The last versions of 2HC2 are equipped with extremely hard pipes which can’t be unbound by the method described above without damage. I hurry to rejoice you: having made some experiments we found out the solution of the problem. More precisely, we already knew WHAT should be done – to anneal the pipes to soften the material. The problem was HOW to do this. I describe the technology.
You need the following set of tools for annealing:
A balloon of 300th gas and a burner with onboard piezolighter will cost nearly 55$, face shield (namely face shield, protective spectacles are inappropriate) and thick gloves – more 10$. Thick apron is also useful although I get by with a thick jacket.
Let me explain the reasons for such precautions: there is some amount of water in the pipe. I assume you know what happens with internal pressure when all this water at temperature near 400° C turns into superheated stream. In most cases the soldering doesn’t sustain the overheating and the vapour bursts through the canted end (naturally, the pipe is broken). If the solder sustains some seconds more…
This is quite harmless incident – the pipe remained a single piece and flew only a meter. Sometimes the pipes are torn in pieces which can be found later in far corners of kitchen. If you have the equipment mentioned above you get off with a five-minute ringing in the ears only; without the equipment you risk to be hit with a piece of a burning hot metal in a vitally important body part.
I hope I frightened you enough :). Let’s proceed to the procedure itself. Thus, we must anneal the pipe in the bends not overheating it at that. The ruse consists in the fact that if you heat the pipe evenly the internal pressure will exceed the critical pressure before the copper heats up to the temperature necessary for annealing. As a result the pipe will be broken. Thus, we need a localized overheating while the most amount of water in the pipe stays in initial aggregative state. How can it be achieved? The solution is simple: you must put the pipe into a cup with cold water and heat up its upper end.
Set the minimal jet and heat not long: 8-10 seconds. It’s desirable not to retard the jet in one place; at the same time don’t move it along the whole pipe – you must heat up the bend only. If the gas has a higher combustion temperature (400 and higher) you must heat the pipe up less time. The indicator of correct heating is the blue tint that appears on the coating of nickel immediately when you take away the burner. If the nickel coating stays virgin light this means that you underheated the pipe; repeat the procedure.
Proceed to next stage. Having laid the burner aside (don’t forget to switch it off) and having observed the obscuration of the pipe, take the pliers prepared in advance, grasp the pipe and put it in cold water quickly: at sudden cooling, copper unlike steel undergoes process inverse to hardening. Material becomes softer, what we need. Repeat the operation with second bend, then take the pipe-bending device and easily unbind the pipe: after such processing copper stretches like plasticine.
Theoretically, the same procedure can be performed by means of standard soldering “stick” ака butane stick. But in this case you’ll have to heat it up longer, and the heat pipe will have enough time to “recall” its function and boil the water in the cup making a fool of the experimentalist. I’m too lazy to test it, don’t take it amiss :).
In the same way you can manage with the pipes having wick made of sintered copper powder which are used in most processor coolers (they don’t want to unbind without annealing). The difference is that the more advanced wick doesn’t allow to heat a small piece of pipe quickly: you have to heat it long time and with a mighty burner only; the butane “stick” is inappropriate here. Luckily, while one part of the pipe is in the water we can heat red the necessary part: water around the pipe will bubble but internal pressure will stay endurable. The main point that there wouldn’t be left enough water in the pipe end hanging in the air for a burst. Thus, when unbinding, for example, П-shaped pipes from Igloo 5600 it’s sensible to put into a cup (more precisely, into a basin) both “legs”.
It’s more difficult to determine the criterion of correct heating here. You may define exactly when the pipe is burnt red: the burner flame right away behind the pipe changes its colour from blue into yellow. There is no harm in this but it’s not always possible to heat it up to such temperature: the heat transfers into the cup with water. This is also not a big trouble: lower temperature is sufficient for successful annealing, but the problem is that we can’t state exactly when the heating should be stopped. As a result we have to act in hit-and-miss fashion. Correctly annealed copper (in case it is not nickeled) loses luster and obtains dull dirty rust tint with black burn marks. But you can make final decision regarding the success in annealing only at unbinding – the distinctive “plasticine” feeling can hardly be confused with anything else.