JPH0523551A - Perfection testing apparatus - Google Patents

Abstract

PURPOSE:To provide an apparatus with high measurement precision for perfection testing of a precision filtration membrane filter cartridge. CONSTITUTION:A filter cartridge's perfection testing apparatus characterized in that prior to the perfection measurement of a filter cartridge by applying atmospheric pressure to a primary side of a precision filtration membrane filter cartridge, a liquid is supplied to the filter cartridge at a flow rate of 1m<3>/h or less 1m<2> membrane surface area of the filtration membrane to be filtered, and perfection of the filter cartridge is measured by closing a secondary side valve of a filter housing and applying back-pressure of 1kg/cm<2> or more after it is wetted with the liquid.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for testing the integrity of a microfiltration membrane filter cartridge. Microfiltration membrane filter cartridges are used in the pharmaceutical industry, alcoholic beverages in the food industry, the electronics industry that performs fine processing such as the manufacturing industry and the semiconductor manufacturing industry, and further used in laboratories of various industries. Used for filtering water and pure water, 10 microns or less,
In particular, it is a filter for efficiently filtering fine particles of 1 micron or less and microorganisms. To ensure filtration results, these microfiltration membrane filter cartridges are integrity tested prior to filtration to ensure the absence of pinholes and other defects and then subjected to actual filtration. The present invention relates to a new method with high accuracy for such a pre-filtration integrity test.

[0002]

2. Description of the Related Art Conventionally, in order to increase the filtration area and facilitate handling, a microfiltration membrane is usually a pleat that is formed by folding the membrane into pleats and forming a cylindrical shape to form partition walls inside and outside the cylinder. A mold cartridge filter or a microfiltration membrane is adhered to both sides of a disc-shaped support frame, and the disc-shaped cartridge filter is used as a filter that forms a partition wall inside and outside the support frame by stacking these in multiple stages. At this time, it cannot be said that the processed filter does not suffer from defective sealing of the adhesive portion or damage to the filter. Therefore, the microfiltration membrane filter cartridge is rigorously inspected to confirm its integrity, that is, there is no sealing failure during processing as described above, and that there is no major defect such as bacteria permeation in the filter. To be done.

The "bubble point method" is one of the conventional integrity inspection methods for microfiltration membrane filter cartridges.
There is. The principle of the inspection method by the bubble point method is as follows. That is, as shown in FIG. 1, assuming a cylindrical capillary tube 31 as a pore model of a microfiltration membrane and placing it in a liquid tank 32, the following equation holds in this capillary phenomenon. ρh = 2σ cos θ / r In the above formula, r is the radius of the capillary, ρ is the specific gravity of the liquid, h is the height of the liquid rising in the capillary, σ is the surface tension of the liquid, and θ is the liquid and the microfiltration membrane. The contact angles are shown. Next, the product of the height h of the liquid 33 and the specific gravity ρ that have risen is equal to the capillary force per unit area of the capillary 31, that is, the pressure p, and the following formula is established. p = ρh Here, if a gas pressure p that overcomes this capillary force is applied,
The liquid 33 in the capillary tube 31 is pushed out, and gas is blown out from this capillary tube for the first time. Since the gas pressure p is inversely proportional to the diameter d of the capillary 31, d = 4σ cos θ / p At first, the gas blows out from the capillary having the maximum diameter. The gas pressure p at this time is the “bubble point”. If there are large holes in the microfiltration membrane that allow bacteria to pass,
This bubble point (pressure p) is lower than that of a normal microfiltration membrane, and it is detected that the microfiltration membrane is abnormal.

The "diffusion flow method" is used for the integrity test on the cartridge type microfiltration membrane having a large filtration area.
The inspection method called is commonly used. When a gas pressure lower than the bubble point is applied to a microfiltration membrane that is wet with liquid and the pores are filled with the liquid, the liquid remains in the pores and blocks the pores. However, according to Henry's law, gas dissolves in liquid in proportion to its absolute pressure. Therefore, there is a difference in the concentration of the gas that can be dissolved in the liquid between the entrance and the exit of the hole, and the gas dissolved at the entrance of the hole diffuses and reaches the exit side of the hole, where it is vaporized. Therefore, the microfiltration membrane whose pores are completely filled with the liquid allows the gas to permeate the membrane though the amount is small even when a gas pressure lower than the bubble point is applied. This permeation amount is difficult to observe with a small membrane area, but can be easily detected with a filter cartridge with a large membrane area. The solubility of the gas in the liquid is H, the diffusion coefficient of the gas in the liquid is D, the porosity of the film is Φ, the film thickness is L, the film area is S, and the pressure difference between the primary side and the secondary side of the film is P. Then, the permeation flow rate (diffusion flow rate) Q of the gas should be obtained according to the following formula, if the filter cartridge has the same configuration, a constant permeation flow rate. Q = DHPSΦ / L When the diffusion flow rate of a filter without defects is known in advance, the gas permeation amount is measured by applying a gas pressure slightly lower than the bubble point to measure the gas permeation by diffusion and The presence or absence of gas permeation from the defective portion can be determined.

