Patent Application
20130174649
The subject matter disclosed herein relates to a fluid leak detection system, and more specifically to a fluid leak detection system having a controller with control logic for monitoring the fluid leak detection system and determining if a leak condition exists.
Traditionally, gas turbine flame detectors have been used to ensure the presence of a flame during gas turbine light-off and operation. Some flame detectors employ a cooling coil that uses water (which may contain a mixture of various anti-freeze constituents) as a cooling medium to keep a flame detector sensor below a threshold temperature. However, a leak may occur in the cooling water circuit. Leakage of the cooling water may cause the casing of the gas turbine or components located within the casing to need replacement. Replacement of the casing or the components located within the casing may become time-consuming and costly.
Cooling water may also be employed to cool a liquid fuel purge system as well in a gas turbine. Specifically, cooling water may be used to cool a three way liquid fuel valve. Cooling water may also be employed to cool check valves of the liquid fuel purge system. Specifically, cooling water is used to maintain an internal check valve or three way valve temperature below the coking threshold of the liquid fuel. However, a leak may also occur in the cooling water circuit of the liquid fuel purge system, which may also cause the water cooled valve to operate incorrectly. The leak may also cause casing or other gas turbine component issues.
According to one aspect of the invention, a fluid leak detection system is provided and includes a fluid conduit, a fluid-cooled device having an inlet and an outlet, an inlet flow meter, an outlet flow meter, and a controller. The inlet flow meter is fluidly connected to the fluid conduit. The inlet flow meter monitors the inlet of the fluid-cooled device for an inlet temperature and an inlet flow rate. The inlet flow meter has an inlet flow meter drift versus process fluid temperature curve and an inlet flow meter drift versus ambient temperature curve. The outlet flow meter is fluidly connected to the fluid conduit. The outlet flow meter monitors the outlet of the fluid-cooled device for an outlet temperature and an outlet flow rate. The outlet flow meter has an outlet flow meter drift versus process fluid temperature curve and an outlet flow meter drift versus ambient temperature curve. The controller is in communication with the inlet flow meter and the outlet flow meter. The controller includes a memory having the inlet flow meter and outlet flow meter drift curves stored therein. The inlet flow meter drift versus process fluid temperature curve being different from the outlet flow meter drift versus process fluid temperature curve and the inlet flow meter drift versus ambient temperature curve being different than the outlet flow meter drift versus ambient temperature curve. A zero flow condition where flow of fluid in the fluid conduit is substantially halted and the inlet flow rate and the outlet flow rate are saved in the memory of the controller as well.
The controller includes control logic for monitoring the ambient temperature, inlet flow meter for the inlet temperature and the inlet flow rate and the outlet flow meter for the outlet temperature and the outlet flow rate. The controller also includes control logic for compensating measurement drift due to the temperature of the process fluid and from the ambient temperature and the percentage of error in the respective flow rates. Specifically, the controller includes control logic for determining the difference between the inlet temperature and the outlet temperature. The memory of the controller includes a set of data stored therein that indicates a percentage of error in flow rate based on the difference between the inlet temperature and the outlet temperature. The controller further includes control logic for determining the difference between the inlet flow rate and the outlet flow rate. The controller includes control logic for calculating an actual flow rate difference between the inlet flow rate and the outlet flow rate. The actual flow rate difference is based on the percentage of error in flow rate, the difference between the inlet flow rate and the outlet flow rate, and the zero flow condition. The controller also includes control logic for indicating a leak condition in the fluid leak detection system if the actual flow rate difference is above a threshold value.
