Principle of Pulsating Vacuum Sterilization
Principle of Pulsating Vacuum Sterilization
1. The working principle of pulsating vacuum sterilizer
The pulsation vacuum sterilizer is a method of using saturated steam as the sterilization medium and applying instruments to force the pulsating vacuum air out. After several times of vacuuming and several times of steam injection, the sterilization chamber meets the defined vacuum degree. Then, the saturated steam is filled in to meet the specified pressure saturation to better sterilize the sterilized material, which mainly includes two periods of pulsating vacuum and pre-vacuum.
Pulsating vacuum is to vacuum the sterilization chamber several times. After one vacuum is completed, a certain amount of steam is put into the sterilizer to fuse the remaining air and steam to satisfy a certain amount of steam, and then vacuum is performed Work, enter the steam sterilization mode after several times of vacuuming Z.
Pre-vacuum refers to a method in which high-pressure steam sterilization implements a vacuum once before entering the steam in the sterilization chamber, removes the air in the sterilization chamber as much as possible, and then merges into the steam for sterilization.
The basic principle of pulsation vacuum sterilization is to use the negative pressure generated by the vacuum pump to extract the cold air in the sterilization chamber, and then input the saturated steam to implement the sterilization work. Vacuum drying is the last procedure of Z.
The complete engineering procedure is: preparation-pulsation-heating-sterilization-steam exhaust-drying and completion.
2. The basic principle of pulsating vacuum sterilization
The basic principle of pulsating vacuum sterilization is that after the microorganisms are subjected to heat, the movement of protein molecules will accelerate and collide with each other, so that the bond connecting the peptide chain will be broken, and the molecules will be transformed from a regular tight structure to disorder. With the scattered structure, a large number of hydrophobic groups will be exposed on the surface of the molecule, and they will merge into a very large polymer to precipitate and solidify, that is, by irreversibly destroying structural proteins and enzymes to achieve the purpose of killing microorganisms.
Factors affecting the sterilization effect
1. Physical/chemical conditions
Various environmental factors in the process of bacterial spore formation will affect the heat resistance of the spores. For example, when the temperature is higher and there are divalent cations (such as Ca2+, Fe2+, Mg2+, Mn2+), the heat resistance of spores is enhanced. In contrast, when the pH exceeds the range of 6.0 to 8.0, or when spores are formed in high-concentration salt water or phosphate, the heat resistance decreases.
The heat resistance of spores in nature is related to environmental conditions, such as solution concentration, moisture (relative equilibrium humidity), pH, physical factors that can damage spores, and chemicals that have YZ effects on spores, etc., all of which will affect the spores Heat resistance.
The heat resistance of spores encapsulated in crystals or organic matter is usually significantly higher than that of non-occluded spores. Therefore, when the soil-occupied spores and the spores isolated and cultured from the soil are sterilized at the same time under a certain temperature condition, in order to obtain the same sterilization effect, the sterilization time required for the former at the same sterilization temperature It is more than ten times higher than the latter.
Since the sterilized product is contaminated by spores in the soil, such as contamination caused by unfiltered air particles during transportation, or contamination by personnel or other objects, it will be difficult to completely kill the spores. Because of this, GMP requires all necessary measures to be taken to prevent pollution.
2. Relative humidity
In heat sterilization, water plays an important role in killing bacterial spores. There are only two sterilization methods related to water: moist heat and dry heat. When the humidity reaches saturation [relative humidity (RH) is (or aw=1.0)], the sterilization method is called moist heat sterilization; the sterilization method under the condition of lower relative humidity is collectively called dry heat sterilization.
Experimental data shows that when the temperature is between 90 and 125℃ and the relative humidity is between 20% and 50%, the bacterial spores are more difficult to kill; when the relative humidity is higher than 50% or lower than 20%, it is easier to kill. This has guiding significance for the selection of sterilization conditions.
3. Exposure time
During the sterilization process, the death (killing) of prokaryotic cells follows the rule of first order reaction. The relationship between temperature and the logarithm of spore survival at a certain time is linear in many cases.
That is to say, at a specific sterilization temperature, the death of spores at any time is only related to the concentration of spores at that time, and the time required to decrease the number of spores by one logarithmic unit is not affected by the original concentration of spores.
Structure composition and workflow
1. Structure composition
The pulsating vacuum sterilizer is mainly composed of the sterilizer main body, sealed door, disinfection vehicle, transport vehicle, piping system and control system.
The pulsation vacuum sterilizer uses saturated water vapor as the sterilization medium, and adopts the air removal method of mechanical forced pulsation vacuum. After multiple vacuuming and multiple injections of steam alternately, the sterilization chamber reaches a certain degree of vacuum and then refills. Enter saturated steam, reach the set pressure and temperature, and after a certain duration, achieve the purpose of sterilizing the sterilized material.
2. Work flow
A complete workflow includes: preparation, pulsation, heating, sterilization, exhaust, drying, and 7 processes. The schematic diagram of the pipeline, see the figure below.
When the steam source, water source, compressed air, etc. are normal and open, the equipment will automatically open the air inlet valve F1 after it is powered on, and air into the sterilizer mezzanine through the air inlet pressure reducing valve. The pressure in the mezzanine is controlled by the pressure controller. YK control is generally around 0.22MPa. When the set pressure is reached, F1 closes and starts again and again. At this time, the sandwich steam trap starts to work, drains the condensed water in the sandwich, and preheats the interior of the equipment, and the equipment is in a ready state. After placing the sterilized items, push the sterilizer into the sterilizer and close the sealed door of the sterilizer.
According to the program set by the control panel, first enter the pulsation process, generally set to vacuum 3 times. The F3 pneumatic valve is opened, the F6 and F7 water valves are opened, the vacuum pump runs, and the air in the inner chamber is drawn through the condenser until the set negative pressure value (usually -80kPa). At this time, F3, F6, F7, and vacuum pumps are closed, and the intake valve of the F2 inner chamber is opened, and saturated steam is charged from the mezzanine to the inner chamber. When the set pressure upper limit is reached, F2 is automatically closed, and the inner chamber is vacuumed again. , Repeatedly, until the set number of pulses is completed.
Then enter the heating stage, F3, F6, F7, vacuum pumps are all closed, F2 is opened, steam is injected into the inner chamber, and the temperature of the inner chamber is gradually increased. When the pressure in the inner chamber reaches the limit value, F2 is automatically closed; when the pressure in the inner chamber is less than or equal to When the pressure limit value, F2 automatically opens.
When the temperature of the inner room rises to the set sterilization temperature (132～134℃), it will enter the sterilization stage. The temperature should be maintained above the set temperature, the deviation generally does not exceed ±1℃, and the sterilization time is generally about 6-10 minutes. The pressure of the inner chamber is above 0.258MPa. At this time, the F1, F2, and F5 valves will open and close intermittently.
When the sterilization set time is reached, the sterilization ends, the F3 and F7 valves are opened first and enters the exhaust phase. When the pressure in the inner chamber drops to 30kPa, the F6 valve opens, and the vacuum pump is energized to run to vacuum the inner chamber and enter the drying stage. After the drying is completed, the entire sterilization cycle ends, and the equipment beeps. At this time, the sealed door can be opened and the sterilized items can be taken out.