An inspection method called "pressure holding method" which is similar in principle to the "diffusion flow rate method" is also applied to a filter cartridge having a large area. This method is a method of applying a gas pressure lower than the bubble point to the primary side of a film whose pores are blocked by being wet with a liquid, then stopping the supply of gas and observing a pressure drop for a predetermined time. . Since the gas dissolves and diffuses in the liquid and permeates from the higher pressure side to the lower pressure side, a pressure drop occurs in proportion to the amount of the diffusely permeated gas. Thus, a defect-free filter cartridge of the same construction will experience a certain amount of pressure drop, and a defective filter cartridge will experience a greater pressure drop than a non-defective filter cartridge.

[0006]

As described above, in any method of measuring the integrity of a filter cartridge, the amount of gas permeation and the pressure at which permeation is started by filling the pores of the microfiltration membrane with liquid and applying gas pressure. To measure. Therefore, if there is a portion not filled with liquid in a part of the pores of the membrane, a large amount of gas permeates from there through at a low pressure, and correct measurement cannot be performed. In a filter cartridge, many membranes are folded or stacked in a certain volume,
Bubbles can interfere with the leaking of the membrane, creating a location that does not leak to the liquid. In particular, water, which is often used as a liquid, has a large surface tension, and bubbles are difficult to escape. Therefore, according to JIS K3832, "Testing method for bubble point of microfiltration membrane element and module," 0.3 to 1.0 kg / cm while discharging air from the primary side of the housing.
^A method of applying a filtration pressure difference of ² to leak the liquid while filtering it is proposed. However, even if the liquid is filtered under such conditions, it cannot always be completely leaked,
Particularly in a pleated filter cartridge, it is difficult to completely leak the vicinity of the membrane when sealing. Therefore, the diffusion flow rate becomes larger than the original value, and the bubble point value becomes smaller than the original value, resulting in large fluctuation. For this reason, it is impossible to distinguish between a defective leak and a defect such as a filter hole or tear, and a good product is considered defective.
It is easy to mistake a defective product for a good product. Furthermore, just 0.3
In order to apply a filtration differential pressure of 1.0 kg / cm ^{2 to} the primary side and the secondary side of the membrane, a large amount of water must be permeated.
For this reason, there has been a problem that a large-capacity pump is prepared, and in the pharmaceutical industry, a large amount of expensive distilled water is consumed and the cost becomes high.

[0007]

The above-mentioned problems can be solved by the following means. That is, before the gas pressure is applied to the primary side of the microfiltration membrane filter cartridge to measure the integrity of the filter cartridge, liquid is supplied to the filter cartridge at a flow rate of 1 m ³ / h or less per 1 m ² of membrane area of the filtration membrane. The filter cartridge is characterized by squeezing the valve on the secondary side of the filter housing and applying a back pressure of 1 kg / cm ² or more to measure the integrity of the filter cartridge after wetting it with liquid. Achieved by integrity test equipment. Hereinafter, a detailed description will be given with reference to examples, but the present invention is not limited to the examples.

FIG. 2 shows an example of a microfiltration device which facilitates back pressure load and filtration flow rate adjustment and incorporates a diffusion flow rate measuring device. The microfiltration membrane filter cartridge 2 is mounted on the filter housing 1, and the water supplied from the water supply tank 3 by the pump 4 is filtered and passed through the drain valve 22 to be drained. At this time, the air bleeding valve 1
After sufficient air is exhausted from the valve 5, the valve 15 is closed. Then, the flow control valve 12 is gradually reduced to apply back pressure. When the back pressure becomes too high when looking at the pressure gauge 6, the bypass valve 13 is opened to circulate a part of the water supplied from the pump. The flow rate adjusting valve 12 and the bypass valve 13 are adjusted so that the amount of water passing through the filter becomes a predetermined flow rate. After passing water at a predetermined back pressure and flow rate for a predetermined time, the pump is stopped and the valve 11 is closed to stop the water supply. In order to drain the water in the housing 1, the gas supply valve 20 is opened and clean air whose pressure has been reduced to 0.5 kg / cm ² by the pressure control valve 21 is supplied from the air compressor. When the drainage in the housing is completed, the pressure control valve 21 is operated to increase the air pressure to a predetermined diffusion flow rate measurement pressure. When the pressure gauge 5 reaches a predetermined pressure, the gas supply valve 20 is closed and the diffusion flow rate measurement valve 1
8 and 19 are opened, and the diffusion flow rate is measured by the gas flow meter 8.
In this way, after the diffusion flow rate measurement is completed and the integrity of the filter can be confirmed, the filtered stock solution supply valve 16 and the filtered solution feed valve 17 are opened to perform the intended filtration.

