Microorganisms heat tolerance is different since the various species of itself.Therefore, for the sterilized item’s required time of the sterilization temperature and action time is different according to the contamination degree of sterilized items.And the selection of sterilization temperature and action time depend on sterilization method,item performance,packing material,length of required sterilization process.Generally speaking, the higher the sterilization temperature is, the shorter the time is required. The temperature of saturated steam and its pressure are in a constant relationship.However, when the air in the chamber is not eliminated or completely eliminated, the steam cannot reach saturation. At this time, although the pressure gauge shows that it has reached the sterilization pressure, the steam temperature does not meet the requirements, resulting in the failure of sterilization.
Saturated steam must be satisfied dry(containing moisture <5%> and pure (containing cold air <3.5%>), superheat degree should not exceed 5℃, because saturated steam condenses and releases a lot of latent heat energy, making the item’s temperature rising.At the same time of condensation, its volume shrinks rapidly (1/1600), and it can also generate local negative pressure, which makes the subsequent steam penetrate into the depth of the item. For the superheated steam, on the one hand, the condensation slows down, which is not good for sterilization. This phenomenon is obvious when the superheated steam is above 5℃.In addition, overheating of the steam can lead to items rapid aging.Gas transmission system or the prescribed pressure dropped obviously, the temperature in the jacket is higher or textile is too dry will cause the the production of superheated steam.When steam contains more fine fog, it forms a gas flow barrier and prevents hot penetration, and also increases the difficulty of drying after sterilization.The presence of fog particles is mainly caused by surface blisters and cracks in the boiler with excessive water, which are taken out by rapid steam, or the steam condenses through longer pipes.When steam is mixed with air, the relationship between pressure and temperature is somewhat different from that of saturated steam. At this time, the pressure value shown in the pressure gauge should deduct the partial pressure of air, the sterilization temperature at which it can reach will decrease correspondingly. If this is not paid attention to, the sterilization will fail because the sterilization temperature is not reached.Gas transmission system, the original air in the chamber or the air inside the sterilized articles is not removed will cause the air mixed into the steam.The existence of the air is also because the air is compressed by steam to form air mass, which prevents the steam from contacting with the sterilized articles, thus affecting the penetration of steam into the interior of the sterilized articles, forming a situation of low temperature inside the bag and uneven temperature outside the bag, resulting in the internal sterilization temperature cannot be reached;At the same time, The moisture content of gas in sterilization chamber is reduced due to the presence of air, The decrease of humidity level is not conducive to killing microbicides.