TURBOMACHINE CONTROL SYSTEM FOR HAZARDOUS AREAS

Abstract

A system comprising a turbomachinery provided with a casing and having a rotor mounted on a shaft supported for rotation in the casing; the shaft is associated to a plurality of active magnetic bearings adapted to support the shaft in the casing and associated to a control system through a plurality of wires wherein the control system is housed in a control system compartment external to the casing and located in proximity thereto.

Claims

1. A turbomachine comprising: a casing; a turbomachinery having a rotor mounted on a shaft supported for rotation in the casing; a plurality of active magnetic bearings configured and arranged for supporting the shaft in the casing; an active magnetic bearing control system for controlling the magnetic bearings through a plurality of cables; wherein the active magnetic bearing control system is housed in a control system compartment external to the casing and located in proximity thereto.

2. Turbomachine according to claim 1, wherein the control system compartment is pressurized.

3. Turbomachine according to claim 2, wherein the control system compartment is pressurized with air or with an inert gas.

4. Turbomachine according to claim 3, wherein the inert gas is chosen in the group comprising nitrogen, helium and gas mixtures mainly composed of nitrogen or helium.

5. Turbomachine according to claim 1, wherein the control system compartment comprises an explosion proof cabinet.

6. Turbomachine according to claim 1, wherein the control system compartment comprises a cabinet compliant with the European Union Directive 2014/34/EU.

7. Turbomachine according to claim 1, wherein the cables comprise power cables and signal cables, the power cables connecting the control system with the coils of the magnetic bearings to control the current flowing thereto, the signal cables connecting the control system with sensors in the casing, such sensors comprising position sensors to monitor the position of the rotor.

8. Turbomachine according to claim 7, wherein the power cables are at least two for each coil, each magnetic bearing comprising at least two coils, typically four coils per radial bearing, two coils per axial bearing.

9. Turbomachine according to claim 7, wherein the signal cables are two, four or eight cables for each sensor, the sensors comprising one or more sensors selected from the group comprising: axial position sensors, radial position sensors, shaft speed sensors, vibration sensors, temperature sensors.

10. Turbomachine according to claim 1, wherein the cables pass through a protection system connecting the casing to the control system compartment.

11. Turbomachine according to claim 1, wherein the turbomachinery comprises: a turboexpander or motor having a rotor mounted on a shaft supported for rotation in the casing; a compressor arranged in the casing and comprised of a rotor mounted on the shaft for co-rotation with turboexpander/motor rotor.

12. Turbomachine according to claim 1, comprising a unit control system for the control of the turbomachinery, wherein the magnetic bearing control system and the unit control system are hosted in the control system compartment.

13. Turbomachine according to claim 12, further comprising a user interface connected with the unit control system and positioned in a remote control room located in a safe area far away from the turbomachinery.

14. Turbomachine according to claim 12, wherein the magnetic bearing control system and the unit control system are separate units, the unit control system being located in a safe area remote from the machinery while the magnetic bearing control system is located in the control system compartment exploiting explosion protection in hazardous area close to the machinery.

15. Turbomachine according to claim 14, wherein the user interface is located in the same safe area hosting the unit control system.

16. Turbomachine according to claim 12, wherein the unit control system comprises a main controller and a safety controller, the main controller implementing main controls of the machinery chosen in the group comprising start/stop sequence inclusive of auxiliaries, antisurge control, performance control, load sharing control, while the safety controller performs safety functions like trip logics.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The exemplary embodiments described herein will become more apparent when considered in conjunction with the accompanying drawings wherein:

[0014] FIG. 1 illustrates a turbomachinenamely an expander-compressor unitconnected to an AMB control system according to the prior art;

[0015] FIG. 2 illustrates a turbomachine according to embodiments described herein;

[0016] FIG. 3 illustrates an integrated control system according to embodiments described herein;

[0017] FIG. 4 illustrates the network topology of the control system of the integrated control system depicted in FIG. 3;

[0018] FIG. 5 illustrates an AMB control system separated from the unit control system according to embodiments described herein; and

[0019] FIG. 6 illustrates the network topology of the control system depicted in FIG. 5.

DETAILED DESCRIPTION OF THE INVENTION

[0020] FIG. 1 shows an exemplary turbomachine 1namely an expander-compressor unitconnected to an AMB control system according to the prior art.

[0021] As the AMB control system is located in a control system compartment 4 far away from the turbomachine, intermediate junction boxes 10 are used. These junction boxes act as separation elements between the turbomachine 1 and the AMB control system.

[0022] The junction boxes 10, one for the power cables and one for the signal cables, are installed in the classified area where the turbomachine is installed, not far from the turbomachine. Typically the junction boxes 10 can be installed on the skid supporting the turbomachine or in its vicinity, while the AMB control system is installed in a control system compartment 4 located in a safe area at a distance which can measure up to several hundreds of meters and is typically in the range 100 m to 700 m.

[0023] The cable size from junction boxes 10 to AMB control system depends on the distance between the field and the control system compartment 4. Longer the distance, larger is the required power cable cross section to reduce power loss.

[0024] On the turbomachine side, in typical applications, power cables and signal cables have, respectively, less than 10 mm.sup.2 and 1 mm.sup.2 cross section due to short distance. Larger cross sections are obviously possible.

[0025] FIG. 2 exemplary shows a turbomachine according to embodiments herein. The turbomachine 1 comprises a casing, an expander 2 having a rotor mounted on a shaft 15 supported for rotation in the casing, a compressor 3 arranged in the casing and comprised of a rotor mounted on the shaft for co-rotation with the turbo-expander rotor.