According to another aspect of the invention, a turbine is provided having a fluid leak detection system that includes a fluid conduit, and a fluid-cooled device having an inlet and an outlet. An inlet flow meter is fluidly connected to the fluid conduit, the inlet flow meter monitoring the inlet of the fluid-cooled device for an inlet temperature and an inlet flow rate, the inlet flow meter having an inlet flow meter drift versus process fluid temperature curve and an inlet flow meter drift versus ambient temperature curve. An outlet flow meter is fluidly connected to the fluid conduit, the outlet flow meter monitoring the outlet of the fluid-cooled device for an outlet temperature and an outlet flow rate, the outlet flow meter having an outlet flow meter drift versus process fluid temperature curve that is different than the inlet flow meter drift versus process fluid temperature curve and an outlet flow meter drift versus ambient temperature curve that is different from the inlet flow meter drift versus ambient temperature curve. A shutoff valve is fluidly connected to and selectively blocks a fluid flow through the fluid conduit.
These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.
The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings.
As used herein the terms module and sub-module refer to an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that executes one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality. For example, controllers or control modules may include one or more such modules.
In an aspect, the combustor 104 uses liquid and/or gas fuel, such as natural gas or a hydrogen rich synthetic gas, to run the turbine engine. For example, fuel nozzles 110 are in fluid communication with a fuel supply and pressurized air from the compressor 102. The fuel nozzles 110 create an air-fuel mix, and discharge the air-fuel mix into the combustor 104, thereby causing a combustion that creates a hot pressurized exhaust gas. The combustor 104 directs the hot pressurized exhaust gas through a transition piece into a turbine nozzle (or “stage one nozzle”), causing turbine 106 rotation as the gas exits the nozzle or vane and gets directed to the turbine bucket or blade. The rotation of turbine 106 causes the shaft 108 to rotate, thereby compressing the air as it flows into the compressor 102.
In an embodiment, the inlet valve 226 is a manual valve that is fluidly connected to the fluid conduit 220 and is open during operation of the fluid leak detection system 210. The shutoff valve 222 is located downstream of the inlet valve 226 and is fluidly connected to and selectively blocks or restricts the fluid flow through the fluid conduit 220. Specifically, the shutoff valve 222 is employed to substantially block the flow of fluid to the fluid leak detection system 210 based on certain operating conditions. Downstream of the shutoff valve 222 is the inlet flow meter 224. In one embodiment, the inlet flow meter 224 is a Coriolis flow meter that measures the mass flow rate of fluid traveling through the fluid conduit 220. However, it is to be understood that other types of flow meters from various manufacturers may be used as well. The inlet flow meter 224 monitors an inlet 260 that is fluidly connected the fluid-cooled device 230 for an inlet temperature and an inlet flow rate. The supply manifold 228 is located downstream of the inlet flow meter 224, where the inlet flow meter 224 measures the flow rate and the temperature into the supply manifold 228.
An outlet 262 of the fluid-cooled device 230 is fluidly connected to the return manifold 232. The return manifold 232 is located upstream of the outlet flow meter 236. In one embodiment, the outlet flow meter 236 is a Coriolis flow meter that measures the mass flow rate of the fluid traveling through the fluid conduit 220. However other types of flow meters may be used as well. In an embodiment, the inlet flow meter 224 is provided by a first manufacturer while the outlet flow meter 236 is provided by a second manufacturer. The outlet flow meter 236 monitors the outlet 262 of the fluid-cooled device 230 for an outlet temperature and an outlet flow rate. The outlet flow meter 236 is situated upstream of the check valve 240. The check valve 240 is employed to prevent the ingression of contaminants into the fluid leak detection system 210, and is also employed to reduce or substantially prevent the occurrence of backflow into the fluid conduit 220. The check valve 240 is located upstream of the outlet valve 234. In an embodiment, the outlet valve 234 is a manual valve that is normally open during operation of the fluid leak detection system 210. The inlet valve 226 and the outlet valve 226 may be isolation valves employed during maintenance or system issues.
