Compressor with integrated speed increaser

Abstract

A compressor (100) with an integrated speed increaser (110), the speed increaser (110) comprising a first shaft (111) carrying a gear (112) and supported by a first bearing (112'), at least one second shaft (113) carrying a pinion (114) and connected to one or more impellers of the compressor (100), and a casing (116). The casing (116) supports at least one second shaft (113) with a first shaft (111), a gear (112), an associated bearing (112'), an associated pinion (114) and a bearing (114'), and comprises a frame (118) connected to the compressor casing (116) via a connecting element (117), a shell (119) in which the frame (118) is installed, a flexible element (120) interposed between the connecting element (117) and the pressure containment shell (119), and at least one labyrinth seal (121).

Description

[Technical Field]

[0001] The present invention relates to compressors, particularly those used in heat pump and / or refrigeration systems, where the compressor fluid is in direct contact with the bearings and gears of the gearbox that drives the compressor. [Background technology]

[0002] As is well known, a compressor is a working machine capable of increasing the pressure of a compressible fluid (gas or steam) using mechanical energy. Among the various types of compressors used in industry are the so-called centrifugal compressors, in which energy is transferred to the gas in the form of centrifugal acceleration due to the rotation generally imposed by a prime mover (electric motor, steam turbine, or gas turbine and associated transmission mechanism) on a member called the rotor. The rotor consists of one or more bladed wheels called impellers, rigidly connected to a shaft supported by bearings.

[0003] Centrifugal compressors can be equipped with a single impeller (so-called single-stage configuration) or with several impellers (in this case, a multi-stage compressor). If the impellers are rigidly connected to one or more toothed shafts that are driven by a common gear connected to an electric motor, turbine, or generally a drive system, this configuration is called a compressor with an integral speed increaser, or IGC (short for "Integral Gear Compressor").

[0004] A compressor with an integral speed increaser is a machine in which a shaft connected to a prime mover and supporting a central gear resides within the speed increaser case. The central gear rotates at a slower speed and meshes with at least one pinion (a smaller toothed wheel, therefore rotating at a higher speed) on a corresponding shaft of the compressor. Rotational motion is then transmitted from the pinion to at least one impeller. The number of pinions and the relative number of impellers vary based on the application; for example, they may be equal to two (two-stage compressor). In some cases, an idler gear, called a wheel, is interposed between the central gear and the pinion.

[0005] This type of compressor makes it possible to generate the optimum combination of rotational speed and impeller diameter for each pinion, optimizing the compressor design. All impellers are cantilevered and can be equipped with a pre-swirl device (a set of stator blades that form a space with variable cross section and orientation) located upstream of the impeller itself. At the discharge of each impeller, inter-stage cooling of the gas flow can be performed.

[0006] The combination of these features enables high flow rates and exceptional compression efficiency, even at part load, in a compact design.

[0007] FIG. 1 shows a typical configuration of a compressor 1 with an integral speed increaser, as described in API 617 (American Petroleum Institute) standard for centrifugal compressors. The illustrated compressor is a three-stage compressor, with a first stage inlet 10, a second stage inlet 20, and a third stage inlet 30. Each stage further includes an impeller 11, a diffuser 12, and an exhaust volute 13 within a casing 14. The speed increaser 40 includes a case 41 and includes a slow wheel 42, two pinions 43, a bearing 44 supporting the slow wheel, and a bearing 45 supporting the pinion. Each pinion 43 is provided with an appropriate rotating seal 46 to isolate the speed increaser case from the working fluid (the compressed gas processed by the compressor).

[0008] Among the constraints imposed by the construction of a compressor with an integral IGC speed increaser is the need to provide a number of seals 46 corresponding to the pinion 43 penetrations into the compressor pressurized case 14, thereby limiting or eliminating leakage of process gas towards the case 41 of the speed increaser 40 connected to atmospheric pressure.

[0009] In a typical configuration based on a single pinion seal, each seal minimizes compressor fluid loss to the case in which the gear is housed, allowing gas to be recovered in a vent chamber that remains at atmospheric pressure without pressurizing the speed increaser case.

[0010] The gases collected in the vent chamber may be a potential source of harmful emissions, depending on their chemical composition, and are therefore typically vented to the atmosphere via special chimneys or burned in plant torches.

