signals, through the conduit and/or the flow stream
NONINTRUSIVE FLOW SENSING SYSTEM therein, in combination with means for analyzing the
relative transit times of the signals to derive fluid flow
BACKGROUND OF THE INVENTION velocity, temperature and pressure. The system is par
This invention relates generally to an improved sys- 5 ticularly adapted for monitoring a liquid flow stream,
tem and method for detecting and monitoring fluid flow The flow sensing system includes a pair of ultrasonic
parameters such as liquid flow within a conduit. More flowmeter transducers mounted on opposite sides of the
particularly, this invention relates to a sensing system conduit at longitudinally spaced positions. These flow
and method for measuring fluid flow velocity, tempera- meter transducers are designed to send and receive
ture and pressure in a nonintrusive or noninvasive man- 10 pulsed ultrasonic signals along a line of transmission
ner- extending diagonally across and through the conduit
Fluid flow conduits are widely used in industrial and flow stream. xhe flowmeter transducers generate
processes and the like to deliver fluids in liquid or gase- appropriate outpUtS representative of signal transit
ous form from one location to another. In many in- times in thg am and downstream directions, and
stances, it is necessary or desirable to monitor the fluid 13 .. ... r
j/r r these outputs are coupled to a processor for appropriate
flow to insure proper and/or safe operation of process , , ■ * , . A. v . , „ , • T
equipment. As one example, in a nuclear power plant calculated derivation of the flowstream velocity. In
facility, it is necessary to monitor various liquid flow addltlon' the Pressor responds to these outputs to
parameters such as flow rate, temperature, and pressure. calculate the speed of sound in the flow stream, wherein
Accordingly, in the prior art, a variety of flow monitor- 20 the speed of sound is variable in accordance with fluid
ing devices and techniques have been developed for this pressure and temperature.
purpose. However, in general, these prior art devices In the preferred form, the sensing system further
and methods for monitoring fluid flows have utilized includes an ultrasonic temperature transducer and an
invasive temperature and/or pressure probes mounted ultrasonic pressure transducer, both of which are
to extend through ports in a flow conduit into direct 25 mounted on the conduit in a nonintrusive manner and in
contact with the fluid flow stream. This requirement for a predetermined spatial arrangement relative to the
probe ports in the conduit typically results in a monitor- flowmeter transducers. The temperature transducer is
ing system which is relatively costly to fabricate and positioned in longitudinal spaced relation with one of
maintain, and further wherein the probe ports present rj,e flowmeter transducers and cooperates therewith to
leakage sites for escape of potentially hazardous process 30 ... {he ... dme Qf an ultrasonic temperature
^ujd' ... , signal longitudinally through the conduit. The transit
In recent years, noninvasive sensing systems have .. » ■ i- J- ..<• r»i. , , , , • time of this temperature signal is a direct function of the been developed particularly for use m monitoring cer- ,. . , ° . , .lL , . tain flow parameters of a liquid flow within a conduit. dlstanCe between the cooperating transducers, with this Such noninvasive systems have utilized ultrasonic trans- 35 dlstance ln turn bemS a dlrect functl0n of condult wal1 ducers mounted on the exterior of a flow conduit and temperature. An appropriate temperature representaadapted to bidirectionally transmit and receive pulsed tive outPut S18nal 1S thus provided to the processor, signals diagonally through the conduit and flow stream The pressure transducer is disposed in a selected therein. By measuring the upstream and downstream circumferentially spaced position relative to one of the transit times of these pulsed signals, it is possible to 40 other transducers, such as one of the flowmeter transcalculate the flow velocity of the liquid flow steam. ducers, and cooperates therewith to monitor the transit Moreover, with this transit time information, it is also time of an ultrasonic pressure-indicating signal through possible to calculate the speed of sound in the liquid a portion of the conduit circumference. Since the transit flow stream. time of the ultrasonic signal is a function of the cornWhile noninvasive sensing systems of the type de- 45 bined effects of conduit wall temperature and fluid scribed above are extremely desirable in many operat- pressure applied to the conduit as hoop stress, a resuling environments, their practical utility has been limited tant output signal representing these combined effects is to monitoring of a relatively small number of flow pa- supplied to the processor. However, the processor is rameters. More specifically, noninvasive systems have abk t0 determine the effect attributable to conduit wall not been designed for obtaining accurate and reliable 50 ternperature based upon the temperature signal as demeasurements of the temperature and pressure of the scribed above> such that thg processor can subtract the flow stream. To obtain measurements of temperature temperature portion to derive an indication of fluid and pressure, resort to invasive type monitoring devices sufe ... ^ ...
hasgenerally been required. The derived fluid pressure level is then compared by
There exists, therefore, a significant need for further 55 . , . . r , ~ .,
'. • °. , . c the processor with the previously determined fluid
improvements in sensing systems and methods for . ^ . . _. L ^n-j
noninvasive monitoring of fluid flow within a conduit, sonic velocity. Since the speed of sound in the fluid is a
particularly with respect to monitoring of additional v1anable according to fluid pressure and temperature,
fluid parameters such as temperature and pressure. The the independent determination of fluid pressure permits
present invention fulfills these needs and provides fur- 60 the processor to analyze the sonic velocity to determine
ther related advantages. ^u'd temperature. Thus, in accordance with the invention, fluid velocity, pressure and temperature are all
SUMMARY OF THE INVENTION determined through the use of nonintrusive sensors.
In accordance with the invention, an improved flow Other features and advantages of the invention will
sensing system is provided for monitoring fluid flow 65 become more apparent from the following detailed
within a conduit. The system includes a plurality of description taken in conjunction with the accompany
nonintrusive or noninvasive transducers for sending and ing drawings which illustrate, by way of example, the
receiving a plurality of signals, such as pulsed ultrasonic principles of the invention.
