JP4883463B2 - Steam sterilizer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an operation control method for a steam sterilizer.
[0002]
[Prior art]
In the steam sterilization apparatus, sterilization steam is supplied into the sterilization tank, and the sterilization process is performed on the sterilization object by the heat of the sterilization steam. In addition, when performing supply control of sterilization steam during sterilization, the temperature in the sterilization tank is usually detected, and supply control of sterilization steam is performed based on the detected temperature. In a large-sized steam sterilization apparatus that needs to be controlled with higher accuracy, the pressure in the sterilization tank is detected, and the supply control of the sterilization steam is performed based on the detected pressure. This is because the pressure sensor can detect with higher accuracy among the temperature sensor and the pressure sensor generally used in the steam sterilization apparatus.
[0003]
By the way, in the steam sterilization apparatus, it is necessary to supply a sterilization steam that does not contain much non-condensable gas such as air (for example, in the European standard EN285, the non-condensable gas concentration is 3. 5% (volume ratio) is determined to be less than 5%.) When steam containing a large amount of non-condensable gas is used as sterilization steam, the pressure in the sterilization tank is maintained at a predetermined value. The temperature of the object to be sterilized does not rise sufficiently and may cause sterilization failure. Therefore, in the large-scale steam sterilization apparatus that controls the supply of sterilization steam based on the pressure in the sterilization tank, the temperature in the sterilization tank is detected only at one location as a representative temperature, and thus is not condensed. Even if the sterilization temperature is lowered due to the mixing of the property gas, it is difficult to reliably detect the sterilization temperature, and a countermeasure for preventing the sterilization failure has been demanded.
[0004]
[Problems to be solved by the invention]
The problem to be solved by the present invention is to prevent poor sterilization in a steam sterilization apparatus that controls the supply of steam for sterilization based on the pressure in the sterilization tank.
[0005]
[Means for Solving the Problems]
This invention was made in order to solve the said subject, and invention of Claim 1 was provided in the pressure sensor which detects the pressure in a sterilization tank, and the said sterilization tank lower part or the vapor | steam discharge port vicinity. A temperature sensor, a steam supply valve that supplies sterilization steam from the steam supply line into the sterilization tank, and the steam supply valve is controlled based on the detected pressure of the pressure sensor and maintained at a predetermined pressure for sterilization. A controller for performing a saturation steam temperature (first temperature) A calculated based on a pressure detected by the pressure sensor and a second temperature B detected by the temperature sensor during sterilization. In comparison, the sterilization time is extended based on the lower one of the saturated steam temperature (first temperature) A and the second temperature B.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Next, an embodiment of the present invention will be described. The steam sterilization apparatus according to the present invention includes a sterilization tank, and a pressure sensor is provided in the sterilization tank, and the supply of sterilization steam is controlled based on the pressure in the sterilization tank detected by the pressure sensor. It has become. That is, by controlling opening and closing of the steam supply valve connected to the sterilization tank, the pressure in the sterilization tank is maintained at a predetermined pressure set in advance. This set pressure is a saturated steam pressure corresponding to a predetermined sterilization temperature.
[0008]
Further, the sterilization tank is provided with a temperature sensor, and detects the temperature in the sterilization tank. And at the time of sterilization, the first temperature calculated based on the pressure in the sterilization tank is compared with the second temperature in the sterilization tank detected by the temperature sensor, and the first temperature and the second temperature are compared. Control for adjusting the sterilization time based on the lower temperature is performed.
[0009]
If the entire sterilization tank is filled with saturated steam as sterilization steam, the first temperature and the second temperature are equal. However, if a non-condensable gas such as air is mixed, a temperature difference occurs between the first temperature and the second temperature according to the amount of the mixed gas, and usually the second temperature is the first temperature. Lower than temperature. Therefore, if the temperature difference between the first temperature and the second temperature is equal to or less than a predetermined value, the amount of non-condensable gas mixed is determined to be small, and sterilization control is continued, but in order to prevent poor sterilization The above control is performed. For example, when the second temperature is lower, the sterilization time is extended according to the value of the second temperature. At this time, there is no change in the supply control of the sterilization steam, and as described above, it is performed based on the pressure in the sterilization tank.
