be more complicated than it seems, because copper is a great conductor and losses caused by eddy currents will be small. In worst scenario it might need a few kW's and high frequencies to get reasonable results. Also, alloy might melt before touching evaporator, since it has a small mass :)

But! It surely would be fun to just put evaporator inside heating coil and what you would have to do is only touching with brazing alloy :yepp:

Well done:clap: The oven is the only way to fly! No guess work and no cleaning:up:

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Originally Posted by Tonic

However, I have feeling that it will be more complicated than it seems, because copper is a great conductor and losses caused by eddy currents will be small. In worst scenario it might need a few kW's and high frequencies to get reasonable results.

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Good Point.

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Originally Posted by Tonic

Also, alloy might melt before touching evaporator, since it has a small mass :)

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That could also be seen as an advantage. As the Alloy melts it transfers the heaat to the capillary joints of the evap and helps distributing heat...

edit:
The Problem is not the good electrical conductivity, it is the bad magnetic permeability.

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Originally Posted by german Wikipedia

Conventional built inductive heaters can heat materials with a bad magnetic conductivity with a very bad efficiency factor.

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Originally Posted by gosmeyer

Well done:clap: The oven is the only way to fly! No guess work and no cleaning:up:

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Thanks for the compliments from the evap master *bowingmyhead* !

just wondering, what's the big issue with oxidation? Does it make the block weaker? Hamper performance/flow?

Ruins the system internally ;)

Most important point is that it cause bad heat transfer.

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Originally Posted by n00b 0f l337

Ruins the system internally ;)

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If you blow the tinder after brazing out, there won't be a problem.
Simply use N2/Co2/Propane.... and you have no problems.

No not at all, contamination like that can cause oil problems.

And it really looks ugly... I know, I know, form follows function... but I like clean builds so much...

oxidation is a insulator in a way, so it does hamper performance... I don't think your oxidation from leaving it out in the atmosphere is going to change your temps by 1c though alig, just saying if you braze without purging...

regards

that's good to know, since my torch isn't strong enough and I had to have my dad's friend braze my evap for me (he owns a car repair garage) and didn't purge.

o :P yeah that definately isn't good. you will problably need to soak it in a acid, and oven-bake it. Don't know of any chemicals off the top of my head though

Yesterday I made the evap for August123´s 4-stager. It didn´t turn out exactly as I wished as I used a new silver solder, but I think it´s ok...


http://www.abload.de/img/verdampfer001w5w.jpg

http://www.abload.de/img/verdampfer0028ey.jpg

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Originally Posted by PhilippF

It didn´t turn out exactly as I wished as I used a new silver solder, but I think it´s ok...

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Quality work nevertheless!! That's a good looking evap without a doubt! :clap:

On that photos evap has been cleaned after brazing or not ?

those are your evaps correct? any details of the internals?


great work...

Oxidation turns your oil into liquid sand paper, and will clog your metering devices and cause lots of other issues, heat transfer being the absolute least of the problems

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Originally Posted by teyber

those are your evaps correct? any details of the internals?


great work...

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the evaps are from cold ice ;)

nice work, philipp :)

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Originally Posted by piotres

On that photos evap has been cleaned after brazing or not ?

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I did go over it with a cleaning mesh for about 20 seconds. If I want to have extremely clean evaps, I have to use a lot more gas in cooling down. So I accept a very thin layer of copper oxide (I think some micrometers) and go over it with the cleaning mesh.

Regards,

Philipp

Of topic sorry.

And how exactly is this related to the topic?

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Originally Posted by teyber

oxidation is a insulator in a way, so it does hamper performance... I don't think your oxidation from leaving it out in the atmosphere is going to change your temps by 1c though alig, just saying if you braze without purging...

regards

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is oxidation from leaving it out in the atmosphere different to the oxidation coming from brazing without purging?

i thought it was the same oxidation. just that the process of oxidation takes place much faster. the amount of oxidation is therefore relative.

