FI20206219A1

FI20206219A1 - Thin probe process monitoring

Info

Publication number: FI20206219A1
Application number: FI20206219A
Authority: FI
Inventors: Jan Kåhre
Original assignee: Kaahre Jan
Priority date: 2020-07-31
Filing date: 2020-11-30
Publication date: 2022-02-01
Also published as: FI20205777A1

Abstract

The embodiments of the invention concern a thin probe refractometer structure (TPR), comprising a camera (Camera) inside a cylindrical probe shell arranged and adapted to transmit the optical image outside the probe by an electrical signal (Electrical cable).

Description

THIN PROBE PROCESS MONITORING

FIELD OF THE INVENTION Generally the present invention relates to a thin probe to be used in process monitoring. In particular, the present invention pertains to thin probe structure of arefractometer as indicated in an independent claim directed to such refractometer.

BACKGROUND A process refractometer has been used to measure the concentration of solutions in-line in various processes as such. The Fig 1 discloses a generic process refractometer with three representative optical images view 4.1, view 4.2 and view 43, representing each a different concentration value by the light received via the prism 4, shown on the Brix-scale. The typical components for a generic refractometer in Fig 1 are LED - light source 1, Collimating lens 2, Focusing lens 3, Prism 4, Objective lens 5, and Digital image detector (e.g. a CCD as such) 6. With reference to Fig 2, it is known as such to use in pH meters and turbidity IS — meters certain probe shells with a 12 mm outer diameter as such, which is common probe shell as such in the pharmaceutical industry. Such probe shells for process fittings has been in wide use and certified, also certification comprising sanitary standards like EHEDG and 3A that apply directly to these probes. Probes in a process solution tend to get slags onto the optical surfaces. — Refractometer measurement is sensitive to fouling of the prism surface in contact S with the process liquid. In many applications, a prism washing nozzle has to be ~ installed to regularly clean the prism surface in-line with steam or water. In 3 pharmaceutical reactors, addition of cleaning media is not allowed. Instead, to I clean an instrument, there are process fitting existing on the market which allows > 25 a 12 mm probe to be withdrawn from the process and to be cleaned in an isolated S chamber e.g. by water spray (Fig 2). This fitting is developed and used for pH and O turbidity meters. With probes that have a tip extending into the process liguid, there is another special problem concerning optical measurements: Bending of the probe causes measurement error by shifting the optical image as schematically illustrated in Figs 6 and 7. The bending forces may for example be caused by the flow of the process liquid (Fig 5). The bending examples in Figs 6 and 7 are illustrative. The barrel cross sectional objects illustrate lenses as optical elements.

With reference to Figs 6 and 7, common computing, used by construction engineers calculating bending of beams, will here apply for the probes in process liquid.

An elastic modulus E (also known as modulus of elasticity) is a quantity that measures an object or substance's resistance to being deformed elastically (i.e., non-permanently) when a stress is applied to it. The elastic modulus of an object is defined as the slope of its stress-strain curve in the elastic deformation region: A stiffer material will have a higher elastic modulus. In structural engineering, the second moment of area of a beam I is an important property used in the calculation of the beam's deflection and the calculation of — stress caused by a moment applied to the beam. In a simple example case of a stainless steel 316L pipe with a 12 mm outer diameter, (EI = 102 Nm”), length 1=100 mm and load P=1N (corresponding to a 100 gram weight), the deviation J at the camera end according to Fig 6, with the Fig 7 markings, would be estimated as &= PI3/6EI = 59 micrometers.

O

QA N As the typical pixel size in a digital camera sensor is 14 micrometers, it means - that the measurement error is 4 pixels.

O 2 Conseguently, additional optics is reguired to transmit the optical image from the a - prism to the image detector mounted outside the probe (Fig 6), which adds parts o N 25 — to make the device further complicated in the sensitive parts in known

O N technigues.

N

SUMMARY OF THE INVENTION The objective of the embodiments of the invention is to at least alleviate the problems described hereinabove not satisfactorily solved by the known arrangements and devices, and to provide a feasible refractometer with a thin probe refractometer structure.

