FR2583164A1 - METHOD AND DEVICE FOR DETERMINING THE COLOR AND TURBIDITY OF A FLUID - Google Patents

Abstract

Device and method for determining the colour and the degree of turbidity of a fluid, comprising the projection into the fluid of a white light beam (4); the recovery of the beam (8) after it has traversed the fluid; the chromatic dispersion of the light (11) to form a spectrum comprising a plurality of components; and the measurement of the light intensity of each of said components to determine the colour of the fluid (13-16). According to the invention, the white light includes the radiation in the near infrared field and, in order to determine the degree of the fluid turbidity, the light intensity of the spectrum components relative to said radiation (19) is measured. Application particularly to the control of the transportation of liquid oil products through pipelines.

Description

The present invention relates to a method and a
device for determining the color and turbidity of a
fluid confined by a wall, for example that of an enclosure
te or a pipeline (piping, pipeline, canal, reser
view, container, etc. at atmospheric pressure or under pressure).

The invention is particularly applicable to the control of
pipeline transportation of liquid petroleum products such as
than ordinary petrol or super fuel, diesel, domestic fuel, etc.

The same pipe can be used to transport successively one
either of these products. I1 is therefore interesting for
see what color the product or mixture is
age of products which passes at a given moment in a section
pipeline data.

The present invention makes it possible to carry out the ope
remote rations, without sampling, in a sealed and
safety (detector element containing neither electrical energy
that, nor hot spot), by determining the sorting components
chromatic, diffusion at 900 and transmission to measure
the color, turbidity and opacity of the product.

To this end, the invention relates to a method for
determine the color and turbidity of a confined fluid
by a wall, for example that of an enclosure or a
nalisation, consisting in projecting a beam of light
white in the fluid using a first optical fiber,
to collect the light from the beam after traveling in the
fluid using a second optical fiber, to ensure the
chromatic dispersion of the light collected by the two
xth fiber to form a linear spectrum, to analyze the
spectrum obtained by measuring the relative light intensity
of its components and to be determined according to this ana
lyses the color of the fluid.

According to the invention, this method also consists in
measure the light rate of the laterally scattered beam
in the fluid using a third optic fiber
that to determine the turbidity of the fluid.

 It is thus possible, according to the invention, to detect the possible turbidity of a fluid, which is indicative of the presence of particles or bubbles in the fluid, this detection therefore provides information on the homogeneity and the cleanliness of the fluid transported. In addition, only the measurement of the rate of light scattered laterally with respect to the projected beam makes it possible to detect with certainty this turbidity and to distinguish a cloudy fluid from an opaque fluid.

 Indeed, the measurement of the light transmitted along the axis of the beam, in particular in the near infrared range, does not make it possible to distinguish a cloudy fluid from a fluid opaque to the light radiation used: in both cases , there is a sharp decrease in transmitted light.

On the other hand, only the cloudy fluid is capable of diffusing a large amount of light laterally.

 However, in the case for example of petroleum products which are - with a few exceptions - transparent to radiation in the near infrared (wavelength between 0.75 and 0.85 m), the measurement of the nuation for this radiation, in the axis of the light beam, will determine the turbidity of the product. The white light projected into the fluid indeed includes components in the near infrared.

 Advantageously, the local path of the light beam within the fluid can be extended by reflection.

 The method according to the invention can be implemented, for example, to ensure discrimination between different fluids circulating sequentially in a pipe, or even to determine the variations in level of the interface between different fluids contained in a container, etc.

The invention also relates to a device for determining the color and the turbidity of a fluid confined by a wall, for example that of an enclosure or a pipe, comprising
- a first optical fiber, one end of which is coupled to a white light source and the other end of which is coupled to a first optical system for emitting a beam of light into the fluid
- a second optical fiber, one end of which is coupled to the first optical system for collecting the light beam after passage through the fluid, and the other end of which is coupled to a member for chromatic dispersion of the collected light forming a linear spectrum
- a multipoint linear detector collecting the spectrum to measure the relative light intensity at each of its points; and
means for processing information from the multi-point detector to determine the color of the fluid as a function of this measurement.

