14 - 10 - 2019, by Convergence Industry
Orbital welding: it is fast, accurate and automated. Over the years Convergence Industry has gained high skilled experiences with this technique. In this process we entered some pitfalls we would like to share. Most issues lead back to poor preparation and incorrect use of equipment. We have listed the 10 most common mistakes made in orbital welding so that you don’t have to make them again!
Tubing: straight sawn-off, ground, etc.?
Let’s start with the most important thing: what are you going to weld? It is vital to use tubes of the same diameter and wall thickness. In addition, it is important that the ends are properly cut and deburred. Ready-made products such as corners and adapters for connections to components are in fact always perfectly flat and have no burrs. This is also how the used tubing must be finished.
In general, we use the supplied smoother and more burr-free workpiece that fits on a drill. By clamping this tool onto the appropriate claw, and turning the distance of the grinding head closer, the tubing is finished to 1/10 mm-precision, flat and burr-free.
After cleaning (degreasing plus air cleaning and drying) the workpiece will be ready to be welded. Bad welds, such as convex and concave ones, and breaks or bubbles in the welding work can thus be avoided.
Do the parts to be welded fit well together?
Even an orbital welding machine can’t perform miracles, so prior to start welding, it is important that the parts fit well and straight together. To achieve this, the tubing must be leveled with a special tool, as discussed above. The parts must then be aligned correctly and straight together in the holder, and the seam must be exactly in the middle of the weld point. If this is not the case, the weld will not be watertight, and the welding device will often indicate an error (welding error: weld broken). When this happens, the tubing pieces must be flattened again.
Are the parts to be welded open so that gas can flow through for cooling and shielding?
For proper cooling of the tubing, it is important that the parts to be welded together have 1 input and 1 output. If there is more than one connection to the atmosphere in your welding work, these must be closed. If the gas flow is insufficient, your weld will be weaker and there is a chance that this bulb will stand, collapse or burn in the worst case.
Has the tubing been properly degreased?
This is by far the simplest step in the entire process, but one that – when rushing – is sometimes overlooked or not done properly. If the parts have not been properly degreased, more deposits around the weld will be observed. This is due to the fact that grease and dirt on the parts are burned during welding, which leaves a deposit behind.
Are your gas taps open properly?
If you are sure that the parts to be welded are well-prepared, it is important to check your equipment. When the welding machine is switched on, the two gas bottles (Argon type 5.0) that stand next to the welding table must both be fully opened. One bottle is connected to the workpiece, and the other to the welding machine. Attention must also be paid to the gas tap next to the welding machine, which must be closed to avoid gas escaping. When the welding is to be performed, fully open both taps. After welding, first close the gas tap on the worktable to shut off the gas supply. Afterwards also close the gas bottles.
Do you have sufficient gas pressure?
For orbital welding, it is important that the correct gas pressure is supplied. Therefore, before you start welding, always check the gas pressure on the two gas bottles. Ensure that the reducer from the gas bottle to your worktable is set at approximately 7.5 l / hr. Ensure that the reducer from the gas bottle to the welding machine is set at approximately 8 bar.
Is the electrode the correct length and shape?
The basic function of an orbital welding machine is that an electrode moves radially around the parts to be welded. The electrode is an important part of the welding process as it creates the welding arc. For orbital welding, it is important that the electrode have a consistent shape and length, otherwise deviations in the welding quality can occur. The electrode is made of a tungsten alloy, is grounded at a fixed angle, and the tip is flattened very slightly. These factors ensure good ignition and formation of the welding arc, as well as its stability. The electrode itself has a fixed length to ensure a good fit to the welding machine.
The photos show a contaminated electrode in the welding machine; the point and the angle of the electrode are no longer visible and there is a clear amount of ‘contamination’ on the electrode. This consists of splashed material from the welding itself, but sometimes also because the tip ends up in the weld pool and then welds itself to the parts to be welded.
A new electrode is made according to the procedure and mounted into the welding head at exactly the right distance using a spacer block. In this way, we ensure a consistent ignition and welding process.
Think carefully about the order of your welding work
After preparing your work and checking your device, things can still go wrong. It may sound logical, but can de easily overlooked. While welding several pieces of tubing together, you must think carefully about the welding order. By not following the correct order, part scan possibly no longer fit in the holder. This may, for example, be the case if you weld a T-piece. The solution is to weld an optional extension between them. Always try to plan the good order of your work in advance.
The importance of balance
It is very important that the two parts to be welded lie properly against each other in the welding machine. Therefore, make sure that there is not too much weight on one of the parts. This can cause the part to be skewed in the holder, as a result of which the weld will not adhere well to the two parts. If there is still a lot of weight pressing on the part, try to support it as much as possible.
Weld seam: convex or sagged?
Do you have a convex weld seam or a collapsed one? This must be considered during your preparation. A convex weld happens when gas flow is incorrect. You may forgot to turn the gas on or pinch it upstream of your work process. When gas accumulates, your weld will be pushed out: this will produce a convex weld. If there is no gas flow in the tube, there is a chance that the weld will collapse. You will also get a higher attack on the inside.
Orbital welding at Convergence
If orbital welding is beyond your capabilities, we have the expertise and equipment to be of service to you. We are actually equipped for ¼” and 3/8” though our setup is also capable for 2, 3, 6, 8, 10 & 12mm and 1/8” upto ½”
Click here for more information or contact us directly for our competitive prices and lead time
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