Magpie
lab constructor
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Registered: 1-11-2003
Location: USA
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Mood: Chemistry: the subtle science.
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lab maintenance
Periodically I find it necessary to repair lab equipment. Successfully repairing an item gives me nearly as much thrill as a successful synthesis.
So, for you other maintenance freaks out there I am showing three such recent successful repairs.
The first shows the Ag resoldering of my phosphorus condenser. After 9 runs it had been severely eaten away by heat/chemicals:
resoldered condenser
The second shows a rare Kontes 2-A stopcock on a 125mL pressure equalized addition funnel (19/22). I had been looking for this plug for years and had
seriously considered using the funnel for target practice. I found the plug in a 14/20 funnel bought at surplus for $10.
rare Kontes 2-A stopcock
The third item is another item bought at surplus for $1. It is a small, almost micro sized, bunsen burner. The valve wheel had worn loose and was
non-functional.
Ag soldered bunsen burner valve wheel
[Edited on 23-10-2012 by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
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bahamuth
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Well grown up in a garage so to speak I to find great joy in fixing/building things, though I don't have pictures to show for it..
Quote: Originally posted by Magpie  |
The first shows the Ag resoldering of my phosphorus condenser. After 9 runs it had been severely eaten away by heat/chemicals:
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Is the heat the problem, or is the degradation corrosive? We have a very high heat solder we call "phosphorous solder" in Norway which "hardens" after
initial soldering and increases the melting point. The initial mp is around 750-850 degrees C., and is impossible to remelt with propane after that.
An old Castolin table listed it as very high phosphorous alloy but can't recall the percentage. Maybe it will withstand the P better than Ag...? Worth
to mention that the solder "sticks" are always square and brass-like in color.
Working a lot with silver solder I know that the best silver solder is about 55% silver and that it isn't very resistant against corrosive stuff, the
common silver solder is about 15% silver and is really poor for soldering anything..
Wish I could afford a glass torch to work all my broken Kontes stuff....
Any sufficiently advanced technology is indistinguishable from magic.
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Magpie
lab constructor
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Registered: 1-11-2003
Location: USA
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Mood: Chemistry: the subtle science.
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I really don't know. Before rebuilding much of the solder was gone and what was left was spongy looking. I'm thinking that heat is a factor but also
the 5% NaOH bath that I place it in for cleaning for 2 or 3 days may well be a factor too. The outside surface of the solder really should not be
exposed to the P vapor that is internal to the condenser.
The single most important condition for a successful synthesis is good mixing - Nicodem
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watson.fawkes
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| Quote: Originally posted by bahamuth | We have a very high heat solder we call "phosphorous solder" in Norway which "hardens" after initial soldering and increases the melting point. The
initial mp is around 750-850 degrees C., and is impossible to remelt with propane after that. An old Castolin table listed it as very high phosphorous
alloy but can't recall the percentage. Maybe it will withstand the P better than Ag...? Worth to mention that the solder "sticks" are always square
and brass-like in color
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As I recall, it's around 6-8% P alloy with copper. It's a fairly standard brazing alloy (also called hard
soldering) for joining copper to copper. I have some stamped "0" on it, indicating 0% silver, though P is usually present in silver-bearing alloys as
well. The "hardening" behavior happens because the alloy composition changes when used, with more copper from the brazement diffusing into the filler
metal. This lowers the percentage of P in the joint, raising its subsequent melting temperature.
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bahamuth
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The silver solder alloy you got sounds like something that gets dissolved in alkaline sol., which I find very strange since silver solder is supposed
to be versatile and strong.. Do you have the designation on the solder sticks, or the color (of the outside flux) and the producer? One can check the
alloy and see if something there is the problem.. But still, 5% NaOH wouldn't hurt aluminum much even....
From the color of the solder it really looks like the "low" % silver solder, which is more or less useless if you want the silver properties of the
solder. IIRC it is brittle and sort of hard to flow where one wants to...
