ITCO20100014A1 - SELF-LUBRICATING COATING AND METHOD - Google Patents

Description

TITLE / TITLE:

SELF-LUBRICATED COATING AND METHOD

ART NOTE FIELD OF <1> INVENTION

The realizations of the object disclosed in this document refer in general to methods and systems and, more particularly, to mechanisms and techniques for the formation of a self-lubricating coating.

SUMMARY OF KNOWN ART

Over the last few years, with the increase in the price of fossil fuels, interest in various aspects related to their processing has increased. In addition, there is a greater interest in the production of engines, turbines, compressors, etc. more efficient and reliable to facilitate better production and distribution of oil and natural gas based products.

Such machines usually comprise a stationary part, the stator, and a rotating part, the rotor. The rotor is configured to rotate with respect to the stator in order to compress the medium, or to produce electrical energy, or to transform electrical energy into mechanical energy. The rotor must be able to rotate relative to the stator with as little friction as possible and within a given temperature range. A significant amount of heat is generated by the continuous rotation of the rotor and its weight (which can be between 20 and 20,000 kg and increases friction). The heating occurs mainly in the bearings that support the rotor.

Therefore various mechanisms can be employed to cool the bearings. One of these mechanisms consists in circulating a medium, for example oil, between the rotor and the bearings and removing excess heat by cooling the oil. The oil circulation can be forced by means of a pump. However, in the event of a pump failure, the circulation of the oil stops and consequently the removal of the heat produced in the interface between the rotor and the bearing stops. In such circumstances, oil may be lacking in the interface between the rotor and the bearing, causing the latter to heat up to damage to the rotor and / or bearing itself, as well as to other parts of the machine.

If this anomalous situation is not quickly detected by the operator of the machine, or by a special system, in order to stop operation, the entire machine can be seriously damaged, also causing the interruption of the entire process that uses the machine. this which in the oil and natural gas industry is expensive and undesirable. Even if the fault condition of the machine is identified in a timely manner, it can sometimes be impossible to stop the machine in question immediately, as it is part of a process in which several machines are coordinated and the rapid stop of only one of them is not possible. without interfering with the safety of others.

Therefore it would be desirable to obtain systems and methods capable of offering the operator of the machine a certain time interval between the moment when the machine stops functioning correctly and the moment it is damaged, for example due to the high temperature that occurs when the oil pump fails.

SUMMARY DESCRIPTION

According to an exemplary embodiment, there is a method of forming a self-lubricating coating on a substrate. The method involves spraying at least one layer of liquid metal on the substrate with the addition of an inert gas; adding a compound to the liquid metal when spraying the substrate; forming on the substrate a porous layer comprising metal and compound, wherein the porous layer has a plurality of pores; heating the porous layer to open the pores; filling the open pores with a greasing substance so that this portion of the greasing substance remains stored in one or more pores; and the cooling of the porous layer to close the pores and trap the greasing substance inside the pores.

According to yet another exemplary embodiment, there is a method of operation of a turbine machinery equipped with a safety mechanism for a bearing. The method comprises a rotor rotating relative to a turbine machine stator, in which the rotor is supported by a bearing comprising at least one porous layer in turn comprising a metal and a compound forming a plurality of holes and a greasing substance stored in the pores, which provide a lubricant to the bearing as the rotor rotates to maintain a substantially constant temperature of the bearing.

According to yet another exemplary embodiment, there is a turbine machine which includes a stator configured to remain stationary, a rotor configured to rotate relative to the stator, a bearing configured to support the rotor and facilitate rotation of the rotor, and a self-lubricating liner. on the rotor bearing. The self-lubricating coating comprises at least one porous layer, which in turn comprises a metal and a compound forming a plurality of pores and a greasing substance stored in the pores, while the pores are closed and trap the greasing substance when the bearing operating temperature it remains below a predetermined value.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated into the detailed description and form an integral part thereof, illustrate one or more embodiments and, together with the description, explain such embodiments. In the drawings:

Figure 1 is a diagram of a machine equipped with a stator and a rotor;

Figure 2 is a diagram of a substrate bearing a self-lubricating coating according to an exemplary embodiment;

Figure 3 shows a porous layer according to an exemplary embodiment;

Figure 4 is a flowchart illustrating the method of making a self-lubricating coating on a substrate according to an exemplary embodiment; And

Figure 5 is a flowchart illustrating a method of operation of a turbine machinery provided with a safety mechanism for a bearing according to an exemplary embodiment.

