{"id":12359,"date":"2025-11-07T13:03:41","date_gmt":"2025-11-07T13:03:41","guid":{"rendered":"https:\/\/www.jstconsultancy.cz\/?p=10226"},"modified":"2026-07-31T22:19:35","modified_gmt":"2026-07-31T22:19:35","slug":"how-to-correctly-distinguish-lpc-iii","status":"publish","type":"post","link":"https:\/\/intelligent-kalam.80-240-27-133.plesk.page\/en\/how-to-correctly-distinguish-lpc-iii\/","title":{"rendered":"How to correctly distinguish LPC III"},"content":{"rendered":"

As I have already described in the previous sections, in order for the LPC to work properly, both with regard to the layers and the condition of the furnace, we must follow certain principles. From my personal experience, I know that it is not such a big problem to carburize a few pieces in the furnace, I also did that in 1989 on RDVA furnaces, which were started by ZEZ Praha at that time. Another experience of mine came at a time when we needed to select LPC equipment for Poclain Hydraulics in 2000. We have already tested these on professionally made devices. But I became vigilant when I was told at one test furnace that they had to remove carbon deposits and tar from the carburizing chamber every week.\u00a0 And not a small amount.<\/p>\n

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How is this possible? I have described part of it in the previous chapters. The use of gases other than C2H2 does not make sense, because unlike acetylene, which decomposes catalytically, they decompose thermally, in the volume of the furnace. They are therefore a source of carbon that has no consumption and it is deposited in the furnace. The fact that at that time companies offered ethylene, propane, gas mixtures resulted from patent protection. I remember negotiations about the purchase of equipment with LPC. When I asked why they use propane and not acetylene, the answer was: it’s patented, but when we deliver it to you, feel free to put a bottle of acetylene in there.<\/p>\n

Times have changed. Basically, everyone is only on pure acetylene.<\/p>\n

We also already know that if the saturation period lasts longer than 2 minutes, it loses its meaning. In the furnace, the activity of the atmosphere and the surface of the steel is compared, and with the zero gradient I only supply gas with carbon, which again has no consumption. Other rules apply to the total pressure, flow velocity, flow direction and its optimization inside the chamber, etc.<\/p>\n

If the LPC system is perfected, secondary ethylene is not formed in the furnace from the C2H2 + H2 reaction, and we do not have a problem with the excretion of soot.<\/p>\n

But even that is not enough. Another source of contamination of the heating chamber is quenching oil. On the one hand, due to the penetration of oil vapors from the quenching chamber into the heating chamber, on the other hand, due to the clogging of oil through the transport mechanism. Thus, physical contamination of the chamber with hydrocarbon vapors from the quenching oil occurs.<\/strong> These two phenomena often add up <\/strong>\u00a0and together cause the formation of sticky carbon condensates (tar, soot, polymerized carbon)<\/strong> on walls, heating elements and diffusers.<\/p>\n

After quenching, oil vapours (CnHm) are released in the quenching chamber<\/strong>, which are returned by diffusion or flow into the heating chamber. These vapors, e.g. from mineral oil, polyalkylene glycols, esters, have\u00a0 a lower decomposition point, 300\u2013600 \u00b0C, <\/strong>than acetylene.<\/p>\n

On the hot surfaces of graphite heating elements, or on the surfaces of ceramics, these heavy hydrocarbons are pyrolysed and tar\/soot is formed<\/strong>. When these layers are overlapped with a layer of ethylene pyrolysis, they form a conductive, insulatingly unstable coating <\/strong>that destroys the heating elements or thermocouples.<\/p>\n

Typical manifestations are black paint deposits on the insulation, sticky coatings on the furnace walls, or reverse contamination of the quenching oil.<\/p>\n

To prevent these phenomena, we must respect certain principles when designing a furnace for LPC<\/p>\n