Autoclave Sterilizers: A Comprehensive Guide to Construction and Operation

Autoclaves, an indispensable device in medical facilities and medical research laboratories, have a complex structure but are highly effective. Let's explore in detail the construction of autoclaves and their operating principles.

I. Sterilization Methods

Before delving into the construction of autoclaves, it is essential to understand the common sterilization methods available today. These methods include:

1. Dry Heat Sterilization: Used for sterilizing non-flammable tools, often glassware, test tubes, pipettes, Petri dishes, etc. Dry heat is suitable for sterilizing some glass and metal items. The process involves maintaining a temperature of 170°C for 2 hours or 180°C for 1 hour to eliminate all bacteria and spores. Sterilized dry heat tools can be used for up to 7 days, after which they need to be re-sterilized.

2. Chemical Sterilization: Immersion in a 2% glutaraldehyde solution, avoiding 5% chlorine solutions. Immerse items for 10 hours; after removing them, rinse with sterilized water and store in a sterilized metal container with a labeled lid, including the date and name of the person who performed the sterilization. For items that do not require complete sterilization, a 20-minute immersion to achieve high-level disinfection is sufficient.

3. Wet Heat Sterilization: This is the most common and suitable method for sterilizing all laboratory tools. It is non-toxic, cost-effective, kills spores, and is time-efficient. Sterilization time depends on the temperature and pressure of the autoclave process. This method is widely used in hospitals, laboratories, and medical facilities to sterilize metal tools, rubber, plastics, bandages, environments, chemicals, etc. The temperature is maintained at 110-121°C for 30 minutes, corresponding to a pressure of 1-1.2 atmospheres, effectively eliminating all bacteria and spores. This process is carried out using a specialized device called an autoclave.

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Autoclave Sterilizers

Over 100 years ago, French and German microbiologists used autoclaves as essential equipment in their laboratories. Autoclaves sterilize most bacterial spores at 121°C for 15 minutes, with some special cases requiring 30 minutes. Autoclaves are used in hospitals and laboratories to sterilize bed linens, equipment, etc. Laboratory technicians use them to sterilize microbial culture media and eliminate pathogenic microorganisms. Autoclaves should not be used for certain plastic materials that may melt at high temperatures or deform. The optimal sterilization time depends on the material type, so individual sterilization may be necessary when required.

Sterilized items should be used within 3 days; closed containers or test tubes can be kept sterile for up to one week.

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II. Detailed Construction of Autoclaves

1. Sterilization Chamber

   • Material: Typically made of stainless steel, ensuring durability and the ability to withstand high temperatures and pressures during sterilization.
   • Design: Cylindrical shape, capable of withstanding high pressure.
   • Function: Contains the items to be sterilized and withstands high pressure during the process.

2. Heating System

   • Material: Uses insulated heating elements, often covered with copper or chrome-plated stainless steel.
   • Function: Maintains the necessary temperature for the sterilization process.

1. Pressure Control System

   • Design: Includes copper tubes and electromagnetic valves.
   • Function: Controls and adjusts the pressure inside the sterilization chamber to ensure effective and safe sterilization.

2. Safety System​

See More:

• Function: Includes temperature, pressure, and water level sensors to ensure safety during use.
• How Autoclaves Work
• Industrial Autoclaves: Necessity and Advantages
• Sterilization Process for Medical Tools
• Duration of Sterility After Autoclave Sterilization?

III. Operating Principle of Autoclaves

Autoclaves operate on the principle of using saturated steam at high pressure to destroy bacteria, viruses, and pathogenic microorganisms. This process is typically carried out at a temperature of approximately 121°C (250°F) and a pressure of about 15 psi (pounds per square inch) for 15 - 20 minutes.

The operating principle of autoclaves is based on the principles of pressure and temperature. When water is heated to high temperatures, the pressure inside the autoclave increases, creating a high-pressure environment. This high pressure allows water to remain in liquid form at higher temperatures compared to atmospheric pressure conditions. When the autoclave door is sealed, this high pressure creates a sterilizing environment inside the autoclave, effectively killing bacteria and viruses.