DETAILED DESCRIPTION

The following description of the exemplary embodiments refers to the accompanying drawings. The same reference numerals in different drawings identify the same or similar elements. The following detailed description does not limit the invention. The field of application of the invention is instead defined by the attached claims. The following embodiments are treated, for reasons of simplicity, in relation to the terminology and structure of a compressor. However, the embodiments to be discussed below are not limited to compressors, but can be applied to other systems, including a rotor supported by bearings. Reference throughout the detailed description to "an embodiment" means that a particular function, structure or feature described in connection with an embodiment is included in at least one embodiment of the described object. Therefore, the appearance of the sentence "In one embodiment" at various points of the detailed description does not necessarily refer to the same embodiment Furthermore, the particular functions, structures or features may be combined in any suitable way in one or more embodiments.

According to an exemplary embodiment, part of the rotor, bearing, or both, is coated with a self-lubricating liner configured to store a greasing material while the machine is operating at normal temperature and to release the greasing material when the machine temperature rises beyond a certain threshold temperature.

According to an exemplary embodiment shown in Figure 1, a compressor 10 comprises inter alia a rotor 12 configured to rotate with respect to a rotor 14. The rotor 12 is supported for example at both ends by one or more bearings 16. They are known in the various types of bearings and any of them may be used to support rotor 12. An example of a bearing is the thrust type disclosed in U.S. Pat. 6,361, 215, the entire content of which is incorporated herein by reference.

A thrust bearing 16 employs one or more pads 18 which support the rotor 12 while the oil is injected into the interface 20 between the pads 18 and the rotor 12 to reduce friction and / or cool the interface. A pump (not shown) can be used to pump oil through channel 22 of each shoe at the interface 20 between the shoe 18 and the rotor 12. If the oil were not sent to the interface 20, the temperature in the interface would rise. beyond an acceptable value, which could damage bearing 16, rotor 12, or both. According to an exemplary embodiment shown in Figure 2, a part of the rotor 12 or bearing 16 or both can be coated with a self-lubricating layer 24. The self-lubricating layer 24 can be deposited, as shown in Figure 2, on a substrate 26, which may be part of the rotor 12 and / or the bearing 16. When the self-lubricating layer 24 is deposited on the rotor 12, it is desired that this layer be deposited directly in front of the bearing 16. The layer 24 may comprise a base material 28 deposited on the substrate 24. The base material may be a metal used for the bearing, for example gray cast iron, stainless steel, carbon steel, non-ferrous alloys, etc. In one application, the base material is plastic, for example it comprises a material with low carbon content and high iron, nickel or cobalt content. In another application the base material does not contain Chromium. In yet another application, the base material may comprise a non-ferrous metal, so that the base material is plastic. The base material can be deposited by methods known in the art. For example, the base material can be sprayed onto the substrate. However, in one application the base material 28 is not part of the layer 24. The base material 28 is deposited to ensure better adhesion between the self-lubricating layer 24 and the substrate 26.

A porous layer 30, which provides self-lubricating functionality, is formed on the base material layer 28 or directly on the substrate 26. The porous layer 30 may comprise a metal and a compound that promotes the formation of pores in the porous layer 30. The metal it can be one or more of those used for the bearing, for example gray cast iron, stainless steel, carbon steel, etc., depending on the application, the desired hardness of the layer, the load of the bearings. The compound can be one or more of graphite powder, molybdenum disulfide (MoS2), tungsten sulphide (WS2). The metal is sprayed in the liquid phase on the base material layer 28. For example, it is possible to use plasma or an electric arc to spray the liquid metal and the compound. It is possible to use an inert gas under pressure not only to send the molten metal from the applicator (or other device used to coat the substrate) but also to insert the compound into the molten metal. For example, the inert gas could be nitrogen (N).

The porous layer 30 is shown in Figure 3 as having a plurality of pores 32 distributed across the mixture of metal and compound 34. The number of the plurality of pores 32 depends on many variables. For example, the number of pores may depend on the temperature at which the liquid metal is sprayed onto the substrate, the pressure of the inert gas, the distance between the applicator spraying the liquid metal and the substrate, the specific metal used, the specific compound used, etc. In one application, the thickness of the self-lubricating layer 30 is between micrometers and millimeters.

Once the porous layer 30 has formed on the substrate 26 and the temperature of the assembly has dropped to approximately room temperature (e.g. 25 ° C), the pores are closed, that is, if the porous layer 30 is immersed in a bath of liquid only an insignificant amount of it enters the pores of the layer 30. However, if the layer 30 together with the substrate 26 are exposed (for example immersed) in a high temperature bath, the pores 32 of the layer 30 open and the oil begins to fill the pores. The high temperature range can range from 80 to 500 ° C, depending for example on the type of oil (synthetic or not, etc.). In the example, oil was used, but it is possible to use any greasing material to fill (complete or partially) the pores of layer 30.

