Advances wear and tear on solder within column?

[DistillaMI]

Good afternoon, seeking advice on some maintenance issues that came up.

Taking apart our still this week, new compression gaskets, seals, etc followed by detailed inspection.

Found a few things that worry me. Solder breaking down? Also, found a very small leak at the base of my 4 plate column (the leak looks to be on the bottom side of the pan and very slow), see pics for clarification.

This is an Arnold Holstein still, about 13 years old. They recommended Sodium Hydroxide and Citric Acid for regular cleaning. About 4 years ago I switched to a buffered alkaline detergent (PBW) and then follow it up with a Citric Nitric, RO rise in between. Hoping my chemical choice hasn't helped in the solder degradation. 

It is difficult to get a response from the manufacturer, and its never timely. The boss wants the still put back together asap, so I most likely will not be able to wait for Holstein's response.

I'm wondering why this is happening, what steps I can take to repair the solder and prevent it from happening again. Additionally, my local welder and plumber don't want to mess with trying to fix the solder without knowing what it is (neither of them have experience with stills) and I'm getting pressure to use JD Weld and just get it back up and running. 

Any advise?

[PeteB]

I obviously don't know what type of solder was used, I hope it was not lead based.

I was advised by a stillmaker 10 years ago not to use "silver solder" (a common one in Australia is 2% silver) because it corrodes in a still. I Copper TIG welded it.

I found a crack in the base several years later but had no TIG gas so fixed it with silver solder. After several weeks it leaked again and I discovered that silver solder won't last especially on the base where heat is applied. I estimate it would have taken only 4 weeks to corrode through 1 mm of silver solder. It lasts much longer where there is no applied heat.

Another interesting observation is the pitting in the copper of your column, especially in the second photo. That is caused by sulphur reacting to produce copper sulphate, that is a good thing but it is a good reason to have stills built from thicker copper or they won't last.

[captnKB]

any welds that are thinning out in your still are best repaired by either TIG welding or brazing. Silver solder will degrade very quickly.

[Southernhighlander]

I can't believe that a German still manufacturer was still using solder even 13 years ago.  We have been tigging everything from the beginning.  We never used solder on any of our equipment that has gone to a distillery. 

Trying to tig weld it now would be a nightmare unless every speck of that solder is removed.  The impurities from the solder will create porosities in the weld otherwise.  If you would like to talk to one of my welders about it call 417-778-6100 and tell whoever answers that you would like to talk to Jonathan.  He has decades of sanitary welding experience.  Don't use JB weld.

We have stills out there that have been in service for 8 years and the welds look pristine and they cost 1/3rd the price of a German made still. 

We had a German built still here about three years ago.  The customer had us add a 4 plate copper column and make some other changes.  We had to be really careful because it was soldered.  It actually appeared to be spelter solder that had been poured.   This is a very old method dating back centuries that you don't see anymore.  Anyway, we had to be very careful not to melt the solder.  This still had a massive brass manway that tested positive for lead on the outside but not on the inside (it had probably leached out years ago). The solder joints tested negative for lead.     Judging from the way it was built, this still was anywhere between 30 and 80 years old.  The solder had held up very well for the most part, however I was not impressed by the thickness of the copper on the helmet as it was a great deal thinner than mine.

The newer German stills that I have seen have all appeared to be tig welded.

[DistillaMI]

So general consensus is that copper TIG welding is the preferred method but not without removing the existing solder.

Thanks for the contact Jonathan, I will take you up on that.

Gonna get some flack here, but I did use JB Weld Tank Weld. While I work out a more permanent repair, the company owner told me to get it patched and running asap. I called JB Weld to verify, was told its drinking water safe, resistant to ethanol, chemicals, safe to 300 F, and will turn to ash if it gets too hot (no combustion issues). What issues can I expect with the JB Weld? Is it a safety concern? The JB Weld is not in the vapor path, its on the bottom side of the bottom plate.

I was surprised as well to learn this was all solder. I know what that still costs, I would assume it would be welding at all points.

I'll attach a pic of the JB Weld in place.

Additionally, I'll attach another pic. New still from Holstein made in 2018, still haven't gotten it up and running yet, but it too appears to be soldered.

 

[Southernhighlander]

From my experience JB weld leaches into solvents.  I can't say for sure that it is not safe, but I can't say for sure if it is safe.  I talked to Jonathan about your issue.  He said that for it to be welded all of the solder must be removed. 

 

If you guys do decide to have it repaired with solder, I suggest you contact Col. Vaughn Wilson.  Here is a link to his web site.  He is an Arkansawyer who builds traditional copper stills, using traditional methods.    The guy is incredibly intelligent and really knows his stuff about traditional copper stills.  http://www.coppermoonshinestills.com/

 

 

[Silk City Distillers]

The risk is that regular thermal expansion and contraction cause the JBWeld to break away I would think.  Careful with any downstream pumps.

[OzDistilling]

Are you sure the still is only 13 years old?  Holsteins have been TIG brazing and welding for sometime, well over 13 years, with soldering reserved for only sensitive joints.

Prior to that they did used varios Tin-silver-copper (Sn-Ag-Cu, or "SAC") solders.  SAC solders have fallen from grace in food service, due to the high melting point and cadmium residues. The photos you posted seem to indicate silver leaching in the solder.  But its hard to tell.  Generally I never recommend Nitric Acid as a cleaner or pacification wash as it reacts with the silver and tin more so than say Citic or Sulphuric.  I usually recommend citric for pacification washes.

Another puzzling aspect is the brown stain of the corrosion, indicating presence of Iron. Is your water very hard?  But it could be some other odd tin/silver salt. I have seen this when the weld/joint is contaminated with iron from tools or sanding disks.  Unlikely for Holstiens.

Unless the leak is affecting the still operation (doubtful) I would ignore it.  Repair is complex and really needs an experienced expert.  Resoldering with like solder is your only option.  To remove the legacy solder sufficient for a clean TIG would be impossible.

I would be sending the pics to Holstiens and getting on the phone.  They must have a published repair procedure.

[DistillaMI]

Thanks for all the input. Yes it is definitely solder, we are switching to citric only for acid wash, staying with the brewery wash for cleaning, and. We will probably not get into removing solder to tig weld the still, but will keep an eye on this moving forward to gauge the need of major overhauls. 

Must say, very disappointed that a reputable company like this is still soldering parts of their stills. But live and learn I suppose. Sounds like plain old citric acid is the ticket to stop the breakdown of the existing solder, and that is fine by me. IN the mean time we are waiting further information from Holstein.

Thanks for all of the help!

[Southernhighlander]

On 12/27/2019 at 9:58 AM, OzDistilling said:

.  Resoldering with like solder is your only option.  To remove the legacy solder sufficient for a clean TIG would be impossible.

I would be sending the pics to Holstiens and getting on the phone.  They must have a published repair procedure.

Removing the solder is easy.   Removing the flux on the other hand is a little harder but we have a method that removes it.  Once the flux is removed then tigging it is no problem.

 A few years ago I had an engineer tell me that copper and stainless could not be tiged together.  We tig stainless to copper all of the time.  It's not a joint that should be used where there is a lot of vibration however we have not had any issues with copper to stainless welds on stills.