Not really a repair and perhaps not worth mention in this thread but me and a business partner is building a 3-axis cnc since my city (read town)
doesn't have the shops around to do prototyping for us.
Other than that I can only mention in the passing what I have done at the university labs in the field of repairs.. As most Norwegians just throw away
stuff that is damaged and buy new, or hire repairmen to change a fuse and similar, I have customized a lot of equipment to function (IMO better than
supplied) with simple and reasonable cheap stuff the times I could convince the guys with the funds to trust me fixing the instrument or the item. But
in the other direction I've got a lot of free equipment needing just a cleanup or resoldering because it was to expensive to hire repairmen and the
item would end up on the land fill if not I've saved it... This items are include but are not limited to a; Büchi rotavapor with an old worn vacuum
seal, a stirrer hotplate needing a connection cleanup, Pfeiffer-Balzer vacuum pump with slight corrosion damage, an old HPLC, an all glass water still
and so. Unfortunately my job and my private company work leaves me little or no time to pursue chemistry. Working with CAD design of instrumentation
within molecular biology (company stuff) and as a lab tech in the local uni.
By god, I derail when I get drunk...
-All spelling errors if any are intentional and only to confuse.
Any sufficiently advanced technology is indistinguishable from magic.
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bahamuth
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| Quote: Originally posted by watson.fawkes | | Quote: Originally posted by bahamuth | We have a very high heat solder we call "phosphorous solder" in Norway which "hardens" after initial soldering and increases the melting point. The
initial mp is around 750-850 degrees C., and is impossible to remelt with propane after that. An old Castolin table listed it as very high phosphorous
alloy but can't recall the percentage. Maybe it will withstand the P better than Ag...? Worth to mention that the solder "sticks" are always square
and brass-like in color
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As I recall, it's around 6-8% P alloy with copper. It's a fairly standard brazing alloy (also called hard
soldering) for joining copper to copper. I have some stamped "0" on it, indicating 0% silver, though P is usually present in silver-bearing alloys as
well. The "hardening" behavior happens because the alloy composition changes when used, with more copper from the brazement diffusing into the filler
metal. This lowers the percentage of P in the joint, raising its subsequent melting temperature. |
Oh, just used 20 min. to write the previous response..
I see, it is also called "hard solder" here to...
I've found it to bond tightly to low alloy steel as well if certain Castolin fluxes are used (don't remember which) in conjunction.
Any sufficiently advanced technology is indistinguishable from magic.
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Magpie
lab constructor
Posts: 5939
Registered: 1-11-2003
Location: USA
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Mood: Chemistry: the subtle science.
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| Quote: Originally posted by bahamuth | The silver solder alloy you got sounds like something that gets dissolved in alkaline sol., which I find very strange since silver solder is supposed
to be versatile and strong.. Do you have the designation on the solder sticks, or the color (of the outside flux) and the producer? One can check the
alloy and see if something there is the problem.. But still, 5% NaOH wouldn't hurt aluminum much even....
From the color of the solder it really looks like the "low" % silver solder, which is more or less useless if you want the silver properties of the
solder. IIRC it is brittle and sort of hard to flow where one wants to...
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I don't have any idea about the specifications of the silver solder used. I hire a machinist/welder to do that kind of work as I don't have an
acetylene torch. On this last job he was feeding a silver wire to the weld after first fluxing it heavily. On my autoclave he was feeding a skinny
silver bar. Again I don't know the specifications. I will see if I can find out what he was using on the condenser.
The single most important condition for a successful synthesis is good mixing - Nicodem
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watson.fawkes
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| Quote: Originally posted by Magpie | | I don't have any idea about the specifications of the silver solder used. [...] I will see if I can find out what he was using on the condenser.
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The liquidus temperature of copper-silver is 780 °C. The spongy look you reported might be a symptom
of gas escaping through a partially-molten joint. Given that phosphorus is used to lower the melting point of such alloys, there's a good chance that
the filler metal is simply liquifying.
Probably needs to be welded. Nickel brazing would likely work, but welding would be cheaper.
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