JPH0643089A - Apparatus for testing completeness of membrane filter - Google Patents

Abstract

PURPOSE:To obtain a testing apparatus, which can perform highly accurate detection, measurement, monitoring and recording by supplying fluid into the primary side of a filter under test with a controller for large flow rate, and supplying the fluid after the pressure on the primary side has reached the specified value by the proportional integration control with a controller for the small flow rate. CONSTITUTION:Branching pipes 18 and 20 are connected to the outlet of a cutout valve 16. A small-flow-rate controller 22 is provided in the pipe 18, and a large-flow- rate controller 24 is provided in the pipe 20. A cutout valve 28 is provided at the downstream of the controller 24. These parts are controlled with a main control means 42. In a diffusion flow test mode, preset pressure is always kept constant by the proportional control and the integration control of a controller 22 after the specified pressure has been reached with the controller 24. The balance between the amount of the supplied fluid and the diffusing flow rate is maintained highly accurately. In a bubble- point test mode, the constant pressure increasing curve is controlled with the controller 24, and the sudden change of the increasing rate at the bubble point is computed and obtained at the accurate time interval. Thus, the testing apparatus, which can verify the completeness of the filter highly accurately in both modes, is obtained.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to improvements in membrane filter integrity testing equipment.

[0002]

2. Description of the Related Art Conventionally, various types of integrity testers for nondestructively testing a membrane filter are known.

For example, a conventional membrane filter integrity tester is of the type that records pressure rise curves in chart form with a pen recorder, which operates in bubble point mode and pressure hold mode. In bubble point mode, an arbitrary amount of gas is supplied from the primary side of the membrane filter, and the bubble point is read from the pressure rise chart. However, in the conventional device, the bubble point occurs at a time much lower than the time specified by the filter manufacturer. The pressure rise curve differs depending on the gas supply amount from the primary side and the diffusion flow rate value of the filter. Therefore, it is very difficult to decipher the bubble point from the chart, and validation is impossible.

Further, in the pressure hold mode, an arbitrary amount of gas is supplied from the primary side, and after the pressure is increased to a designated pressure, the gas supply from the primary side is stopped. After a certain equilibration time, the state of the pressure drop on the primary side is output as a chart, which is read by the measurer. In this case, the state of pressure drop is simply displayed in a chart, and factors such as the volume and temperature on the primary side are not considered. Although the measurer has to consider additional elements of the measurement line, it still cannot be correlated with the bacterial challenge test. Therefore validation is not possible.

Further, there is known a diffusion flow type integrity test apparatus to which the pressure hold test method is applied, which operates in each of bubble point, pressure hold and diffusion flow test modes.

Since the bubble point test mode is a mechanical measurement, the measurement error is lower than the human measurement error, but about ± 0.5 kg / cm 2 is still acceptable. In addition, since the measuring method differs depending on the manufacturer, it causes confusion when the number of manufacturers of filters used is several. Further, when performing visual validation while operating the integrity tester, it is difficult for the cartridge type filter to visually determine the bubble point, so validation of the bubble point is a test mode that should be dedicated to the disc filter.

The pressure hold test mode is
Although it is a mechanical measurement, the measurement error is extremely small, but it is difficult to verify the correlation with the pressure hold test method and the bacterial challenge test submitted by the filter manufacturer, and in a strict sense, it is suitable for validation. Absent. This is because the pressure hold test mode method is greatly affected by the primary side volume and the primary side temperature of the filter under test.

The conventional diffusion flow test mode uses the pressure hold test method described above, and calculates the diffusion flow rate value from the primary side volume measured by applying a constant pressure to the primary side of the measurement line and the pressure drop value. I ask, but there are problems in the following points.

A. It does not adopt the measurement method of keeping the primary pressure at the specified pressure.

B. The longer the equilibration time is, the lower the specified pressure becomes.

C. When the temperature of the measurement line becomes high, gas expansion occurs, which makes accurate measurement impossible.

D. Although it is equipped as standard with the function of mechanically determining the volume on the primary side, the error during volume measurement is large. Since this value is the basis, the measurement error is large and the reproducibility is poor.

From the above viewpoints, this diffusion flow type integrity tester also has a problem that it is not correlated with the bacterial challenge test.

