Oxy-fuel cutting is a common industrial process for cutting various materials – more specifically, ferrous metals, such as low-carbon steel, medium-carbon steel, mild steel, iron and titanium. However, the process cannot cut non-ferrous metals that don’t rust, such as stainless steel. Therefore, when cutting steel via the oxy-fuel method, only carbon steel or mild steel with low carbon to medium carbon content will work.
Of course, a high-quality cutting torch is important – that’s a given. However, a cheaper, low-quality torch can affect many variables in the oxy fuel cutting process. The oxygen flow’s purity determines the cutting speed, which can make all the difference between a clean, quality cut and a messy, uneven one – the latter possibly resulting from oxygen flow air entrainment. Overall, oxygen purity must be at least 99.5% - a mere 1% reduction in purity can reduce cutting speed by 25% and might even increase gas consumption by up to 25%.
Look at tip charts, and acetylene torch tips show as the most common type of cutting tool in oxy fuel welding and oxy fuel cutting processes – though propane tips are used as well. The main difference between acetylene propane and torch tips is that the propane variant releases less heat and is thus less efficient at cutting materials. On the other hand, an acetylene torch tip releases much more heat; therefore, it’s far better for cutting.
Equal-pressure torches (also known as balanced-pressure torches) are also a great option. They keep the oxygen and fuel gas pressure equal. Generally, operating pressures vary and depend on the cutting tip type. However, most industrial oxy-fuel cutting tips have an equal-pressure design; this is excellent for having complete control over the acetylene-to-oxygen ratio and important for maintaining a highly carburising or oxidising flame.
Furthermore, the mixing chamber’s design means equal pressure torches have a higher flow rating. Working well with many gas types, such as propylene acetylene, propane, natural gas, and MAPP, the equal pressure torch is more versatile and even safer than the injector torch; because equal gas pressures are applied, flashback is less likely to occur.
When finished, shut off the torch oxygen valve first and then close the torch fuel valve. This simple technique checks both valves for leaks every time the torch is turned off. A snap or a pop sound signals a leaking oxygen valve, while a small flame at the tip’s end indicates a fuel gas leak.
While this tip may seem obvious, so many people – both professionals and hobby oxy-fuel cutters and welders – don’t check O-rings regularly enough. They’re such a small piece of gear, and, as such, they’re often left forgotten – but that’s a huge mistake.
Overall, two types of O-rings for welding and cutting attachments exist: O-ring small and O-ring large. Whatever the type, inspect their state and change any showing signs of wear and tear. Naturally, changing O-rings, cutting nozzles, and welding attachments can be challenging and fidgety; however, lightly smearing special lubricants on the sealing rings and surfaces in the cutting attachment’s connection head can ease the process.
Additionally, note that oil or grease must never be used because many compressed gases like oxygen are highly oxidising and can ignite spontaneously when in contact with oil and grease – even without an ignition source. As a result, lubricants used in oxygen and gas fittings must meet specific requirements and be approved by BAM (German Federal Institute for Materials Research and Testing). These specially designed lubricants are inert, boast oxidation stability and are non-inflammable.
As leading experts in oxy-fuel, plasma cutting and waterjet cutting technology, processes and materials, we at KERF are your one-stop spot for all matters in this sector.
Whether you’d like advice on materials and equipment, have questions about the industry, or are here to avail our top-tier after-sales support service, contact us today for assistance. Our knowledgeable and friendly team awaits at the end of a phone call or email and will be delighted to speak with you.