 According to the invention, this device also comprises a third optical fiber, one end of which is coupled to a second optical system for collecting the light of the beam scattered laterally in the fluid, and the other end of which is coupled to an instrument for measuring this scattered light to determine the turbidity of the fluid.

Preferably, the first and second optical systems are arranged in a probe immersed in the fluid, this probe having walls delimiting a passage crossed by the light beam and bathed by the fluid, the first optical system comprising
- at least two lenses adjacent to one of the walls and respectively coupled to the first and second optical fibers
- a porthole mounted in this first wall, in line with the lenses
- a reflecting member mounted opposite the window in a wall opposite this first wall, for returning the beam of light towards the window; and the second optical system comprising
- at least a third lens which is adjacent to a wall which is perpdicular to the previous two and which is coupled to the third optical fiber; and
- a porthole mounted in the wall perpendicular to the right of the third lens.

 Advantageously, the three optical fibers pass through the fluid confinement wall. I1 can be provided a single and waterproof crossing for the three optical fibers. In addition, the ends of the three optical fibers arranged in the probe can be parallel to each other, the second optical system further comprising a reflecting member for returning to 900 the scattered light, which is placed on the optical path between the fluid and the end of the third optical fiber.

 Preferably, the reflecting member of the first optical system is a cube corner whose diagonal face is substantially normal to the ends of the first and second fibers.

 Likewise, the reflecting member of the second optical system can be a cube corner.

 The multipoint linear detector can be a camera-line detector. Preferably, it is associated with a degraded attenuator making it possible to correct the differences in spectral efficiency of the device (source, fibers, dispersing member, detector) between red and blue.

 Advantageously, an electronic interface with a programmable clock makes it possible to adjust the integration time of the multi-point linear detector as a function of the transmission coefficient of the medium analyzed. This electronic interface is associated with a computer.

 Because the measurement probe requires no electrical energy and is not the seat of any hot spot, the method and the device according to the invention find a preferred application for the study of fluids in an explosive or explosive atmosphere.

 The description which follows, given by way of nonlimiting example, will make it clear how the invention can be implemented.

Ia figure I is a sthómatique view of a device according to the invention
Figure 2 is a detail view, in longitudinal section, of a measurement probe according to the invention, located in a pipe
Figure 3 is a schematic view of a container containing two liquids and equipped with a probe according to the invention.

 In Figure 1 is shown, in cross section, a pipe 1 which can be traversed by a fluid which one wishes to control the color and turbidity at any time.

 A white light source 2 (arc lamp under xenon atmosphere for example) is associated with an optic 3 making it possible to focus the beam of white light on the input end 4a of a first optical fiber 4. This first optical fiber 4 Enters the pipe 1 and leaks inside a probe 10 implanted in the pipe 1 in a leaktight manner.

 The probe 10 has a passage 21 bathed in the liquid. The outlet end 4b of the first optical fiber 4 is associated with an optic 5 arranged in the probe 10 to send, through a window 22, a beam of white light into the liquid located in the passage 21, in direction of a reflecting member 6. This reflecting member is also placed in the probe 10: it is preferably in the form of a cube corner, which makes it possible to obtain relatively large positioning tolerances for the optical components.

 The reflecting member 6 returns the beam of light, offset with respect to the incident beam and in the opposite direction, through the liquid and then through the window 22. An optic 7 arranged on the path of the reflected beam makes it possible to focus the latter on the input end 8a of a second optical fiber 8; this inlet end 8a is arranged inside the probe 10 in the vicinity of the outlet end 4b of the first optical fiber 4. The second optical fiber 8 leaves the pipe 1 to take the light outside that -this. The assembly defined by the optics 5 and 7, the porthole 22 and the reflecting member 6 constitutes a first optical system disposed in the probe 10.

