WO1986007454A1

WO1986007454A1 - Method and device for determining the colour and degree of the turbidity of a fluid

Info

Publication number: WO1986007454A1
Application number: PCT/FR1986/000191
Authority: WO
Inventors: Guy Roger Jean Paul; Patrick Claude Viltart; Michel René Lequime; Claude Maquaire
Original assignee: Societe Des Transports Petroliers Par Pipeline - T
Priority date: 1985-06-06
Filing date: 1986-06-04
Publication date: 1986-12-18
Also published as: FR2583164B1; FR2583164A1; EP0224536A1

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

Method and device for determining the color and the degree of turbidity of a fluid.

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

The invention applies in particular to the control of the transport by pipeline of liquid petroleum products such as ordinary petrol or super fuel, diesel, domestic fuel, etc. The same pipe can be used to transport successively one or the other of these products. It is therefore interesting to be able to determine what is the color of the product or of the mixture of products which passes at a given instant in a given section of pipeline. The present invention makes it possible to carry out the operations remotely, without sampling, in a sealed and secure manner (detector element comprising neither electrical energy, nor hot spot), by determining from chromatic components, the diffusion at 90 ° and the transmission in order to measure the color, turbidity and opacity of the product.

To this end, the invention relates to a method for determining the color and the degree of turbidity of a fluid confined by a wall, for example that of an enclosure or a pipe, consisting in projecting a beam of light into the fluid. white, collect the beam after crossing the fluid, ensure the chromatic dispersion of the light to form a spectrum comprising a plurality of components, and measure the light intensity of each of said components to determine the color of the fluid, characterized in that said light white includes radiation in the near infrared range and, in order to determine the degree of turbidity of the fluid, the light intensity of the components of said spectrum relating to this radiation is measured. 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 the case, for example, of petroleum products which are - with a few exceptions - transparent to near infrared radiation (wavelength between 0.75 and 0.85 μm), the measurement of the attenuation for this radiation, in the axis of the light beam, will determine the turbidity of the product. The white light projected in the fuid indeed includes components in the near infrared.

On the other hand, the measurement of the light transmitted along the axis of the beam, in particular in the near infrared domain, does not make it possible to distinguish a cloudy fluid from a fluid opaque to the light radiation used: in both cases, notes a strong decrease in transmitted light. On the other hand, only the cloudy fluid is capable of diffusing a large amount of light laterally. Also, according to the invention, the rate of light scattered laterally in the fluid is also measured.

In this way, it is possible to detect with certainty the turbidity of the product and to distinguish a cloudy fluid from an opaque fluid.

The invention also relates to a device for determining the color and the degree of turbidity of a fluid, confined by a wall, for example that of an enclosure or of a pipe, comprising a white light source, means for projecting a beam of light in the fluid, from said source, means for collecting the beam after crossing the fluid, means for chromatic dispersion of the light to form a spectrum comprising a plurality of components; and means for measuring the light intensity of each of said components and determining the color of the fluid, characterized in that said means for projecting a beam of white light includes means for projecting radiation into the near infrared.

Advantageously, this device comprises means for collecting the light scattered laterally in the fluid and means for measuring this light.

Advantageously, said means for projecting and collecting light comprise a probe immersed in the fluid and comprising: a recess traversing and bathed in the fluid, which is delimited by at least two opposite parallel walls and a third wall perpendicular to the preceding ones, means for projecting a light beam from one of said parallel walls and towards the opposite wall, means provided on said opposite wall for reflecting said beam parallel to itself, means for collecting the reflected beam, which are adjacent to said projection means, and means for collecting the scattered light, which are arranged on said third perpendicular wall.

Other details and advantages of the invention will appear during the following description of a preferred embodiment of the invention, with reference to the appended drawings in which: FIG. 1 is a schematic view of a device according to the invention; Figure 2 is a detail view, in longitudinal section, of a measuring sunde 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 liquid whose color and turbidity is desired to be controlled 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 "white light" beam on the input end 4a of a first optical fiber 4. This first optical fiber 4 enters the pipe 1 and opens inside a probe 10 implanted in the pipe 1 in a sealed manner.

