Interface cell for measuring fluidic characteristics

Abstract

Interface cell (1) for measuring a fluid characteristic in industrial equipment, comprising a conveying tube (10) for the fluid to be measured, a tube (6) for connection to a pressure sensor (5) or a rupture disk (11) in fluid connection with the conveying tube (10) for the fluid to be measured, the connection tube being closed by a flexible and sealed interface membrane (2). FIGURE 1

Description

Title of the invention: Interface cell for measuring fluidic characteristics Technical field

[0001] The present invention relates to an interface cell for measuring fluid characteristics in industrial equipment, comprising a tube for conveying the fluid to be measured, a tube for connection to a pressure sensor or a rupture disk in fluid connection with the tube for conveying the fluid to be measured. Prior art

[0002] Today, there are various solutions for installing a pressure sensor or a rupture disc on an industrial installation, particularly for equipment used in the health industry. These elements, being in contact with the product, must be cleaned or replaced between each use to avoid the risk of cross-contamination.

[0003] Pressure sensors with a separation membrane commonly called a "diaphragm", and referred to as such in the remainder of this document, and rupture disks are often mounted with clamp connections. There are solid elastomer clamp joints on the market which provide the function of separating the diaphragm from the pressure sensor, the sealing function and the function of transmitting the pressure of the fluid in the cell to the diaphragm of the pressure sensor. However, since these solid joints are not fixed to the fluid paths, they have the disadvantage of not providing the barrier function against the intrusion of contaminants when the pressure sensor is dismantled.

[0004] T-shaped fluid connectors with clamp connection with welded membrane are also known, which allow the mounting with a clamp collar of a pressure sensor, but these devices have a large volume, form a dead arm, difficult to clean and therefore susceptible to a risk of development of a bacterial film. Furthermore, the membrane welding process considerably reduces the choice of materials that can be used for the membrane and the measuring cell, with the risk of degradation of the physical properties of the materials in the weld area. Furthermore, mounting with a clamp collar introduces practical constraints in the assembly: difficulty for a single person to mount the collar while supporting the fluid path and the pressure sensor, risk of degradation of the separator membrane in the event of incorrect operation.

[0005] To overcome these various drawbacks, the invention provides various means techniques. Summary of the invention

[0006] The main objective of the invention is to provide a simple and effective means for protecting the instrumentation used in an installation against possible contaminants while allowing the implementation of high precision measurements.

[0007] To do this, the invention provides an interface cell for measuring fluid characteristics in industrial equipment, comprising a connection tube to a pressure sensor or a rupture disk allowing the fluid to be conveyed to the pressure sensor or the rupture disk, the connection tube being closed by a flexible and sealed interface membrane fixed by embedding a seal in a contact face of the connection tube for sealed closure of the interface cell, said sealed closure allowing transmission of the fluid pressure from the interface cell to the pressure sensor or rupture disk by deformation of the interface membrane as a function of the pressure level of the fluid circulating in the interface cell.

[0008] This arrangement allows measurements of the cell fluid pressure to be made while providing a microbial barrier at zero or low relative pressure.

[0009] Advantageously, the interface cell comprises a tube for conveying the fluid to be measured, said one connection tube being in fluid connection with this conveying tube and arranged perpendicular to the latter.

[0010] This type of architecture makes it possible to create a T-shaped assembly in a simple and practical manner.

[0011] The invention also provides a pressure measurement system comprising an interface cell as previously described and a pressure sensor comprising a diaphragm serving as a support for the interface membrane of the cell, for transmitting the pressure exerted by the interface membrane to the pressure sensor, and for enabling the interface membrane to withstand an internal pressure greater than the resistance of the interface membrane alone.

[0012] Thus, in an example of execution for tests with a 0.35mm thick EVA (Ethyl Vinyl Acetate) membrane, the unsupported interface cell manages to hold a hydraulic or pneumatic pressure of the order of 0.2 bar, which is largely sufficient to guarantee the barrier function. Once supported by the diaphragm of the pressure sensor or by the rupture disk membrane, the pressure resistance can reach values ​​greater than 4.5 bar.

[0013] The pressure sensor is of any type: pressure gauge, electronic sensor, pressure switch, etc.

[0014] Advantageously, the pressure measuring system comprises a cover with lever designed to allow centering and coupling of the interface membrane against the pressure sensor diaphragm.

[0015] The invention also provides an overpressure protection system comprising an interface cell as previously described and a rupture disk fixed against the interface membrane in order to provide a safety member against overpressure.