[0014]

SUMMARY OF THE INVENTION Therefore, the object of the present invention is based on the measurement method of the diffusion flow test at the time of data preparation of the bacterial challenge test, without being affected by the change in the primary side volume and temperature of the measurement line, and the primary side. It is an object of the present invention to provide a membrane filter integrity tester capable of detecting, measuring and monitoring the diffusion flow rate within a certain period of time with extremely high accuracy while maintaining a constant pressure by adopting a mass flow control method.

[0015]

To achieve this object, the present invention provides
In a membrane filter integrity tester that tests the integrity of the membrane filter under test by sending fluid to the primary side of the membrane filter under test, a large flow rate that can rapidly supply a large amount of fluid to the primary side of the membrane filter. The mass flow controller and the fluid supplied by the large flow mass flow controller stop the operation of the mass flow controller when the pressure on the primary side of the membrane filter reaches a predetermined level, and at the same time the small flow rate of the fluid is transferred to the membrane filter. A small flow controller for supplying to the primary side, a pressure detecting means for detecting the pressure on the primary side of the membrane filter under test and generating a detection signal, and a small flow rate according to the value of the detection signal received from the pressure detecting means. Main controller for proportional / integral control of controller Providing encompasses membrane filter integrity test system and.

The present invention will be described in detail below with reference to the accompanying drawings.

Referring to the drawings, the membrane filter integrity test apparatus according to the present invention comprises an inlet 10 for introducing a fluid used for a test, a safety valve 14 connected through a protective filter 12 connected to this inlet, and this safety valve. And a shutoff valve 16 connected to 14. Branch pipes 18 and 20 are connected to the outlet side of the shutoff valve. A small flow rate mass flow controller 22 is provided in one branch pipeline 18, and a large flow rate mass flow controller 24 is provided in the other branch pipeline 20. Downstream of this large flow rate mass flow controller. Is provided with another shutoff valve 28.
These branch pipelines 18 and 20 merge at a merge point 30 to form a discharge pipeline 34 leading to an outlet 32. A pressure sensor 36 is connected to the discharge conduit 34 immediately downstream of the confluence 30. Further, on the further downstream side, a switching valve 38 is connected to the discharge conduit 34, and this switching valve 38 can block the discharge conduit 34 and connect the outlet 40 to the outlet 32. ing.

All of the above movable parts are main control means 4
It is controlled by two. Thereby, when the fluid is supplied from the primary side of the filter casing and the filter element (including the disc type and the cartridge type), the internal pressure sensor 3 of the integrity tester
6 (Diffuse flow rate can be measured precisely and minute pressure drop that occurs during diffusion can be measured), while measuring the diffusion flow rate with high accuracy, it is also high in the pressure hold test mode and bubble point test mode. It makes it possible to measure with accuracy, and it is possible to confirm the integrity of the system as well as the integrity of the filter itself.

When the membrane filter integrity tester is activated, pressure values are sampled every 10 seconds and stored in memory (Table 1 in FIG. 4). For example, when the Pn point is used as a reference, first, the sum of the front and rear .SIGMA.P1 to .SIGMA.P4 is obtained, and Pn.times. {(. SIGMA.P2--P1) / (. SIGMA.P4--P
3)} to obtain Pn '. The same calculation is repeated by sequentially increasing n to create table 2 in FIG. 2, 3
If you refer to the simulation graph of
The minimum value of is equal to the BP point (FIG. 2). Next, Pn '=-((ΣP2'-ΣP1') is calculated from the table 2 to create the table 3 of Fig. 4. The conversion from the table 2 to the table 3 is based on the data accuracy (resolution) of the actual machine. This has the effect of averaging the fluctuations that occur, and the table 3 does not ramp up.The BP value is detected as the pressure value corresponding to the positive maximum value of the table 3, but actually the table 3 is moved to the right by 5 points. It is searched after shifting (Fig. 3).

Another point to note is that the pressure increase is initially set at a supply flow rate of 0.1 bar / min.
Further, when the graph is output, the negative values in Table 3 are not printed. Further, the 13 samples before the start of the test and before the end of the test are out of the range of the BP value because the before and after data necessary for calculation are not available. Furthermore, there are two conditions for ending the BP test. (1) The process ends when the maximum pressure is reached. And (2) 0.004 in 10 seconds
When the pressure rise rate falls below the bar, the sample is thirteen thundered and then finished (at the start of the test, the pressure rises at 0.016 bar / 10 seconds).