[0011] In another typical configuration, the sealing system consists of a "double" seal with a barrier fluid (e.g., nitrogen) between the two seals, always at a pressure higher than the working fluid pressure. In addition to being expensive and very thick axially, double gas seals often have unacceptable properties, such as continuous intrusion of the barrier fluid into the process gas.

[0012] In many cases, this leakage is not a problem, but in other cases (especially closed-loop heat pump applications), it is extremely detrimental to system performance for the barrier fluid to get onto the process side, and the barrier fluid is typically nitrogen, a non-condensable gas.

[0013] Even if this solution is adopted and sophisticated seals are used, it is not possible to avoid loss of working fluid or intrusion of barrier fluid into the process. Therefore, in applications where negligible leakage of fluid towards the gearbox casing is required or where contamination of the working fluid by the barrier fluid is desired, compressor configurations with integral speed increasers are not effective. Other known solutions adopted, especially in single shaft machines, are: All stages are mounted on a single shaft with a single seal installed corresponding to the shaft penetration into the pressurized box. In this case, the shaft can be connected to a drive, for example an electric motor with a gearbox, installed outside the area pressurized by the process gas. Alternatively, all seals are eliminated and the gears and prime mover drive are enclosed in a sealed compartment pressurized with compressor fluid. Summary of the Invention [Problem to be solved by the invention]

[0014] These solutions are typical for compressors for heat pumps and the refrigeration industry, which have a single shaft supporting the compressor impeller. However, compressors with a single shaft in which the compressor wheel is cantilevered or mounted between bearings cannot achieve the performance and compactness of compressors with integrated speed increasers as described above.

[0015] On the other hand, in an IGC integral gearbox compressor, it is difficult to design a pressurized case that can accommodate multiple shafts and bearings and at the same time maintain the correct relative positions of the shafts and gears, i.e., have the ability to withstand pressures (even pressures of several bars) with acceptable deformation.

[0016] The above explanation is further supported by the fact that, according to the prior art, the casing of a compressor with an integrated speed increaser having multiple shafts is, according to the prior art, made of flat plates, which, due to their properties, are insufficiently able to withstand pressure and, in any case, exhibit unacceptable deformations when subjected to internal pressure. The casing is the structure that supports and positions the shaft bearings, which determines the correct alignment of the gears; for example, misalignment of the pinion caused by deformation of the casing due to the application of internal pressure can cause improper contact with the gear teeth, resulting in vibrations and a reduced service life of the gears.

[0017] Finally, for these reasons, according to the prior art, compressors with pressurized gearboxes are limited to applications with a single shaft and cylindrical case, while multi-shaft compressors have an atmospheric case with seals on each pinion.

[0018] Therefore, there is a need for a compressor design solution with an integral speed increaser that overcomes or at least mitigates the above-mentioned drawbacks. [Means for solving the problem]

[0019] The object of the present invention is to provide a solution, especially for multi-shaft compressors, with an integral speed increaser having a single seal on the low speed gear shaft, with negligible compressor fluid losses to the atmosphere and / or no intrusion of barrier fluid into the process. Naturally, this solution is also applicable to single stage applications, i.e. with a speed increaser having a single pinion and a single impeller.

[0020] According to this solution, the gearbox case must withstand the pressure associated with the presence of working fluid coming from the various stages of the compressor. For this purpose, the gearbox case comprises a frame supporting the pinion and bearings, installed in an external containment shell with the function of containing the pressure of the process gas. The internal frame is thus perfectly balanced against the fluid pressure and can be made using flat plates without the risk of excessive deformation.

[0021] Additionally, a flexible element is also needed and foreseen to allow the expansion of the pressure containment shell when deformation is applied without exerting undue force on the internal frame supporting the bearing (which remains substantially undeformed), thus maintaining the shaft position within an acceptable range regardless of the pressure level within the gearbox case.

[0022] Thus, according to one aspect of the present invention, there is described a compressor with an integral speed increaser and having the features set out in the independent product claims attached hereto.

