Flame welder buying guide

Guide written by:
Michael, Professional and passionate welder, Sheffield

Michael, Professional and passionate welder, Sheffield

63 guides
How many welders are actually in love with their torch? No one knows, but if there's one welding process loved and cherished above all others, it's flame welding. Let's follow the lovers and discover the art of flame welding. Fire ahead!...

Important features

  • Mono-gas
  • Bi-gas
  • Autogenous
  • Temperature
  • Size

Weld and welding: what’s the difference?


Welding
involves uniting two or more parts into a continuous structure.

"Welding" refers to the process and "weld" to the joint produced by this process.

I've had my wrist slapped before for forgetting the distinction... A first piece of advice, start on a good footing!


What's the anatomy of a welding torch assembly?

Everyone's heard the phrase, but there's an ocean of difference between the blowtorch held in one hand and used in plumbing or to caramelize a crème brulée and the dual gas blowtorch. We're talking about melting metal here!


Multi-purpose single-gas torch (also known as soldering lamp)

Consisting of either a cylinder or a disposable cartridge of butane or propane; a preset regulator; and a hose connected to a handle with a  heating control knob, this has served plumbers for generations to braze, bend or tin-plate pipes. Through flame contact, an interchangeable burner lets you reach temperatures of up to 1600°C. The cartridges have a lifetime of one to two hours maximum, depending on the job.





Bi-gas torch

Unlike the above mono-gas system, an oxidizer - oxygen - is added to obtain an optimum temperature of 2800-3000°C. Bi-gas torch sets are well-presented and compact, easy to store, and highly practical for small repairs in plumbing as well as for newcomers to autogenous welding. In addition, kit are supplied with extra-small nozzles for jewellery repair. Again, duration of use is limited.




Autogenous or oxy-acetylene welding

Another bi-gas setup used in industrial and modern plumbing applications, this set consists of:

  • Bottled acetylene, dissolved at 17 bars, as fuel; the "warhead" (top of the bottle) colour-coded brown;
  • An oxygen cylinder, pressurized to 195 bars, as an oxidizer; white warhead;
  • Two separate adjustable pressure regulators;
  • Two flexible hoses of different colours: blue for oxygen, red for acetylene;
  • A specialized torch that ensures an appropriate mix of the two gases. Different levels of precision can be achieved with interchangeable nozzles of varying sizes.



Why oxyacetylene welding is a favourite with welders

There is a reason why welders prefer using an oxyacetylene setup: the flame produced by the torch has some excellent qualities:

  • It's as hot as it gets, between 3100 and 3200°C - and produces three different heat zones: The tip, the pink plume (ooh pretty!) and the blue-coloured reducing zone, the crucial part of the flame for autogenous welding. I first learned that from a metalwork teacher donkey's years ago - you'll never forget once you've got the knack.
  • It's easy to adjust, with a range of interchangeable nozzles provided on a star-shaped stand. These always come with the torch and are classified in terms of flow in l / min. They must always be kept clean to give a flawless flame tip: a good welder always has his welder's reamer in his pocket.

Installation advice


For safety reasons, a one-way valve, identical in colour to the hose in question, is placed on each hose as close as possible to the torch, to prevent the flame recoil into the gas bottles. This type of accident can result from a poorly maintained blowtorch, so take care.


How does a flame welder work?

ManoMano

For single gas setups, all you need to do is heat to the melting temperature of the filler metal (e.g. tin or silver solder) without forgetting to use some stripper on your components beforehand.
 
In this case, the welded components themselves are not melted. Only the filler metal is melted in the welding process. Melting temperatures vary between metals; base your choice of equipment and operating settings on the properties of your filler metal.
 
Depending on the size of the component to be welded, different burners are used to concentrate the heat at the point of welding. For tricky welds, you can get dedicated nozzles that avoid the risk of damage to the surrounding area.
 
A single-gas torch can also be used to heat a component prior to shaping, strip paint from sheet metal or even make creme brulee!
 
