Integrally geared turbomachinery rotor

Abstract

A rotor for an integrally geared turbomachine, able to provide protection to a pinion shaft (130, 230, 330) from the action of aggressive gases wherein the rotor comprises: the pinion shaft (130, 230, 330);a first stub (110, 210, 310), wherein the first stub (110, 210, 310) has a first portion configured to receive the first end (121, 221, 321) of a tie rod (120, 220, 320), and a second portion configured to engage with a portion of the pinion shaft (130, 230, 330), wherein the first stub (110, 210, 310) is made of a material resistant to aggressive gas.

Description

TITLEIntegrally Geared Turbomachinery Rotors.DESCRIPTIONTECHNICAL FIELD

[0001] The subject matter disclosed herein relates to an integrally geared compressor and / or expander rotor, in particular, a rotor for such unit designed to tolerate gases that are not compatible with the gear teeth material (i.e. a mixture containing hydrogen sulfide =H2S, known as sour gas).BACKGROUND ART

[0002] Turbomachinery is extensively used in the gas and oil extraction industry for various applications, including fluid compression, converting electrical energy into mechanical energy or vice-versa, fluid liquefaction, and more. One of such machines is an integrally geared compressor and / or expander (IGC / IGE).

[0003] In an integrally geared compressor unit, the impeller is mounted on the shaft of the speed increaser. This design allows the impeller to rotate at a higher speed than the drive shaft to achieve efficient energy transfer to the processed gas. The impeller is directly fixed to the shaft of the speed increaser, allowing it to rotate at very high speeds and enhancing the gas compression capacity. In an integrally geared expander unit, the wheel is mounted instead on the shaft of the speed reducer but still connected to the high speed shaft of the gear.

[0004] The structural elements of these IGC / IGE units, such as the gears, must be made from high-strength materials to withstand high forces and speeds. However, such materials are prone to suffer from sulfide stress corrosion orhydrogen embrittlement phenomena, which typically can be overcome using materials exhibiting a lower hardness level (i.e. materials listed in NACE MR0175), which are not practical to be used for gears manufacturing due to lower mechanical properties. There seems to be no steel alloy that is both resistant to sour gases and suitable for manufacturing gear toothed components.

[0005] Typically, equipment handling extremely sour or acidic gas presents significant challenges in terms of safety and reliability. Ensuring process gas containment under any possible operational scenario is crucial to prevent serious hazards to people and the environment. Extremely aggressive gases, associated with corrosion and stress corrosion cracking phenomena, require special focus on the reliability and robustness of the design to ensure machinery integrity and gas containment throughout the equipment's lifespan.

[0006] Studies and projects have documented the selection of shaft and stator components based on operating conditions, gas composition, and site environment. Base materials and protective coatings for severe sour and acidic gas applications are well-documented. The design of dry gas seals and seal gas systems involves specific solutions in terms of layout, design characteristics, and material selection, aimed at increasing the safety and reliability of dry gas seals handling acidic seal gas.

[0007] Gaskets, such as the one described in patent document JP2024034759, are known. Their purpose is to prevent gas on the hub side from leaking towards the impeller-shaft cavity. However, they have multiple drawbacks:• It is difficult to assess, after assembly, whether they are correctly positioned and undamaged;• There is no way to assess during machine operation if such a seal is still effective. On stator elements, it is possible to have two gaskets in series with a leakage monitoring system in between to identify malfunctions;• Even if the gasket is functioning correctly, in high-pressure CO2 applications, the gas may reach approximately 200 bar pressure, resulting in a small but non-zero leakage. The cavity will thus be contaminated;• Additionally, from the ogive, the gas may still leak towards the cavity.The same gasket concept can be applied but still with the aforementioned drawbacks.

[0008] On compressor / expander elements, dedicated material selection is required, but this aligns well with industry experience in sour gas treatment. On the gear side, the only element that may come into contact with process gas is the gear pinion. Gear pinions typically have integral gearing (e.g., gear teeth are machined on a single shaft forging) and require hard materials for wear and stress resistance. This contrasts with NACE MR0175 requirements: materials suitable for contact with sour gas typically have low strength and hardness to prevent cracking phenomena such as sulfide stress corrosion.

[0009] The gear may come into contact with process gas in the region where it connects to the impellers. This region has connection elements that lead to stress concentration, such as Hirth connections and tie-rod threads, which increase the risk of H2S -induced failures if in contact with process gas.

[0010] Failures related to such mechanisms are sudden, with no possibility to identify the approaching failure in advance. This differs from the corrosion mechanism, which is a gradual process and can be identified during machine maintenance operations. A failure of a rotating element, particularly in low-pressure stages where cast casings are considered, may not be contained, thus impacting personnel safety due to the possible release of toxic process gas.

