JPS627827B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention can be used for handling dangerous pathogens, genetic modification experiments, etc.
This invention relates to an exhaust device attached to a safety cabinet of a device for preventing accidents. Safety cabinets are used in medical research institutes and hospitals that handle dangerous pathogens such as internationally infectious diseases, genetic engineering research institutes that conduct gene recombination experiments, and pharmaceutical and chemical manufacturers. The safety cabinet consists of the main body of the safety cabinet,
and an exhaust device to maintain negative pressure inside the main body. Figure 1 shows an example of a safety cabinet body.
The entire structure including the exhaust system is shown in FIGS. 2 and 3. In FIG. 1, the safety cabinet is of a closed type, and consists of a main body case 1, a see-through window 3, a glove 10, a glove port 9, etc., and is placed and fixed on a leg 2. A filter case 12 to which an intake pipe having a gate valve 6 is attached, a filter case 12 to which an exhaust pipe 8 having a gate valve 7 is attached, and a lighting box 11 are attached to the upper part. A high performance filter 4 and a high performance filter 5 are housed in each filter case 12, respectively. Place dangerous biological materials, etc. inside the cabinet 13, and see through the transparent window 3.
Operate by putting your hand into the glove 10 while looking inside. Since there is not enough space for a single cabinet, the necessary number of single cabinets are often connected to form a multiplex system as shown in the figure. The cleanliness of the inside of the cabinet 13 is increased by a high-performance filter 4 on the air inlet side, and a high-performance filter 5 on the air outlet side prevents used biological materials from leaking to the outside. Note that the inside of the cabinet 13 is maintained at a negative pressure by utilizing the pressure loss of the high-performance filter caused by the exhaust, to prevent biological materials inside from leaking to the outside due to a defect in the main body case 1 or the like. FIG. 2 shows a conventional example. The safety cabinet main body 15 is provided in the installation chamber 14.
The supply and exhaust system of the safety cabinet body 15 and the supply and exhaust system of the safety cabinet body 15 are completely independent. In Figure 2, 1
6 is a blower, 17 is a high-performance filter, 18 is a blower, 19 is an intake pipe, 20 is an exhaust pipe, 21 is a high-performance filter, 22 is a movable valve, 23 is a movable valve, 24 is an exhaust fan, 25 is an exhaust fan, 26 is a high performance filter,
27 is a movable valve, 28 is a movable valve, 29 is an exhaust fan, 3
0 is an exhaust fan, and 31 is outside air. As is clear from the figure, two exhaust fans are provided for each system, so that they can be immediately switched to use in the event of a failure. FIG. 3 shows another conventional example. In this case, compared to the case shown in FIG. 2, the blower 18 to the safety cabinet main body 15 is omitted, and the air in the installation chamber 14 is sucked into the safety cabinet. Installation room 14 in both Figures 2 and 3
The pressure in the safety cabinet 15 is about -5 mmAq relative to the outside air 31, and the pressure inside the safety cabinet 15 is about -15 mmAq relative to the pressure in the installation chamber 14, that is, relative to the outside air 31.
It is set to be about 20mmAq. The most important thing in a safety cabinet is to prevent the release of dangerous biological materials (pathogens, viruses, etc.) inside the cabinet. For this reason, the following safety measures have been taken. (1) The main body of the safety cabinet shall be a sealed type. (2) Exhaust the air inside the safety cabinet to maintain negative pressure. (3) Exhaust air and supply air are treated with high-performance filters and discharged after being cleaned. The above-mentioned safety measures are also taken in the conventional examples shown in FIGS. 2 and 3, which are sufficient for normal operation, but there are problems when various failure factors are considered. The problem is related to the load control in item (2) above. In the conventional example, since the safety cabinet is built in a place where there are few earthquakes, no consideration is given to the fact that the safety cabinet main body may be destroyed by external force. However, in Japan, it is extremely dangerous unless safety measures are taken against destruction caused by earthquakes. As shown in Figure 1, safety cabinets are designed to connect many cabinets and use them as a closed type.
They are usually quite long, have little flexibility when the floor shakes during an earthquake, and are extremely likely to be destroyed. In the case of those shown in Figures 2 and 3,
Although a certain amount of exhaust gas is always pumped out to create a negative pressure inside the cabinet, this does not prevent cracks, holes, etc. from appearing in the transparent window 3 of the cabinet body, the main body case 1, etc., or the globe 10 being torn during an earthquake. etc., the pressure difference between the inside 13 and the outside of the cabinet is very small, and the amount of air sucked through cracks, holes, etc. is small, and it may not be possible to prevent the dangerous biological materials inside from spreading to the outside. . In this case, the problem can be solved by increasing the exhaust air volume from the beginning, but in the conventional examples shown in Figures 2 and 3, the safety cabinet and the air conditioning of the room where it is installed are From this point of view, it is an all-fresh system. These devices are normally operated continuously for safety reasons, but if the exhaust air volume is large from the beginning, a large amount of heating and cooling energy will be wasted, so it is necessary to suppress the exhaust to a minimum level. Therefore, as a way to improve safety in the event of an accident such as an earthquake and to save energy during normal operation, the exhaust air volume of the safety cabinet system is usually reduced.
Operate while maintaining negative pressure, and if any accident (destruction, crack, hole, etc.) occurs in the safety cabinet body, increase the exhaust capacity and exhaust air volume to ensure sufficient intake of air from the accident area. In addition, it is possible to prevent dangerous biological materials inside the cabinet from leaking out of the cabinet body. However, in this case, simply increasing the exhaust capacity causes various problems. That is, not all safety cabinet bodies are always used, and the number of cabinets used may change depending on the content of the experiment. In this case, if a blower with a fixed capacity is used, the following problems arise. (1) If all the cabinets are in use, there will be insufficient exhaust air, and sufficient air cannot be taken in from the accident cabinet. (2) If there are few cabinets in use and many gate valves 7 are closed, the air volume to the accident cabinet will be excessive, and in the worst case,
An excessive pressure difference is applied to the high-performance filter 5 of the safety cabinet, and there is a risk that the filter will be destroyed by exceeding the withstand pressure. To solve this problem, it is necessary to adjust the displacement according to the number of safety cabinets used. An object of the present invention is to provide an exhaust system for safety cabinets that has an exhaust control method that can maintain a constant negative pressure even when the number of safety cabinets in use changes, without damaging high-performance filters. There is something to do. The safety cabinet exhaust system according to the invention comprises:
An exhaust pipe is provided with an in-pipe pressure detection unit, a movable valve, and a pressure control unit, and in response to a signal from the detection unit, the control unit operates the movable valve and controls the air pressure in the exhaust pipe to a set pressure. This device is characterized by: In a preferred embodiment of the safety cabinet exhaust system according to the present invention, the pressure setting values are a normal setting value suitable for normal operation and a large emergency setting value of negative pressure to be used in case of a safety cabinet accident, The normal set value is manually or automatically switched to the emergency set value in response to a signal issued from a pressure detection section provided in the cabinet when the pressure within the cabinet exceeds a specified value. Hereinafter, the apparatus of the present invention will be explained based on drawings of embodiments. First, the basics of the apparatus of the present invention will be explained based on FIG. Figure 4a shows the safety cabinet in its normal condition. Since the safety cabinet is a closed type, only the exhaust air volume Q ₂ minutes is taken in, and the air volume Q ₂ = Q ₁ (intake air volume)
It is. Furthermore, since the same high-performance filters 4 and 5 are used, the pressure losses (PL ₁ , PL ₂ ) are the same, that is, PL ₁ =PL ₂ . Therefore, if the pressure P ₂ in the exhaust pipe 8 is set to -30 mmAq, for example, the pressure P ₁ inside the safety cabinet 13 becomes -15 mmAq. Figure 4b shows the safety cabinet in an accident condition. If there is a hole in the main body case due to damage to the glove or glass, there will naturally be no pressure loss at the hole compared to the high-performance filter 4, so
Q ₁ ≒0, and an air volume almost equal to the exhaust air volume is taken in from the accident area. This intake is shown in Figure 4b.
It is shown in Q ₃ . If the exhaust is a constant air volume,
Q ₂ =Q ₃ . As mentioned above, this air volume is
Since the amount is set to a small amount in order to prevent energy wastage in all-fresh air conditioning, the intake air speed in the accident area becomes slow, making it impossible to prevent the spread of dangerous biological materials inside the safety cabinet. For this purpose, constant pressure control is used that allows the pressure in the exhaust pipe to be set in two stages. In case of an accident, the pressure in the exhaust pipe is reduced to a large negative pressure as an emergency operation.
For example, switch to -45mmAq. Since the working pressure of high-performance filters is generally up to 50 mmAq, it is appropriate to set it to -45 mmAq even during emergency operation. Figure 4c shows the pressure loss characteristics of the high-performance filter with respect to air volume. In the case of FIG. 4b, Q ₁ ≈0, so the pressure inside the safety cabinet 13 is almost the same as that outside. Therefore, the entire pressure of the exhaust pipe 8 is applied to the high-performance filter 5, and PL ₁ ≒0,
PL ₂ ≒45mmAq. As shown in Figure 4c, 15mmAq during normal operation and 45mmAq during emergency operation.
, the air volume B at that time is approximately three times the air volume A during normal operation. Therefore, the exhaust air volume Q ₂ automatically becomes approximately three times as large, and Q ₂ ≒
Since Q ₃ , the intake air from the accident area also increases by about 3 times. Table 1 shows a table comparing the above-mentioned exemplary values during normal operation and emergency operation.

