Non-destructive integrity detection method for filter element and filter medium

Abstract

The invention provides a non-destructive integrity detection method for a filter element and a filter medium, which comprises the following steps of: performing integrity detection on the filter element and / or the filter medium in a dry environment to set a pressure value and a flow rate of gas to penetrate through the filter element and / or the filter medium, and observing the pressure value of the gas penetrating through the filter element and / or the filter medium to determine the integrity of the filter element and / or the filter medium. When the pressure value of the gas penetrating through the filtering element and / or the filtering medium is in pressure balance, checking is completed, and integrity judgment is conducted according to the pressure value of the gas in the pressure balance state. Compared with traditional integrity detection, the filtering element and / or the filtering medium do not need to be wetted in advance and can be directly detected; in the filter element and / or filter medium production process, the dry test method can be adopted, each filter element or filter medium can be rapidly detected, and the detection process is not destructive and does not affect the use of the filter element and filter medium.

Description

Technical Field

[0001] The present invention relates to the technical field of performance detection of filter elements, and particularly to a filter element and a non-destructive integrity detection method for a filter medium. Background Art

[0002] Integrity testing is a certification for controlling the production quality of filter elements. In the biomedical industry, integrity testing ensures the safety of the sterilization process, and can determine the integrity of the filter itself, the tightness of the filtration system, the correct installation of the process, that the filter is not damaged and meets the manufacturing specifications.

[0004] Integrity testing can be divided into two categories: destructive testing and non-destructive testing. The data of both destructive and non-destructive testing must be related to obtain the data of the user's integrity testing, which is a regulatory requirement and also the verification reason for test applications.

[0005] In the filtration industry, non-destructive detection methods for the filtration accuracy and integrity of filter elements usually detect by methods such as diffusion flow, bubble point or pressure decay. The accuracy and reliability of the above detection methods are generally recognized in the industry, but their disadvantages are also very obvious: (1) The filter element needs to be wetted. The wetting process is time-consuming and laborious, and if the wetting is insufficient, it will lead to test failure and multiple retests are required; after wetting, the product needs to be dried, wasting time and energy, or causing the product to be damaged and unable to be used twice.

[0006] (2) The test procedure is usually very time-consuming. Taking the detection of the bubble point on an integrity testing instrument once as an example, to explore the bubble point value, a long time of pressure stabilization is required, and then the pressure is increased in fixed steps. Therefore, a complete bubble point detection procedure usually takes 20 - 40 minutes.

[0007] Therefore, in order to meet the detection requirements of the non-destructive integrity of filter elements for producers and customers conveniently and quickly, inventing a "non-destructive" integrity detection method that can be "quickly" executed when the filter element is "dry" is a new method that the industry urgently needs to develop. Although some researchers have used a gas containing multiple components to permeate through the filter medium to be tested, and judged whether the filter medium is intact or not according to its permeation rate or the components permeated, this method needs to select gases specifically according to different materials of the filter medium or filter element. In addition, it is also necessary to compare and analyze the amount of gas permeated to give a judgment, and the process is still cumbersome.

[0008] In view of this, it is necessary to improve the integrity testing method in the prior art to solve the above problems. Summary of the Invention

[0009] The object of the present invention is to disclose a non-destructive integrity testing method. Through an integrity detection program, when the filter element is in a dry state and the balance pressure is used as the detection method, the filtering accuracy and integrity of the filter element can be quickly distinguished within a detection time of less than 1 minute.

[0010] To achieve the above object, the present invention provides a non-destructive integrity detection method for a filter element and a filter medium. The integrity of the filter element and / or the filter medium is detected in a dry environment without pre-wetting the filter element and / or the filter medium, and the integrity is judged only by the pressure value of the gas passing through the filter element and / or the filter medium.

[0011] In some embodiments, the integrity of the filter element and / or the filter medium is detected in a dry environment. A gas with a set pressure value and flow rate passes through the filter element and / or the filter medium, and the pressure value of the gas passing through the filter element and / or the filter medium is observed. When the pressure value of the gas passing through the filter element and / or the filter medium reaches pressure balance, the inspection is completed, and the integrity is judged according to the gas pressure value at the time of pressure balance.