The probe 10 has a passage 21 bathed in the liquid. The exit 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 the 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, by total reflection on two of its walls, 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. It will be noted that, if the use a pair of mirrors can actually be envisaged to fulfill the function played by the cube corner, the relative positioning of these two mirrors will be very delicate. The cube corner therefore very advantageously eliminates this positioning problem.

An optic 7 disposed 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 to form a linear spectrum, an optic 12 and a multipoint linear detector 13 allowing to analyze this linear spectrum. The multipoint linear detector 13 is including 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 include, 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 inhomogeneity of transmission, due in particular to the emission characteristics of the white light source

2, at the spectral attenuation of the first and second optical fibers 4 and 8 to the sensitivity of the multipoint linear detector 13, the transmission is four to five times greater in red than in blue.

By using a degraded attenuator 16 having for example a transmission coefficient of 100% in blue (λ = 0.4 μ m) and 20% in red (λ = 0.8 μ m), the differences in efficiency will be significantly corrected and the repeatability of the measurement improved.

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 easily determined thanks to the multipoint linear detector 13 and to the processing means constituted by the electronic interface 14 and by the computer 15. The color recognition makes it possible to identify the nature of the product or of the mixture of products circulating in the pipeline.

We will overcome the possible turbidity of the product by playing on 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 allows not only to determine the color of the product circulating in line 1, but also to determine the possible turbidity thereof, and in particular to distinguish a cloudy product from a product opaque to the light radiation used.

To this end, a porthole 18 associated with an optic 17 and disposed 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, disposed 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.

For different products, the coefficient T of transmission in the near infrared (0.75 to 0.85 μm) was measured by means of the second optical fiber, and the flux D of light scattered at 90 ° by means of the third optical fiber. The products tested fell into two categories:

- cloudy products obtained by adding water to different petroleum products (that is to say transparent products in the near infrared), and stirring 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 _water : _water volume concentration (as an indication) in%

C _gross : _gross volume concentration in%

T: near infrared transmission in%

D: 90 ° scattering expressed in mV, output voltage of the photomultiplier used.

A. Cloudy products:

A.1. - Water in a colorless product (naphtha)

C T D water

0.00 100 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 11 40

0.10 0.04 30 B. Opaque products:

B.1. - Crude in a colorless product (naphtha)

C _gross 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)

C _gross 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 (concentration of crude oil increasing).

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 90 ° by an opaque product (maximum D = 8) and by a cloudy product (minimum D = 30).

The third fiber, transmitting light scattered at 90 °, 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 axis of the beam, will be a measure representative of the turbidity of these products: the observed attenuation cannot indeed correspond than a scattering of light. For this type of product, the use of 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 may have great lengths, which makes it possible to carry out the processing of information at a point distant from the measurement point, and therefore under conditions of safety and comfort that are easier to obtain than at the site of the measurement itself.

In Figure 2 is shown, in cross section, a pipe 31 of circular section. This pipe 31 is provided with a lateral opening, in the form of a nozzle formed by a cylindrical sleeve 32 arranged perpendicular to the longitudinal axis of this pipe 31. The cylindrical sleeve 32 ends in a flange 33. A base 34 serving as a cover makes it possible to close the lateral opening of the pipe and is fixed in leaktight manner to the flange 33. Furthermore, a measurement probe 30 is fixed in leaktight manner and by means of screws, to the base 34. The measurement probe 30 mainly comprises a hollow cylindrical body 35, with an 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 end caps of fiber 36, 37 are arranged two lenses 38, 39, and in front of them a window 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 generally in the 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 the prism 44 disposed facing each other define, with the wall portion of the plate 42 located between them, and perpendicular to these walls, a recess or 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 prism in the corner of a 90 ° deflection cube, and a porthole 49 which opens tightly into the 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 an appropriate 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, by virtue of a channel 55 which places the interior of the probe body 35 and the plate 42 in leaktight communication, 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 lie one below the other in a container 64. The mixture of fluids is supplied via a line 65, the upper fluid 62 being taken off through a pipe 66 associated with a pump 67 and the lower fluid 63 discharged through a pipe 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. color detected by the probe 60 indicates the fluid in which it bathes. The change in color indicates that the interface 61 is opposite the probe 60.