Autoclaves come with various features, but the basic principle includes three main stages:

• AIR REMOVAL > HEATING > STERILIZATION > COOLING

1. Air Removal: Expels cold air from inside the autoclave since air is a poor conductor of heat, leading to uneven temperatures inside. Medical autoclaves typically use vacuum pumps to remove air (Prevacuum). Retort autoclaves cannot use vacuum methods due to sudden pressure changes that might deform products. Instead, they use gravity-based air removal, where saturated steam is pumped inside the chamber while air valves are opened to expel cold air. This prevents sudden pressure changes inside and outside the product, balancing the pressure.

   Medical autoclaves usually supply steam through a single line, ensuring even distribution due to the pressure differential inside. Retort autoclaves for packaged foods use multiple steam inlets to ensure even contact with the product.

2. Heating: Larger Retort autoclaves may have fans to enhance steam diffusion, helping products reach sterilization temperatures faster and minimizing heat-induced changes in food. This stage gradually increases the temperature inside the autoclave to the required level for sterilization, ensuring all bacteria, viruses, and harmful microorganisms are completely eliminated.

   Autoclaves start heating from room temperature to the sterilization temperature, typically 121°C.

3. Cooling: Medical and material autoclaves use a process called drying during this stage. Cooling is achieved by releasing air valves to reduce temperature and pressure inside or using a vacuum pump for drying. Retort autoclaves may have a crucial difference in this stage. In addition to releasing air valves, they might spray cold water or air to cool the product while balancing the pressure inside. When the product temperature cools to a certain point (usually below 90°C), the machine automatically stops the cooling water or air supply, and air valves reduce the pressure to atmospheric levels.

   Autoclave Doors

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IV. Types of Autoclaves

Autoclaves are classified based on several factors such as size, capacity, usage purpose, and sterilization technology. Here are some common classifications:

1. By Size and Capacity:

   • Mini Autoclaves: Small-sized, suitable for small operating rooms or clinics.
   • Industrial Autoclaves: Larger and with greater capacity, serving healthcare facilities, hospitals, large surgical rooms, and medical manufacturing plants.

2. By Sterilization Technology:

   • Heat Sterilization: Uses high temperatures to kill bacteria and viruses.
   • Chemical Sterilization: Uses chemicals such as formaldehyde or ozone for sterilization.
   • Ultraviolet Sterilization: Uses ultraviolet light to destroy bacteria and viruses by damaging their DNA.

3. By Purpose:

   • Medical Autoclaves: Specifically designed for sterilizing medical instruments like surgical knives, scissors, and kits.
   • Food Autoclaves: Used for sterilizing food, beverages, etc.

V. Considerations When Purchasing an Autoclave

When choosing an autoclave, consider the following factors:

• Size and Capacity: Ensure it fits your usage needs and storage space.
• Material: Choose autoclaves made from high-quality, heat-resistant, and easy-to-clean materials like stainless steel.
• Sterilization Capacity: Ensure the autoclave's capacity matches the types of items and materials to be sterilized.
• Convenience and Safety: Opt for models with safety features, ease of use, and maintenance.

VI. Autoclave Usage Guide

Introduction and usage instructions for autoclaves.

VII. Additional Considerations

• Take time to assess your needs and choices.
• Consider the origin and reputation of the manufacturer or supplier.
• Evaluate the costs associated with using the autoclave.
• Balance your budget.
• Understand the payment policy.
• Consider hygiene and cross-contamination aspects when using the autoclave.

Where to Buy Reliable Autoclaves

With over 10 years of experience in providing laboratory tools, equipment, and chemicals, Duc Duong is committed to offering the highest quality autoclaves at reasonable prices and providing prompt and effective warranty and maintenance services.

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DUC DUONG TECHNOLOGY SCIENCE  COMPANY LTD

Address: 1014/67 Tan Ky Tan Quy, Binh Hung Hoa, Binh Tan, HCM

Tel: (028) 3762 8042 - 3762 8043 - 3750 8514 - 3750 8793

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Email: ducduong@ducduongco.com

Website: www.ducduongco.com