 The output end 8b of the second optical fiber 8 is associated with an optic 9, a member 11 (a prism for example) for chromatic dispersion of light po1 :.

 fcrmer a linear spectrum, an optic 12 and a multipoint linear detector 13 allowing this linear spectrum to be analyzed. The multipoint linear detector 13 is in particular a camera-line detector.

 The information delivered by the multipoint linear detector 13 is sent to a computer 15 through an electronic interface 14 mainly comprising an analog-digital converter and a programmable clock.

Advantageously, the multi-point linear detector 13 may comprise, against its receiving face of the light spectrum, a degraded attenuator 16 making it possible to correct the differences in light output of the system between blue and red. Indeed, due to this transmission inhomoqeneite, due in particular to the emission characteristics of the white light source 2. to the attenuation
j spectral of the first and second optical fibers 4 and 8 and the sensitivity of the linear detector mustipoint 13, the transmisssion is four to five times greater in red eye than in blue.

 By using a degraded attenuator 16 having for example a transmission coefficient of 10C% in blue (= 0.4 Fm) and 2C 9 in red (1 = 0.8 em), the differences in efficiency will be significantly corrected and repeatability of the improved measurement.

 The device according to the invention makes it possible to recognize at any time the color of the product circulating in the pipe 1. In fact, the light having passed through the product has a spectrum representative of its color, the latter being determined by the linear multipoint detector 13 and the processing means constituted by the electronic interface 14 and by the computer 15. The recognition of the color makes it possible to identify the nature Gu product c: R. CV: mixture of products circulating in the pipeline.

 The possible turbidity of the product will be overcome by varying the integration time of the multipoint linear detector 13, thanks to the programmable clock of the electronic interface 14.

 Very advantageously, the device according to the invention makes it possible not only to determine the color of the product circulating in the pipe 1, but also to determine the possible turbidity of the latter, and in particular to distinguish a cloudy product from an opaque product. to the light radiation used.

 To this end, a porthole 18 associated with an optic 17 and arranged inside the probe 10, in line with the passage 21 bathed by the liquid, makes it possible to collect the light in a direction substantially perpendicular to the axis of the beam of incident light introduced into the pipe through the first optical fiber 4. This light is sent into a third optical fiber 19 associated with a light measuring instrument 20 (avalanche photodiode or photomultiplier, for example). The assembly defined by the window 18 and the optics 17 constitutes a second optical system, placed in the probe 10.

 Laboratory tests carried out using this device with three optical fibers have made it possible to highlight the need for having the third optical fiber to distinguish a cloudy product from a product opaque to the light radiation used.

Hour different products, it was measured the coefficient of transmission in the near infrared (0.75 to 0.85 film) by means of the second optical fiber, and the flow D of scattered light at 900 by means of the third fiber optical
The products tested fell into two categories
- cloudy products obtained by adding water to different petroleum products (ie - transparent products in the near infrared), and mixing by a turbine system
- opaque products obtained by adding crude oil to these same petroleum products.

The tests concerned three petroleum products
- naphtha, a colorless product
- diesel, yellow product
- domestic fuel, red product
The test results for the first two products are shown below
C: volume concentration of water
water (for information) in%
Gross: gross volume concentration in%
T: near infrared transmission in%
D: diffusion at 900 expressed in mV, voltage
of the photomultiplier used.

A. Cloudy products
A.1. - Water in a colorless product (naphtha)
CTD
water
O, OQ 100 7
0.01 95 40
0.10 80 60
0.50 20 55
1.00 4 60
A.2. - Water in a yellow product (diesel)
C water TD
0.00 100 8
0.01 51 40
0.05 ll 40
0.10 0.04 30
B. Opaque products
B.1. - Crude in a colorless product (naphtha)
Cbrut TD
0 100 7
0.1 60 6
0.5 6 5
1.0 0.2 5
B.2. - Crude in a yellow product (diesel)
Cbrut TD
0 100 7
0.1 90 5
0.2 64 5
0.5 32 8
1.0 13 4
From the above results, it appears that the near infrared T transmission decreases when
- the turbidity of the product increases (increasing water concentration)
- the opacity of the product increases (increasing crude concentration).