[0016] This arrangement allows the rupture disc to remain out of contact with the fluid until the burst pressure has been exceeded. The interface membrane having negligible pressure resistance does not delay the rupture of the rupture disc in the event of overpressure and does not modify its burst pressure. Brief description of the drawings

[0017] All the details of the embodiment are given in the following description, supplemented by figures 1 to 8, presented solely for the purposes of non-limiting examples, and in which: Fig.l

[0018] [Fig.l] [Fig.l] is a side view of a first example of a pressure measurement system comprising an interface cell with a membrane and a pressure sensor; Fig.2

[0019] [Fig.2] [Fig.2] shows another example of a pressure measuring system comprising an interface cell with membrane and a pressure sensor; Fig. 3

[0020] [Fig.3] [Fig.3] is a front view of another example of a measuring system pressure comprising an interface cell with membrane and a pressure sensor, further comprising a centering system with lever cover; Fig.4

[0021] [Fig.4] [Fig.4] shows the measuring system of [Fig.3] in side view; Fig.5

[0022] [Fig.5] [Fig.5] is a perspective view of the measuring system of Figures 3 and 4; Fig.6

[0023] [Fig.6] [Fig.6] shows an example of the installation of a rupture disc on a interface cell; Fig.7

[0024] [Fig.7] [Fig.7] shows a graph illustrating a comparison of measurements performed with an interface cell and with a reference pressure probe; Fig.8

[0025] [Fig.8] [Fig.8] shows a histogram illustrating the number of points per in range of measurement differences. Description of the embodiments

[0026] Figures 1 and 2 illustrate two examples of interface cells 1. The interface cell 1 makes it possible to connect in a sealed manner a measuring instrument such as a sensor 5 or pressure gauge, or a rupture disk 11. In the examples illustrated, the interface cell 1 comprises an interface membrane 2 mechanically embedded in a groove 12 for embedding the measuring cell with a seal 3, allowing a sealed mounting of the membrane 2.

[0027] This arrangement offers a double advantage. First of all, it prevents the intrusion of contaminants from the ambient atmosphere into the interior of the interface cell. It also provides excellent resistance to mechanical stresses during handling of the interface cell, such as slight pressure against the membrane, friction against other surfaces, slight pressure or depression in the measuring cell.

[0028] For the efficiency and accuracy of the measurements, the interface membrane 2 must allow a full transfer of the pressure of the fluid (air or liquid) inside the interface cell to the pressure sensor 5 or the rupture disk 11. The membrane 2 must therefore be sufficiently thin, of the order of magnitude a few micrometers to the millimeter, for example with a thickness of 0.35mm tested successfully as shown in Figures 7 and 8. The interface membrane must also be elastic or plastic in order to be able to press under pressure against the diaphragm or rupture disk, form a barrier against intrusions, and chemically and mechanically resist the chemical solutions contained in the cell, or the chemical or physical sterilization means (irradiation, etc.) for the sanitization or sterilization of the cell.

[0029] In the example of [Fig.l], the interface cell 1 is T-shaped serving as a connection with a tube 10 for conveying a fluid to be controlled. The conveying tube 10 has two inlets / outlets 4 on either side of the central axis of the T. The connection of the two inlets / outlets 4 can be of any type: ringed connection for mounting on flexible piping, but also any type of connection, or welded or embedded with the remainder of the fluid path containing the fluid.

[0030] In the example of [Fig.2], the interface cell 1 only comprises a connection tube 6 which can be straight or curved. As in the previous example, the other orifice can be of any type: tri-clamp connection, but also any type of connection, or welding or embedding with the remainder of the fluid path containing the fluid to be controlled. Thus, an example of application of this variation consists of connecting the interface cell 1 to a tank, or an in-line container (such as a debubbler) to install a pressure probe 5 or a rupture disk 11.

[0031] As illustrated in Figures 1 and 2, the sealed embedding 8 of the membrane 2 in a contact face 7 of the interface cell 1 by means of a seal 3 is carried out as follows. The interface cell 1 comprises a connection tube 6 taking for example the form of a bore forming a fluid passage corresponding to the diameter of the pressure sensor 5 or the rupture disk 11 used with the interface cell. The connection tube 6 ends by forming a contact face 7. This contact face 7 comprises a groove 12 preferably trapezoidal or semi-trapezoidal. The groove 12 must be sized according to the rules of the art in mechanics, considering that the torus diameter of the seal considered for the design is equal to the diameter of the seal 3 used plus twice the thickness of the membrane 2, because the latter is found embedded, stuck between the toric seal and the trapezoidal groove 12.The seal 3 which has the function of embedding the membrane 2 can be made of elastomer (for example EPDM, nitrile or fluoroelastomers) or plastomer (for example PTFE).

[0032] In the case of the examples of figures 1 and 2, the embedding 8 of the membrane 2 is included in a clamp type connection 14. This allows the mounting of a pressure probe 5 or a rupture disk 11 (as shown in [Fig.6]) whose diaphragm 13 is mounted on a clamp connection 14 of the same size as that of the cell 1. The mounting of the clamp collar 14 makes it possible to center and apply the diaphragm 13 of the pressure probe 5 or of the rupture disk against the membrane 2 of the cell.

[0033] This assembly can be used in certain functions, where the presence of a dead arm is acceptable, or for assemblies with large piping where the ratio between the diameter of the piping and the length of the arm closed by the membrane is less than two or three, where said arm is considered a dead arm.

[0034] In the example of Figures 3 to 5, a pressure probe 5 with separator 13 is mounted on the interface cell 1 by means of a cover and lever 9. This type of mounting allows centering and applying the membrane 2 against the pressure probe 5 or the rupture disc 11. This configuration also has the advantage of quickly mounting, without tools, the interface cell 1 with controlled crushing. In this mounting, the seal 3 has a spring function to constrain the lever mounting with an appropriate force for the stability of the mounting, and to accept the manufacturing tolerances on the mounting, otherwise the lever mounting could require excessive clamping force or a loose mounting, not allowing proper operation.