[0023] Further preferred and / or particularly advantageous ways of implementing the aforementioned system are described according to the characteristics set out in the attached dependent claims. [Brief explanation of the drawings]

[0024] The present invention will now be described with reference to the accompanying drawings, which illustrate some non-limiting implementations of the present invention. [Figure 1] 1 shows a cross-sectional view of a compressor equipped with an integrated speed increaser according to the prior art; [Figure 2a] 1 shows a schematic partial longitudinal cross-sectional view of a compressor equipped with an integrated speed increaser according to a preferred embodiment of the present invention; [Figure 2b] 1 shows a schematic front view of a compressor equipped with an integrated speed increaser according to a preferred embodiment of the present invention; [Figure 3] FIG. 3 is an enlarged detail view of the compressor of FIG. 2. [Figure 4] FIG. 3 is a simplified basic diagram of a lubrication and sealing system for the compressor of FIG. 2 according to a first embodiment. [Figure 5] 3 is a simplified diagram of a lubrication and sealing system for the compressor of FIG. 2 according to a second embodiment. [Figure 6] 3 is a simplified diagram of a lubrication and sealing system of the compressor of FIG. 2 according to a third embodiment. [Figure 7] FIG. 7 is an enlarged detail view of FIG. [Figure 8] FIG. 10 is a simplified diagram of a lubrication and sealing system for the compressor of FIG. 2 according to a fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0025] 2a and 2b, a compressor with an integral speed increaser according to a preferred embodiment of the present invention is shown generally at 100.

[0026] In this exemplary embodiment, the compressor is multi-stage, with pinion shafts arranged circumferentially around the low speed wheel, and each pinion carrying one or two impellers. Note that the compressor is also fitted with a single pinion.

[0027] For simplicity of presentation, not all compressor stages connected to pinion 114 are shown in FIG. 2 (these are of known type and in any case similar to those shown in FIG. 1), but the integrated speed increaser 110 is shown diagrammatically.

[0028] The speed increaser 110 includes: A first "low speed" shaft 111 connected to a prime mover (not shown, as it is of a known type) that supports a gear 112 ("bull gear" in English), which rotates at a low speed, i.e. at the speed of the prime mover. For example, the rotational speed of the first shaft 111 and gear 112 can be in the range of 1000 rpm to 3600 rpm. At least one second shaft 113 carrying a pinion 114. The at least one second shaft 113 is arranged circumferentially around the gear 112. The pinion 114, having a smaller diameter than the gear 112, meshes with the gear 112, causing the rotation of the second shaft 113 to be faster than the rotation speed of the first shaft 111, the speed being determined trivially by the ratio of the number of teeth of the gear 112 and the pinion 114. The second shaft 113 is then connected to one or more impellers (not shown) of the compressor 100. Preferably, as in the embodiment described, the speed increaser 110 is provided with up to four shafts 113 and four pinions 114 arranged circumferentially with respect to the gear 112. However, the number of pinions 114 and shafts 113 may be equal to one, the number being related to the head to be processed by the compressor and the size of the scrolls arranged circumferentially around the wheel 112. Both gear 112 and pinion 114 may be helical or straight-tooth type gears. Depending on the application, an idler gear may be installed between gear 112 and pinion 114. Gear 112 and associated shaft 111 are supported by bearings 112' (only the one to the right of gear 112 is highlighted in FIG. 2), and pinion 114 and associated shaft 113 are supported by corresponding bearings 114' (only the one to the right of gear 114 is highlighted in FIG. 2). The bearings may be of the swing stud or bushing type, or of the rolling type. A mechanical seal 115 is installed at one end of the low-speed shaft 111 and connected to the compressor drive. This is a typical seal for most rotary machines such as pumps and turbines when the speed of the shaft 111 is in the range of 1000 rpm to 3600 rpm. The seal is oil-lubricated and may be either a single seal or a double seal. The double seal may contain a barrier fluid such as nitrogen or oil.

[0029] The advantage of having a seal on a shaft with a low rotational speed is that it provides a strong, stiff shaft at a circumferential speed acceptable for the seal. In fact, the sliding speed between the seal's rotor and stator rings is proportional to the angular rotational speed times the diameter, and stiffness is proportional to the fourth power of the diameter. This simple consideration underscores the need to mount a seal on a shaft with a lower rotational speed and have a sufficiently stiff shaft relative to the seal's circumferential speed to accommodate negligible fluid losses. Furthermore, any potential losses in this seal have an absolutely negligible effect, since they do not interact with the process when a potential rotary seal mounted on the pinion to which the compressor stages are connected does not result.

