Patent Application
20110192465
1. Field of the Invention
The present invention relates to valve sensor systems and, more specifically, to a sensor system for detecting faulty valves in a vacuum sewer system.
2. Description of the Prior Art
Vacuum sewer systems are commonly used in areas without a substantial natural gradient that allows gravity flow of sewage to a treatment plant. Such systems are often used in beachside and island residential areas because in such areas most houses are topographically nearly as low as or lower than the elevation of the sewage treatment plant.
In a vacuum sewer system, as shown in
The sewage flows through the sewage main 30 into a collection tank 52 at a vacuum station 50. Sewage pumps transfer the sewage from the collection tank 52 to the wastewater treatment facility or nearby gravity manhole. Differential air pressure is the driving force in vacuum sewer systems. Typically, vacuum sewer lines are kept under a vacuum of −50 kPa to −70 kPa created by the vacuum pump 52 located at the vacuum pump station 50. This pressure differential provides the energy required to open the vacuum interface valves and to transport the sewage.
For various reasons, a vacuum interface valve 24 can get stuck in an open, or partially open position. When this occurs, air can flow freely from the air relief tube 40 into the sewage main 30. This causes a loss of vacuum in the sewage main 30, which results in the vacuum pump 52 over working and wasting energy.
In a vacuum sewer system in which many different collection pits are serviced by a common sewage main, a stuck open valve is usually detected when the vacuum pump at the vacuum station cycles “on” an unusually high number of times during a given hour. Once a stuck valve is detected, a technician has to shut off each leg of the system along the main until the leaking valve is detected. This can be quite time consuming and costly, as it takes at least one hour to detect the existence of a faulty valve and it can take several hours to determine which valve on the line is faulty. It can also leave many homes on the line without sewer service while their systems are being shut down during the leak detection process.
It has been proposed to retrofit existing vacuum interface valves with underground electronic valve position detection switches. However, doing so would require digging to the valve level to install such switches and also would require installing electrical power systems and underground communication systems that are coupled the switches. Thus, installing such switches would be both difficult and costly.
Therefore, there is a need for a detection system for faulty vacuum interface valve that can quickly detect a faulty valve, but that can be installed without requiring access to the inside of a collection pit.
The disadvantages of the prior art are overcome by the present invention which, in one aspect, is a sensor unit for detecting an open vacuum interface valve coupled to a gravity sump that is pneumatically coupled to an air relief tube of a vacuum sewage system. The sensor unit includes an open valve sensor, a communication device, a processor and a power source. The open valve sensor is in pneumatic communication with the interior of the air relief tube. The processor is in electronic communication with the open valve sensor and the communication device. The processor is configured to read a sensed value from the open valve sensor and cause the communication device to transmit an alarm signal when the sensed value meets predefined criteria. The power source provides power to the open valve sensor and to the communication device.
In another aspect, the invention is a system for detecting an open vacuum interface valve coupled to a gravity sump of in a vacuum sewage system. The system includes a plurality of sensor units and at least one monitoring station. Each sensor unit of the plurality of sensor units includes at least one air relief tube pressure sensor coupled to an interior portion of the air relief tube, at least one ambient pressure sensor disposed outside of the air relief tube, a communication device and a processor in electronic communication with the air relief tube pressure sensor, the ambient pressure sensor and the communication device. The processor is configured to read a first pressure from the air relief tube pressure sensor and a second pressure from the ambient pressure sensor periodically, calculate a difference between the first pressure and the second pressure, cause the communication device to transmit an alarm signal to a network when the difference meets predefined criteria, a memory that stores identifying data that is uniquely associated with the sensor unit and wherein the alarm signal includes the identifying data and a power source for providing power to the air relief tube pressure sensor, the one ambient pressure sensor and the communication device. At least one monitoring station receives the alarm signal. The monitoring station includes a computer configured to correlate the identifying data with the sensor unit and to display an identification of which sensor unit that has detected an open vacuum interface valve.
In yet another aspect, the invention is a method for detecting an open vacuum interface valve coupled to a gravity sump coupled to a vacuum sewage system, in which a pressure drop is detected inside of an air relief tube coupled to the vacuum sewage system, in which the pressure drop is associated with the open vacuum interface valve. When the pressure drop is sustained for a predetermined amount of time, then a signal is transmitted to a monitoring station. The signal includes data that identifies the open interface valve.
These and other aspects of the invention will become apparent from the following description of the preferred embodiments taken in conjunction with the following drawings. As would be obvious to one skilled in the art, many variations and modifications of the invention may be effected without departing from the spirit and scope of the novel concepts of the disclosure.
A preferred embodiment of the invention is now described in detail. Referring to the drawings, like numbers indicate like parts throughout the views. Unless otherwise specifically indicated in the disclosure that follows, the drawings are not necessarily drawn to scale. As used in the description herein and throughout the claims, the following terms take the meanings explicitly associated herein, unless the context clearly dictates otherwise: the meaning of “a,” “an,” and “the” includes plural reference, the meaning of “in” includes “in” and “on.” Also, as used herein, “global computer network” includes the Internet.
As shown in
Detection may occur in one of several ways. For example, as shown in
Returning to
As shown in
A processor 118 receives the internal air pressure from the pressure transducer 114 determines if a pressure drop that is characteristic of a stuck open valve has occurred. In another embodiment, the processor merely collects the pressure data and transmits it to the central monitoring station where the determination of whether the valve is stuck open is made. If a sufficient pressure drop is sensed, the processor 118 determines if the pressure drop lasts for a period of time that would indicate that the valve is stuck open (i.e., when the pressure drop is sustained for longer that the pressure drop expected from a normal emptying of the sump). A memory 120 stores the data from the pressure transducer and a unique identification of the sensor (which can be used to identify the location of the stuck open valve by pairing the unique identifications of all sensors with locations in a sump location database), along with any necessary program data. In an alternative embodiment, the sensing unit could include a microphone configured to sense sound inside of the air relief tube and a signal processor to determine if the sound corresponds to the sound made by a stuck open valve.
An ambient pressure transducer 126 (as shown in
A communications device, such as a mesh network transceiver 124 (e.g., a Zigbee® mesh network transceiver) or a networking radio, transmits data from the sensor unit 110 to the central monitoring station. If a mesh network transceiver 124 is used, then the sensor units 110 work together to form a mesh network, which can cover a wide distance, yet expend relatively little power. A power source, such as a battery 122 (e.g., a lithium ion battery) or a solar power cell, powers the transducers, the processor and the communications device. The sensing unit 110 may be placed in a protective housing 112 with a gasket 116 used to prevent air leakage into the air relief tube when in use.
As shown in
As shown in
While the sensed data may be evaluated locally by the processor, it may also be transmitted to the central monitoring station to be evaluated there. In this case, the sensed data, a timestamp and a sensor unit are all transmitted to the central monitoring station. The central monitoring station could periodically poll each of the sensor units, or the sensor units could be programmed to upload the data to the central monitoring station on a periodic basis. It is also possible that both a central monitoring station evaluation and a local evaluation are performed to increase reliability of the system.
A similar method could be employed if another quality of the air relief tube is being sensed to determine if the valve is stuck open. For example, if a sound sensor is being used, the system could compare the sound being sensed to a characteristic of the sound that would be expected if the valve were stuck open. In such a system, the sensed sound could be transformed (using well known signal processing techniques, such as with a digital signal processor) into a frequency domain representation and this representation can be compared to a frequency domain representation of the sound made by an open valve. If the representations are the same, or within a predetermined margin of each other, for a period of time that would indicate that the valve is stuck open, then an alarm will be issued. The sound sensor could also be configured to detect a higher sound volume than normal (or a higher volume than normal of certain frequency components of the sound in the air relief tube).
The above described embodiments, while including the preferred embodiment and the best mode of the invention known to the inventor at the time of filing, are given as illustrative examples only. It will be readily appreciated that many deviations may be made from the specific embodiments disclosed in this specification without departing from the spirit and scope of the invention. Accordingly, the scope of the invention is to be determined by the claims below rather than being limited to the specifically described embodiments above.