[0035] Figures 1 to 4 show the example of association of the measuring cell with a diaphragm pressure gauge, but are equally applicable with other pressure sensor technologies provided with a diaphragm: pressure switch, electronic pressure probe, etc.

[0036] To verify that the interface membrane exerts minimal interference on the measurement in usual applications, i.e. less than O.lbar, comparative measurements were carried out using a fluid circuit containing a pump, an interface cell with interface membrane, a class 1 precision reference pressure probe, and an outlet restriction valve to vary the pressure in the fluid circuit.

[0037] The pressure of the two measuring instruments is carried out continuously. The curve in [Fig.7] shows the trajectory over time of the pressure measured by the two measuring instruments. From this reading, the difference in measurement between the two instruments is measured, and the histogram in [Fig.8] is plotted, showing the number of points per interval of measurement differences.

[0038] It can be seen that the error is always less than 0.1 bar, and very largely around 0.02 bar, an offset which corresponds to the resistance of the membrane to the pressure. This difference can be integrated into the measurement in order to reduce the error accordingly. Errors greater than 0.03 bar correspond to the measurement points during rapid increases or decreases in pressure, linked to the differences in response time between the two instruments, and not to the effect of the membrane. This test of principle makes it possible to demonstrate that the membrane exerts a minor disturbance on the pressure measurement. Examples of using the interface cell

[0039] The previously described interface cell 1 is mainly used in the context of so-called "single-use" processes in the pharmaceutical industry, where all of the piping and instrumentation, i.e. all of the surfaces in contact with the product used, are replaced between production cycles, batches or during product changes to avoid cross-contamination.

[0040] These processes very often require pressure gauges or pressure probes to regulate the pressure of fluids, liquids or gases, for example in frontal or tangential filtration processes where the filters need to work in a determined hydraulic pressure range.

[0041] These processes may also require safety components such as pressure switches (pressure threshold electrical contact) coupled with the actuator causing the pressure or with a discharge valve or rupture discs, in order to protect the process and users against a risk of overpressure. For example: protecting a degasser (debubbler) used in chromatography upstream of a chromatography column, to avoid the risk of explosion linked to overpressure in gas or liquid.

[0042] Other examples of methods, without the list being limiting, can be: disposable bioreactor (in 2D or 3D bag), liquid preparation or storage bag, liquid transfer or mixing systems which each have a limit of re pressure resistance and may therefore require pressure measurement to prevent the risk of overshoot.

[0043] The invention can also be used in cases of use of corrosive solutions where the elastic interface membrane can protect the diaphragm (separator) of the pressure sensor or the rupture disk against the risk of degradation by oxidation. The invention can also be used in the case of use of a dangerous or toxic product, requiring disassembly or reuse of the pressure sensor or the rupture disk. The latter, not being in direct contact with the product, does not present a risk to the operator who disassembles them or mounts them on the membrane. List of reference signs

[0044] 1. Interface cell for fluidic measurement 2. Flexible and waterproof interface membrane 3. Sealing gasket 4. Fluid inlet / outlet 5. Pressure sensor 6. Connecting tube 7. Contact face 8. Embedding 9. Lever hood 10. Delivery tube 11. Rupture disc 12. Embedding groove 13. Separator 14. Clamp collar

Claims

Claims

1. Interface cell (1) for measuring fluid characteristics in industrial equipment, comprising a tube (6) for connection to a pressure sensor (5) or a rupture disk (11) allowing the fluid to be conveyed to the pressure sensor (5) or the rupture disk (11), the connection tube being closed by a flexible and sealed interface membrane (2) fixed by embedding (8) a sealing gasket (3) in a contact face (7) of the connection tube (6) for sealed closure of the interface cell (1), said sealed closure allowing transmission of the fluid pressure from the interface cell (1) to the pressure sensor (5) or rupture disk by deformation of the interface membrane (2) as a function of the pressure level of the fluid circulating in the interface cell (1).

2. Interface cell according to claim 1, comprising a conveying tube (10) for the fluid to be measured, said one connection tube (6) being in fluid connection with this conveying tube (10) and arranged perpendicular to the latter.

3. Pressure measuring system comprising an interface cell (1) according to any one of claims 1 or 2, and a pressure sensor (5) comprising a diaphragm (13) serving as a support for the interface membrane (2) of the cell (1), for transmitting the pressure exerted by the interface membrane (2) to the pressure sensor (5), and for enabling the interface membrane (2) to withstand an internal pressure greater than the resistance of the interface membrane (2) alone.

4. A pressure measuring system according to claim 3, comprising a lever cover (9) designed to allow centering and coupling of the interface membrane (2) against the diaphragm of the pressure sensor.

5. Overpressure protection system comprising an interface cell (1) according to any one of claims 1 or 2 and a rupture disc fixed against the interface membrane (2) in order to provide an overpressure safety member.

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