The focus here is on autogenous welding, a process similar to bi-gas welding but a little more sophisticated.


How are welding torches classified?

Torches are classified by size, from smallest to largest. Of course, your choice will depend on the thickness of metal sheet or components you're working with. As a rule of thumb, a flow rate of 100 l/min per 1mm of thickness is about right; the wire diameter of your filler metal is equivalent to the thickness of your sheet metal. Clearly No. 2 below is more suited to heating pieces of metal to be forged!


Classification of welding torches


No. 00

Nozzles from 10 to 40 l/min; small welding torch.

No. 0

Nozzles from 50 to 200 l/min; most commonly used type of torch.

No. 1

Nozzles from 250 to 1000 l/min; high-temperature torch.

No. 2

Nozzles from 1250 to 5000 l/min; heavy-duty welding torch.

First-time use of a flame welder



So, the gas cylinders are connected, the pressure regulators set at a pressure of 0.05-0.1 bar for the acetylene (C2H2) and 1-1.5 bar for the oxygen (02).
 
Your torch will have two adjustable knobs, one for each gas, identifiable by their colour. First turn up the acetylene, followed by the oxygen (1/4 turn of bottle cock is enough); then ignite your torch with the dedicated gas ignition button and adjust your flame so it has a fine, sharp tip.
 
Have a go at heating some metal sheet to practise the art of melting - it doesn't matter if you make a few holes the first time round, you're learning!

Once you've mastered melting, move on to welding using an appropriate filler metal (diameter and type).
 
To begin with, while you're working out your settings, it's common for droplets of molten metal to fly around - so watch out for your work clothes! Repeat until you've got the right settings for what you want to do.
 
A piece of advice about your acetylene bottle: since the gas is dissolved in acetone, avoid running the bottle down completely and don't lie it down - both risk burning acetone in your torch, resulting in a rubbish flame and poor welding results.


User advice


If you want to be economical, you can get a device that starts and cuts off gas flow as soon as you attach / detach your torch.


Common accidents and malfunctions


Due to the nature of the device, malfunctions are not uncommon; however, more often than not there's nothing major to worry about!
 

Uncontrolled flame


Caused by a reduction in the pressure of one of the gases or bad condition of the torch.

Clicking / snapping noise


Either the opening of the torch nozzle is blocked - in which case you should clean it with a welder's reamer - or the nozzle is becoming overheated, in which case you should cut the acetylene and leave the oxygen running to cool it down.

Visible flames inside the torch


Caused by overheating of the nozzle; turn off the gas supply and restart.

Sooty flame


This is when the flame becomes black and dirty. Make sure your gas flow is appropriately adjusted.


Tips for choosing...


To summarize, choosing a welding torch is about having a precise understanding of the range of what you need it to achieve. Having thus narrowed down the available options, you'll find an impressive range of products to suit you.

Just relax and let yourself be lured in by the beautiful coloured glow of your perfect welding torch... But don't get too close!


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Guide written by:

Michael, Professional and passionate welder, Sheffield 63 guides écrits

Michael, Professional and passionate welder, Sheffield

I was trained as a pipe worker and welder and worked in the industry for 15 years, going all over the UK for large-scale projects. When I decided it was time to stay closer to home - to have time for my own DIY - I took over a local metal shop and eventually went on to become head of a professional engineering firm.

I'm retired now, but I haven't stopped working with my hands. I recently built my own metalwork studio at home - a lifelong dream! I use my welding skills to make sculptures and bespoke furniture. With my studio, I managed to find a piece of paradise where I can let my imagination run wild.

I also love going around to local auctions and boot sales. I always find some interesting old object or tools that I can add to my collection or transform into works of art.

Now that I have the time, I've turned my hand to decorating, painting on canvas and gardening. I'm always developing new technologies and tools to bring my ideas to life. And I'm always happy to give others advice on how they can make their dreams a reality, too!

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