By: Frank Caprio | On: April 3, 2018
In steelmaking, continuous casting units are capable of producing a wide variety of shapes and profiles, which are then cut into manageable lengths after they have solidified. While this cutting operation can sometimes be performed with large shears, cutting torches are often used for thicker materials such as slabs and billets. These cutoff torches are oxy-fuel units, where a fuel gas (such as acetylene, propane, et al.) is mixed with oxygen to create a flame hot enough to heat the steel to a bright orange-red.
Interestingly, the flame itself does not cut the steel, but instead heats the steel to the proper temperature so that oxidation can occur. Once the steel is hot, high-pressure cutting oxygen is streamed through the center of the torch tip, oxidizing the metal (think of it as high-speed, temperature-controlled “rusting” of steel). The molten oxidized metal is blown away from the cut groove, eventually producing a relatively smooth, even cut.
The hoses supplying the oxygen and fuel gas to the torch are suspended above the hot strand of cast steel, and are often contained in flexible hose carrier systems (sometimes called “cat tracks”) that prevent the hoses from sagging. Despite this protection, the heat radiating from the casting can cause premature failure of rubber hoses that are normally used on oxy-fuel torches. Because of this, many cut-off systems employ PTFE hoses with stainless steel outer braids for the oxygen and fuel supply lines. The PTFE hoses have better temperature ratings than rubber hose, and can accept the crimped-on, brass weld fittings used for oxygen and fuel gas connections. However, this often does not solve the problem. Even PTFE hose tubes can begin to deteriorate when exposed to the radiant heat from the castings.
At these cutoff torches, we have seen instances where the inner tube of non-metallic hoses deteriorates and travels downstream, clogging the small orifices in the face of the nozzle. This can cause major problems: if you can’t cut the steel, you can’t move it out of the way! The entire casting line may have to be shut down in order to replace the clogged nozzle. This unplanned downtime and loss of production can cost hundreds of thousands of dollars, but it can be easily avoided. Installing a flexible corrugated metal hose for the oxygen and fuel supply lines eliminates any problems caused by deterioration of non-metallic hoses. Additionally, our Masterflex and Extraflex hoses are so flexible, they can easily fit into the tightest bends required by the hose carriers without kinking or collapsing like PTFE or rubber hoses. Just remember: any hose (metal, rubber, PTFE, etc.) that will be used to convey oxygen must be cleaned and degreased for oxygen service. Hose Master has the capability of cleaning our assemblies to CGA specification G4.1: Cleaning Equipment for Oxygen Service.
So, the next time the caster maintenance guy wants to buy a less expensive product, ask him what happens if the cutoff torch tip clogs. Then do him a favor and recommend Hose Master corrugated metal hose. He won’t mind paying a little extra up front to avoid the huge cost of an unplanned shutdown, and you’ll be his go-to for everything that has anything to do with hose!
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