In the diffusion flow test mode, after the set pressure is reached, the output of the small flow rate controller keeps the set pressure constant by the proportional / integral control, so that the balance between the fluid supply amount and the diffusion flow amount can be accurately adjusted. I can keep it. For example, for large capacity filter housings and filters with high diffusion flow, increase the fluid supply
For small capacity filter housings and filters with low diffusion flow, pressure can be maintained by reducing the fluid supply. In the proportional control, the difference between the set pressure and the current pressure is proportionally amplified to control the fluid supply amount. Integral control is
It plays the role of preventing oscillation (data disturbance) due to proportional control,
The control amount is averaged. By combining these two types of control methods, the fluid supply amount will eventually converge,
It becomes equal to the fluid diffusion flow rate value, and that value is output.

The point of the control method of this combination is:
It is in the setting of each constant of proportionality and integral. As a demonstration, various experiments were conducted using different filter elements and housings (to investigate the effect of the volume difference), and it was confirmed that stable data could be obtained regardless of the diffusion flow rate value and changes due to the volume difference. However, the larger the volume of the filter housing, the longer it takes to converge the fluid supply amount. For very large volume filter housings, this can be addressed by changing the mass flow controller to a larger one. The point is that the convergence judgment is made when the control amount change within about 1 minute is within 1 cc / minute, and it is designed so as to prevent the involvement of other electrical accuracy, and the measurement error is made extremely small.

This method therefore eliminates the need for volume calculation or measurement of the filter housing altogether. The measured value is the absolute flow rate value (including system leak)
Can be measured as

In the bubble point test mode, similarly to the diffusion flow test mode, first, an appropriate amount of fluid is supplied by the large flow rate mass flow controller, and the pressure is increased by increasing the pressure by about 0.1 Kg / cm 2 per minute. Control so that a rising curve is obtained. Based on this, at the time of bubble point measurement, a fixed amount of fluid is supplied so as to make a minute pressure increase regardless of the volume of the casing. When the bubble point is reached, the amount of fluid passing through the membrane rapidly increases, and the rate of pressure increase per unit time decreases. By sampling this series of changes and the pressure rise curve from the start to the end of measurement at accurate time intervals, the change point of the pressure rise rate per unit time can be calculated. It has been confirmed by theory and experiment that the rate of pressure rise is perfectly proportional to the time when a constant amount of fluid is supplied to the primary side of the membrane filter by controlling the mass flow controller.

[0025]

According to the present invention, it is possible to obtain a membrane filter integrity tester capable of verifying the integrity of a membrane filter with high accuracy in the diffusion flow test mode and bubble point test mode.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a membrane filter integrity test apparatus according to the present invention.

FIG. 2 is a graph showing changes in values by the membrane filter integrity test apparatus of the present invention.

FIG. 3 is a graph showing changes in values by the membrane filter integrity test apparatus of the present invention.

FIG. 4 is a diagram illustrating a calculation method in the membrane filter integrity test apparatus of the present invention.

[Explanation of symbols]

 10 ... Inlet 12 ... Protective filter 14 ... Safety valve 16 ... Shutoff valve 18 ... Branch line 20 ... Branch line 22 ... Small flow controller 24 ... Mass flow controller 26 ... Shutoff valve 28 ... Shutoff valve 30 ... Confluence point 32 ... Outlet 34 ... Discharge pipe 36 ... Pressure sensor 38 ... Shutoff valve 40 ... Discharge port 42. ..Main control means

Claims (1)

[Claims] 1. A membrane filter integrity test apparatus for testing a membrane filter under test by sending fluid to the primary side of the membrane filter under test, which is capable of rapidly supplying a large amount of fluid to the primary side of the membrane filter. When the pressure on the primary side of the membrane filter reaches a predetermined level by the flow controller and the fluid supplied by this large flow controller, the operation of the large flow controller is stopped and at the same time a small flow rate of fluid is transferred to the primary side of the membrane filter. Small flow controller to supply,
Pressure detection means for detecting the pressure on the primary side of the membrane filter under test and generating a detection signal, and main control means for receiving the detection signal from the pressure detection means and proportionally / integrally controlling the small flow rate controller according to the value. Membrane filter integrity tester including and.