Welding Tips and Tricks

Hi. I am newbie to gas welding aside from some little propane work done with my dad decades ago. I know safety is first.

This is a learning project for me.

I want to remove the brass soldered brass cap from a small copper boiler.

I intend to use MAPP gas. Is this just welding it on in reverse? Do I need to do something special?

Is there a way to remove the solder in case I resolder the brass cap back on? In electronics desoldering I have seen a copper mesh wick used to remove solder. Is there such a thing in gas welding? I will try to post image of boiler. Thanks in advance.

First I presume it's some kind of silver solder.

If you are using mapp gas + oxygen, ok.

If it's just the hand held bottle/ torch, it won't be enough- you'd need at least two of these going around the pipe at the same time.

I presume the heater rods come out with the cap. You'll probably find the solder on these will melt too.

No there is no wicking process used outside of electronics that I'm aware of.

I've never used solder wick outside of electronics work, but I can't see any reason that it wouldn't work the exact same for cleanup on joints like that. Just use the biggest wick you can find (#6 is the largest I have ever seen), use lots of flux, and don't scorch the wick with the torch as you are heating the part. Heat the part and melt the solder, and once the solder is fully flowing, then add the wick quickly. Saturate the wick in flux beforehand. May also be helpful to preheat that part in an oven before all of these operations.

Edit: You can also use a damp cellulose sponge to flow the solder and then knock/wipe the molten solder off of the part. Be quick with your swipes, and be mindful of where the molten solder is going when it gets slung off of the part.

Thanks for comments.

Might this tip work with just MAPP alone?


https://youtu.be/pxMWQyVXtxU

Coldman wrote:First I presume it's some kind of silver solder.

If you are using mapp gas + oxygen, ok.

If it's just the hand held bottle/ torch, it won't be enough- you'd need at least two of these going around the pipe at the same time.

I presume the heater rods come out with the cap. You'll probably find the solder on these will melt too.

No there is no wicking process used outside of electronics that I'm aware of.

This is made in Thailand so might even be tin/lead solder as some hvac places sell tin/lead solder. Boiler is not foodsafe it is from shower heater.

Do you think during assembly the cap is brazed on first then the heating rods?

Firstly I don't think you'd get that tip to fit a mapp gas bottle.
If it's soft solder, the normal mapp gas torch will do it. If it's silver solder, you'll need fuel/oxy to get enough heat into it or at least 2 x mapp gas bottles.

My guess is the heaters were soldered in first, then the cap to the body. We haven't see the other end, do the heaters come out the other end or do they hair pin bend and come back out the same end?

Coldman wrote:Firstly I don't think you'd get that tip to fit a mapp gas bottle.
If it's soft solder, the normal mapp gas torch will do it. If it's silver solder, you'll need fuel/oxy to get enough heat into it or at least 2 x mapp gas bottles.

My guess is the heaters were soldered in first, then the cap to the body. We haven't see the other end, do the heaters come out the other end or do they hair pin bend and come back out the same end?

All the heaters are on the cap side. I expect the heaters will all come out with the cap.

It’s old enough I doubt it’s silver solder. Propane should be enough. MAPP is definitely enough. When unsoldering old stuff you want to go with less heat, warm it all up slowly so that all the solder gets soft at the same time. I would ask before you open it, what’s the real problem. If the elements are good then they may just need cleaned. Flush it with some rydlime if it works but just doesn’t seem to work well. Ohm out the elements first. If the elements test bad then get a whole new heater for $400.

Poland308 wrote:It’s old enough I doubt it’s silver solder. Propane should be enough. MAPP is definitely enough. When unsoldering old stuff you want to go with less heat, warm it all up slowly so that all the solder gets soft at the same time. I would ask before you open it, what’s the real problem. If the elements are good then they may just need cleaned. Flush it with some rydlime if it works but just doesn’t seem to work well. Ohm out the elements first. If the elements test bad then get a whole new heater for $400.

Good advice.

One of the elements died. I already have a replacement unit so this is a learning experience for me. Boiler is from an AEG multipoint heater that is at the high price end in SE Asia. I bought it after other less expensive units failed thinking it's worth the extra money but it too like the cheaper units, failed. It's design uses a minimum of electronics, #boiler thermostat, a rotating power switch #off. #1. #2. and #3. low medium high and water pressure sensing switches. Never needed high as it was too hot. Was just connected to one shower.
New unit, a Sharp for less than 1/3 price is more than hot enough and also does not impede water flow as did AEG/Steibel but internally shows significant PCB's. In past I have changed heating elements in espresso machines boiler by swapping old for new with a new gasket. Seems these are made without replaceable heating elements. Soldered in just like the SSD and RAM many Apple computers.

