PROCESS FOR PICKLING OR DESCALING A CONCRETE SURFACE |
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申请号 | US13701618 | 申请日 | 2011-05-09 | 公开(公告)号 | US20130074881A1 | 公开(公告)日 | 2013-03-28 |
申请人 | Jacques Quintard; Frederic Richard; Charles Truchot; | 发明人 | Jacques Quintard; Frederic Richard; Charles Truchot; | ||||
摘要 | A method for pickling or descaling a concrete surface employing at least one jet of liquid nitrogen at cryogenic temperature below −100° C. at a pressure of at least 500 bar, distributed by the discharge orifice of at least one nozzle for distributing the jet of liquid nitrogen. At least a portion of the distributing nozzle is protected by a resistant material haying a hardness of at least 7 on Mohs' scale. Preferably, the resistant material is deposited externally on at least a portion of wall of nozzle. Advantageously, the material is selected from tungsten carbide, boron carbide, titanium carbide, silicon carbide, cubic boron nitride, alumina and corundum. | ||||||
权利要求 | |||||||
说明书全文 | The invention relates to a method for pickling or descaling a concrete surface employing one or more jets of nitrogen at cryogenic temperature and at high pressure, in particular of liquid nitrogen under pressure. It is known that it is possible to use one or more jets of liquid nitrogen for pickling or descaling certain surfaces or coatings. During such an operation, three effects of each jet of liquid nitrogen are combined, namely:
In certain applications, such as descaling of concrete, it is mainly the “blast effect” of liquid nitrogen that comes into action for executing the work that is required. In this case, each jet of liquid nitrogen “explodes” the concrete surface and propels the constituents of the concrete in all directions. Now, it is found in practice that after a variable time in use, for example after some hours of use, the descaling devices used for distributing the liquid nitrogen become less efficient. After investigation, it was found that their loss of efficiency is due to wear of the nozzles 1 for distributing the liquid nitrogen with which these descaling devices are equipped, as shown in In fact, the constituents of the concrete that are detached by the nitrogen jets 10 strike the nozzle or nozzles 1 for distributing the jets of liquid nitrogen, causing premature erosion of them. In other words, the stripped concrete that is detached from the substrate under the action of the jet or jets of liquid nitrogen will cause deterioration of the nozzles, which are generally made of stainless steel, typically a stainless steel of grade 316. In fact, the present inventors have demonstrated that premature wear of the liquid. nitrogen distributing nozzles is the direct cause of the gradual loss of efficiency of the methods of pickling or descaling, since a degraded nozzle ejects a jet of liquid nitrogen that is noncoherent and dispersed, and therefore less effective. An obvious solution would be to replace the eroded nozzle or nozzles. Now, a frequent need to replace the nozzles of a device for pickling or descaling concrete gives rise to a significant cost and a loss of productivity during the phases of replacement and maintenance of the nozzles of the device. Moreover, said nozzle replacement is not always easily achieved, notably when the operation of concrete pickling or descaling takes place in an environment where human intervention is very limited, or even forbidden, and where preventive maintenance must be as limited and as quick as possible, such as in certain chemical or nuclear vessels. Thus, the problem to be solved is to be able to avoid the drop in efficiency of methods for pickling or descaling concrete, without the necessity of frequent replacement of the nozzles of the pickling or descaling device employed. The solution is a method for pickling or descaling a concrete surface employing at least one jet of liquid nitrogen at cryogenic temperature below −400° C. at a pressure of at least 500 bar, distributed by the discharge orifice of at least one nozzle for distributing the jet of liquid nitrogen, characterized in that at least a portion of the distributing nozzle is protected by a resistant material having a hardness of at least 7 on Mohs' scale. Depending on the particular case, the method of the invention can comprise one or more of the following characteristics:
The invention will now he explained in more detail referring to the appended drawings, where: According to the invention, in order to carry out pickling or descaling of a concrete surface 7, a device for distributing liquid nitrogen under pressure is used, which is equipped with one or more, preferably several nozzles 1, each suitable for and designed for delivering, via their discharge orifice 2, a jet of liquid nitrogen at very high pressure, i.e. typically at a temperature of the order of −150° C. to −200° C. and at a pressure between 1000 and 5000 bar. The problem that arises is to avoid or minimize wear of the nozzles 1 caused by the projection 9 of debris and other constituents of the concrete 7, during the actual pickling or descaling by means of the jet or jets 10 of liquid nitrogen, as illustrated in For this purpose, according to the invention, all or part of distributing nozzle 1 is protected by means of a resistant material having a hardness of at least 7 on Mohs' scale, advantageously of at least 8 on Mohs' scale. As examples, the resistant material can be tungsten carbide, boron carbide, titanium carbide or silicon carbide, cubic boron nitride, alumina or corundum. In all cases, a material will be used having a hardness greater than or equal to that of concrete (between about 7 and 9 on Mohs' scale) and in particular greater than that of stainless steel (less than about 7 on Mohs' scale) so as to minimize the erosion caused by the impacts of concrete debris on the external wall of the nozzle or nozzles 1. According to a first embodiment illustrated in According to a second embodiment illustrated in According to a third embodiment depicted in The coating layer 4 can have a thickness between 5 and 50 μm. According to a fourth embodiment illustrated in |