[0012] In some embodiments, multiple filter elements and / or filter media are detected for integrity in a dry environment and tested under the same test conditions. The higher the gas pressure value, the higher the filtering accuracy of the filter element and / or the filter medium.

[0013] In some embodiments, the filter element and / or the filter medium is a porous membrane material or a filter paperboard.

[0014] In some embodiments, the method includes the following steps: Step 1: Install the filter element and / or the filter medium on a test fixture. An air inlet device is connected to one side of the filter element and / or the filter medium, and a pressure display is connected to the other side of the filter element and / or the filter medium. Step 2: Adjust the pressure valve and set a predetermined gas pressure value and flow rate. Step 3: Introduce gas and observe the pressure display on the test fixture. When the gas passing through the filter element and / or the filter medium gradually reaches balance, the detection is completed, and the gas pressure value at this time is recorded.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) Compared with traditional integrity detection, the filter element and / or filter medium do not need to be pre-wetted, and can be directly detected; (2) According to the gas pressure value passing through the filter element and / or filter medium, when the pressure is balanced, the integrity and filtration accuracy of the filter element and / or filter medium can be judged based on the pressure value; (3) During the production process of the filter element and / or filter medium, this dry testing method can be used to quickly detect each filter element or filter medium, and the detection process is non-destructive and does not affect the use of the filter element and filter medium. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of the test tooling shown in the present invention; Figure 2 Equilibrium pressure test curve of the filter element with low filtration accuracy shown in the present invention; Figure 3 Equilibrium pressure test curve of the filter element with high filtration accuracy shown in the present invention; Figure 4 Comparison chart of test data between the equilibrium pressure method and the bubble point method shown in the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0017] The present invention will be described in detail below in conjunction with the embodiments shown in the drawings. It should be noted that these embodiments are not intended to limit the present invention, and any equivalent transformation or substitution in terms of function, method, or structure made by those of ordinary skill in the art based on these embodiments shall fall within the protection scope of the present invention.

[0018] A non-destructive integrity detection method for a filter element and a filter medium, which performs integrity detection on the filter element and / or filter medium in a dry environment, without pre-wetting the filter element and / or filter medium, and only judges the integrity based on the pressure value of the gas passing through the filter element and / or filter medium.

[0019] When performing integrity detection on the filter element and / or filter medium in a dry environment, a gas with a set pressure value and flow rate passes through the filter element and / or filter medium, and the gas pressure value passing through the filter element and / or filter medium is observed. When the gas pressure value passing through the filter element and / or filter medium is in pressure balance, the inspection is completed, and the integrity is judged based on the gas pressure value at the pressure balance.

[0020] In addition, multiple filter elements and / or filter media can also be subjected to integrity detection in a dry environment, and tested under the same test conditions. The greater the gas pressure value, the higher the filtration accuracy of the filter element and / or filter medium.

[0021] The above test method is simply referred to as the "balanced pressure" method, which can test porous membrane materials (such as ceramic membranes, PES membranes, PVDF membranes, PP membranes, PTFE membranes, PE membranes, etc.) or filter paperboards (such as cellulose filter boards, depth filter paperboards, etc.).

[0022] In the present invention, through an integrity detection program, when the filter element is in a "dry" state, with the balanced pressure as the detection method, through a "detection time of less than 1 minute", the filtration accuracy and integrity of the filter element can be quickly distinguished.

[0023] As Figures 1-3 shown, the present application uses an integrity tester for detection, which specifically includes the following steps: Step 1: Install the filter element and / or filter medium on the test tooling (i.e., the integrity tester). An air inlet device (i.e., the outlet air pipe of the integrity tester) is connected to one side of the filter element and / or filter medium, and a pressure display is connected to the other side of the filter element and / or filter medium. Step 2: Adjust the pressure valve and set a predetermined gas pressure value and flow rate at the air inlet of the integrity tester. Step 3: Start the program mode, and the integrity tester starts to work, that is, introduce gas, and observe the pressure display on the test tooling. When the gas pressure value gradually tends to balance after passing through the filter element and / or filter medium, the detection is completed, and record the gas pressure value at this time.