Attached is pic of unit with bad boiler as well as newer Sharp unit.

If it's soft solder then you should have no problem getting it apart.

I would first heat the joint slightly and give it a light wire brush by hand with a toothbrush type brush. To clean the surface and allow the solder to flow back out freely

Then would heat up bit by bit and let the solder flow back out of the joint for tubes I'll normally have then horizontal for disassembly and roll as required, less stuff gets on the tube this way I find. Sometimes compressed air is needed to blow out remainders or corroded solder that no longer flows.

Looks like you have a crimp or two on the end cap to deal with of they hold too tightly for removal. Usually a icepick is employed for the gentle persuading of the dimple crimp.


But to be honest most of the newer built things I've ever unsoldered just fall apart with sloppy joints and fitups so you may even just be able to pick the tube out of the cap while hot, who knows till you try.

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Problem with most instantaneous water heaters is small passages don’t work well with bad water. The minerals build up so fast The only way to stay ahead is flush it with a descaling agent every few weeks. The cost of the chemical averages out to the cost of replacing the units. So even then it’s expensive. Look into an indirect boiler with a water maker tank. Cost more to put in but protects the boiler and the water maker tanks are much easier to clean.

Toggatug wrote:If it's soft solder then you should have no problem getting it apart.

I would first heat the joint slightly and give it a light wire brush by hand with a toothbrush type brush. To clean the surface and allow the solder to flow back out freely

Then would heat up bit by bit and let the solder flow back out of the joint for tubes I'll normally have then horizontal for disassembly and roll as required, less stuff gets on the tube this way I find. Sometimes compressed air is needed to blow out remainders or corroded solder that no longer flows.

Looks like you have a crimp or two on the end cap to deal with of they hold too tightly for removal. Usually a icepick is employed for the gentle persuading of the dimple crimp.


But to be honest most of the newer built things I've ever unsoldered just fall apart with sloppy joints and fitups so you may even just be able to pick the tube out of the cap while hot, who knows till you try.

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Much appreciated. The crimps don't apear to contact the copper boiler. I am waiting to receive the MAPP torch.

Poland308 wrote:Problem with most instantaneous water heaters is small passages don’t work well with bad water. The minerals build up so fast The only way to stay ahead is flush it with a descaling agent every few weeks. The cost of the chemical averages out to the cost of replacing the units. So even then it’s expensive. Look into an indirect boiler with a water maker tank. Cost more to put in but protects the boiler and the water maker tanks are much easier to clean.

True and good points. A pre-heater filter might help slow the minerals.

I soaked the boiler in white vinegar for a couple of days.

Indirect boiler is better but I just have 1 bedroom condo in a warm climate so only need hot water for 1 shower. Clothes washer and sinks cold water fine and not too cold at that. Indirect boiler takes up much more space than a tankless heater.

FYI have a look at the locally available water heaters. They can be installed out of sight in bathrooms that have in wall hot and cold lines to shower. About 31 baht / USD
https://www.homepro.co.th/c/PLU0501

This is link to one that failed. They market is as German High quality engineering. Same unit branded AEG or Steibel. Made in SE Asia
https://www.stiebel-eltron.in/en/produc ... _ste_.html

Vinegar is an acid and it will work but you need to expose the system for much longer because it it weak.
https://clrbrands.com/Products/CLR-Hous ... st-Remover
Using something like this will speed up the process. Commercially we use.
https://www.amazon.com/Rydlyme-Cleaner- ... 208&sr=8-5

Works much faster and won’t harm metals.
But even with good chemicals your limited by the basic design of an instantaneous heater. They are designed to be disposable.

Poland308 wrote:Vinegar is an acid and it will work but you need to expose the system for much longer because it it weak.
https://clrbrands.com/Products/CLR-Hous ... st-Remover
Using something like this will speed up the process. Commercially we use.
https://www.amazon.com/Rydlyme-Cleaner- ... 208&sr=8-5

Works much faster and won’t harm metals.
But even with good chemicals your limited by the basic design of an instantaneous heater. They are designed to be disposable.

CLR is great. I used to use in the states. Have never seen in Bangkok. Some espresso machine rebuilders use stronger acid to quickly clean the boiler. I could but don't want to mess with it nor store it. Will leave vinegar in for a few days.

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