[0030] The speed increaser 110 also includes: A casing 116 that contains the shafts 111, 113, the gears 112, 114, the bearings 112', 114' and the working fluid and is capable of withstanding relative pressure. It may carry a number of pinions 114, preferably three pinions spaced 120° apart. The casing 116 in turn includes a frame 118 that is housed within a pressure containment shell 119, and a flexible element 120. In particular: The frame 118 supports the first shaft 111, gear 112 and associated bearing 112', and the second shaft 113, pinion 114 and associated bearing 114', and is connected to the compressor casing (internal compressor parts not shown) via connecting elements 117, e.g., flange compressor supports. The frame 118 comprises two half frames 118', at least one of which is bolted to a central ring 118" (for assembly purposes) connected to the compressor base. The frame 118, except for the central ring 118", is entirely inside the pressure containment shell 119. The frame 118 is provided with a circumferential opening that allows the recovery of lubricating oil at the bottom of the pressure containment shell 119. The oil is discharged from the bottom of the shell 119 and transported via a pipe with a flexible bellows to, for example, a pressurized oil control unit connected to the first suction of the compressor. The frame 118 has support flanges for the compressor casing, or more generally, seals 130 on the shaft 113 that support the casing of the compressor stage, rigidly connected (e.g., bolted or welded) between the impeller and the speed increaser 110. These seals 130 may be labyrinth seals 121, or labyrinth seals and oil seals 206, as described in more detail with reference to Figures 4 and 5, respectively. The frame 118 can accommodate one or more flanges 117 (e.g., three), on which corresponding compressor stage cases are mounted. A containment shell 119 with pressure containment functions. The frame 118 is located inside the containment shell 119, which allows the frame 118 to be perfectly balanced against the fluid pressure and can be made using flat plates without the risk of excessive deformation. The containment shell 119 can be formed from two half shells 119', which are flange-connected to a central ring 118". The two half shells 119' can be split, for example, along a vertical central plane and can be made, for example, toroidal, elliptical, or with a flat, rounded bottom. A gasket such as an O-ring can be used to seal the shell flange 119 to the inner frame ring 118. A number of connection means (for example, bolts) hold the gasket and the bottom tightly together under gas pressure (for example, pressures that can reach 10 bar or more). Advantageously, the pressure containment shell 119 has openings corresponding to the bearings 112', 114', which are closed by removable covers, for inspection of the gears (gear 112, pinion 114) and for maintenance of the bearings. A flexible element 120 (e.g., a bellows or a flexible diaphragm) is disposed between the connecting element 117 and the pressure containment shell 119. Referring also to FIG. 3, the flexible element 120 allows the pressure containment shell 119 to deform under the influence of internal pressure without transmitting excessive force to the connecting element 117 (i.e., the compressor support flange), which would distort the internal frame 118 supporting the bearing. This maintains the position of the first shaft 111 within an acceptable range regardless of the pressure level within the casing 116. In other words, the flexible element 120 decouples the frame 118 from the shell 119, effectively eliminating deformation of the frame 118 due to the pressure experienced by the shell 119. This maintains proper engagement between the pinion 114 and the wheel 112, and prevents relative movement between the stator and rotor sections of the compressor due to the pressure. The flexible element 120 is equipped with a gasket to prevent gas leakage from the pressurized shell 119. Alternatively, the flexible element can be welded to both the connecting element 117 and the shell 119 to avoid leakage of fluid to the atmosphere.

[0031] Advantageously, the speed increasers 110 are also provided with seals 130 downstream of the compressor impellers, housed on each shaft 113 carrying a pinion 114, between the corresponding impeller and the speed increaser. These seals 130 limit the leakage of the fluid processed by the compressor (process fluid) towards the casing 116 of the speed increaser 110. In particular, the seals 130 are mounted between the connecting element 117 and the pinion 114.

[0032] A specific diagram of the seal lubrication circuit for the mechanical seal 115 and the seal 130 used in the speed increaser is developed. As an example, consider the case where there is a seal 130 in addition to the mechanical seal 115 on the first shaft 111.