It will be noted that the probe according to the invention, described with reference to FIG. 2, is a one-piece assembly grouping together the means for projecting a beam of light into the fluid and the means for collecting the light. Such a probe can thus be inserted very easily into any enclosure or pipe.

Tests carried out by the Applicant have made it possible to demonstrate the mechanical resistance of the probe: it has been observed that the latter withstands satisfactorily the pressure of 150 bars prevailing in a pressure pipe.

Claims

1.- Method for determining the color and the degree of turbidity of a fluid confined by a wall, for example that of an enclosure or a pipe, consisting of:

- projecting a beam of white light into the fluid;

- collect the beam after crossing the fluid;

- ensuring the chromatic dispersion of light to form a spectrum comprising a plurality of components; and

- measure the light intensity of each of said components to determine the color of the fluid, characterized in that said white light includes radiation in the near infrared range and, in order to determine the degree of turbidity of the fluid, we measure l light intensity of the components of said spectrum relating to this radiation.

2. A method according to claim 1, in which the rate of light scattered laterally in the fluid is measured.

3.- 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.

4.- Application of the method according to claim 1 or claim 2, characterized in that it is used to determine the variations in level of the interface between fluids of different color (62, 63) contained in a container.

5.- Device for determining the color and the degree of turbidity of a fluid confined by a wall, for example that of an enclosure or a pipe, comprising:

a source of white light, means for projecting a beam of light into the fluid, from said source, - Means for collecting the beam after crossing the fluid;

- means for chromatic dispersion of light to form a spectrum comprising a plurality of components; and

- Means for measuring the light intensity of each of said components and determining the color of the fluid; characterized in that said means (2 to 5) for projecting a beam of white light includes means for projecting radiation in the near infrared.

6.- Device according to claim 5, which comprises means (17 to 19) for collecting the light scattered laterally in the fluid and means (20) for measuring this light.

7.- Device according to claim 5, wherein said means for projecting and collecting light comprises a probe (30) immersed in the fluid and comprising: - a recess (45) passing through and bathed in the fluid, which is delimited by at at least two opposite parallel walls and a third wall perpendicular to the previous ones;

- means (38, 40) for projecting a light beam from one of said parallel walls and in the direction of the opposite wall;

- Means (44) provided on said opposite wall for reflecting said beam parallel to itself;

- means (39, 40) for collecting the reflected beam, which are adjacent to said projection means

(38, 40):

- Means (47 to 49) for collecting the scattered light, which are arranged on said third perpendicular wall.

8.- Device according to claim 7, wherein said means for reflecting the light beam comprises a cube corner (44) of a transparent material.

9.- Device according to claim 7 or claim 8, wherein the means for collecting the scattered light comprises means (48) for reflecting the scattered light, parallel to said beam of light.

10.- Device according to any one of claims 5 to 9, in which said light source (2), said chromatic dispersing means (9, 11) and said means (20) for measuring the scattered light are arranged at distance from said enclosure (1) and are respectively connected to said means (5, 22) for projecting a beam and to means (7, 22 and 17, 18) for collecting light, by means of at least one optical fiber (4, 8, 19).

11.- Device according to claim 10, wherein said enclosure (31) comprises a probe introduction opening, which is closed by a cover (34)., The probe (30) being fixed on said cover (34) and each optical fiber (50 to 52) passing through it in a sealed manner.