Engineering:Thermal lance

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Short description: Thermal tool that cuts dense heavy materials
Thermal lance
Thermal lance.2004-8-4.jpg
Thermal lance cutting a railroad bridge to prepare for replacement
Other names
    • thermic lance
    • oxygen lance
    • burning bar

A thermal lance, thermic lance, oxygen lance, or burning bar is a tool that heats and melts steel in the presence of pressurized oxygen to create very high temperatures for cutting. It consists of a long steel tube packed with alloy steel rods, which serve as fuel; these are sometimes mixed with aluminum rods to increase the heat output.

Operation

Simplified principle and graph of temperature (T) vs distance from the reacting tip (d) of a thermal lance[1]

One end of the tube is placed in a holder and oxygen is fed through the tube. The far end of the tube is pre-heated and lit by an oxyacetylene torch. An intense stream of burning steel is produced at the working end and can be used to cut rapidly through thick materials, including steel and concrete.[2] The tube is consumed by the process within a few minutes.

Applications

Often used as a heavy duty demolition tool, the thermic lance is also used to remove seized axles of heavy machinery without damaging the bearings or axle housing. This technique is often used on the pins and axles of large equipment such as cranes, ships, bridges, and sluice-gates. In addition, thermal lancing is used to clean the bottom of steel furnace pots, which accumulate a skull layer of slag and iron during operation.[3]

Principle of operation

Steel wool can burn at atmospheric (20%) concentrations of oxygen because it has a high surface area-to-mass ratio and relatively low mass, which prevents the heat from being dissipated in the bulk of the material.[4] When the oxygen concentration is increased, steel wool will burn faster.[5] Burning steel wool is simply the rapid oxidation of iron into Fe2O3; the thermal lance uses steel rods which will burn with a sufficiently high supply of concentrated oxygen.

The temperature at which a thermal lance operates varies depending on the environment.[6] Some estimates put the maximum temperature at 4,500 °C (8,130 °F),[7] while others calculate it to be 2,730 °C (4,950 °F).[8]

Alternative fuels

Thermal lances have been constructed for demonstration using foodstuffs (including bacon and dried spaghetti) as the fuel instead of steel rods; a supply of pure oxygen is more important to drive rapid oxidation than the fuel being burned.[9][10]

History

Leo Malcher filed for a patent in 1922 entitled "Process of attacking compact mineral material, noncombustible in oxygen". The patent uses "a suitable disintegrating flux to act upon the material at the point where it is desired to attack it ... the fuel employed in the example to be described is metallic iron, and is arranged in the form of two concentric pipes". The annulus between the two pipes was filled with a flux (sodium carbonate borax and sodium chloride in equal proportions) and oxygen was supplied through the inner tube.[11]

See also

  • Chemistry:Thermite – Pyrotechnic composition of metal powder, which serves as fuel, and metal oxide

References

  1. ↑ Martí-Rosselló, T.; Ray, P.; Li, J.; Lue, L. (2021). "Numerical Model for the Combustion of a Thermal Lance". Industrial and Engineering Chemistry Research 60 (21): 7788–7801. doi:10.1021/acs.iecr.1c00532. https://strathprints.strath.ac.uk/76441/1/Marti_Rossello_etal_IECR_2021_Numerical_model_for_the_combustion_of_a_thermal_lance.pdf. 
  2. ↑ "What is a Thermic Lance?". https://www.thermiclance.com.au/what-is-thermic-lance/. 
  3. ↑ "Thermal Lancing case study - dust collector extends deskulling operation". AAF International. https://www.aafintl.com/en/power-and-industrial/case-studies/environmental-products/optiflo/optiflo-thermal-lancing. 
  4. ↑ Emspak, Jesse (October 24, 2017). "Here's How Steel Wool Burns (and Why It Looks Like the Death of Krypton". LiveScience. https://www.livescience.com/60764-watch-steel-wool-burn.html. 
  5. ↑ "Combustion of Steel Wool". University of Washington, Department of Chemistry. https://chem.washington.edu/lecture-demos/combustion-steel-wool. 
  6. ↑ LaGuardia, Thomas S. (2004). "Chapter 16.3: Characterization; Description of Select Technologies". The Decommissioning Handbook. New York: ASME Press. pp. 4‐46. ISBN 978-0-89448-041-6. https://books.google.com/books?id=Q7hbcjNRLxAC&pg=PT314. 
  7. ↑ Kosanke, B. J.; Sturman, B.; Kosanke, K.; von Maltitz, I.; Shimizu, T.; Wilson, M. A.; Kubota, N.; Jennings-White, C. et al. (2004). Pyrotechnic Chemistry. Journal of Pyrotechnics. p. 124. ISBN 978-1-889526-15-7. https://books.google.com/books?id=Q1yJNr92-YcC&pg=PA124. 
  8. ↑ Wang, Haorong; Hlavacek, Vladimir; Pranda, Pavol (2004). "Model Analysis of Thermal Lance Combustion". Industrial & Engineering Chemistry Research 43 (16): 4703. doi:10.1021/ie030729r. 
  9. ↑ Gray, Theodore (April 15, 2009). "Bacon: the Other White Heat". https://www.popsci.com/bacon/. 
  10. ↑ Nathan, Mike (February 11, 2011). "Thermic lance made from spaghetti". https://hackaday.com/2011/02/11/thermic-lance-made-from-spaghetti/. 
  11. ↑ Leo M Malcher, US patent grant 1494003A, issued May 13, 1924

External links

  • U.S. Patent 3,921,542 (oxygen-supplied thermic lance, invented by Ernst Brandenberger)
  • U.S. Patent 3,460,223 (device for fixing holes by method of smelting, especially into buildings, invented by Berczes et al.)



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