[0033] The mechanical seal 115 on the first shaft 111 (low-speed shaft) serves to minimize the loss of working fluid outside the compressor and integrated speed increaser 100, i.e., to the external environment, while the seal 130 is used to minimize the flow of working fluid inside the casing 116 of the speed increaser 110. These are therefore seals that restrict the flow inside the machine. The reduced flow is beneficial for the compressor's efficiency and also reduces the amount of fluid pressurizing the gear casing 116, reducing the mixing between the lubricating oil and the process fluid (typically an organic fluid in the case of a heat pump) inside the casing 116. The casing 116 is actually pressurized by the working fluid, the pressure level of which depends on the inlet flow rate and the flow rate extracted in gas phase from the tank, for example, via a duct connected to a lower-pressure space using a compressor or an ejector system. Thus, an equilibrium state is reached that determines the specific concentration of the process fluid in the lubricating oil. This concentration is best kept as low as possible so as not to unduly alter the oil's lubrication properties. Additionally, reduced pressure levels in the gearbox improve efficiency by reducing ventilation losses, and improve gear and bearing lubrication by reducing foaming and solubilization of process fluids in the oil (which causes a decrease in viscosity).

[0034] Several possible forms of implementation of the lubrication and sealing system are described below, the choice of which will depend on the particular application.

[0035] Figure 4 shows a simplified basic diagram of a lubrication and sealing system according to a first embodiment. In this figure, and in the following Figures 5-8, the compressor working fluid paths are shown with solid arrows, and the lubricant paths are shown with broken arrows. Furthermore, when describing various components, the terms "downstream" and "upstream" are used relative to the direction of movement of the working fluid or lubricant.

[0036] This first embodiment of the lubrication and sealing system is suitable for applications where the pressure in the compressor is relatively low (eg, less than 10 barA) since the oil tank is fluidly connected to the compressor.

[0037] 4 shows a schematic representation of a compressor 100, which by way of example is provided with two impellers 101, 102 for the first and second compression stages, respectively, mounted on the same shaft 113, with a suction line or duct 103 upstream of the first impeller 101 and a delivery line or duct 104 downstream of the second impeller 102. In the same Figure 4, the speed increaser 110 is also diagrammed with a seal 115 towards the external environment and at least one internal labyrinth seal 121.

[0038] Further, in FIG. 4, a lubrication and sealing system 200 using oil lubrication is shown, which includes: An oil tank 201. In the absence of a pressure reducing system, this is a pressure slightly higher than the suction pressure of the first stage of the compressor, e.g., 2.1 bar compared to 2 bar in the suction line 103. Conversely, if a pressure reducing system (positive displacement or dynamic, as shown in Figure 4 and described below) is present, the pressure in the tank can be suitably reduced, e.g., to a value of 1.1 barA (as shown in Figure 4). An oil pump 202 downstream of and in fluid communication with the tank 201, which further pressurizes the oil, for example at a pressure of 10 bar. An oil conditioning system consisting of a thermostatic cooling system 209 downstream of the pump 202 and a filtering system 210 downstream of the cooling system 209. A differential hydraulic regulation system 211 for the pressure present in the oil tank, equalized with the displacement of the speed increaser 110. · A delivery branch 203 from the oil pump 202. This splits into a first supply branch 204 for oil to the mechanical seal 115 and a second supply branch 204' that distributes oil to the bearings and sprays for gear lubrication.

[0039] The oil, together with the working fluid leaking through the labyrinth seal 121, is conveyed by gravity to the bottom of the casing 116 of the speed increaser 110 and from there to the tank 201 where separation of the liquid and vapor phases takes place. To facilitate separation, the tank is not completely filled but is fitted with devices to maximize the free liquid surface and to facilitate separation of the liquid and vapor, such as a septum, heater 212, etc.

[0040] The vapor (associated with the working fluid or oil) is conveyed along a return line 213 connecting the tank 201 to a low-pressure system area, for example the suction line 103 of the compressor 100. The return line 213 advantageously includes a separation system, for example a demister 214, for removing liquid particles entrained in the fluid flow, and the aforementioned pressure reduction system 215, including a mechanical or dynamic compressor. The figure shows an ejector 216 and an associated control system consisting, in its simplest form, of a regulator 217, which adjusts the driving fluid 218 of the ejector 216 according to the pressure required in the tank 201, for example 1.1 barA as shown in FIG. 4.