The inlet flow meter 224 and the outlet flow meter 236 are both configured for monitoring fluid temperature and fluid flow rate of the fluid conduit 220 at their respective locations. The drift versus process fluid temperature curve and drift versus ambient temperature curve represents the change in flow rate measurement accuracy of a flow meter that is caused by changes in process and ambient temperature. In one embodiment, the inlet flow meter 224 and the outlet flow meter 236 are different types of flow meters. Flow meter types include, but are not limited to, the following examples, Coriolis, orifice, ultrasonic, Venturi and V-cone flow meters. In embodiments, the inlet flow meter 224 and outlet flow meter 236 may be provided by different manufacturers, where the flow meter types may be the same or different. The inlet flow meter 224 and the outlet flow meter 236 may each have different drift versus process fluid curves and drift versus ambient temperature curves provided by the manufacturer and are used to improve measurement accuracy.
A Coriolis flow meter is also referred to as a mass flow meter or inertial flow meter and is a device that measures how much liquid is flowing through a tube by measuring the amount of mass flowing through the device. In orifice flow meters, fluid passing though an orifice constriction experiences a drop in pressure across the orifice. This pressure change can be used to measure the flow rate of the fluid. Ultrasonic flow meters measure the velocity of a fluid by using the principle of ultrasound by using sensors, such as ultrasonic transducers. Venturi flow meters include a Venturi tube where fluid flow rate is measured by reducing the cross sectional flow area in the flow path which generates a pressure difference, where the pressure difference is used to determine the flow rate. V-cone flow meters also use a pressure differential measurement in a flow path to determine flow rate.
With continued reference to
The memory of the controller 250 also includes a zero flow condition, where fluid flow in the fluid conduit 220 is substantially halted, and the inlet flow rate at the inlet 260 and the outlet flow rate at the outlet 262 are compared to one another and stored in the memory of the controller 250. Specifically, during zeroing of the controller 250, the flow of fluid through the fluid conduit 220 is substantially halted for a specified period of time where the fluid conduit 220 is filled with fluid. As a result, there is substantially zero flow of fluid through the fluid conduit 220, which may lead to a corresponding reading of zero flow output by both the inlet flow meter 224 and the outlet flow meter 236. However, sometimes the inlet flow meters 224 and outlet flow meters 36 may produce a non-zero flow rate during a time of substantially zero flow. In this case, the non-zero flow rate from the inlet flow meters 224 and outlet flow meters 236 may be used as the zero flow condition.
The memory of the controller 250 also includes a set of data that indicates a percentage of error in flow rate in the fluid conduit 220 based on the temperature at the inlet 260 and the outlet 262. The difference in temperature between the inlet 260 and the outlet 262 is typically referred to as the sensing drift difference between the inlet flow meter 224 and the outlet flow meter 236. As the difference between the temperature at the inlet 260 and the outlet 262 increase, the percentage of error in flow rate in the fluid conduit 220 increases. The percentage of error in the flow rate may be based on the maximum flow rate in the fluid conduit 220.
The controller 250 includes control logic for monitoring the inlet flow meter 224 for the inlet temperature and flow rate at the inlet 260, and the outlet flow meter 236 for the outlet temperature and flow rate at the outlet 262. The controller 250 includes control logic for determining the difference between the inlet temperature from the inlet flow meter 224 and the outlet temperature from the outlet flow meter 236. The controller 250 also includes control logic for determining the difference between the inlet flow rate from the inlet flow meter 224 and the outlet flow rate from the outlet flow meter 236.
The controller 250 further includes control logic for calculating an actual flow rate difference between the inlet flow meter 224 and the outlet flow meter 236. Specifically, the actual flow rate difference represents the real difference between the flow of fluid in the fluid conduit 220 at the inlet flow meter 224 and the outlet flow meter 236 during operation of the fluid leak detection system 210. The controller 250 calculates the actual flow rate difference based on the percentage of error in flow rate (from the drift versus process fluid temperature curves and drift versus ambient temperature curves), the zero flow condition, and the difference between the inlet flow rate from the inlet flow meter 224 and the outlet flow rate from the outlet flow meter 236. The actual flow rate difference may be calculated by subtracting the inlet flow Flownin from the outlet flow Flowout. The inlet flow meter 224 and the outlet flow meter 236 have different errors and tolerances, wherein the controller 250 accounts for these differences due to the differing meter types and/or manufacturers. Moreover, when the flow of fluid in the fluid conduit 220 is substantially halted, then
m
readi
=m
actuali
+m
errori≈0 and
m
reado
=m
actualo
+m
erroro≈0.
