Electrical computers and digital data processing systems: input/ – Input/output data processing
Patent
1998-07-30
2000-08-29
Lee, Thomas C.
Electrical computers and digital data processing systems: input/
Input/output data processing
73 5402, 73 5441, 73592, 73596, 340603, G01N 1100, G06F 1300
Patent
active
061122548
DESCRIPTION:
BRIEF SUMMARY
This invention relates to the detection of density and consistency changes in liquids, more particularly although not exclusively sludges in waste water plants, and extends to the control of pumping equipment responsive to such detection.
In the treatment of waste water, the pumping of sludges is extensively used to transfer such sludges between stages in the treatment process, and maintenance of correct sludge densities is critical to the proper operation of certain stages of treatment. Under static conditions, there is a tendency to separation into sludge and aqueous phases, and in pumping from a body in which such separation has occurred, there is a tendency for the aqueous phase to `tunnel` through the sludge and be pumped preferentially to the sludge. In some circumstances also, sludge density may become excessive. This makes it difficult to maintain a correct sludge density in a destination vessel, but we are not aware of any means currently available that will detect reliably the density of sludge being pumped by a sludge pump. Similar problems arise in other applications where liquids having mixed phases or variable density are being pumped.
Attempts have been made to detect sludge density by acoustic methods, but problems have arisen as a result of pump noise, unpredictable responses of pipework associated with pumps, and very high acoustic absorbtion by typical sludges.
Proposals have also been made in U.S. Pat. No. 4,145,917 to measure the properties of liquid in a vessel by applying a transducer to the wall of a vessel to project pulses ultrasonic energy into a liquid, and measuring characteristics of the response to these pulses.
It has now been found that a predictable, reliable and rapid detection of the nature of liquid in pipework associated with pumps can be achieved utilizing ultrasonic techniques.
According to the invention, there is provided a method of detecting changes in nature of liquid in a vessel, by applying pulses of ultrasonic energy to the vessel, in which the vessel is a pipe, the pulses are applied to a wall of the pipe to propagate therearound, sensing ringing of the pipe wall responsive to such propagation, analyzing at least one parameter of said ringing to determine a signature found to be modified according to the nature of liquid within the pipe, and comparing the signature so obtained with stored data to determine the nature of said liquid, the frequency of the ultrasonic energy being sufficiently high that its wavelength is small compared with the cross-sectional dimensions of the pipe and that it lies above a spectrum of noise associated with pumping.
The invention also extends to methods for controlling pumps operating upon liquids subject to "tunnelling", or other instructions of unwanted phase or density anomalies.
Further features of the invention will be apparent from the following description with reference to the accompanying drawings, in which:
FIG. 1 is a diagrammatic illustration of a typical installation of the invention;
FIGS. 2 and 3 are plots of the response obtained from a particular installation responsive to changes in liquid density of sewage sludge; and
FIG. 4 is a simplified flow diagram illustrating processing of signals in an embodiment of the invention.
Referring to FIG. 2, two high frequency ultrasonic transducers 2 and 4, having an equal resonant frequency typically of about 150 kHz, are applied to opposite sides of an entry pipe 6 to a pump 8 in a waste water treatment plant by means of housings 10 and 12 which may be attached to the pipe by magnets 14 or clamps. Although two separate transducers are shown, respectively for applying ultrasonic energy to the pipe and for picking up the response, a single transducer could be utilized, with suitable provision to isolate receiver circuits associated with the transducer from transmitter circuits, similar to that provided in other ultrasonic applications using a common transducer both for transmitting and receiving ultrasound.
The transmitter transducer 2 is pulsed by a pulse generator 16, which
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Cherek Bogdan
Lee John Joseph
Lee Thomas C.
Milltronics Ltd.
Peyton Tammara
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