[Table] In this way, using two-stage switching constant pressure control instead of constant air volume control has a great effect on improving safety performance and saving energy during normal operation. The reason why the pressure inside the exhaust pipe during normal operation is -30 mmAq is because the Ministry of Education Notification No. 42 stipulates that the pressure inside the cabinet be -15 mmAq.
In addition, the reason for setting it to -45 mmAq during emergency operation is to protect the high performance filter as mentioned above. However, a feature of two-stage switching pressure control is that just by switching to a 1.5 times higher pressure in this way, the intake air volume increases approximately three times. Next, actual control examples in the apparatus of the present invention are shown in FIGS. 5 to 8. FIG. 5 shows an electrical control method using a pressure switch, and FIG. 6 shows its operating characteristics. In FIG. 5, according to this embodiment, a high-performance filter 21 and movable valves 22', 23' whose opening degree can be controlled are sequentially provided in the middle of an exhaust pipe 20 leading from inside the safety cabinet 1 to exhaust means 24, 25. Further, pressure detection means 32 and 33 are provided for detecting the pressure in the safety cabinet 1 or in the exhaust pipe 20 before reaching the high performance filter 21. Also, opening control means 50 and 5 control the opening of the movable valve 22' so that the outputs of the pressure detection units 32 to 35 are constant.
1 will be provided. To explain in more detail, 32 and 33
is a differential pressure switch for upper and lower limit switches for normal operation.
_L1 and differential pressure switch _L2 . Further, 34 and 35 are a differential pressure switch _H1 and a differential pressure switch _H2 , which are upper and lower limit switches for emergency operation. Which operation is to be performed is normally selected by the emergency changeover switch 38. The control means 50 and 51 are actuated by the upper and lower limit signals of these differential pressure switches, and the movable valve 22' or 23' operated by the motors 52 and 53 are varied to change the air volume and keep the pressure in the exhaust pipe constant. Control. Furthermore, there are two exhaust systems, which are selected by an exhaust system changeover switch 39. The operating characteristics are shown in Figure 6. First, during normal operation, if the pressure is within the upper and lower limits set by the differential pressure switches _L1 and _L2 , the movable valve 22' maintains a constant pressure at a constant opening. keep. If the pressure decreases for some reason, such as an increase or decrease in the number of cabinets used,
If the lower limit value _L1 is exceeded, the differential pressure switch will activate the control means 50.
works to increase the valve opening, returning the pressure to its original level and keeping it at a constant pressure. FIG. 6a shows the differential pressure characteristics of the normal cabinet. In addition, if an accident occurs in a cabinet as shown in Figure 6b, the pressure in that cabinet will be almost the same as that outside, so if the alarm set value set in the cabinet body is turned off, the alarm will cause the alarm to be activated manually or automatically. Switch to emergency operation. In case of emergency operation, the differential pressure switch
The opening of the movable valve increases until the pressure set by H ₁ and H ₂ is reached, maintaining a constant pressure for emergency operation.
Note that FIG. 6c is a diagram showing changes in the opening degree of the movable valve. Fig. 7 shows an example of a pneumatic control block diagram that uses air pressure, and Fig. 8 a, b, and c are its operating characteristic diagrams, corresponding to Fig. 6 a, b, and c. There is. In FIG. 7, 40 is a pressure detection section;
1 is a pressure regulator, 42 is a set pressure switching three-way solenoid valve, 43 is a three-way solenoid valve, 44 is a three-way solenoid valve, 45
and 46 are control valves with positioners. The operation is the same as the electric type described above, and is clear from the drawings, so the explanation will be omitted. In addition, Vcc
is the switching power supply for the solenoid valve, P and Q are valves 45 and 46
Powered air inflow pipe for movable. The apparatus of the present invention is constructed as described above, and can perform pressure control so that the internal pressure of the cabinet is always constant. Therefore, even if the number of safety cabinets in use changes, a constant negative pressure can always be maintained.