[0011] It would be desirable to have an element that allows maintaining a mechanical connection between the gear and the impeller but prevents gas from flowing through the cavity and contacting the gear.SUMMARY

[0012] According to a first aspect a rotor for an integrally geared turbomachine, which is able to provide protection to ae pinion shaft from the action of aggressive gases, wherein the rotor comprises: the pinion shaft;a first stub , wherein the first stub has a first portion configured to receive the first end of a tie rod, and a second portion configured to engage with a portion of the pinion shaft wherein the first stub is made of a material resistant to aggressive gas.

[0013] According to a second aspect an integrally geared turbomachine comprising a rotor for an integrally geared turbomachine.BRIEF DESCRIPTION OF THE DRAWINGS.

[0014] A more complete appreciation of the disclosed embodiments of the subject matter and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:Fig. 1 illustrates a schematic view of a first embodiment of an integrally geared turbomachine rotor.Fig. 2 illustrates a schematic view of a portion of an integrally geared rotor ofFig. 1.Fig. 3 illustrates a schematic view of a second embodiment of an integrally geared turbomachine rotor.Fig. 4 illustrates a schematic view of a portion of an integrally geared compressor / expander with a rotor ofFig. 3Fig. 5 illustrates a schematic view of a third embodiment of an integrally geared turbomachine rotor.DETAILED DESCRIPTION OF EMBODIMENTS

[0015] This document describes a rotor designed for an integrally geared turbomachine compressor / expander, aimed at protecting the pinion shaft from the effects of aggressive gases. The rotor features a first stub, which is configured to receive one end of a tie rod and engage with a portion of the pinion shaft. This first stub is made from a material that is resistant to aggressive gases and meets NACE standards. Currently, the shafts of integrally geared compressors / expanders are made from materials that are not NACE compliant or tolerant to sour / acid gases, making these machines unsuitable for aggressive environments. The present invention focuses on integrally geared compressors / expanders for aggressive gases. By constructing the shaft end of the pinions with NACE-compliant material, the machine becomes resistant to aggressive gases while preserving the main components in the core of the shaft, including the gear, thrust collar, and journal bearing.

[0016] The NACE-compliant stub shaft end is connected to the main shaft using a shrink-fit connection, which also connects to the impeller (typically via a Hirth coupling), the DGS seat, and the sensor target surface, which may be cladded directly onto the shaft end. With the shaft end made from NACE-compliant material, aggressive gases will come into contact only with this portion of the shaft, preventing damage. Meanwhile, the core of the shaft comprising the gear, thrust collar, and journal bearing remains protected from aggressive gases through a clean gas buffering layer.

[0017] The document describes various connection methods between the first stub and the pinion shaft, including shrink-fit, flanged, and secondary tie-rod connections. Additionally, the rotor includes a second stub designed to receive the other end of the tie rod, which passes through an impeller of theturbomachine. The impeller is mechanically connected to the first stub using methods such as hirth, friction, flanged, or tapered couplings. The rotor can also be configured with a nut as the second stub, and the connection between the first stub and the pinion shaft can be achieved through shrink-fit, flanged, or secondary tie-rod connections. These configurations ensure a robust and reliable connection, which is crucial for the proper functioning of the turbomachine in environments with aggressive gases.

[0018] Reference now will be made in detail to embodiments of the disclosure, an example of which is illustrated in the drawings. Each example is provided by way of explanation of the disclosure, not limitation of the disclosure. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present disclosure without departing from the scope or spirit of the disclosure. In the following description, similar reference numerals are used for the illustration of figures of the embodiments to indicate elements performing the same or similar functions. Moreover, for clarity of illustration, some references may be not repeated in all figures.

[0019] Considering Figures a rotor for an integrally geared turbomachine, able to provide protection to at least a pinion shaft 130, 230, 330 from the action of aggressive gases . advantageously the rotor comprises: the pinion shaft 130, 230, 330; and a first stub 110, 210, 310, wherein the first stub 110, 210, 310 has a first portion configured to receive the first end 121, 221, 321 of a tie rod 120, 220, 320, and a second portion configured to engage with a portion of the pinion shaft 130, 230, 330, wherein the first stub 110, 210, 310 is made of a material resistant to aggressive gas, ensuring durability and longevity in harsh environments.

[0020] Advantageously the material resistant to aggressive gas is a NACE compliant material, because materials compliant with NACE (NationalAssociation of Corrosion Engineers) standards are designed to withstand environments containing hydrogen sulfide (EES). As is well known, one of the most relevant standards is NACE MR0175 which provides guidelines for the selection and qualification of metallic materials used in oil and gas production environments containing H2S. This compliance ensures that the rotor can operate reliably in sour environments, reducing maintenance costs and downtime

[0021] As shown in Figures, the rotor also comprises: a second stub 150, 250, 350, wherein the second stub 150, 250, 350 is configured to receive a second end 122, 222, 322 of the tie rod 120, 220, 320 ; and the tie rod 120, 220, 320 configured to pass through an impeller 140, 240, 250 of the turbomachine, wherein the tie rod 120, 220, 320 having the first end 121, 221, 321 joined with the first stub 110, 210, 310 of the pinion shaft 130, 230, 330 and the second end 122, 222, 322 joined the second stub 150, 250, 350. This configuration ensures a secure and stable connection, enhancing the overall performance and reliability of the turbomachine.