[0010]
Here, most of the air is mixed as a non-condensable gas, and the air tends to accumulate at the bottom of the sterilization tank due to the specific gravity. Therefore, when the amount of air mixed in increases, the temperature at the bottom of the sterilization tank decreases. Therefore, in order to accurately detect air contamination, the temperature sensor is provided in the lower part of the sterilization tank (preferably near the bottom steam outlet).
[0011]
Further, in the sterilization apparatus, when the temperature difference between the first temperature and the second temperature exceeds the predetermined value, the following control is performed. The lower temperature in the sterilization tank is detected as the second temperature, and the upper temperature in the sterilization tank is detected as the third temperature. And said 1st temperature, said 2nd temperature, and said 3rd temperature are compared, respectively, and the following control is performed based on this comparison result.
[0012]
That is, when the first temperature and the third temperature are equal and the second temperature is lower than the predetermined value above these temperatures, it is determined that the amount of non-condensable gas mixed in exceeds the allowable amount. Thus, the control corresponding to the mixing of the non-condensable gas is performed. As the corresponding control, a control is performed to discharge the non-condensable gas in the sterilization tank or the sterilization control is stopped to issue an alarm. In the non-condensable gas discharge control, if the temperature difference between the first temperature and the second temperature is equal to or less than the predetermined value, the non-condensable gas discharge control is terminated and the process proceeds to sterilization. . Further, when the second temperature and the third temperature are equal and the difference between these temperatures and the first temperature exceeds the predetermined value, it is determined that an abnormality has occurred in the pressure sensor. The sterilization steam supply control based on the pressure in the sterilization tank is changed to the sterilization steam supply control based on the second temperature or the third temperature. Here, the two controls of the non-condensable gas mixture control and the sterilization steam supply change control are preferably both performed. However, only one of them may be configured.
[0013]
As described above, according to the above configuration, even in the steam sterilization apparatus that controls the supply of sterilization steam based on the pressure in the sterilization tank, it is possible to prevent sterilization failure and perform reliable sterilization processing. Further, when the amount of non-condensable gas mixed in increases, it is possible to determine this and take measures such as discharging the non-condensable gas. Furthermore, the abnormality of the pressure sensor can be determined, and the control content can be changed and the sterilization process can be continued even when an abnormality occurs in the pressure sensor.
[0014]
【Example】
Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings. In FIG. 1, the steam sterilization apparatus in this invention is provided with the sterilization tank 1, and is provided with the door 2 which opens and closes the front opening part (code | symbol abbreviation) of this sterilization tank 1. In FIG. A steam supply line 3 for supplying sterilization steam is connected to the rear surface of the sterilization tank 1, and a steam supply valve 4 is provided in the steam supply line 3. Therefore, the supply of sterilization steam into the sterilization tank 1 is controlled by controlling the opening and closing of the steam supply valve 4. Further, a heating means (not shown) is provided on the peripheral wall of the sterilization tank 1, and the sterilization tank 1 is heated from the outside. The heating means has a jacket structure or a heating tube structure, and heating steam is supplied to the inside.
[0015]
A first discharge line 5 is connected to the bottom surface of the sterilization tank 1, and a steam trap 6 is provided in the first discharge line 5. A second discharge line 7 is branched from the upstream side of the steam trap 6 in the first discharge line 5, and a discharge valve 8 is provided in the second discharge line 7.
[0016]
Further, a pressure sensor 9 and a first temperature sensor 10 are provided on the top surface of the sterilization tank 1, and a second temperature sensor 11 is provided on the lower rear surface of the sterilization tank 1. The pressure sensor 9 detects the pressure in the sterilization tank 1. The first temperature sensor 10 detects the temperature of the upper part in the sterilization tank 1, while the second temperature sensor 11 detects the temperature of the lower part in the sterilization tank 1. Here, the detection end (reference numeral omitted) of the second temperature sensor 11 is arranged in the vicinity of the discharge port (reference numeral omitted) provided at the upstream end of the first discharge line 5. This is because non-condensable gas such as air tends to accumulate in the vicinity of the discharge port, and the presence or absence of non-condensable gas can be accurately determined by detecting the temperature in the vicinity of the discharge port. .