The substrate 26 and the layer 30 are then cooled to room temperature to seal the pores, so that this absorbed greasing material is stored inside the pores 32. This substrate bearing the self-lubricating layer 30 is then used in one or more of the machines discussed above. Therefore, when one such machine does not supply oil at the interface between the rotor and the bearing, the interface temperature exceeds the pore opening temperature of the self-lubricating layer 30, which results in the release of the greasing material from the porous layer 30 into the interface between rotor and bearing.

This self-lubricating layer 30, depending on its size and distribution on the bearing and / or rotor, can offer the machine operator minutes, if not hours, of safe operation even in the event of failure of the main oil supply mechanism. . In this way, the operator has enough time to shut down the entire processing line in a controlled manner without compromising the safety of the other machines that make it up.

Although intuitively it may seem appropriate to provide a thick self-lubricating layer 30 to obtain a greater reserve of greasing material, it has nevertheless been found that a thick layer is subject to breakage, and therefore is of shorter duration. Furthermore, fractures in the thick layer let the greasing material escape earlier than expected and can also compromise the adhesion of the porous layer to the substrate. Conversely, a thin layer is undesirable as it does not retain a sufficient amount of greasing material. Therefore, the correct thickness of the self-lubricating layer 30 depends on the type of machine, the weight of the rotor, the number of shoes, the number of bearings, etc.

According to an exemplary embodiment illustrated in Figure 4, there is a method for making a self-lubricating coating on a substrate. The method involves a step 400 where at least one layer of liquid metal on the substrate is deposited by spray with the addition of an inert gas; a step 402 where a compound is added to the liquid metal while spraying the substrate; a step 404 where the formation on the substrate of a porous layer comprising metal and compound takes place, in which the porous layer has a plurality of pores; a step 406 where the porous layer is heated to open the pores; a step 408 where the filling of the open pores with a greasing substance occurs so that this portion of the greasing substance remains stored in one or more pores; and a step 410 where the porous layer is cooled to close the pores and trap the greasing substance inside the pores.

Note that the gas used to deposit the liquid metal can be an inert gas. However, nitrogen (N2) can be used to deposit ferrous layers as it is less expensive. Furthermore, nitrogen gas (N2) can impart more plasticity to the porous layer, which is desirable. Nitrogen gas (N2) is better than Argon or compressed air as it avoids oxidation of the alloy elements in the liquid metal and also does not alter the composition of the deposited layer.

According to an exemplary embodiment illustrated in Figure 5, there is a method of providing a safety mechanism for a turbine machine bearing. The method comprises a pitch 500, where a rotor rotates with respect to a stator of the turbine machine; a step 502 in which the rotor is supported by a bearing which comprises at least one porous layer in turn comprising a metal and a compound forming a plurality of holes and a greasing substance stored in the pores; and a step 504 where a lubricant is supplied to the bearing as the rotor rotates to maintain a substantially constant temperature of the bearing.

The disclosed exemplary embodiments offer a system and method for providing a greasing material in the event of a failure of a suitable greasing material supply system. It must be clear that the present description does not intend to limit the invention. On the contrary, the exemplary embodiments are intended to apply to alternatives, modifications and equivalent solutions, which fall within the spirit and scope of the invention as defined by the attached claims. Furthermore, in the detailed description of the exemplary embodiments, numerous specific details are shown in order to allow a comprehensive understanding of the claimed invention. However, the art expert would understand that various realizations can be implemented without such specific details.

Although the features and elements of the current exemplary embodiments are described in the embodiments in particular combinations, each feature or element can be used individually without the other features and elements of the embodiments or in various combinations, with or without other features and items described here.

This written description uses examples of the disclosed object to allow any expert in the art to implement this object, including the creation and use of any device or system and the execution of the incorporated methods. The scope of the patent object is defined by the claims and may include other examples that may arise for those skilled in the art. Such other examples are to be understood as an integral part of the scope of the claims.

