Measuring and testing – Volume or rate of flow – By measuring vibrations or acoustic energy
Reexamination Certificate
2002-01-14
2003-07-01
Williams, Hezron (Department: 2855)
Measuring and testing
Volume or rate of flow
By measuring vibrations or acoustic energy
Reexamination Certificate
active
06584860
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to methods for determining the insertion depth of flow sensing probes, for measuring diameters of the pipes in which they are inserted and for detecting the fill depth of those pipes.
2. Background Information
Insertion probes for sensing flow rate are typically installed in a pipe using an insertion fitting mounted on the pipe. Compared to the more conventional full bore in-line flow sensors, which sense most, or all, of the fluid flowing through the pipe, these probes typically cost much less to purchase and install, and can be removed and reinstalled with relative case. Their main detriment is a reduction in measurement accuracy which occurs because probes generally sense the flow rate of only a small fraction of the total fluid in the pipe. There is also a potential for additional loss of accuracy if a probe is installed at other than a selected position, if the inside diameter of the pipe is not known accurately, or if the pipe is only partially filled. This invention relates to flow probe improvements for minimizing such accuracy degrading effects.
The flow rate through a round pipe is not the same everywhere through its flow cross section. Moreover, the distribution of local flow rates at the point of measurement also varies with the total volumetric flow rate. However, it is known that sensing the flow rate with a probe set at some selected points (e.g., approximately 11% of the pipe diameter in from the inside surface of the pipe) provides a good estimate of the total volumetric flow rate through the pipe. Deviation from that position is likely to produce additional and unnecessary measurement errors. Hence, arrangements for setting and checking the probe's depth are important. Commercially available means for measuring the depths of some probes consist of linearly graduated portions of the probe's stem or of attached parts that are observed visually. While these arrangements are satisfactory in some applications they are useless in others because of such factors such as poor lighting and cramped quarters during installation. Moreover, because of additional space required for the graduated portion, these probes can not be used in all installations. Because they usually determine penetration depth with respect to a known position of an insertion pipe fitting, these arrangements lead to errors if additional fittings are added during installation and change the distance between the reference point and the center of the pipe. Furthermore, the penetration depth cannot be readily determined remotely for checking the installation, as is often desired when troubleshooting. Hence, a significant problem in the flow probe art is that of accurately positioning a flow-sensing portion of the probe at a predetermined location within a pipe. Although selection of the predetermined location is an important part of flow measurement, it is not part of the present invention.
Insertion flow probes are often mounted on pipes which have been insufficiently or erroneously documented. Unfortunately, this usually occurs with pipes which are partially hidden or thermally insulated. Specifications and/or installation drawings are also often in error as to the internal diameter of the pipes. To counteract this source of flow sensing error a convenient means is required for measuring the internal diameter of the pipe.
It is therefore an object of the present invention to provide means that are essentially integral to the basic flow sensing probe and which enable its penetration depth and the internal diameter of the pipe that it is mounted on to be determined and observed both locally and remotely as desired.
BRIEF SUMMARY OF THE INVENTION
The above and other objects are satisfied with a variety of sensing arrangement, which include both acoustic and optical means that are exemplified in accordance with various preferred embodiments of the present invention.
In one aspect of the invention a flow sensor comprising a flow probe having an insertable end for insertion into a pipe is improved by adding to it a position sensing device adjacent the insertable end of the probe. When in use, a flow sensing device can supply an electrical flow signal responsive to a rate at which a fluid in the pipe flows past a portion of the probe adjacent its insertable end, and the position sensing device can supply an electrical position signal responsive to a distance between the position sensing device and a selected portion of either a portion of the pipe or a portion of a probe insertion fitting into which the composite probe is inserted.
A feature of the invention is that it provides a method of positioning a flow probe within a pipe in which a fluid is flowing when an insertable end of the probe is inserted into the fluid through an insertion fitting. The probe, in this case, selectively provides either an electrical flow signal output representative of a rate of flow past a selected portion of the probe adjacent its insertable end or an electrical position signal responsive to a distance between a position sensing device adjacent the insertable end of the probe and either a selected portion of the pipe or a selected portion of the insertion fitting. The method comprises the steps of: a) inserting the insertable end of the probe into the pipe; b) energizing the position sensing device; c) displaying, to an operator, an indication of the measured distance; and d) moving the probe until the indication of distance reaches a selected valued.
Some embodiments of the invention use a transducer array capable of forming a steered beam of acoustic energy for both fluid flow sensing and pulse-echo distance measurement. In apparatus of this sort at least two transducers are mounted adjacent the insertable end of a probe. A first of these transducers comprises at least one transducer element and is selectively operable to generate a first acoustic beam directed at an acoustic transducer array and receive at least a portion of a second acoustic beam generated by the acoustic transducer array and to provide a first time-of-flight flow output responsive to the received beam. The second of these transducers comprises the transducer array, which is selectively operable to: a) generate the second acoustic beam directed at the first acoustic transducer; b) receive at least a portion of the first acoustic beam generated by the first transducer and provide a second time-of-flight flow output therefrom; c) generate a third acoustic beam that is not directed at the first acoustic transducer, but that is rather directed at a portion of the pipe in which the probe is installed; and d) receive a portion of the third acoustic beam and provide the pulse-echo output therefrom. Preferred embodiments of this sort provide a reflecting surface portion of the probe situated so that an acoustic beam generated by one or the other of the two transducers is reflected to the other transducer.
A first specific embodiment of the invention comprises a flow sensing turbine probe adjacent its insertable end. A probe of this sort is taught in Feller's U.S. Pat. No. 4,829,833, the disclosure of which is herein incorporated by reference. The probe also holds a pulse-echo distance transducer which is periodically activated to produce bursts of acoustic energy directed at an inside surface of the pipe distal from the probe insertion fitting used to mount the sensor. The acoustic echoes are received by the transducer and amplified to produce corresponding electrical pulses. The measurement of the difference in time between the transmitted and received pulses is proportional to the distance separating the transducer and the inside pipe surface across from the transducer. That distance is added to the distance from the transducer to the center of the flow sensing element on the flow probe, the total then being subtracted from the known inside diameter of the pipe to yield the insertion depth. This addition and subtraction of distances is ideally performed electronic
Feldman Marvin J.
Feller Murray F.
Kiewit David
Thompson Jewel V.
Williams Hezron
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