[0041] 4 may present an inherent limitation due to the difficulty of reducing gas leakage through the labyrinth seal 121 as the pressure in the compressor 100 increases. Although it is possible to increase the pressure in the lubrication system consistent with the compressor pressure, for technical reasons (e.g. related to the required thickness of the tank and pump and / or related to the properties of the lubricating oil), it is not recommended to increase the pressure in the tank beyond 5-10 barA.

[0042] Large leakage from the labyrinth seal 121 may affect the thermodynamic performance of the compressor and the sizing of the separation system downstream of the tank, as the flow will tend to drag oil droplets and their vapors towards the process.

[0043] To overcome this challenge, more advanced seals, such as creeping carbon or "dry" seals, can be used in place of simple labyrinth seals, or in conjunction with seal rings that use special surface treatments to create fluid lift forces that separate the rings when rotated, creating fluid passages on the order of a few microns.

[0044] 5, it is also possible to add an oil seal 206 with a floating ring to the labyrinth seal 121. This type of seal has the advantage that it can use the same fluid as that used to lubricate the speed increaser.

[0045] Thus, FIG. 5 shows a second embodiment of the lubrication and sealing system.

[0046] The diagram in Figure 5 is similar to that described in Figure 4 with respect to the low speed shaft lubrication and mechanical seal 115, but the seal at the end of the pinion is a significant change.

[0047] The delivery branch 203 further divides into a third supply branch 205 that supplies a floating ring oil seal 206. This seal is ensured by injecting oil between the two floating rings at a pressure (e.g. 0.2 bar) slightly higher than the pressure existing in the chamber between the labyrinth seal 121 and the oil seal 206 (discharge branch 207). The oil pressure between the rings is controlled, for example, by a differential regulator 205', which regulates the flow according to the pressure in said discharge branch 207 of the compressor side seal.

[0048] The oil leaving the floating ring is discharged directly to the low-pressure oil tank 201 via pipes or channels present in the casing and via a discharge branch 207 connected to a separator vessel 208 equipped with an automatic drainage device. This discharge branch 207 has a higher pressure than the casing 116 of the speed increaser 110, thereby reducing leakage of working fluid through the labyrinth seal 121 compared to that which occurs using the first embodiment of Figure 4. This second implementation of the seal lubrication system therefore increases the efficiency of the compressor 100 and improves the separation of oil from the working fluid, especially in high-pressure applications with suction pressures greater than 3-4 barA.

[0049] A high-pressure discharge branch 207 downstream of the oil seal 206 conducts the oil and gas discharged from the labyrinth seal 121 to a separator vessel 208, which separates the liquid from the gas phase. The liquid is discharged using an automatic drain in the oil tank 201, and the gas phase of the working fluid is taken from the top of the separator vessel 208 and transferred via a return line 219 to an area with lower pressure, such as the suction line 103 of the compressor 100. This return line 219 may contain a device for separating oil droplets, such as a "demister" 220, and a flow regulator, such as an orifice 221 or a valve, to limit the fluid velocity in the pipe. Excessive velocities in the pipe (e.g., greater than 30 m / s) would impair the function of the separator vessel 208 by drawing oil droplets from the discharge branch 207 toward the compressor suction.

[0050] Level control in the separator vessel 208 with automatic drainage may be achieved by a float valve or by an actuated valve that opens in relation to the oil level measurement.

[0051] An automatic drain device in the separator vessel 208 prevents gas from leaking directly from the compressor casing into the oil tank and pressurizing it. In this system, the only process fluid transferred to the oil tank 201 is that dissolved or entrapped in the discharged oil. This minimizes the volume of the pressure reduction system 215, with obvious advantages in terms of efficiency and cost.

[0052] The oil that is discharged from the seal 206 into the casing 116 of the speed increaser 110 at a pressure lower than that present in the discharge branch 207 is discharged into the tank 201 together with the lubricating oil.

[0053] A third embodiment of the lubrication and sealing system will now be described with reference to Figures 6 and 7. In these figures, some components are not depicted as they are identical to those already described in Figures 4 and 5.

