Patent Application
20130294896
This disclosure relates generally to mechanical rotating mechanisms, and more particularly, to a method, an apparatus and/or a system of increasing wear resistance of a part of a rotating mechanism exposed to fluid flow therethrough.
A rotating mechanism such as a centrifugal pump may be utilized to pump fluids including abrasive materials. One or more part(s) (e.g., seal ring(s) in a centrifugal pump, impeller of the centrifugal pump) of the rotating mechanism may be constantly worn down due to the exposure thereof to the fluid flow. The aforementioned one or more part(s) may be manufactured with a material having a coefficient of thermal expansion different from that of a metal constituting a working wheel (e.g., impeller) of the rotating mechanism. However, the aforementioned material may not be suitable for fluids including significant abrasive impurities (e.g., fluids obtained from boreholes of water, raw oil).
The presence of significant abrasive impurities may wear down the one or more part(s) such that a clearance between elements of the rotating mechanism engaged through the one or more part(s) may be increased. When the clearance increases, volumetric losses associated with the rotating mechanism also increase, thereby reducing the efficiency of the rotating mechanism.
Disclosed are a method, a system and/or an apparatus of increasing wear resistance of a part of a rotating mechanism exposed to fluid flow therethrough.
In one aspect, a method of increasing wear resistance of one or more part(s) of a rotating mechanism includes manufacturing the one or more part(s) with a portion thereof configured to be exposed to wear during fluid flow associated with the rotating mechanism having a dimension different from that of a desired dimension, applying a protective coating of an aluminum bronze alloy to the portion through welding deposition, and mechanically treating the protective coating. The method also includes applying one or more layer(s) of solid-alloy over the protective coating through electro-erosion deposition, and continuing the mechanical treatment of the protective coating and/or the one or more layer(s) of solid-alloy after the solid-alloy deposition to obtain the desired dimension of the portion.
In another aspect, a part of a rotating mechanism having increased wear resistance to fluid flow associated with the rotating mechanism includes a portion configured to be exposed to wear during the fluid flow associated with the rotating mechanism. The portion is manufactured to have a dimension different from that of a desired dimension thereof. The portion includes a protective coating of an aluminum bronze alloy deposited thereon through welding, and one or more layer(s) of solid-alloy deposited over the protective coating through an electro-erosion process. The protective coating is mechanically treated after deposition thereof, and the mechanical treatment of the protective coating and/or the one or more layer(s) of solid-alloy is continued after the solid-alloy deposition to obtain the desired dimension of the portion.
In yet another aspect, a rotating mechanism includes a part having an increased wear resistance to fluid flow associated with the rotating mechanism. The part includes a portion configured to be exposed to wear during the fluid flow associated with the rotating mechanism. The portion is manufactured to have a dimension different from that of a desired dimension thereof. The portion includes a protective coating of an aluminum bronze alloy deposited thereon through welding, and one or more layer(s) of solid-alloy deposited over the protective coating through an electro-erosion process. The protective coating is mechanically treated after deposition thereof. The mechanical treatment of the protective coating and/or the one or more layer(s) of solid-alloy is continued after the solid-alloy deposition to obtain the desired dimension of the portion.
The methods and systems disclosed herein may be implemented in any means for achieving various aspects. Other features will be apparent from the accompanying drawings and from the detailed description that follows.
Example embodiments are illustrated by way of example and not a limitation in the figures of accompanying drawings, in which like references indicate similar elements and in which:
Other features of the present embodiments will be apparent from accompanying Drawings and from the Detailed Description that follows.
Disclosed are a method, an apparatus and/or a system of increasing wear resistance of a part of a rotating mechanism exposed to fluid flow therethrough. Although the present embodiments have been described with reference to specific example embodiments, it will be evident that various modifications and changes may be made to these embodiments without departing from the broader spirit and scope of the various embodiments.
Thus, in one or more embodiments, as the fluid leaves the center of impeller 102, low pressure is created at the inlet thereat, thereby causing more fluid to flow toward the inlet. In one or more embodiments, the curvature of vanes 108 (or, blades) may enable the centrifugal acceleration or the force therefrom to push the fluid in a tangential and a radial direction. In one or more embodiments, the kinetic energy of the fluid emerging out of impeller 102 may encounter a resistance to the flow thereof, firstly created by volute casing 104 that slows down the fluid, and then at discharge nozzle 110, where the kinetic energy is converted to pressure energy and the fluid forced into discharge piping (not shown). One of ordinary skill in the art would be familiar with the working of centrifugal pump 100, and, therefore, additional details thereof have been skipped for the sake of convenience and brevity.