The aforesaid objective(s) are achieved according to the present invention as claimed refractometer in claim 1.

The aforesaid objective is achieved by the embodiments of a system/method in accordance with the present invention.

— A refractometer according to an embodiment of the invention according to present disclosure is a Thin Probe Refractometer (TPR), comprising a camera inside a cylindrical probe arranged and adapted to transmit the optical image outside the probe by an electrical signal.

The refractometer according to an embodiment has a thin probe of the refractometer’s outer diameter that is half an inch or less.

The refractometer according to an embodiment comprises such a camera that is a standard mass-produced camera.

The refractometer according to an embodiment has a thin probe with a length that is less than 10 meters, optionally less than 5 meters, further optionally less than 3 — meters or even less than 1 meter, but advantageously over 5 centimeters.

N The refractometer according to an embodiment has such a thin probe has a length 2 that is over 2.5 centimeters, optionally over 5 centimeters, further optionally over S 15 centimeters or even more than 20 centimeters, but advantageously less than 55 E centimeters. O 25 According to an embodiment the thin probe refractometer has a flexible probe shell 3 structure, to provide some bendability for the shell of the probe of the N refractometer. According to an embodiment of the invention the bending radius can be less than 50 % of the length of the probe, optionally less than 25% of probe length, further optionally less than 15 % of the probe length, but over 5 % of the probe length.

Such embodiments surprisingly allow utilization of long thin probe refractometers in limited space to surround the process location (also at outside side of the mount-in surrounding locations), so that the long probe can be bent when mount and operate without in-liquid-bending originating errors as such of known refractometers.

A thin probe refractometer system according to an embodiment comprises at least one refractometer according to an embodiment, and a probe washer device to retrack the thin probe at the process location and wash the thin probe in the washer device in isolation outside the process and also to put the thin probe as washed back to the process location.

As far as the author knows, nobody has been able to make a 12 mm probe refractometer at the priority date of the present disclosure.

The refractometer probe bending in a liguid as a source of errors is eliminated by the embodiments of the invention, as the camera is placed in the tip of the probe before any bending occurs. — This facilitate mountings to locations that has been impossible for non-bendable refractometer structure.

In addition, the embodied structure also eliminates the otherwise unavoidable loss of accuracy caused by any additional optics, providing also a simple structure, being insensitive for vibration for example, such that often are present in industrial environment. — With the embodiments of the invention of the present disclosure, also the problem o of prism fouling in a reactor is conseguently solved, as such thin probe N refractometer can be used with the already available washing devices, as - applicable.

With the embodiments of the invention, such a pull-out probe washer & system can be used also for an embodied refractometer, solving the problem of i 25 — prism fouling in a reactor, with the same thin probe structure comprising the 2 camera near the prism inner side at the refractometer tip, as the simpler structure S also tolerates better moving in and out to the washer device.

The bendability also N facilitates freedom to select the washer device location more freely in respect to the refractometer probe mounting location into the process vessel.

It is also an advantage of an embodied 12 mm thin probe refractometer that the process fittings of physically similar pH and turbidity meters are already certified as such.

The utility of the present invention follows from a plurality of factors depending 5 on each embodiment.

The expression “a number of” refers herein to any positive integer starting from one (1), e.g. to one, two, or three.

The expression “a plurality of” refers herein to any positive integer starting from two (2), e.g. to two, three, or four.

Different embodiments of the present invention are disclosed in the dependent claims.

Embodiments of the invention also solves a problem to transfer an optical image from the tip by a thin probe, in contrast to the known structures of process refractometers that are used in limited specific industrial applications.