[0017]
Further, the steam supply valve 4, the discharge valve 8, the pressure sensor 9, the first temperature sensor 10 and the second temperature sensor 11 are connected to the controller 12 by signal lines (reference numerals omitted), respectively. . The sterilization control including opening and closing of the steam supply valve 4 and the discharge valve 8 is performed according to a preset program.
[0018]
Next, the operation of the above configuration will be described. In the above configuration, an object to be sterilized (not shown) is accommodated in the sterilization tank 1, the door 2 is closed, and the sterilization process of the object to be sterilized is performed. In the sterilization process, first, the discharge valve 8 is opened, and the air in the sterilization tank 1 is discharged. The air is discharged by opening the steam supply valve 4 to supply steam and pushing out the air by the steam. Further, a vacuum pump (not shown) may be provided in the second discharge line 7 and suction may be performed by this vacuum pump.
[0019]
Then, after the discharge of air in the sterilization tank 1 is completed, the discharge valve 8 is closed, sterilization steam is supplied through the steam supply line 3, and the sterilization tank 1 is filled with sterilization steam. Put it in a state. When supplying the sterilization steam, the steam supply valve 4 is controlled to open and close based on the pressure in the sterilization tank 1 detected by the pressure sensor 9, and the pressure in the sterilization tank 1 is set to a predetermined value. The pressure is maintained. For example, when the sterilization temperature is set to 135 ° C., the pressure in the sterilization tank 1 is maintained at 0.216 MPa.
[0020]
At the time of sterilization, the first temperature A is calculated based on the pressure in the sterilization tank 1 by the pressure sensor 9, and the second temperature sensor 11 sets the second temperature B to the lower part in the sterilization tank 1. The temperature is detected, and the first temperature sensor 10 detects the upper temperature in the sterilization tank 1 as the third temperature C. Here, when calculating the first temperature A, an Antoine equation (an empirical relationship between vapor pressure and temperature) is used. And these 1st temperature A, 2nd temperature B, and 3rd temperature C are compared, respectively, and the following control is performed at the time of sterilization.
[0021]
Hereinafter, the specific content of control is demonstrated based on FIG. First, in step S1, the temperatures A, B, and C are compared. In step S2, it is determined whether or not the difference between the first temperature A and the second temperature B is a predetermined value (for example, 4 ° C.) or less. If it is equal to or less than the predetermined value, the process proceeds to step S3, and control is performed to adjust the sterilization time based on the lower one of the first temperature A and the second temperature B.
[0022]
Here, when the inside of the sterilization tank 1 is filled with saturated steam as sterilization steam, the first temperature A and the second temperature B are equal. However, when a non-condensable gas such as air is mixed, a temperature difference is generated between the first temperature A and the second temperature B according to the mixed amount. Normally, air is the majority of the non-condensable gas, so that the non-condensable gas accumulates at the bottom of the sterilization tank 1 and the second temperature B becomes lower than the first temperature A. Therefore, when the temperature difference between the first temperature A and the second temperature B is equal to or less than the predetermined value, it is determined that the amount of non-condensable gas mixed is small, and sterilization control is continued. In order to prevent poor sterilization, the above control is performed.
[0023]
For example, when the sterilization temperature is set to 135 ° C., the pressure in the sterilization tank 1 is maintained at 0.216 MPa, and the sterilization time is automatically set to 3 minutes. At this time, the first temperature A is calculated as 135 ° C. based on the Antoine equation. And if said 2nd temperature B is 132 degreeC by mixing of noncondensable gas, based on the value of the lower 132 degreeC, sterilization time will be automatically extended to 5 minutes. It has become. Further, even after the sterilization time is extended, the supply control of the sterilization steam is performed so that the pressure in the sterilization tank 1 is maintained at 0.216 MPa as described above.