Thus, in one or more embodiments, volumetric losses in centrifugal pump 100 may be caused by the presence of clearances in slot-hole sealing(s), located between impeller 102 and volute casing 104 and accomplished through seal ring(s) 204, or, between individual seal ring(s) 204. In one or more embodiments, volumetric losses may be enhanced due to the separation of high pressure region(s) and low pressure region(s) of centrifugal pump 100 by such slot-hole sealing(s). To reduce the aforementioned volumetric losses, seal ring(s) 204 made of thermoplastic polymer material may be utilized that, due to a coefficient of thermal expansion thereof being different from that of the metal utilized in impeller 102, leads to a decrease in the value of clearance between an inner diameter of a seal ring 204 and an outer diameter of impeller 102. While this may enable an increase in the efficiency of centrifugal pump 100, the aforementioned solution may not be effective when centrifugal pump 100 is utilized to pump fluids including abrasive impurities (e.g., liquid obtained from boreholes of water, raw oil) because the constancy of the mechanic wear process actually leads to a decrease in the efficiency of centrifugal pump 100.
Increasing wear resistance of the material constituting impeller 102 and seal ring(s) 204 may enable decreasing volumetric losses in centrifugal pump 100 when fluids including abrasive impurities are pumped therethrough. Wear-resistant metal alloy coatings may be employed for the aforementioned purpose. First, the part (e.g., impeller 102, seal ring(s) 204) may be manufactured with a size of the surface exposed to wear being less than the required size. Then, the metal alloy (e.g., aluminum bronze) coating may be applied through melting and the part mechanically treated to the desired size thereof. While the aforementioned technique may be largely effective, the resistance(s) of existing kinds of metal alloys such as aluminum bronze may not be sufficient enough to tackle fluids including high concentration(s) of abrasive particles such as sand.
In one or more embodiments, a method of increasing wear resistance of part(s) of centrifugal pump 100 that overcomes limitations associated with the other method(s) discussed above is disclosed herein. In one or more embodiments, a desired part (e.g., impeller 102, seal ring(s) 204) of centrifugal pump 100 may first be manufactured with a size of a surface thereof most exposed to abrasive wear being different from a required size by a thickness of a protective coating to be applied on the surface. In other words, in one or more embodiments, the size of the surface may be equal to the difference between the required size and the thickness of the protective coating. In one or more embodiments, a layer of metal alloy coating (e.g., aluminum bronze) may then be melted on the surface through, for example, Metal Inert Gas (MIG)/Metal Active Gas (MAG) welding. In one example embodiment, the metal alloy may be based on copper containing 6-10% aluminum and 9-18% of manganese, iron and nickel to be used as aluminum bronze. In one or more embodiments, the metal alloy coatings may be well applicable on steel surfaces, and may be sufficiently wear resistant with high corrosion resistance to water and, even, salt water (e.g., sea water). In one or more embodiments, the melting of the metal alloy coating (e.g., aluminum bronze) may be conducted using an electric arc on the surface of a part (e.g., impeller 102, seal ring(s) 204) of centrifugal pump 100.
In one or more embodiments, following the application of the protective coating, mechanical treatment (e.g., turning, milling, grinding; mechanical treatment depending on the detail required) of the coating is performed. In one or more embodiments, then a layer of solid-alloy coating based on small-grained carbides of metals (e.g., tungsten, vanadium, chromium) may be applied on top of the metal alloy (e.g., aluminum bronze) coating. In one or more embodiments, the process of applying the layer of solid-alloy coating may involve electro-erosion, with an electrode made of the solid-alloy and transfer of the metal carbide particles on the surface of the part. In one or more embodiments, different kinds of single-carbide and multi-carbide solid alloys including 6-12% cobalt (serving as binding agent) and carbides of metals may be used as the material for the electrode.