 The measurement of T transmission alone cannot therefore be a criterion for differentiating a cloudy product from an opaque product.

On the other hand, there appears a minimum difference of a factor of order 4 between the light D scattered at 900 by an opaque product (Dmaximal = 8) and by a cloudy product (minimum D = 30)
The third fiber, transmitting light scattered at 900, is therefore necessary to distinguish a cloudy product from an opaque product.

 In the particular case of transparent products in the near infrared, the measurement of the possible attenuation for this radiation, in the beam axis, will be a measure representative of the turbidity of these products: the attenuation observed cannot indeed correspond than scattering of light. For this type of product, the use of the third optical fiber and the second optical system will therefore not be necessary.

 It will be noted that all of the measurements are carried out using a probe comprising no electrical energy or hot spot and which can therefore be installed in an explosive or explosive atmosphere (defined, for example, by AFNOR NFC standards 23.514 or CENELEC 50014). The fibers can have great lengths, which makes it possible to carry out information processing at a point distant from the measurement point, and therefore under conditions of safety and comfort easier to obtain than at the place of measurement .

 In Figure 2 is shown, in cross section, a pipe 31 of circular section. This pipe 31 is provided with a lateral access, in the form of a nozzle constituted by a cylindrical sleeve 32 arranged per pendulum to the longitudinal axis of this pipe 31. The cylindrical sleeve 32 ends in a flange 33 on which is tightly fixed, by its base 34 and by means of bolts, a measurement probe 30.

 The measurement probe 30 mainly comprises a hollow cylindrical body 35, of outside diameter slightly smaller than the inside diameter of the cylindrical sleeve 32, disposed in this sleeve and fixed in leaktight manner to the base 34. The end of the probe body 35 opposite the base 34 carries two end caps of optical fiber 36, 37 juxtaposed and arranged parallel to the longitudinal axis of the probe body 35. In front of the fiber end caps 36, 37 are arranged two lenses 38, 39, and in front of these a porthole 40 sealingly closing the probe body 35.

 On the outer lateral wall of the probe body 35 is made a flat 41 intended to receive a plate 42 in the general form of a plate. The plate 42 extends inside the pipe 31, beyond the probe body 35, and it carries at its corresponding end a probe head 43. The probe head 43 is equipped with a reflecting member under the shape of a cube corner prism 44, the diagonal face of which faces the porthole 40.

 The respective walls of the porthole 40 and of the prism 44 disposed opposite each other define, with the wall portion of the plate 42 situated between them, and perpendicular to these walls, a passage 45 traversed by a fluid which flows in the pipe 31 .

 The free face of the plate 42 carries an end piece of optical fiber 46 which is parallel to the two end pieces 36, 37 housed in the probe body 35. The end piece 46 is optically coupled with the passage 45 by a lens 47, a corner cube prism returning to 900, and a porthole 49 which opens in leaktight manner in passage 45.

 The probe 30, as defined above, is connected to a data acquisition system, of the type described in relation to FIG. 1, by means of three optical fibers 50, 51, 52. These fibers are, at the outside of the probe 30, protected by a suitable sheath 53, this sheath opening into the probe body 35 by means of a sealed passage 54 fixed to the base 34 of the probe 30.

The optical fibers 50, 51 are respectively connected to the end caps of fibers 36, 37 of the probe body 35.

The optical fiber 52, gracie to a channel 55 putting in sealed communication the interior of the probe body 35 and the plate 42, joins the end fitting 46 of the plate 42.

 FIG. 3 illustrates the use of a measurement probe 60 to determine the variations in level of the interface 61 between fluids 62, 63 of different color and density which are immiscible and which lie one at a time. below the other in a container 64. The mixture of fluids is supplied by a line 65, the upper fluid 62 being withdrawn by a line 66 associated with a pump 67 and the lower fluid 63 discharged by a line 68 associated with a valve 69.

