Patent Application
20070295402
With reference to
The gas supply sub-system 10 can be arranged in multiple configurations. In a preferred configuration, a primary source of pressurized gas supply is a compressor 12 that maintains an accumulator tank 14 charged to a predetermined pressure. A motor 16 that drives the compressor 12 communicates with a pressure switch 18 that activates the compressor 12 when the pressure in the accumulator 14 falls below a predetermined level. The pressure switch 18 deactivates the compressor 12 when the pressure in the accumulator 14 reaches a second predetermined level.
The compressor inlet is equipped with air dryer and air filter units 20. Additionally, the accumulator tank 14 is equipped with a manual or automatic drain valve 22 that drains any condensate that collects in the accumulator 14. The accumulator 14 is also equipped with a safety relief valve 24 to protect the gas supply system from over-pressurization. A non-return valve 26 is incorporated to prevent backflow into the compressor 12 when it is not in operation.
In addition to the accumulator 14, which is continuously kept charged by the compressor 12, the gas supply system is equipped with a backup gas bottle or bottles 28. Gas supply to the downstream pressure control sub-system 50 can be switched between the accumulator 14 and the backup gas bottle 28 by means of a manual or automatic valve arrangement 30, which can comprise two one-way valves or a single three-way valve.
This arrangement provides a reliable source of actuation gas in the event of a compressor or system failure. A “system failure” is an event when the pressurized gas supply and control system become incapable of providing pressurized gas, modulated as per the electrical command, to the actuators 100, 101. In this situation, first the accumulator 14 provides the necessary pressurized gas, and after it gets depleted, the backup gas bottle 28 is utilized. The backup gas bottle 28 is provided with an automated or manual shut-off valve 32 and a mutual or independent pressure regulator 34 (in case of multiple bottles).
With continued reference to
In an exemplary application with reference to the active seals discussed above, a computer controller can determine a current operating state of the turbomachinery and the desired configuration of the seals (e.g., maintain open, open, maintain closed, close), and based on this information, the controller generates the electrical command that represents the desirable or target actuation pressure. The same controller or a second controller (indicated by the I/P block in
The pressure control sub-system 50 preferably utilizes at least two independent lines for each downstream volume as required by the number of actuators and/or seal segments that have to be actuated independently (in the exemplary application). As shown in
The possibly multiple redundant pressure control valve assemblies 52 are connected to the downstream actuator 100, 101 via a selector switch 62. Only one pressure control assembly is operational per line at any given time if redundant lines are employed. If the controller detects that one pressure control valve assembly has failed, the controller will automatically switch the selector switch 62 to an alternate pressure control valve assembly.
Further downstream, the system is equipped with singular or multiple relief valves 64. The relief valves 64 provide further protection from over-pressurization in the event of a failure of the pressure control sub-system 50. The pressure relief valves 64 also provide protection to the system from damage in the event of an unexpected pressure spike, for example, resulting from moisture in the gas. The system further incorporates a combination of manual and automatic isolation valves 66 that isolate the entire system from the actuators 100, 101 in the event that the pressure control sub-system 50 or the gas supply sub-system 10 fails such that no repair is possible, and/or a failure of the downstream volume, e.g., the actuators 100, 101.
The system is controlled by a computer/controller that accepts and processes signals, such as pressure measurements, machine operating conditions, etc., from the turbomachinery, generates appropriate commands that are sent to the pressure control valve assembly 52, and handles fault detection and accommodation. The controller continually monitors or estimates the pressure inside the actuators 100, 101 to ensure that the pressure matches the commanded value.
In the exemplary turbomachinery environment, the system provides clean and dry gas at modulated pressures thereby preserving the life of the actuators and reliable active seal operation. Additionally, the system incorporates features that minimize the possibility of dirt and moisture in the system, which can damage the components and actuators, and eventually the seals. The design allows the user to choose between two independent gas supply systems. Additionally, the system provides a high degree of reliability utilizing several levels of redundancy that make it insensitive to single-point failures. In this context, three transducers are preferably used for each pressure measurement for locations within the turbomachinery (e.g., PT233H, PT233I, PT233J) as well as each downstream volume (e.g. PT233D, PT233E). The transducer arrangement effects a triple redundancy. Accurate pressure measurement is important for reliable operation of the system. If, for a given pressure measurement, the controller detects that one transducer is reading something different from the other two, the controller ignores the aberrant one. This redundancy maintains reliability against single point or component failures.
Individual components can be isolated and serviced while the system is on-line without interrupting the pressurized gas supply to the actuators. Still further, the system has been designed with safety features including relief valves and pressure regulators that ensure that the system is never over-pressurized, and isolation valves and non-return valves that ensure that the system can be cut off from the actuators and that there is no undesirable backflow.
While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
