FR2547367A3 - CENTRIFUGAL PUMP WITH AUBES PROTECTED AGAINST WEAR - Google Patents

Abstract

A. CENTRIFUGAL PUMP WITH BLADES PROTECTED AGAINST WEAR. B. CHARACTERIZED IN THAT THE BLADE WHEEL 2 IS PROVIDED, AT LEAST AT ITS SEALING POINTS 3, 4 AND OR AT ITS SUPPORT POINTS, WITH A METAL PROTECTION LAYER 5 APPLIED BY SPRAYING, WELL ADHESIVE AND RESISTANT TO WEAR. C. THE INVENTION RELATES TO A BLADE WHEEL OF A CENTRIFUGAL PUMP PROTECTED BY METAL PROJECTION AGAINST WEAR.

Description

The invention relates to a centrifugal pump with blades protected against wear.

  a centrifugal pump comprising at least one impeller housed in a housing and sealed. The overpressure at the outlet of a centrifugal pump impeller requires sealing locations from the inner periphery to the outer circumference of the impeller, otherwise leakage or leakage occurs. leaks or gaps may especially be generated between the impeller and the diffuser c 8 té suction at the inlet of the wheel, between the blades and the housing, in the case of open wheels, at the place of the gland and compensating members for the axial force, and between two adjacent stages of a multi-stage centrifugal pump. In order to keep the gap losses as small as possible, the interstices (blocking sections) between the rotor and the stator are naked-bare as small as possible, this in itself carries the big

  risk that in case of impurities in the circulating fluid, foreign bodies do not arrive in the small interstices causing, after a short time, local overheating, until a melting of the material occurs and that the engine drive stops.

  In order to solve the problem thus posed, it is known to screw, glue or press into the housing or 2.

  in the impeller, rings of wear-resistant material, rings of this kind are designed as wear parts and can be replaced in case of excessive wear.

  As a result, the paddle wheel itself, which is comparatively very expensive in manufacturing, does not need to be used.

to be changed.

  The object of the invention is to create a centrifugal pump provided with a paddle wheel, of the type indicated in the preamble, in which the mentioned drawbacks are overcome, and aims in particular at producing, by means of very simple means , a centrifugal pump that is particularly resistant to wear and supports in sequence, long-lasting use with great safety

Operating.

  The invention relates, for this purpose, to a centrifugal pump of the type indicated, which is characterized in that

  the paddle wheel is provided, at least at its sealing points and / or at its points of support, with a protective layer of metal applied by projection, which is well adhered and resistant to wear.

  The protective layer according to the invention, a well adhering and wear-resistant metal layer, applied by projection to the sealing points and / or the fulcrums of the impeller, provides the advantage of allowing to provide paddle wheels, which are comparatively costly in manufacturing, with highly effective, very light weight shielding, and this in places under heavy stress, where erosions or cavitations occur. With centrifugal pump blades, the greatest wear always occurs on the rotating part, the impeller, and never on the fixed part (housing), or on the ring designed as a lost part of wear. after the state of the art described

  above, and that the invention allows to delete.

  Coating or projection application

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  3 ,. is carried out according to the invention, according to the process designated as "flame injection" method, using solid materials having both properties of resistance to wear and rust prevention than a very weak the difference in tension with respect to the counterpoise The places corresponding to the sealing points, fulcrums or blocking sections in which the

  Interstitial losses are constituted so as to be in the form of long throttling surfaces or labyrinths.

  In order to prevent the rotating part from attaching to the fixed part, according to the invention, different surface hardnesses of material are used, that is to say that in particular the protective layer is constituted in one piece. material having a surface hardness greater than the surface hardness of the support members and / or

adjacent stationary casings.

  The protective layer is preferably made of metal oxides having a high wear resistance; it is resistant to corrosion and has a low coefficient of contraction There is

  Particularly advantageously, the material of the protective layer is a rustproof material. Thus, the protective layer may consist of an alloy of oxides of Al, Ti, Si and / or other oxides.

  The protective layer may optionally be further treated with wet grinding in order to

  to develop well polished surfaces.

  It is, of course, known from the state of the art (see German Offenlegungsschrift No. 24 13 382) that protective layers against contacts or slips are produced by thermal spraying. However, the protective layers thus obtained by projection are planned on

  fixed construction elements, and not on rotary parts such as paddle wheels.

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  The invention will be better understood with the aid of the description below and the attached drawing representing

  an exemplary embodiment of the invention.

  The single figure of this drawing is a partial sectional view showing quite schematically, how is the impeller of a centrifugal pump made according to the invention. In the figure of the drawing there is shown, in axial section, a impeller 2 of a centrifugal pump 10 1 (which has been indicated only by this reference without representing it) This impeller 2 is constituted in a manner known per se and comprises in the axial direction

  sealing points 3, 4 of the housing on the periphery.

  At these detent points 3, 4, of the impeller 15, the protective layers 5, resistant metal layers, were applied by spraying, according to the method designated as the "flame injection" process. at

  wear and corrosion as well as firmly adherent.

  Prior to a spraying operation the base surface of the paddle wheel is suitably prepared, for example by sandblasting or roughening it by mechanical means. As a result of this preparation, it is applied by spraying. an adherent layer based on Ni / Al from filiform metal and then, as a cover layer, a protective layer 5 having the characteristics specified above in the form of powder, using a metal spray gun to a distance of about 70 to 200 m. The metal to be applied by projection is ame30 born for this purpose, by a mechanism of advance in a burner nozzle of the metal spray gun, o this metal is melted in a gas flame fuel / oxygen The molten metal is sprayed with a stream of air

  compressed and the particles thus obtained are projected in the plastic state on the paddle wheel at the pre-

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5.

  seen; they agglutinate solidly to each other to form a well compacted injected layer.

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Claims (4)

  R 3 V 8 NDIOATI 0 N a 1. Centrifugal pump (1) with at least one impeller (2) housed in a housing and sealed, characterized in that the impeller (2) is provided, at least in its (3, 4) and / or at its support points, a protective layer (5) applied by projection, well adherent and resistant to wear. Centrifugal pump according to Claim 10, characterized in that the protective layer (5) consists of anti-rust material,   Centrifugal pump according to either of Claims 1 and 2, characterized in that the protective layer (5) consists of a material with a surface hardness greater than the surface hardness of the support elements. and / or adjacent stationary casings.   4. Centrifugal pump according to any one of claims 1 to 3, characterized in that the protective layer (5) consists of an alloy of oxy20 Al-Ti-Si and / or other oxides.