[0024]
If it is determined in step S2 that the difference between the first temperature A and the second temperature B is not less than or equal to the predetermined value, the process proceeds to step S4, where the first temperature A and the third temperature It is determined whether C is equal and the second temperature B is lower than the predetermined values A and C by more than the predetermined value. When this determination condition is satisfied, it is determined that the amount of the non-condensable gas mixed exceeds the allowable amount, the process proceeds to step S5, and the control for discharging the non-condensable gas in the sterilization tank 1 is performed. Specifically, with the steam supply valve 4 closed, the discharge valve 8 is opened to discharge non-condensable gas. Next, the discharge valve 8 is closed and the steam supply valve 4 is opened to generate steam. Supplying and pressurizing the inside of the sterilization tank 1, and repeating these discharge and pressurization alternately a plurality of times. And if the temperature difference of said 1st temperature A and said 2nd temperature B becomes below the said predetermined value, the discharge control of noncondensable gas will be complete | finished and it transfers to a sterilization process (illustration omitted). Therefore, in this step 5, it is possible to reliably detect that the mixing amount of the non-condensable gas exceeds the allowable amount, and it is possible to continue the sterilization control by discharging the non-condensable gas. It has become.
[0025]
On the other hand, if the determination condition is not satisfied in step S4, the process proceeds to step S6, where the second temperature B and the third temperature C are equal, and the difference between these temperatures B, C and the first temperature A is the same. Is determined to exceed the predetermined value. When this determination condition is satisfied, it is determined that an abnormality has occurred in the pressure sensor 9, the process proceeds to step S 7, and the second temperature is controlled from the supply control of the sterilization steam based on the pressure in the sterilization tank 1. B or supply control of sterilization steam based on the third temperature C is changed. Therefore, the abnormality of the pressure sensor 9 can be detected with certainty, and when the abnormality occurs in the pressure sensor 9, the sterilization process can be continued by changing to the supply control of the sterilization steam according to the temperature. This is effective in practical use.
[0026]
Further, when the determination condition is not satisfied in step S6, the process proceeds to step S8, where it is determined that some abnormality has occurred in any of the devices, and an alarm to that effect is issued.
[0027]
Next, another embodiment will be described. In the embodiment, in step S5 shown in FIG. 2, the discharge control of the non-condensable gas is performed. Instead, the sterilization control is performed. It is also possible to perform control to stop and issue an alarm to that effect.
[0028]
【Effect of the invention】
According to the first aspect of the present invention, even in the steam sterilization apparatus that controls the supply of sterilization steam based on the pressure in the sterilization tank, it is possible to prevent sterilization failure and perform reliable sterilization processing.
[0029]
According to the second aspect of the present invention, when the amount of the non-condensable gas mixed in increases, it can be determined to take measures such as discharging the non-condensable gas. The abnormality of the pressure sensor can be determined, and even when an abnormality occurs in the pressure sensor, the control content can be changed and the sterilization process can be continued, which is practically effective.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing an embodiment of a steam sterilization apparatus according to the present invention.
FIG. 2 is a flow explanatory diagram showing an embodiment of an operation control method according to the present invention.
[Explanation of symbols]
1 Sterilization tank A First temperature B Second temperature C Third temperature

Claims (1)

A pressure sensor for detecting the pressure in the sterilization tank, a temperature sensor provided in the lower part of the sterilization tank or in the vicinity of the steam outlet, a steam supply valve for supplying sterilization steam from the steam supply line to the sterilization tank, A controller for controlling the steam supply valve based on the detected pressure of the pressure sensor to maintain a predetermined pressure and sterilizing,
The controller compares the saturated steam temperature (first temperature) A calculated based on the detected pressure of the pressure sensor with the second temperature B detected by the temperature sensor during sterilization, and the saturated steam temperature (First temperature) A steam sterilization apparatus that extends the sterilization time based on the lower one of A and the second temperature B.

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