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Originally Posted by teyber

o :P yeah that definately isn't good. you will problably need to soak it in a acid, and oven-bake it. Don't know of any chemicals off the top of my head though

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a good way to clean the evaps from oxidation is to boil them in a pot with salt and vinegar. after that they need rinsing in fresh water and quick drying with a kitchen towl. its probably a good idea to dry them in the oven to get rid of the water inside the evap. they will look as new.

philipp

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Originally Posted by PhilippF

I did go over it with a cleaning mesh for about 20 seconds. If I want to have extremely clean evaps, I have to use a lot more gas in cooling down. So I accept a very thin layer of copper oxide (I think some micrometers) and go over it with the cleaning mesh.

Regards,

Philipp

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Use a 5% Hydrogen mix in with your sheilding gas as an oxygen scavenger.

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Originally Posted by FLuxUs

is oxidation from leaving it out in the atmosphere different to the oxidation coming from brazing without purging?

i thought it was the same oxidation. just that the process of oxidation takes place much faster. the amount of oxidation is therefore relative.



a good way to clean the evaps from oxidation is to boil them in a pot with salt and vinegar. after that they need rinsing in fresh water and quick drying with a kitchen towl. its probably a good idea to dry them in the oven to get rid of the water inside the evap. they will look as new.

philipp

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thats very easily asking for big problems- You must do repeated rinses with very pure iso alcohal in a ultrasonic cleaner after you rinse a evap with vinegar. the acid is really bad for the compressor oil. If you don't cap off a evap for a while it "discolors" but doesn't get that, for a lack of proper name, terrible black cr*p that will flake off and possibly clog your metering device

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Originally Posted by teyber

thats very easily asking for big problems- You must do repeated rinses with very pure iso alcohal in a ultrasonic cleaner after you rinse a evap with vinegar. the acid is really bad for the compressor oil. If you don't cap off a evap for a while it "discolors" but doesn't get that, for a lack of proper name, terrible black cr*p that will flake off and possibly clog your metering device

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well i quess my experience with copper pots, distiller parts, etc. doesnt apply then in that area. how come i never get that flaky black cr** on other copper things that i cleaned that way?:confused: thx for warning me though i would have probably cleaned my first evap that way.:eek: glad i havent had the time...

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Originally Posted by FLuxUs

well i quess my experience with copper pots, distiller parts, etc. doesnt apply then in that area. how come i never get that flaky black cr** on other copper things that i cleaned that way?:confused: thx for warning me though i would have probably cleaned my first evap that way.:eek: glad i havent had the time...

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your right your experiance doesn't apply in this area as this is some thing entirely differant. allot of people make the mistake of under estimating the problems cuased by water and such.

The oxide basicly turns your oil into liquide sand paper and the water turns it into acid.

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Originally Posted by Xeon th MG Pony

your right your experiance doesn't apply in this area as this is some thing entirely differant. allot of people make the mistake of under estimating the problems cuased by water and such.

The oxide basicly turns your oil into liquide sand paper and the water turns it into acid.

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thats why i thought getting the copper oxide off with salt and acid and then properly rinsing off the acid with distilled water and then properly getting rid of the water by drying the evap in the oven would work.

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Originally Posted by FLuxUs

thats why i thought getting the copper oxide off with salt and acid and then properly rinsing off the acid with distilled water and then properly getting rid of the water by drying the evap in the oven would work.

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Not really, you have to dehydrate the unit verry theroely, much better to not let oxidization to form in the first place!

If you use a acid, you need a base to neutralize it or a whole lot of flushing. some alkaline soda ash(sodium carbonate) will neutralize the acid. Use ph test strips,unless you have a water analysis test kit.


In systems where the water is acidic I use chemical injection pumps to pump in a metered amount of soda ash dissolved in water to bring the ph into a normal range.

I know of a few homes where there ground water was very acidic and the installers didn't test the water(well water) a hydronic heating system with copper tube was installed. In 10 to 15 years they had a sprinkler system instead of a heating system..

well, i am sure due to the CO2 from the atmosphere every water is slightly more acidic as it contains bicarbonate and hydronium ions that formed as a result of the CO2, while carbonic acid is only formed in strong acidic solution. however, distilled purified water has a ph of 7, unless exposed to air where it will reabsorb the CO2 and becomes slightly more acidic again. nonetheless, i dont know weather that process takes place that quick. i mean when rinsing the evap. with distilled purified water properly and drying it straight away i dont think it will have actually even dropped from 7.0pH to 6.9pH. i could be wrong though.