In one or more embodiments, the micro-hardness of the top layer of the protective coating may be increased several times based on the thickness of the layer and the kind of solid-alloy. In one or more embodiments, it may not be feasible to utilize alloys including less than 6% of cobalt or more than 12% of cobalt due to the lowering of wear resistance of the protective coating caused by the surface thereof becoming fragile or the lowering of the micro-solidness respectively. In one or more embodiments, therefore, it may be preferable to use solid alloys based on, for example, tungsten carbide, with the addition of vanadium carbide and chromium carbide for high solidness and wear resistance thereof.
In one or more embodiments, application of the coating through electro-erosion may be conducted using standard equipment therefor. In one or more embodiments, the model of one or more device(s) constituting the standard equipment may be chosen based on a required thickness of the layer of the solid-alloy coating. In one or more embodiments, the maximum achievable thickness of the layer of the solid-alloy coating and a given productivity of the process of the application thereof directly depend on a value of the electrode current in the electro-erosion process when the working value of the current is 0.5-20 amperes. In one or more embodiments, it may be desirable to apply two or more layers of the solid-alloy coatings (e.g., up to 10 layers) in order to achieve uniformity thereof and to reduce surface roughness. In one or more embodiments, each of the layers of solid-alloy coatings may have the same chemical composition (and, hence, properties). Alternately, in one or more embodiments, at least two of the layers of solid-alloy coatings may have different chemical composition.
In one or more embodiments, the electrode involved in the electro-erosion deposition process may be made of solid-alloy that optimally includes 6-12% of cobalt and 88-94% of carbides of tungsten, chromium and vanadium.
Now example experimental results associated with an impeller 102 made of molding steel is discussed herein. Firstly, mechanical treatment of the surface of impeller 102 in the area(s) of the slot-hole sealing, separating suction and forcing chambers was done to a size (252 mm) different from the required size of 254 mm through a lathe. Following the mechanical treatment, an aluminum bronze coating was melted onto the surface using a Nobitec SW 517 wire of 0.8 mm diameter in an inert gas medium (argon) on Kuhtreiber®'s KIT-384 apparatus. The composition of melted metal was 6.5% aluminum, 2.6% nickel, 12.5% manganese, 0.02% lead and the rest copper Impeller 102 was fixed on a welder's table. After the application of the aluminum bronze coating, the mechanical treatment thereof was conducted on a lathe to a size lesser than that required by the thickness of a planned solid-alloy coating (30 m). The thickness of a coating was 0.97 mm The hardness of the aluminum bronze coating was 220 MPa as per the Vickers test, and was measured as an average of five readings.
Following the hardness measurement, five layers of solid-alloy coating were applied until the thickness thereof was 30 μm. The final diameter of impeller 102 on the surface being strengthened was 254 mm Hardness of the resulting solid-alloy coating was 1800 MPa. A rod made of solid alloy U8 from Tribo Hartmetall melted from powder having a grain size of 0.5 μm (8% cobalt, 91% tungsten carbide, 1% chromium carbide and vanadium carbide) was used as the electrode in the electro-erosion process.
Moreover, tests on abrasive wear resistance during friction of the surface were additionally conducted on a specimen of melted steel including 0.3% of carbon, assuming water as the fluid. For a slot-hole clearance of 0.2 mm and water having sand-particles with friction composition of 100-300 μm being delivered to the clearance, speed of rotation shaft 202 being 1500 rpm and a test duration of 100 hours,
Thus, exemplary embodiments described within the context of current method 306 provide for a method of increasing wear resistance of one or more part(s) of centrifugal pump 100. While exemplary embodiments have been discussed within the context of a centrifugal pump 100, the same method (e.g., current method 306) applies to increasing wear resistance of one or more part(s) of any rotating mechanism (e.g., turbines) configured to have fluid flow therethrough. The concepts discussed herein, therefore, are not limited to merely a centrifugal pump 100.
In one or more embodiments, operation 408 may involve applying one or more layer(s) of solid-alloy over the protective coating through electro-erosion deposition. In one or more embodiments, operation 410 may then involve continuing the mechanical treatment of the protective coating and/or the one or more layer(s) of solid-alloy after the solid-alloy deposition to obtain the desired dimension of the portion.
Although the present embodiments have been described with reference to specific example embodiments, it will be evident that various modifications may be made to these embodiments without departing from the broader spirit and scope of the various embodiments. Accordingly, the specification and the drawings are regarded in an illustrative rather than a restrictive sense.