[0024] The filter element (filter medium) can quickly (within 30 s) reach pressure balance under a certain air pressure and flow rate, and under the same air inlet conditions, the higher the filtration accuracy, the greater the pressure balance value.

[0025] The principle of this method is as follows: Most of the filter materials have a microporous structure and a large porosity. When gas passes through the filter material, due to the resistance effect, the gas pressure value on the permeate side of the filter material will gradually increase. When the gas fills and passes through the largest micropores of the filter material, the change in the gas pressure value on the permeate side will tend to be stable. When the gas completely fills and passes through the micropores of the filter material, the gas pressure value will gradually tend to and maintain an equilibrium state.

[0026] Compared with the commonly used bubble point method, the detection method of the "balanced pressure" method disclosed in the present invention can also quickly and clearly complete the integrity detection and filtration accuracy detection of the filter element / filter medium.

[0027] I. Filtration accuracy detection: As shown in Table 1 and Figure 4As shown in the figure, deep cardboard filter elements with different filtration precisions are selected, and the bubble point method and the "equilibrium pressure" method are respectively used for detection. It can be seen from Table 1 that both of these two integrity detection methods, equilibrium pressure and bubble point, can distinguish filter cardboard with different precisions. The higher the filtration precision, the higher the equilibrium pressure and bubble point values.

[0028] Table 1 Data correlation between the "equilibrium pressure" method and the bubble point method Cardboard model FC010 FC070 FC110 FC180 FC240 FC260 FC350 FC600 Balancing pressure (mbar) 10 67 112 173 235 257 352 598 Bubble point (mbar) 50 90 120 150 190 210 250 340 Furthermore, the "equilibrium pressure" method can have a higher detection precision than the bubble point method and is easier to distinguish the fine structure of the product. As shown in Table 2, when the bubble points of the filter elements (or filter media) are relatively close, it is often impossible to distinguish the differences between products through the bubble point method. However, in deep filtration, these subtle differences can reflect different interception effects. As shown in Table 2, the "equilibrium pressure" method can adjust the inlet air pressure to amplify the difference in equilibrium pressure values and clearly distinguish the characteristics of the products. From the following data, the average bubble points of the three types of cardboard are all 60, but by increasing the inlet air pressure, when the inlet air pressure is ≥ 3 bar, the filtration precision of the products is more clearly characterized.

[0029] Table 2 Comparison of the differences between the "equilibrium pressure" method and the bubble point method in detection data II. Integrity detection The "equilibrium pressure" method can quickly detect a large number of filter elements (or filter media), which can not only save time but also efficiently screen out non-integrity filter elements (or filter media). This detection method does not pre-wet the filter elements (or filter media) and will not cause irreversible damage to the filter elements (or filter media), especially for filter elements (or filter media) that cannot be wetted.

[0030] In this embodiment, deep cardboard filter elements are still selected. In the experimental design, three pieces of cardboard with the same precision are damaged by acupuncture or bending, and the equilibrium pressure and bubble point of the cardboard before and after damage are respectively detected. The experimental data are shown in Table 3. The test results show that the "equilibrium pressure" method is as reliable as the bubble point method and can pick out intact and damaged cardboard: for the damaged cardboard, its equilibrium pressure will decrease to varying degrees according to the damage situation, and the bubble point cannot be measured; for the cardboard that is not significantly damaged, the equilibrium pressure remains the same as before, and the bubble point also remains the same. The experiment shows that the equilibrium pressure can be used to detect the integrity of the filter element and is as reliable as the bubble point data. In addition, it can be seen from multiple groups of equilibrium data that the repeatability stability of the equilibrium pressure is more observable.

[0031] Table 3 Data comparison between the "equilibrium pressure" method and the bubble point method for detecting cardboard with different damage degrees The test tooling used in the present invention is an integrity tester, which can select different program modes to test the filter element and / or filter medium to be tested, and the test results can be directly read through the display interface. At the same time, the integrity tester used in the present invention can be pre-edited in the processing software as needed to convert the data measured under different program modes into a unified value for the operator to read.

