Among the most frequently asked questions in the workshop, we find those relating to torches, their correct use and safety devices .
Before delving into the subject, we remind you that there is a regulation on the subject, the UNI11627 which is from 2017, which helps us to understand which provisions must be used both for the assembly of the torches and for the safety devices.
Let's see, step by step, how to make the correct assembly of a torch .
How to choose the right type of torch?
First of all it is essential to understand what work we need to perform. Each job, in fact, has its own type of dedicated torch .
Let's start with the cutting torch. It is made up:
- cutting lance - for acetylene, for propane or a mixture of many gases
- tip - knowing this aspect is essential; it is not possible and unsafe to use a propane tip on an acetylene torch or vice versa.
The first thing to do, therefore, is to understand if the torch is good for both propane and acetylene tips .
Generally speaking, speaking of propane can also mean referring to alternative fuels such as methane, butane, etc.
The second thing to do is to define the type of cut : what is the maximum thickness?
The third thing is to evaluate the handle , that is to understand if we also need it for other uses, for example to weld or heat.
Our advice is to choose a cutting torch if you do not need to do other operations. This torch , in fact, is monobloc, so it does not have a detachable lance with respect to the handle.
How to recognize a propane or acetylene tip?
Normally the tips for acetylene have a hole where the gas comes out, which then forms the flame, flush with the top.
The tips for propane, on the other hand, are slightly hollow , because the heat and the point of greatest heating of the flame is reached slightly later than for acetylene.
It is a tip with a slightly recessed shape compared to the top.
Above the tips, usually, there are the initials of the manufacturer . Sometimes, however, they can be consumed and not read well. So you have to be careful and check. The same goes for the smaller tips as well.
Why be careful in choosing the tip type?
The tips are not all the same. They can be compatible between one brand and another. However, be careful, even if they look alike, small differences in the fitting of the seat can cause problems, because they do not fit together perfectly.
It is always advisable to use the original tips . There are also copies on the market, but they can be slightly different and don't make the torch work well. In the worst case scenario, accidents could also occur.
How to assemble a torch in the correct way?
Once we have chosen a type of torch, we know what type of gas to use, consequently we can choose the type of tip.
Let's move on to the practical part:
- we take a torch with flat seat tips and use acetylene
- we tighten with a torch key and tip, lightly; you don't need to tighten a lot, then the heat will do its part
- the handle is mounted on the lance , it stops and tightens slightly with a wrench
- the torch is mounted.
Let's go back to the tips for a moment. For acetylene, the tips can be for various thicknesses.
The smaller ones obviously have a smaller hole. Which is better to choose?
Think about two elements:
- pay attention to the fact that the width of the cut is greater in the tip which has greater reach, which therefore has a higher capacity of thickness of cut
- take into account the cost of gas . A smaller tip would consume more gas and, consequently, the cylinders would be exhausted sooner.
How to adjust for the pressure to be applied?
Regarding consumption, inside the box of the torch cutting lance, in addition to the instruction booklet, there is a table concerning the pressures , to be used both for combustible gases and for combustion gases (combustion gases are , for example, oxygen. Fuels, on the other hand, acetylene, etc.).
This table gives a fairly precise indication of the pressure to be used . It is not true that if you give more pressure, the torch cuts more.
The pressures must be those indicated in the table by the manufacturer. There is a range to be respected to ensure an optimal cutting of the torch.
The torches characterized by the lowest consumption are those of Harris ; a brand famous precisely for having torches with low gas consumption, with the same cut, with other brands. In addition to this they are also quieter.
Safety valves: what is there to know?
Done the assembly of the tip, done the assembly of the handle. We have a torch ready.
At this point we have to talk about valves on the handle, on the tube and on the reducers .
Let's start with the oxygen valves . It is recognized by the right-handed fillet. Beware that there are valves that resemble those to put on the handle, but they only serve to help pressure.
You have to look at the arrow that indicates the flow of the gas, the direction of the gas, that is, an arrow that indicates the direction in which the gas arrives from the cylinder.
Then there are the gas valves . Gas valves are suitable for both acetylene and propane, methane and other gases. And they are characterized by the left thread.
At this point we can mount the classic hose connectors and then insert the tube. Or we can mount the quick couplers.
Let us pause for a moment on the tube. The pipes are specific according to the type of gas . They are usually distinguished by color: that of acetylene is red-blue; the one for propane is orange orange-blue.
Also, you can opt for a twin tube. That is, all two tubes connected together. They are the most used, but according to your needs you can also prefer single tubes.
How to do the complete assembly of the valves?
Follow these steps:
- pushing well all the way, place the connections on the pipes
- tighten the zip ties to prevent leaks
- at this point you can insert the optional valves , if the pipe exceeds ten meters (these are non-return valves). Here, too, you have to be careful of the flow. The arrow must go in the opposite direction to the arrival from the cylinder
- tighten with the key
- arrange the quick couplings. To stop the gas on a pressure reducer, the female must be attached only under pressure and the male must be attached to the pipe. There is a blue dot on these quick valves to indicate gas, while for oxygen there is a red dot
- the tube is ready
- prepare the pressure reducers . So safety valves for the gas. You can use the quick coupling after the safety valve. Attention, the quick coupling must always be added, it does not replace the safety valve in any way
- the same goes for the oxygen reducer . Let's take the valve, the connections are conical inside, so they act as a gasket. In the case of oxygen, hydrocarbons are not used for any reason, therefore no type of oil is used in this pressure reducer.
- as regards the quick coupling on the handle , they are used to quickly disassemble the torch and are not mandatory, while the safety valves are.
The procedure must be repeated for both oxygen and gas. When the round is completed, the assembly is finished.
In summary, here's what you need to check:
- tip suitable for the type of torch
- flow arrow for correct mounting of safety valves
- quick couplings, two meters away, if you exceed ten meters of pipe
- non-return valves on the pressure reducers, which must be connected to the cylinder.
These steps will help you do precise and safe work