Heat penetration

Molds can be of any shape and can include corrugated or rib constructions to increase their stability and stiffness (large, flat walls can be difficult if not impossible). The thickness of their walls is limited to allow heat penetration. 

The relationship between temperature and pressure holds true only in the presence of pure steam adulteration with air contributes to a partial pressure but not to the temperature of the steam. Thus, in the presence of air the temperature achieved will reflect the contribution made by the steam and will be lower than that normally attributed to the total pressure recorded. Addition of further steam will raise the temperature but residual air surrounding articles may delay heat penetration or, if a large amount of air is present, it may collect at the bottom of the sterilizer, completely altering the temperature profile of the sterilizer chamber. It is for these reasons that efficient air removal is a major aim in the design and operation of a boiler-fed steam sterilizer. 

In the case of heat sterilization processes, the supporting data required include heat distribution and heat penetration studies (usually at least three runs at the minimum process parameters), with calculation of... 

In the vulcanisation of thick rubber articles the temperature may be stepped up in stages to ensure adequate heat penetration to the interior before the external surface begins to cure. Such a cure schedule is termed a step cure. Step post cures are used with thick section rubber articles to ensure that volatiles are released gradually without causing damage, such as porosity, due to an over rapid release. 

Design practices stem from standard fire test procedures in which the temperature history of the test furnace is regarded as an index of the destructive potential of a fire. Thus, the practice of describing the expected effects and damage mechanism is based on temperature histories. This standard design practice is convenient but lacks accuracy in terms of structural performance. The severity of a fire should address the expected intensity of the heat flux that will impact the structure and the duration of heat penetration. A simple analysis of the expect nature of an unwanted fire can be based on the heats of combustion and pyrolysis of the principal contents in the facility. The heat of combustion will identify the destructive nature of the fire, while the heat of pyrolysis will identify the severity of the fire within the compartment itself and will also identify the destructive potential of the fire in adjacent spaces. 

The care of microfiber products is similar to that of the normal fiber materials made from the same polymer. One caution is heat sensitivity. Because the fibers are so fine, heat penetrates easily causing them to scorch or glaze more quickly than normal fibers if too much heat is applied or heat is applied over too long a period. Typically, microfibers are wrinkle-resistant, but if ironing is done, it should be accomplished using lower temperatures and only as directed. 

Prior to initiating loaded chamber heat penetration studies, a container mapping study should be conducted. The intent of this study is to determine the coolest point within a liquid-filled container. 

In subsequent loaded chamber heat penetration studies, penetration thermocouples should be positioned within the container at the previously determined cold spot. The temperature profile of the container should remain constant among different sterilizing chambers, utilizing steam heat as the sterilizing medium. 

Loaded Chamber Heat Penetration Study — Load Cool Point... 

Load cool points are dependent on load conhgurations and the types of items that comprise the load (liquid-hlled containers, process equipment, etc.). Prior to conducting heat penetration studies, maximum and minimum load conhgurations must be established. The penetration thermocouples are positioned within liquid-hlled containers at the cool point previously determined by container mapping studies. The probed containers should be distributed uniformly throughout the load. When the load consists of multiple layers or pallets, a sufficient number of thermo-couple-probed containers should be employed to provide an equal representation among layers. 

Heat penetration studies conducted on maximum and minimum loads should be repeated until temperature data are obtained for all representative areas of the load. It may be necessary to reposition thermocouples in order to study different areas. Several runs, usually three of each thermocouple conhguration, will provide conhdence in the repeatability of the temperature prohle. 

A heat penetration study dehning load cool points is not limited to load conhgurations composed of liquid-hlled vials. The same principles can be applied to process equipment loads (hlters, hoses, etc.) subject to steam sterilization. Penetration thermocouples are positioned at points within the process equipment suspected to be the most difficult for steam heat penetration. Temperature data are obtained from representative maximum and minimum loads in order to establish temperature prohles... 

Heat penetration studies are also employed to determine points within a load configuration that achieve higher temperatures and consequently greater Fq values. The temperature data obtained may be significant when heatable products are involved in the sterilization process and the potential for product degradation exists. The cool points established for a specified load and configuration will eventually be utilized to control the exposure time in subsequent routine production runs. The temperature sensors that control sterilization-cycle-exposure time at process temperature may be positioned within the load at the previously detected cool point. Consequently the entire load is exposed to sufficient heat lethality and achieves the desired Fq value. 

Lethal rates can be determined from the temperature data obtained from the heat penetration studies. The temperature data are converted by the following formula ... 

Biological castles are employed during heat penetration situations in order to demonstrate the degree of process lethality provided by the sterilization cycle. Calibrated biological indicators utilized for this purpose function as bioburden models providing data that can be utilized to calculate Fq or substantiate and supplement physical temperature measurements obtained from thermocouples. 

The sterilization test functions required to qualify or validate the sterilizer will include process heat distribution, process heat penetration, and process microbial and depyrogenation validation, as applicable. 

Heat penetration runs may be conducted in conjunction with required heat distribution mns. 

Each heat penetration run shall include thermocouple temperature sensor probe containers distributed throughout the tunnel, per planned and traceable location diagram. 

The number of heat penetration test containers per run shall agree with that required for heat distribution thermocouples. 

The heat penetration sample containers shall be loaded into the tunnel carrier in an orientation consistent with planned production run loading and the corresponding container heat mapping study loading method. 

All heat penetration data collected during each run must meet the requirements for the corresponding specification. 

Heat penetration test containers of corresponding container size and type and fill volume shall be placed adjacent to the challenge test items in each mn. 

Autoclave (Steam Sterilizer) Heat Penetration Study of Once in a year ... 

Note 1 Separate study should be performed for different loads/sizes. Note 2 Heat penetration and pyrogen test should be performed at beginning, middle, and end of the operations. 

The production operating ranges/windows established from the heat penetration runs must assure all products in the test mns will meet the calculated requirement for the corresponding specification. 

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