[0032] For example (1), the "bubble point method" program can be selected. By using the measured bubble point value and converting it into the filtration accuracy (pore size) using the following formula, when the measured bubble point value is greater than the standard minimum bubble point value, the filter integrity test is qualified.

[0033] Among them, P = bubble point pressure θ = liquid-solid contact angle γ = surface tension of the wetting liquid B = Bechold capillary action constant D = maximum pore size.

[0034] (2) For another example, select the "diffusion flow" program. Set a diffusion flow test pressure (generally 80%) at the minimum bubble point pressure. Gas molecules follow Fick's law and pass through the liquid in the wetted filter pores, dissolve from the upstream high-pressure side into the liquid, and diffuse to the downstream atmospheric pressure side. The gas flow rate on the low-pressure side is the forward flow or diffusion flow. At a given test pressure, if the measured result is lower than the standard diffusion flow limit value, the integrity test is qualified.

[0035] Among them, K = solubility / diffusion coefficient P1, P2 = system pressure difference A = membrane area ρ = membrane porosity L = effective path length.

[0036] When the integrity tester selects the "equilibrium pressure" program, it can quickly detect the value when the gas pressure passing through the filter element (or filter medium) reaches equilibrium according to the preset pressure value, and judge the filtration accuracy and integrity of the filter element (or filter medium) based on this value. To facilitate obtaining the filtration accuracy of the filter element (or filter medium), calculations can be made based on the value when the gas pressure reaches equilibrium, or the bubble point value can be obtained based on the corresponding relationship between this value and the bubble point. These only need to perform data conversion according to actual needs. Of course, corresponding control programs can also be preset in the integrity tester to directly read on the integrity tester.

[0037] The above test procedures can be selectively selected according to the filter element and / or filter medium to be tested. This instrument can perform a variety of standard functions and can be used for testing in various membrane filtration systems in ways such as bubble point, diffusion flow, equilibrium pressure, and water intrusion.

[0038] The series of detailed descriptions listed above are only specific descriptions of the feasible implementation modes of the present invention, and they are not intended to limit the protection scope of the present invention. Any equivalent implementation modes or changes made without departing from the technical spirit of the present invention should be included within the protection scope of the present invention.

[0039] In addition, it should be understood that although this specification is described according to implementation modes, not every implementation mode only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A non-destructive integrity detection method for a filter element and a filter medium, characterized in that, The integrity of the filter element and / or the filter medium is detected in a dry environment without pre-wetting the filter element and / or the filter medium. Only the pressure value of the gas passing through the filter element and / or the filter medium is used to judge the integrity.

2. The non-destructive integrity detection method of the filter element and the filter medium according to claim 1, wherein, The integrity of the filter element and / or the filter medium is detected in a dry environment. A gas with a set pressure value and flow rate passes through the filter element and / or the filter medium, and the pressure value of the gas passing through the filter element and / or the filter medium is observed. When the pressure value of the gas passing through the filter element and / or the filter medium reaches pressure balance, the inspection is completed, and the integrity is judged based on the gas pressure value at pressure balance.

3. The non-destructive integrity detection method for the filter element and the filter medium according to claim 2, characterized in that, The integrity of multiple filter elements and / or filter media is detected in a dry environment and tested under the same test conditions. The higher the gas pressure value, the higher the filtration accuracy of the filter element and / or the filter medium.

4. The non-destructive integrity detection method of the filter element and the filter medium according to claim 2, characterized in that, The filter element and / or the filter medium is a porous membrane material or a filter paperboard.

5. The non-destructive integrity detection method for a filter element and a filter medium according to claim 4, characterized in that, It includes the following steps: Step 1: Install the filter element and / or the filter medium on the test fixture. An air inlet device is connected to one side of the filter element and / or the filter medium, and a pressure display is connected to the other side of the filter element and / or the filter medium. Step 2: Adjust the pressure valve and set the predetermined gas pressure value and flow rate. Step 3: Introduce the gas and observe the pressure display on the test fixture. When the gas passing through the filter element and / or the filter medium gradually reaches balance, the detection is completed, and the gas pressure value at this time is recorded.

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