[0022] Advantageously the second stub 150, 250, 350 is a nut, and the second portion of the first stub 110 is joined with the pinion shaft 130 through a shrink fitted connection. This method provides a robust and precise fit, minimizing the risk of misalignment and mechanical failure.

[0023] It is to be noted the impeller 140, 240, 340 is joined with the first stub 110, 210, 310 through a mechanical connection (i.e. hirth, friction, flanged, tapered, etc.) coupling one to each other. This mechanical connection ensures efficient power transmission and reduces vibration, contributing to the smooth operation of the turbomachine.

[0024] Advantageously the second end 122, 222, 322 of the tie rod 120, 220, 230 is joined with the second stub 150, 250, 350 provides additionalstability and support to the rotor assembly.

[0025] According to first embodiment shown in Fig. 1 the second portion of the first stub 110 is joined with the pinion shaft 130 through a shrink fitted connection. This connection method ensures a tight and secure fit, enhancing the structural integrity of the rotor.

[0026] In particular, the internal diameter of the second portion of the first stub 110 is smaller than the external diameter of the portion of the pinion shaft 130, allowing the shrink fitted connection. This precise fit reduces the risk of mechanical failure and extends the lifespan of the rotor.

[0027] According to second embodiment shown in Fig. 3 the second portion of the first stub 210 is joined with the pinion shaft 230 through a flanged connection 260. This method provides a strong and reliable connection, suitable for high-stress applications.

[0028] According to third embodiment shown in Fig. 5 the second portion of the first stub 310 is joined with the pinion shaft 330 through a second tie-rod 321a connection which engages on its first portion with first stub 310 and on the second portion with a second stub 350 on the opposite side of the pinion shaft 330. This configuration offers enhanced stability improving the overall performance of the turbomachine.

[0029] Furthermore, an integrally geared turbomachine comprising the innovative rotor for an integrally geared turbomachine, able to provide protection to the pinion shaft from the action of aggressive gases is equipped with a first stub. This design ensures that the turbomachine can operate efficiently and reliably in harsh environments, reducing maintenance requirements and extending the operational lifespan of the equipment.

[0030] The innovative design of the rotor also allows for easymaintenance and replacement of the stub shafts. By using standardized connections such as Hirth couplings and flanged connections, the rotor components can be quickly disassembled and reassembled, minimizing downtime and maintenance costs.

[0031] The rotor's ability to accommodate various mechanical connections (e.g., Hirth, friction, flanged, tapered) provides flexibility in its application across different turbomachines. This versatility ensures that the rotor can be adapted to meet the specific requirements of various industrial applications, making it a highly valuable component in the field of turbomachinery

Claims

CLAIMS1. A rotor for an integrally geared turbomachine, able to provide protection to a pinion shaft (130, 230, 330) from the action of aggressive gases, wherein the rotor comprises:the pinion shaft (130, 230, 330);a first stub (110, 210, 310) wherein the first stub (110, 210, 310) has a first portion configured to receive the first end (121, 221, 321) of a tie rod (120, 220, 320), and a second portion configured to engage with a portion of the pinion shaft (130, 230, 330),wherein the first stub (110, 210, 310) is made of a material resistant to aggressive gas.

2. The rotor of claim 1, wherein the material resistant to aggressive gas is a NACE compliant material.

3. The rotor of claim 1, wherein the rotor also comprises:a second stub (150, 250, 350), wherein the second stub (150, 250, 350) is configured to receive a second end (122, 222, 322) of the tie rod (120, 220, 320)- the tie rod (120, 220, 320) configured to pass through an impeller (140, 240, 250) of the turbomachine, wherein the tie rod (120, 220, 320) having the first end (121, 221, 321) joined with the first stub (110, 210, 310) of the pinion shaft (130, 230, 330) and the second end (122, 222, 322) joined the second stub (150, 250, 350).

4. The rotor of claim 3, wherein the second stub (150, 250, 350) is a nut.

5. The rotor of claim 1, wherein the impeller (140, 240, 340) is joined withthe first stub (110, 210, 310) through a mechanical connection coupling one to each other.

6. The rotor of claim 1, wherein the second portion of the first stub (110) is joined with the pinion shaft (130) through a shrink fitted connection.

7. The rotor of claim 1, wherein the internal diameter of the second portion of the first stub (110) is smaller than the external diameter of the portion of the pinion shaft (130), allowing the shrink fitted connection.

8. The rotor of claim 1, wherein the second portion of the first stub (210) is joined with the pinion shaft (230) through a flanged connection (260).

9. The rotor of claim 1, wherein the second portion of the first stub (310) is joined with the pinion shaft (330) through a second tie-rod (321a) connection which engages on its first portion with first stub (310) and on the second portion with a second stub (350) on the opposite side of the pinion shaft (330).

10. An integrally geared turbomachine comprising a rotor according to any one of claims 1 to 9.

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