[0054] 6 and 7 are used when the temperature of the working fluid at the compressor delivery inlet is extremely high, e.g., greater than 200°C, e.g., exceeding the maximum allowable oil temperature and resulting in the formation of sludge and carbon deposits. Furthermore, in this embodiment, "oil migration" towards the process can be avoided as much as possible by reducing the flow through the separator.

[0055] In this configuration, which is completely similar to the previous one, except as explained below, a vent or equalization chamber 222 is added, which is connected via a recirculation line 223 to an area of ​​relatively low pressure downstream of the labyrinth seal 121, such as the compressor suction line 103. Compared to the previous configuration, in this case there is more than one labyrinth seal 121, and between them there is an injection chamber 224 into which appropriately cooled process fluid vapor is injected from a heat exchanger 225, for example at 150°C, to prevent the hot gases from coming into contact with the oil discharged from the oil seal 206.

[0056] To minimize the consumption of gas used to block the hot gases, a control using a sonic orifice 226 calculated to have a cooled gas velocity (for example, an average of 15 m / s under the labyrinth, which is sufficient to prevent leakage of hot gases from the vent chamber 222) is used to prevent oil migration from the seal towards the compressor 100. Alternatively, the control can be performed by a valve or a calibrated hole.

[0057] This control also has the advantage of minimizing the flow rate of gas passing from the discharge branch 207 and from the separator vessel 208, with the obvious benefit of being able to prevent oil migration towards the process.

[0058] Due to the type of flow control by sonic orifice, it is recommended to connect the return branch 227 coming from the separator vessel 208 to the vent chamber 222, thus balancing as evenly as possible the division of the flow from the injection chamber 224 towards the vent chamber 222 and the discharge branch 207 of the oil seal 206. In fact, the pressure difference established across the labyrinth seal using this control system is extremely low, in the order of hundredths of a bar, and is therefore greatly influenced by the design of the pressure equalization line.

[0059] 8, a fourth embodiment of a lubrication and sealing system is described, which can be advantageous for minimizing gas flow in the working fluid into the traps of the separator vessel 208. Gas flow can be a source of process contamination.

[0060] This embodiment is therefore applicable when there is a need for highly accurate pressure regulation but no need to create a barrier using cooling gas. Gas leaking in a controlled manner from the vent or equalization chamber prevents oil migration from the seal toward the compressor. Control over the pressure difference regulating the gas flow at the outlet of the labyrinth seal 121 is achieved by connecting the return branch 227 of the separator vessel 208 to the vent or equalization line 223 at the narrow section 223', where the average flow velocity is greater. A pressure difference is thus created between the environment upstream of the labyrinth seal 121 and the narrower section 223' due to the reduction in static pressure caused by the acceleration of the fluid in section 223' (Bernoulli's principle). For example, a velocity of 15 m / s ahead of section 223' and a velocity of 30 m / s in the narrow section of section 223' reduces the passage area in the duct by a factor of 2, sufficient to create the desired pressure difference.

[0061] Finally, according to the present invention, a compressor with an integrated speed increaser has a single mechanical seal against the external environment, which requires excellent sealing performance, and this seal is mounted on the shaft with the slowest rotational speed. The compressor thus solves the technical problem of reducing the number of seals and minimizing the loss of working fluid to the outside. The compressor also includes a gearbox casing that can withstand the pressure of the compressor's working fluid while maintaining the relative positions of the different pinions within an acceptable range. The technical problem of manufacturing a pressurized casing with these characteristics is solved by providing the gearbox casing with a rigid frame that supports the pinions and bearings, an outer containment shell within which the frame is located, and flexible elements that allow the containment shell to expand without exerting excessive force on the inner frame. Depending on the application, i.e., the pressure and temperature values, the most appropriate lubrication and sealing method can be used.

[0062] It should be understood that in addition to the methods of implementing the invention as described above, many further variations exist. It should also be understood that the methods of implementation are merely exemplary and do not limit the scope of the invention, its applications, or its possible configurations. Rather, while the above description will enable one skilled in the art to implement the invention in accordance with at least one of the exemplary configurations, it should be understood that many variations of the described components are possible without departing from the scope of the invention, as defined in the appended claims.