The higher the back pressure applied to the filter cartridge when water is passed prior to the integrity test, the greater the effect. It is effective to apply a back pressure of ² kg / cm ² or more. Unless a back pressure of at least 1 kg / cm ² or more is applied, it is difficult to effectively reduce the amount of water flow.
When a back pressure of 1 kg / cm ² is applied, the flow rate of the liquid is 1 m ² of membrane area.
Per 1m ³ / h or less, 3 minutes to 10 at 0.5m ³ / h or more
By passing a minute, the filter is sufficiently wet with water and the integrity can be measured. When a back pressure of ² kg / cm ² is applied, the flow rate of the liquid is 1 m ³ / h or less per 1 m ² of the membrane area, and 0.1 m ³ / h or less is 3 to 10 minutes, and the filter is sufficiently water It becomes wet and the integrity can be measured.

It is not known why the membrane gets wet well when back pressure is applied to pass water. The present inventors presume that the mechanism is as follows. That is, the seal portion of the microfiltration membrane is sealed, for example, by inserting the membrane into a hot melt resin and cooling and solidifying the membrane. Unlike the holes in the film other than the sealing portion, the holes in the film at the time of sealing are dead ends, so that the air in the film at the time of sealing cannot be pushed out only by passing water. Therefore, when the membrane is sealed, the air is obstructed and water cannot enter the hole. For this reason, it may be difficult to get wet only by sealing with a simple liquid flow. However, when back pressure is applied here, the solubility of air in water increases dramatically, and the remaining air is dissolved and removed in a short time, and water can easily permeate after the air is removed in this way. Estimated to be As can be seen from the above estimation, no matter how high back pressure is applied, it is not possible to sufficiently wet the filter cartridge by simply immersing it in water and simply applying pressure, and water is passed at some flow rate to permeate the membrane. It is necessary. If the flow rate is too low, the water flow is partially biased, and it is difficult for the water to flow, especially when sealing the membrane existing in the corner of the cartridge. Therefore, it is desirable to apply the flow rate of at least 0.1 m ³ / h or more per 1 m ² of membrane area. Therefore, it goes without saying that the water used is preferably degassed in advance. However, even water in which air is dissolved to the limit can be sufficiently used because the solubility is dramatically increased by applying back pressure. It is not yet clear how many times the temperature of the water used is appropriate. Higher water temperatures make water less soluble in air and are unsuitable for this purpose. On the other hand, when the water temperature is high, the surface tension of water decreases, and it is considered that the water easily penetrates into the pores.

When the integrity measurement of the present invention is carried out in an actual production site, the flow control valve 12 and the bypass valve 1 are used.
3 is an automatic valve, and in conjunction with the pressure gauge 6 and the flowmeter 7, the liquid flow conditions are automatically adjusted, and the integrity measurement is performed automatically after the liquid flow is finished for a predetermined time. It can also be used in conjunction with a bubble point measuring device or the like. Wet the filter cartridge for 5 minutes by changing the water flow conditions, load 2.5 kg / cm ² of compressed air on the primary side of the filter cartridge, measure the diffusion flow rate under 10 conditions for each, and measure the average value. The results of the comparison are shown in Table 1. Original correct diffusion flow rate is about 10 ml
As will be described below, the air permeation flow rate of the insufficiently wetted filter cartridge is a large air permeation flow rate by adding the diffusion air flow rate and the air flow rate that leaks the part not wetted by water. The filter cartridges used in Table 1 are Astropore P manufactured by Fuji Photo Film Co., Ltd.
A pleated cartridge filter of SMCP20SW (membrane area 0.7 m ² ).

[0012]

[Table 1]

[Brief description of drawings]

FIG. 1 is a principle diagram of a capillary phenomenon.

FIG. 2 is a flowchart showing one embodiment of the integrity measuring apparatus of the present invention.

[Explanation of symbols]

1 Filter housing 2 filter cartridge 3 Water supply tank 4 pumps 5 Primary side pressure gauge 6 Secondary pressure gauge 7 Liquid flow meter 8 Gas flow meter 11 Water supply valve 12 Flow control valve 13 Bypass valve 14 Drain valve 15 Air bleeding valve 16 Filtration stock solution supply valve 17 Filtrate delivery valve 18 Diffusion flow rate measurement valve 19 Diffusion flow rate measurement valve 20 gas supply valve 21 Pressure control valve 22 Drain valve 23 Filtration stock solution supply line 24 Lines leading to air compressors or nitrogen cylinders 31 cylindrical capillaries 32 liquid tank 33 Liquid sucked into the capillary

Claims (2)

[Claims] 1. A water supply device having (1) a water supply tank, a pump and a valve for bypassing the pump and automatically adjusting the amount of bypass water, on the primary side of a filter housing having a microfiltration membrane filter cartridge mounted thereon.
(2) An integrity test device, in which an integrity test device is installed, and (3) a flow rate control device including a pressure gauge and a flow rate control automatic valve is installed on the secondary side of the filter housing. 2. Prior to measuring the integrity of the filter cartridge by applying gas pressure to the primary side of the microfiltration membrane filter cartridge, 1 per 1 m ² of membrane area of the filtration membrane is used.
After the liquid is supplied to the filter cartridge at a flow rate of m ³ / h or less and filtered, the secondary side valve of the filter housing is squeezed and a back pressure of 1 kg / cm ² or more is applied to wet the filter cartridge with the liquid. The integrity test method for a filter cartridge according to claim 1, wherein the integrity is measured.