[0026] The shaft 15 is supported in the casing by means of a plurality of bearings. In some embodiments a first radial bearing can be arranged at a first end of shaft 15. A second radial bearing can be provided at a second end of the shaft 15. In some embodiments one or more axial bearings can further be provided. A different number of magnetic bearings can be foreseen, e.g. depending upon design choices and/or requirements of the expander-compressor unit. More variability in the number of bearings, and thus of the cables, can be found in motor-compressor units which are part of the present disclosure.

[0027] One, some or all said bearings can be magnetic bearings and more specifically AMBs 14. AMBs 14 are known to those skilled in the art and will not be described in greater detail herein.

[0028] AMBs 14 require an electronic control system 7, which provides power and control signals to the magnetic bearings. According to embodiments disclosed herein the AMB control system 7 is housed in a control system compartment 4 external to the casing and located in proximity thereto. In some embodiments, the control system compartment 4 is pressurized to guarantee that the electronics inside is safe from possible contamination with the process gas of the turbomachine. In an embodiment the control system compartment 4 is located at a distance typically not greater than 20 m from the casing of the turbomachine 1.

[0029] The control system compartment 4 may house only the AMB control system 7 or an integrated control system comprising the AMB control system 7 and the turbomachinery unit control system 8 (UCS).

[0030] A turbomachinery control system 8 is based on PLC hardware and typically comprises a main controller 108 and a safety controller 208. The main controller 108 implements the machine start/stop sequence inclusive of all auxiliaries, antisurge control, performance control and load sharing control, while the safety controller 208 implements trip logics and other safety functions.

[0031] The unit control system 8 is generally hosted in a control cabinet with front door opening located in a safe area far away from the turbomachine. The operator interface is usually a PC with touchscreen panel located in the cabinet (HMI 121) or remotely connected (DCS 122) through a firewall 123 preferably provided with redundant connection.

[0032] In existing systems, the unit control system and the AMB control system 7 are independent and located in a safe area.

[0033] FIG. 3 shows an integrated control system according to embodiments herein. In this configuration, the AMB control system 7, the main controller 108 and the safety controller 208 are all hosted in a control system compartment 4 comprising an explosion proof cabinet and located in a classified hazardous area close to the machinery & auxiliary baseplate 11, while the user interface 121 (HMI) is positioned in a remote control room 12 located in a safe area as best shown in FIG. 4.

[0034] FIG. 5 shows a control system according to a further embodiment wherein the AMB control system 7 and the unit control system 8 are separate units. Like in existing systems, the main controller 108 and the safety controller 208 are located in a safe area 13 remote from the turbomachinery 2.

[0035] The user interface 121 (HMI) can be positioned in the unit control system area 13 or in a dedicated control room 12 in safe area connected to the unit control system 8 while the AMB control system 7 is installed in a control system compartment 4 comprising an explosion proof cabinet and located in hazardous area close to the machinery & auxiliary baseplate 11 as best shown in FIG. 6.

[0036] Remotely connected user interface 122 (DCS) through a firewall 123 preferably provided with redundant connection can be employed like in existing systems as well as emergency shut down system 124 (ESD) interfaced with the unit control system 8.

[0037] Since the electric and electronic components can be affected by the processed gas of the turbomachine, the control system compartment 4 is preferably pressurized and filled with air or an inert gas, for instance nitrogen. In the context of the present description and attached claims, the term inert gas also encompasses noble gases, such as helium, for instance, as well as gas mixtures, for instances mixtures mainly composed of nitrogen or helium.

[0038] In some embodiments, the control system compartment 4 comprises a pressurized cabinet, for example an ATEX cabinet according to European Directive 2014/34/EU.

[0039] In some embodiments a connector flange can be provided on the casing of the turbomachine and on the control system compartment 4 for the passage of cables 5, 6 which connect the expander-compressor unit 1 to the control system compartment 4. Suitable passages, channels or protective sheaths 304 can in practice be used to protect and contain the wiring in order to prevent damages during assembling of the components of the expander-compressor unit and/or during operation thereof. In some embodiments, the cables pass through a protection system connecting the casing to the control system compartment 4.

[0040] Electric connection between the electronic components of the control system compartment and the magnetic bearings can be obtained, for example, by means of pairs of electric connectors 101-204, 201-104 arranged on a surface of the casing and on a surface of the cabinet of the control system compartment 4.

[0041] In some embodiments, the control system compartment 4 comprises an explosion proof cabinet, for example an ATEX cabinet according to European Directive 2014/34/EU.

[0042] The cables connecting the control system compartment 4 with the casing of the turbomachine 1 typically comprise power cables 5 and signal cables 6. The power cables 5 connect the control system compartment 4 with the coils of the active magnetic bearings to control the current flowing thereto, while the signal cables 6 connect the control system with sensors 9 located in the casing. Such sensors may, for example, comprise position sensors, radial and/or axial, to monitor the position of the rotor, temperature sensors, vibration sensors, shaft speed sensors, accelerometers.

[0043] In an embodiment each active magnetic bearing comprises at least two coils, typically four coils per radial bearing, two coils per axial bearing, each driven by a couple of power cables.

[0044] Embodiments have been mainly illustrated with reference to an expander-compressor unit, but the teaching of the present disclosure can be used for any type of turbomachine having magnetic bearing, such as, for example, expander-generator, motor-compressor, motor, generator, turbo-generator units.

[0045] The description of exemplary embodiments refer to the accompanying drawings. The same reference numbers in different drawings identify the same or similar elements. The following detailed description does not limit the invention. Instead, the scope of the invention is defined by the appended claims.

[0046] Reference throughout the specification to one embodiment or an embodiment means that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the subject matter disclosed. Thus, the appearance of the phrases in one embodiment or in an embodiment in various places throughout the specification is not necessarily referring to the same embodiment. Further, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments.