Patent Application
20070006656
The present invention relates generally to non-destructive testing techniques, and more particularly, to a system and method for monitoring the condition of tubes and pipes used in industrial applications.
In the operation of industrial systems such as boilers, heat exchangers and other process flow tubes or pipes, material deposition on the inside of the tubes or pipes can block heat transfer or cause flow restrictions. In the case of boilers, this heat transfer blockage or flow restriction can lead to the development of “hot spots” or areas not cooled by the water flowing inside the tubes.
These hot spots can cause a degradation of the tube, possibly leading to rupture of the tube. Rupture of boiler tubes and process piping may critically injure personnel in the vicinity. In addition, rupture or blockage of tubes can cause expensive repair costs and related loss of production, as forced outages are required to correct deposit-related failures. Furthermore, deposition or fouling of heat exchangers reduces the efficiency of the heat exchanger, leading to increased process costs. This is because heat flux from the hot fluid to the cooler fluid may be hindered due to the deposition within the tubes.
One conventional method of measuring deposit accumulation within tubes and pipes is by determining the presence and measuring the dimensions of deposits within these vessels via borescopes. This method may require flow of fluid within the tube to be stopped, the tube drained of fluid, and the borescope inserted into the tube through an access port and guided to the area of interest. Similarly, another traditional method of estimating the deposit buildup in boiler tubing requires representative tube sections to be physically cut from the boiler, followed by laboratory tests for the deposit thickness. These methods cause forced outages.
There is therefore, a need for a system and method for monitoring and tracking the condition of tubes within a heating system without long durations of suspended operation.
According to one aspect of the present technique, a system and method for determining deposition parameters within an industrial heating system is provided. The system includes a phased array probe arranged adjacent to a tube within the industrial heating system. The phased array probe transmits and receives signals. A processing unit is in communication with the phased array probe for processing the received signals to generate data on deposition parameters of the tube. A display unit is coupled to the processing unit for displaying the data.
In accordance with another aspect of the present technique, a system and method for determining parameters of a tube within a heating system is provided. The method includes receiving signals by a probe placed adjacent to a tube, processing the received signals for generating data on parameters of the tube, and displaying the data on a display unit.
In accordance with still another aspect of the present technique, a system and method for providing maintenance of tubes within a heating system is provided. The method includes receiving acoustic signals by an ultrasound probe placed adjacent to each of the tubes, processing the received acoustic signals for generating an internal image of each of the tubes, and alerting personnel based on the internal image of each of the tubes.
These and other advantages and features will be more readily understood from the following detailed description of preferred embodiments of the invention that is provided in connection with the accompanying drawings.
In one exemplary embodiment, boiler 12 includes tubes 14 that allow passage of fluid within a boiler chamber 16 either for regulating the temperature within the boiler chamber 16, or for preheating the material within boiler 12. For maintaining uniform temperature within the boiler chamber 16, a fluid such as water may be passed into the boiler 12 via tubes 14 as shown by arrow 18. The fluid passed into the tubes 14 thus allows uniform application of heat to the material within boiler 12.
Similarly, preheating the material within boiler 12 may be performed by passing steam into the boiler tubes 14 in a direction reverse to that shown by arrow 20. The steam may condense into water and can flow out through the tube 14 in the direction opposite to that shown by arrow 18.
Over a period of usage, there may be formation of thin layers of deposits within the insides of the tubes 14, as illustrated in circle II. This is due to dissolved material in the fluid passing through the tubes 14. Referring now to
The probe 24 may transmit a signal, such as an acoustic signal 26a into the tube 14, which undergoes reflection from the opposite surface of the tube 14. The reflected signal 26b is received by the probe 24 and may be converted into an electrical signal prior to processing. Referring back to
Referring now to
In a different embodiment, a phased array ultrasound probe 24 may be utilized for generating an image of the deposit 22 or for determining the thickness of deposit 22. A phased array ultrasound probe 24 includes an array of ultrasound transducers whose signals are combined after appropriate time delays. The resulting signal generated may be detected with a suitable detector, such as a square law detector. Phased array ultrasonic technique controls generation of an ultrasonic beam with desired characteristics (such as beam focus and beam direction), and electronically controls beam scanning over the length of the probe 24.
According to another embodiment, the time it takes for the acoustic signals 26b to reflect from the walls of the tube 14 or the acoustic signals 26c to reflect from the deposits 22 may be utilized for determining the dimensions of the deposit. Because deposit 22 will render the tube's inner dimensions narrower at locations where deposit 22 exists, such a technique may be implemented. Based on the amount of time it takes for the acoustic echoes 26b, 26c to return to the ultrasound probe 24, the control circuitry 30 may compute the dimensions of the deposit 22. Furthermore, the control circuitry 30 may generate a cross-sectional image of the entire tube 14 including the deposit 22, based on the same principle.
The aforementioned techniques may therefore determine the dimensions of the deposit 22. For example, the size or the thickness of the deposit 22 may be determined. Because the deposit 22 may restrict the diameter of the tube 14, fluid flow velocity within the tube 14 increases. Therefore, flow patterns of the fluid, such as a change in fluid flow velocity, may be computed by the control circuitry 30, based on the dimensions of the deposit 22.
Turning now to
The control circuitry 30 can therefore differentiate the change in fluid flow velocity with and without a deposit layer 22, in the illustrated embodiment. Thus, control circuitry 30 can visualize any blockage in the fluid flow within the tubes 14. An image of the flow pattern within the tubes 14 may be produced by the control circuitry 30 using the characteristics of phased array ultrasound technology previously discussed with respect to
Another method related to the Doppler shift technique is a B-Flow imaging technique. The B-Flow imaging technique highlights the locations where fluid flow exists. The B-Flow imaging technique relies on immobility of the echo signals, which is an echo subtraction filtering technique. The tube 14 and the deposit 22 are stationary, while the fluid flow is dynamic. Several image frames or image lines may be captured as described previously with respect to
Moreover, alternate processing techniques, such as spectral Doppler analysis or signal correlation may be applied to detect and quantify flow states. For example, spectral processing is achieved by acquiring the Fourier Transform of signals (e.g., range-gated echo samples) from beams that interrogate the same spatial direction. Similarly, correlation processing (e.g., time-domain correlation processing) correlates echo segments of one beam to the echo segment for the substantially same spatial direction, but at a later point in time.
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.
