You often create welds of tubes made of stainless steel with a thickness of less than 3 mm (requiring a single welding pass by fusion) or tubes of more than 5mm thickness (maybe needing several layers).
This question is often raised when it comes to equipping a factory, or a site, in terms of welding equipment: manual TIG welding or automated orbital TIG welding?
It is not a question of comparing the manual welder to the machine, as the work done by a qualified welder cannot be compared to the repetitive tasks done by the machine. It is more about comparing the different situations and knowing the solution that suits you best. Here the 4 most important criteria to be considered in order to choose the most adequate solution:
1. Cost for tube preparation and consumables
We can distinguish two different types of tube preparation before welding:
- A simple preparation by cutting the tube and/or bevelling: if the surface quality is not sufficient, you have to proceed to a bevelling of the tube otherwise a simple cut of the tube is sufficient. Then you align the tubes and make a tack weld before final welding.
- You also might need a groove for tube preparation if you have a thickness of more than 3mm. This groove will give a better penetration of the weld with perfect sealing and protection.
GROOVE AND FILLER METAL
By manual welding, the preparation of the tubes consists of creating a V-groove and aligning the tubes, whilst keeping a small distance between the tubes for placing the welding rod. The penetration is realized by passing the wire from the interior. Under these conditions you will need a high amount of wire to fill the groove.
In case of automated welding, you will prepare V- or J-grooves according to the thickness of the tubes to be welded … to create an arc. In this case, the space to be filled is smaller and you will need less filler metal.
INERT GASES
If you proceed to a manual weld with a distance between the tubes to be welded, you will consume more inert gas compared to automated welding with sealed welding joints where less gas is added to the process. The gas consumption is one important item to consider in terms of productivity : automated welding is more interesting, ( cost effective).
ELECTRODES
By using automated welding you will use less electrodes, as the welding equipment allows you to work without any contact between the electrode and the weld pool – in choosing an orbital TIG welding solution. Mechanical guiding systems guarantee a constant distance between the electrode and the tubes (in the case of open welding heads). Even more sophisticated options can be considered, for example the arc voltage control (AVC), which regulates the tension of the arc between the electrode and the tubes, and thus the distance between them.
In both cases, you avoid a contact of the electrode with the weld pool and any contamination of the weld seam by tungsten inclusions. You also reduce the consummation of electrode. The strike of the arc is done in a repetitive way with a machine-controlled distance between the electrode and the tubes, enhancing the lifetime of the electrodes.
2. Operators and qualifications
QUALIFIED WELDERS AND TECHNICAL OPERATORS
You have to differentiate a welder from an operator. The welder is more qualified and he has a non-measurable advantage: his technical know-how!
The operators on orbital welding machines may have a less important training than a qualified welder, as most of the tasks are realised by the machine. The operator is in charge of the successful functioning in the right sequence. He will follow-up automated tasks that do not require more important qualifications.
For your information: the training an operator for simple fusion welding takes just two days, and for multi-layer welds twice three days! So there is no possible comparison to the complete training of a certified welder.
DIFFICULT SITUATIONS
There is another point that mustn’t be neglected: the situation of the work place and in particular when surrounding conditions are confined or difficult. For some tasks, the welders have to remain in an uncomfortable or dangerous position for a very long time. In these cases orbital TIG welding help to preserve the health of the welders when it comes to work in locations difficult to access.
3. Real welding time: time of arc functioning
When you want to choose the most adapted process you also have to consider the real welding time. There is a certain difference between manual TIG welding and automated orbital TIG welding.When you weld in a manual way, the welding time can be longer as the welder sometimes needs a break, and the concentration of the welder is not always at the same level.
These are points to be considered as we talk about human beings. So we are not talking about welding speed, as there is not a big difference between manual and automated speed in general (excepted under difficult welding conditions), but the global period of using arc time.
When you use an orbital TIG welding equipment you know the real arc time in advance, as you know when the arc is stroke and when the machine will finish the weld. When you proceed to manual welding, all depends on the welder. He is automatically influenced by the context, the environment, extra-professional aspects, the painfulness of work, …When we talk about difficult welding situations, we consider of course the security of the welder and the working conditions, and automated orbital TIG welding is the better solution in these cases.
But that is not all. In fact, we know all that a welder is able to realise a weld in a confined place and that the final result will be of good quality, but it is important to point out that the working speed will be lower. When your aim is to obtain good quality, an orbital welding machine will have a better time performance compared to manual welding, as you have to consider the difficulties of the working conditions.
4. Cost of quality and gain in time
When I speak about quality, I also consider the lack of quality, and in particular the amount of money you can lose because of discarded material. In the case of a bad quality weld, the manual welding process will have a much higher rate of scrap dependant on the aptitudes and the condition of the welder. Welds are rejected and have to be repaired or repeated.
In the case of automated orbital TIG welding, discards are very low: 99% of the welds are accepted (even 100% if all the parameters are well managed). This means a gain in terms of time and money: you never work on the same weld twice!
Thanks to these 4 criteria you can understand that orbital welding can be used for a large range of situations, and help manual welders to perform in difficult or dangerous situations.The real challenge is to find the right balance for your company: between qualified welders, and the right equipment, in order to use both where they are at their most useful, to produce the best quality.
The return on investment cannot be defined in advance when you consider manual welding and automated welding. Several elements are unknown when you start a project, such as the number of welds to be realised, the cost of the operator, the final application and their requirements. Some customers amortize an orbital welding machine with only one project, so why not you?
To summarize, I wish to point out at least 6 advantages:
1. Training of the employees, operator – welder
2. Gain of gas consumption
3. Gain of electrode consumption
4. Gain of filler metal linked to the weld preparation
5. Optimized arc time
6. Quality: less discarded welds after control (x-ray inspection)