 The probe 60 is immersed in the container 64 and connected to a data acquisition system of the type of that of FIG. 1 by means of optical fibers 70. The optical fibers 70 pass through the free surface of the fluid to exit the container 64. The color detected by the probe 60 indicates the fluid in which it bathes. The change in color signals that the interface 61 is facing the probe 60.

Claims (12)

 1.- Method for determining the color and the turbidity of a fluid confined by a wall, for example that of an enclosure or a pipe, consisting in:  - project a beam of white light into the  fluid using a first optical fiber,  - collect the light from the beam after traveling in  the fluid using a second optical fiber,  - ensure the chromatic dispersion of light  collected by the second fiber to form a  linear spectrum,  - analyze the spectrum obtained by measuring the intensity  relative light of its components, and  - determine based on this analysis the color  of the fluid, a method characterized in that it further consists in measuring the light rate of the beam scattered laterally in the fluid using a third optical fiber (19), to determine the turbidity of the fluid.  2.- Method according to claim 1, characterized in that it further consists in lengthening by reflection the local path of the beam within the fluid.  3.- Application of the method according to claim 1 or claim 2, characterized in that said measurement of the level of scattered light is used to distinguish between a cloudy product and an opaque product.  4.- Application of the method according to claim 1 or claim 2, characterized in that it is implemented to ensure discrimination between different fluids flowing sequentially in a pipe.  5.- Application of the method according to claim 1 or claim 2, characterized in that it is implemented to determine the variations in level of the interface between different fluids (62, 63) contained in a container.  6.- Device for determining the color and the turbidity of a fluid confined by a wall, for example that of an enclosure or a pipe, comprising  - a first optical fiber, one end of which is  coupled to a white light source and whose  the other end is coupled to a first system  optic to emit a beam of light into the  fluid,  - a second optical fiber, one end of which is  coupled to said first optical system to collect  said beam of light after passage through the fluid,  and the other end of which is coupled to a  chromatic dispersion of the light collected for  mant a linear spectrum,  - a multipoint linear detector collecting said  spectrum to measure relative light intensity  in each of its points,  - means for processing information from  multipoint linear detector to determine  function of this measurement the color of the fluid, device characterized in that it further comprises a third optical fiber (19) one end of which is coupled to a second optical system (17, 18) for collecting the light of said beam scattered laterally in the fluid , and the other end of which is coupled to an instrument for measuring (20) this scattered light so as to determine the turbidity of the fluid.  7.- Device according to claim 6, characterized in that said first and second optical systems are arranged in a probe (30) immersed in the fluid, this probe having walls defining a passage (45) crossed by said light beam and bathed by the fluid, said first optical system comprising  - at least two lenses (38, 39) adjacent to one  of said walls and respectively coupled to the first  (50) and second (51) optical fibers,  - a porthole '40) mounted in this first wall,  in line with said lenses (38, 39),  - a reflecting member (44) mounted opposite said  porthole (40) in a wall opposite this first  wall, to return the beam of light to  said window (40), and the second optical system comprising  - at least a third lens (47) which is  adjacent to a wall perpendicular to the two  previous and which is coupled to said third  optical fiber (52), and  - a porthole (49) mounted in said perpendicular wall  re, in line with said third lens (47).  8.- Device according to claim 7, characterized in that the three optical fibers (50, 51, 52) pass through the confinement wall of the fluid (34).  9.- Device according to claim 8, characterized in that there is provided a single and sealed passage (54) for the three optical fibers (50, 51, 52).  10.- Device according to any one of claims 6 to 9, characterized in that the ends (36, 37, 46) of the three optical fibers arranged in the probe (30) are parallel to each other, said second optical system comprising in in addition to a reflecting member (48) for returning the scattered light to 900, which is placed on the optical path between said fluid and the end (46) of said third optical fiber (52).  11.- Device according to any one of claims 6 to 10, characterized in that the reflecting member of said first optical system is a cube corner (44) whose diagonal face is substantially normal to the ends (36, 37) of said first and second fibers (50, 51).  12.- Device according to claim 10, characterized in that the reflecting member of said second optical system is a cube corner (48).