[Brief explanation of the drawing]

Figure 1a is a front view of the main body of the safety cabinet, Figure 1b is a sectional view of the same as above, Figures 2 and 3 are front views of different embodiments of the entire safety cabinet including the exhaust system, Figure 4a 4 and b are front views of the embodiment of the safety cabinet connected to the device of the present invention in normal and accident states, FIG. Figures 6 a to c are diagrams explaining the operating characteristics of the apparatus of Figure 5, and Figure 7 is an exhaust system diagram of an embodiment of the apparatus of the present invention using an electric control system. Exhaust system diagrams of the embodiment, FIGS. 8a to 8c, are diagrams for explaining the operating characteristics of the apparatus shown in FIG. 7. 1...Main body case, 3...See-through window, 4...High performance filter A, 5...High performance filter B, 8...
Exhaust pipe, 10...Glove, 13...Inside the cabinet, 14...Installation room, 15...Safety cabinet body, 17, 21, 26...High performance filter, 22, 23, 27, 28...Movable valve, 32,
33, 34, 35...Differential pressure switch of pressure detection section, 38...Normal emergency switching switch, 39...Exhaust device switching switch, 40...Pressure detection section, 41
. . . Pressure regulator, 50, 51 . . . Control means.

Claims (1)

[Claims] 1. A high-performance filter and a movable valve whose opening can be controlled are sequentially installed in the middle of the exhaust pipe leading from the inside of the safety cabinet to the exhaust means, and a portion of the inside of the cabinet or the exhaust pipe before reaching the high-performance filter is A pressure detection means for detecting pressure, and an opening control means for controlling the opening of the movable valve so that the output of the pressure detection section is constant based on the output of the detection section. Safety cabinet exhaust system.