where merrori is the error of the mass flow rate at the inlet flow meter 224, merroro is the error of the mass flow rate at the outlet flow meter 236, mreadi is the mass flow rate reading by the inlet flow meter 224, mactuali is the actual mass flow rate at the inlet flow meter 224, and merrori is the error in mass flow rate at the inlet flow meter 224 read by the controller 250. This zero flow condition is used to provide a calibration of the inlet flow meter 224 and outlet flow meter 236. Also, mreado is the mass flow rate reading by the outlet flow meter 236, mactualo is the actual mass flow rate at the outlet flow meter 236, and merroro is the error in mass flow rate at the inlet flow meter 236 read by the controller 250. In the event there is fluid flow through the fluid conduit 220 and the fluid leak detection system 210 is substantially leak free, then:
The controller 250 includes control logic for indicating a leak condition in the fluid leak detection system 210 if the actual flow rate difference is above a threshold value. For example, in one embodiment if the difference between the mass flow rate mreadi read by the inlet flow meter 224 and the mass flow rate mreado read by the outlet flow meter 236 is above the threshold value, then the controller 250 determines that a leak condition in the fluid leak detection system 210 has occurred. Specifically, in one embodiment the fluid leak detection system 210 includes an indicator or an alarm 280 that is in communication with the controller 250, where the alarm 280 emits a visual indicator or sound to alert an operator that a leak condition has occurred. In one example, the controller 250 may also be in communication with a computing screen, which is not illustrated, where the controller 250 sends a signal to the screen to display a visual indicator that informs an operator that the leak condition has occurred.
Several types of leak conditions may exist. In one embodiment, the controller 250 may include control logic for calculating a level one leak condition, which occurs if the actual flow rate difference is above a level one threshold value. In this situation, the controller 250 includes control logic for sending a signal to the alarm 280. The alarm will then emit a level one tone or visual indicator. A level two leak condition may occur as well if the actual flow rate difference is above a level two threshold value. The level two threshold value is greater than the level one threshold value. During the level two leak the controller 250 includes control logic for sending a signal to the alarm 280 for emitting a level two tone or indicator. The level two tone or indicator is typically louder or brighter than the level one tone or indictor, in an effort to alert an operator of a leak condition that may require greater attention.
In addition to the alarm 280, two different approaches may be used as well if the level two leak condition occurs. In a first approach, the controller 250 is in communication with a turbine (not shown) for sending a signal to the turbine indicating that a turbine shutdown condition is created or induced in an effort to substantially reduce the risk of turbine trip and to reduce the amount of fluid leakage. The turbine shutdown condition enables the turbine to shut down safely and restrict or block fluid flow to the sensor. Alternatively, in another embodiment the controller 250 further includes control logic for sending a signal to the shutoff valve 222 to substantially block the flow of fluid to the inlet 260 of the fluid-cooled device 230. Thus, in the event a leak is detected, fluid may no longer flow through the fluid conduit 220, which may reduce the occurrence of fluid leakage in the system.
In embodiments, the depicted fluid leak detection system 210 provides a system for detecting fluid leaks in portions of a gas turbine system, such as a cooling circuit for a gas flame detector, wherein differing flow meters 224, 236 are provided. The system's controller 250 is configured to adjust for differences in error and tolerance between the different flow meters, which provides flexibility in system architecture and maintenance. For example, if the inlet flow meter 224 and outlet flow meter 236 are initially provided as the same type and manufacturer, but the inlet flow meter 224 fails, the system enables replacement of the inlet flow meter 224 with a different type of meter. This flexibility may be useful when certain flow meters are in stock or a type or brand of flow meter is discontinued.
While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.