Minicameras as such are mass products and consequently extremely cheap. As being used in a thin refractometer probe according to an embodiment, that benefits the use of such a camera in a refractometer probe; and consequently, reduces the refractometer manufacturing costs which will be considerably lower than by any other designs.

o 20 According to an ensemble of examples of embodiments of the invention, the N thickness of a minicamera is less than half of the probe shell thickness. According Tv to a further variant the thickness of the minicamera is less than half of the probe

O 9 thickness minus probe shell material thickness at the minicamera location in the

I & probe. According to an embodiment the mini camera length is more than 1.3 times N 25 — the thickness of the minicamera. According to an embodiment variant the length

O < of the minicamera is more than twice or three times the thickness of the

O N minicamera, but according to an embodiment variant the length of the minicamera is less than 11 times the thickness of the minicamera. According to a further embodiment variant, the minicamera length is less than 6 times of the thickness of the minicamera, but according to an embodiment variant, the length is less than 3 times the thickness of the minicamera.

BRIEF DESCRIPTION OF THE RELATED DRAWINGS Figs 1 and 2 illustrate known techniques as such. Therefore, next the embodiments of the invention are described in more detail with reference to the appended drawings in which Figs. 3 and 4 illustrate examples on probe shell structure to be used with embodiments of the present invention, Figs 5, 6 and 7 illustrate flow forces and probe bending of known refractometers, Figs 8 and 9 illustrate example embodiments of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS Fig 9 illustrates an embodiment according to the invention of the present disclosure concerning a thin probe refractometer (TPR) embodied as using a digital —minicamera inserted close to the prism tip in a cylindrical thin refractometer probe to be inserted into a process liquid (Fig 9, Fig 8). The probe shell being indicated by textural diagonal lines. The numbers in the Fig 9 embodiment indicate the components corresponding the functionalities of typical components for a generic refractometer as follows: A LED - light source 1, Collimating lens 2, Focusing lens 3, Prism 4, Objective lens o 5 for optical fiber coupling in such embodiments, where the optical signal is O transferred to a remote location. In an optional embodiment the reference number = 5 illustrates a camera interface 5 to transfer the image from the camera to a remote o location via the illustrated electrical cable by an electronic signal therein, and E 25 Digital image detector (e.g. CCD) 6 of the camera to observe the image and to o transfer to a form of electrical signal. The LED light source 1 can be optionally O located to a further remote location to a suitable location at the end of the probe, S and the light so being brought through an optical fiber to the collimating lens 2. However, although these components as such has been available for long time, the embodied arrangement of them in the thin probe refractometer has not been seen before in refractometers, according to the knowledge of the author.

The reference numbers 5 and 6 in Fig 9 refer to a minicamera mounted close at the prism. The light source 1 may be mounted close to the prism, or alternatively be transmitted from a remote light source by an optical fiber. A probe with about 12 mm outer diameter is called here as thin probe. The detail Light power, refers to the corresponding light production by a light source, near the tip, like a LED (light emitting diode) energized by a power cable/wires, or an optical fiber to guide the light from a remote light source.

Further, embodying the camera of the thin probe refractometer as a matrix image detector makes economically feasible to use it as standard matrix image detector, instead of the usual line image detector in known refractometers. With a matrix detector, a user has a family of optical images, instead of only one. The using of statistical methods to combine the images, in a controller or similar functionality used interface arranged to read the images, the accuracy of measurement will increase considerably. According to an embodiment, the image combining can be made in dedicated microprocessor to stack the images for defining image details and their borders on statistical methods based on the stacked image members in the stack.

— Process refractometers as such are equipped with a built-in temperature sensor to o measure the process temperature. The reason is the need for temperature N compensation of the refractive index measurement. The measured concentration - Conc% of the process media depends on the refractive index RI and the process temperature T: : 25 Conc%=f(RI;T) S It is also advantageous to employ embodied refractometer also as a temperature O transmitter. But a traditional refractometer as such is not built for an accurate measurement of process temperature. The generally accepted good practice according to the known technigues as such is to measure process temperature by using a thermowell to protect the temperature measuring element at a temperature measurement location of the thermowell.

A thermowell probe shell as such can form a thin probe for the temperature measurement (Fig 3), according to an embodiment by a refractometer, when according to an embodiment of the invention it is possible to mount an embodied refractometer with the embodied refractometer structure into a thermowell.

Further, by the embodiments of the invention, an existing thermowell measuring temperature can be directly replaced by a same mounting location fitting thin probe refractometer with a standardized probe measuring both temperature and — concentration.