Claims (10)

CLAIMS / CLAIMS 1. A method for forming a self-lubricating coating on a substrate, comprising: spraying with a gas of at least one layer of liquid metal on the substrate; adding a compound to the liquid metal when spraying the substrate; the formation of a porous layer comprising the metal and the compound, wherein the porous layer has a plurality of pores; heating the porous layer to open the pores; filling the open pores with a greasing substance so that part of the greasing substance is stored in one or more pores; And cooling the porous layer to close the pores and trap the greasing substance inside the pores. The method of claim 1, wherein the liquid metal may consist of a metal used for a bearing, gray cast iron, stainless steel, carbon steel or non-ferrous alloys. The method of claim 1 wherein the compound can be one or more of graphite powder, molybdenum disulfide (MoS2), tungsten sulfide (WS2) or a combination thereof. 4. The method of Claim 1, further comprising: the formation of a base material on the substrate before spraying, with a low Carbon content and a high Iron, Nickel or Cobalt content or a non-ferrous plastic metal, so that the porous layer forms on the base material and adheres better to the substrate. The method of Claim 1, wherein heating is carried out by immersion of the porous material in the greasing substance at a predetermined temperature. The method of Claim 1, wherein the substrate is a compressor bearing. 7. The method of Claim 1, wherein the gas comprises Nitrogen (N). 8. A method of operating a turbine machine equipped with a safety mechanism for a bearing, comprising: the rotation of a shaft with respect to a stator of the turbine machine; supporting the shaft with a bearing that includes at least one porous layer, comprising a metal and a compound that form a plurality of pores and a greasing substance stored in the pores; And the supply of a lubricant to the bearing while the shaft rotates so that an operating temperature of the bearing is substantially constant. 9. The method of Claim 8, further comprising: a failure in the supply of lubricant; the increase in bearing temperature; And the opening of the pores of the porous layer (at least one in number) so that the stored greasing substance comes out of the pores and lubricates the bearing. 10. A turbomachine comprising: a stator configured to be fixed; a shaft configured to rotate relative to the stator; a bearing configured to support the shaft and facilitate shaft rotation; And a self-lubricating coating applied to the bearing or shaft; wherein the self-lubricating coating comprises at least one porous layer, in turn comprising a metal and a compound forming a plurality of pores and a greasing substance stored in the pores; And the pores are closed by trapping the grease when the bearing operating temperature is below a predefined value. (ADR / Pa) CLAIMS / CLAIMS: 1. A method for providing a self-lubricated coating on a substrate, the method comprising: spraying with a gas at least a layer of liquid metal on the substrate; adding a compound to the liquid metal while being sprayed on the substrate; forming a porous layer on the substrate that includes the metal and the compound, wherein the porous layer has plural pores; heating the porous layer to open the pores; flooding the open pores with a greasing substance such that part of the greasing substance is stored in one or more pores; and cooling the porous layer to close the pores and trap the greasing substance inside the pores. 2. The method of Claim 1, wherein the liquid metal is one of a metal used for a bearing, gray cast iron, stainless steel, carbon steel, or non-ferrous alloys. 3. The method of Claim 1, wherein the compound is one of graphite powder, Molybdenum disulfide (MoS2), Tungsten sulfide (WS2), or a combination thereof. 4. The method of Claim 1, further comprising: providing a base material that includes a low carbon content and high content of Fe, Ni or Cobalt or a plastic non-ferrous metal on the substrate prior to spraying so that the porous layer is formed on the base material to better adhere to the substrate. 5. The method of Claim 1, wherein the heating is achieved by immersing the porous material in the greasing substance at a predetermined temperature. 6. The method of Claim 1, wherein the substrate is a bearing of a compressor. 7. The method of Claim 1, wherein the gas includes nitrogen (N). 8. A method for operating a turbo-machinery having a safety mechanism for a bearing, the method comprising: rotating a shaft relative to a stator of the turbo-machinery; supporting the shaft with a bearing that includes at least a porous layer, the at least a porous layer including a metal and a compound that form plural pores and a greasing substance stored in the pores; and providing a lubricant to the bearing while the shaft rotates such that an operation temperature of the bearing is substantially constant. 9. The method of Claim 8, further comprising: failing to provide the lubricant; increasing an operation temperature of the bearing; and opening the pores of the at least a porous layer such that the stored greasing substance exits the pores and lubes the bearing. 10. A turbo-machinery, comprising: a stator configured to be fix; a shaft configured to rotate relative to the stator; a bearing configured to support the shaft and facilitate a rotation of the shaft; and a self-lubricated coating provided on the bearing or the shaft, wherein the self-lubricated coating includes at least a porous layer, the at least a porous layer including a metal and a compound that form plural pores and a greasing substance stored in the pores, and the pores are closed trapping the greasing substance when an operational temperature of the bearing is below a predetermined value.