Claims

1. A compressor (100) for a working fluid having an integral speed increaser (110), the speed increaser (110) comprising: a first shaft (111) connected to the motor, carrying a gear (112) and supported by a first bearing (112'); at least one second shaft (113) supporting a pinion (114), arranged around the gear wheel (112) and connected to one or more impellers of the compressor (100), the second shaft (113) being supported by a second bearing (114'), the pinion (114) and the gear wheel (112) meshing directly or indirectly with each other; a mechanical seal (115) installed at one end of the first shaft (111); a casing (116) containing shafts (111, 113), gears (112), pinions (114), bearings (112', 114') and a working fluid; And the casing (116) a frame (118) supporting a first shaft (111), gears (112), associated bearings (112'), at least one second shaft (113) with associated pinions (114) and bearings (114'), and connected to the compressor casing (116) via connecting elements (117); a shell (119) containing the pressure of the working fluid and in which the frame (118) is installed; a flexible element (120) interposed between the connecting element (117) and the pressure containment shell (119); - at least one labyrinth seal (121) housed on each second shaft (113) and mounted between the connecting element (117) and the pinion (114).

2. The frame (118) comprises two half frames (118') and a central ring (118") to which the two half frames (118') are connected; The compressor (100) of claim 1, wherein the central ring (118") extends out from the containment shell (119).

3. The compressor (100) of any one of claims 1 to 2, wherein the shell (119) comprises two half shells (119') connected to a central ring (118'').

4. The compressor (100) of claim 3, wherein the two half shells (119') are split along a vertical centerline and are fabricated with dished ends.

5. The compressor (100) of any one of claims 1 to 4, wherein the flexible element (120) is a bellows or a flexible diaphragm or an elastic sealing element.

6. The compressor (100) according to any one of claims 1 to 5, wherein the mechanical seal (115) is a single seal.

7. The compressor (100) of any one of claims 1 to 6, wherein the mechanical seal (115) is a double seal containing a barrier fluid.

8. an oil tank (201) in which the separation of the liquid and gas phases of the mixture of oil and working fluid takes place; an oil pump (202) downstream of and in fluid communication with the tank (201); an oil conditioning system downstream of the pump (202) and consisting of a thermostatically controlled cooling system (209) and a filtering system (210) downstream of the cooling system (209); a hydraulic regulation system (211); a delivery branch (203) from the oil pump (202) that is divided into a first supply branch (204) of oil to the mechanical seal (115) and a second supply branch (204') that distributes oil to the bearings and sprays for lubrication of the pinion (114) and gears (112); A compressor (100) according to any one of the preceding claims, comprising a return line (213) connecting the tank (201) to the suction line (103) of the compressor (100).

9. The compressor (100) of claim 8, comprising a pressure reduction system (215).

10. 10. The compressor of claim 9, wherein the pressure reduction system comprises an ejector and a regulator for adjusting a driving fluid of the ejector according to a pressure required in the tank.

11. The compressor (100) according to any one of claims 8 to 10, wherein the tank (201) is equipped with a device suitable for separating the liquid and gas phases.

12. The compressor (100) of any of claims 8 to 11, wherein a demister (214) is positioned along the return line (213).

13. a floating ring oil seal (206) supplied by a supply branch (205) located downstream of the delivery branch (203) and equipped with oil injection between the two floating rings; a differential regulator (205') that regulates the flow depending on the pressure in the discharge branch (207) located downstream of the oil seal (206); The compressor (100) according to any one of claims 8 to 12, comprising a self-draining separator vessel (208) located downstream of the discharge branch (207).

14. The compressor of claim 13, further comprising a return line (219) connecting the separator vessel (208) to the suction line (103) of the compressor (100).

15. The compressor (100) of claim 14, wherein a demister (220) is installed along the return line (219).

16. The compressor (100) of claim 14 or 15, wherein at least one flow regulator is installed along the return line (219).

17. a vent chamber (222) connected to the compressor suction line (103) via a recirculation line (223) and located downstream of the labyrinth seal (121); an injection chamber (224) located between the labyrinth seals (121) and into which gas cooled by a heat exchanger (225) is injected; 14. The compressor of claim 13, further comprising a sonic orifice (226) or a valve or gauge port for gas velocity control.

18. The compressor of claim 17, wherein a return branch (227) connects the separator vessel (208) to the vent chamber (222).

19. 18. The compressor of claim 17, wherein a return branch (227) connects the separator vessel (208) to the vent line (223).

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