Thereby installing a new refractometer at minimal cost and simpler structure and so saving a mounting location from the process vessel.

In addition, the temperature value measured by the embodied thin probe refractometer represents the measured concentration by the same instrument better than in separate locations measured, as accurate measurement of the temperature can be made within the same location as the concentration.

An embodied refractometer provides a flexible mounting facility to use the thermowell chassis as to provide a wide spectrum of technical solutions how to mount the probe to the process.

This is embodied in Fig 3, how to utilize optional thermowell chassis a), b), c) and d) for an embodied thin probe refractometer mounting (TPR, thin probe refractometer, as also used for abbreviation). o Figs 5, 6 and 7 illustrate flow forces acting in a process fluid to load the probe N chassis by the flow forces.

A probe as such may be vulnerable to forces from = process fluid velocity, but these forces can be estimated process conditions & specifically, and so to embody an optimized chassis for the embodied thin probe i 25 refractometer for the mount, the TPR to be mounted in a process conditions 2 dedicated way to its location to measure concentration as well as punctually related S temperature at the same location.

N The flow estimation and the chassis selection can thus follow the accepted standard, ASME PTC 19.3 TW-2016, for example.

The selection of the probe diameter B (Fig 4) 1s critical. The larger the B, the more robust the probe. The smaller the B, the faster the temperature measurement. A step-shank thermowell is a compromise (Fig 4). For a fast temperature measurement, the thermowell standard suggests a tip diameter B of 12.7 mm (0.5in or as marked also as 0,57.) for a mere temperature measurement. The embodiments of the invention make this way of mounting also possible to add the thin probe refractometer data from the same location as the temperature being measured by an embodied thin probe refractometer. Embodiments of the invention according to the disclosure, make it also possible to — design very long probes, as illustrated in Fig 8. In Fig 8 example of an optional embodiment, there is in a glass lined pharmaceutical reactor (Reactor), a long thin probe refractometer being mounted, with the probe diameter D and total length 1;+13, immersed into the pharmaceutic process liquid (Liquid) by depth/length 1, as submerged under the liquid level. In the example, the long probe TPR has to be mounted from the top of the reactor and reach down to the process liquid to the depth hb. Such a probe can typically have a length 1; +15 of 3 m, for example. The embodiments of the invention allow design of a refractometer that sets actually no practical limit on the possible probe length in theory. The thickness of the probe (D) in the schematic Fig 8 in respect to the probe length 11+13 is not limited only to — the shown example. The symbol DN denotes to a probe nozzle diameter, into o which the thin probe refractometer can fit. S Conseguently, a skilled person may on the basis of this disclosure and general = knowledge apply the provided teachings in order to implement the scope of the & present invention as defined by the appended claims in each particular use case = 25 — with necessary modifications, deletions, and additions. o 3

S

Claims

1. A refractometer characterized in that the refractometer is a thin probe refractometer (TPR), comprising a camera inside a cylindrical probe arranged and adapted to transmit the optical image outside the probe by an electrical signal.

2. The refractometer of claim 1, wherein the thin probe of the refractometer’s outer diameter 1s half an inch or less.

3. The refractometer of claim 1 or 2, wherein the camera is a standard mass-produced mini camera.

4. The refractometer of claim 1, 2 or 3, wherein the probe has a length that is less than 10 meters, optionally less than 5 meters, further optionally less than 3 meters or even less than 1 meter, but advantageously over 5 cm.

5. The refractometer according to anyone of the claims 1 to 4, wherein the probe has a length that is over 2.5 centimeters, optionally over 5 centimeters, further optionally over 15 centimeters or even more than centimeters, but advantageously less than 55 centimeters.

6. The refractometer according to anyone of the previous claims, wherein N the probe refractometer has a flexible thin probe.

N = 20

7. A probe refractometer system, characterized in that the system O comprises at least one refractometer according to anyone of the claims E 1 to 6, and a probe washer device to retrack the probe at the process 2 location and wash the probe and also to put the probe as washed back

O Q to the process location. &