For many years, autoclaves have been essential equipment in fields such as microbiology, healthcare, pharmaceuticals, bacteriology, food, and veterinary medicine. The demand for autoclaves is increasing, so the selection of the right autoclave is also of significant concern.
When specifying or purchasing an expensive and complex device, it is essential to ask the right questions to get the correct answers about the product. Similarly, when buying an autoclave, it is crucial to understand your usage needs to ensure the device you purchase has the right configuration to handle your work effectively. This is especially important if you need to demonstrate this to a certification agency.
The following information will provide you with more details about autoclaves, helping you make the right choice for your intended use.
I. STRUCTURE OF THE AUTOCLAVE
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Capacity Depending on the sterilization sample requirements, the number of culture bottles to be sterilized, and the volume of each bottle, choose the appropriate internal diameter of the autoclave to optimize the number of samples per autoclave cycle.
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Type of Sterilization Chamber
a) Vertical Chamber Autoclaves with vertical sterilization chambers allow samples to be loaded from the top. The chamber is usually cylindrical to increase pressure resistance and reduce the size of the device. This is the most common type of autoclave on the market today due to its safety, reasonable price, and suitable size for most research and testing facilities.
- Smaller size – usually does not require much width and depth outside the chamber space, saving laboratory space.
- Typically used for sterilizing tall cylindrical samples like fermenters and culture bottles.
- Recently, it has become less popular due to the difficulty of lifting heavy baskets and containers. This type requires a hoist to make usage easier or selecting an autoclave with a lower height to reduce lifting height.
b) Horizontal Chamber Autoclaves with horizontal sterilization chambers allow samples to be loaded from the front. The chamber can be cylindrical or rectangular. Front loading facilitates the integration of automatic door opening/closing functions or loading/unloading devices. Additionally, small benchtop autoclaves also feature horizontal door openings to save workspace.
- Easier sample loading and unloading, especially if using trolleys.
- Larger size – larger capacity requires more space, unlike vertical chambers that usually only increase in height with increased capacity.
c) Round Chamber
- Thinner chamber walls as less steel is needed to support the chamber, making it lighter and less costly.
- Round chambers do not have pressure concentration points, so pressure is evenly distributed, reducing deformation and improving steam circulation.
- Less usable space, although steam circulation is improved.
d) Square Chamber
- Greater capacity compared to round chambers of the same volume, saving work capacity.
- Requires proper sample placement to ensure steam circulation is not restricted.
- Pressure tends to concentrate at the corners, so materials must be thicker to withstand pressure, increasing costs.
- Type of Door
a) Manual Screw Bolt Door
- Simple technique, less costly, requires little maintenance.
- Requires space for opening/closing.
- Less convenient compared to one-action doors, although the time for opening/closing is negligible.
b) One-Action Door
- Less complicated than program-controlled doors, less costly, requires little maintenance.
- Easier and faster operation.
- Requires space for opening/closing.
c) Sliding Door
- Light, simple, and quick operation.
- Does not require space for opening/closing.
- Complex technique, higher cost, requires maintenance.
- Increases the size of the autoclave.
d) Double Doors
- Horizontal chamber design with two doors. One door for loading samples and one door for retrieving sterilized products. Typically used in GMP-compliant clean rooms for manufacturing medical devices, pharmaceuticals, or clean room labs.
- Requires technical expertise and space, higher cost.
- Safety Systems
- Temperature sensor
- Pressure sensor
- Door sensor
- Water level sensor
II. FEATURES
- Sterilization Materials
- Instruments: forceps, scissors, clamps, inoculating loops, surgical instruments, dental instruments, cosmetic tools, etc.
- Packed liquids: culture bottles, heat-resistant plastic bottles, etc.
- Fabrics and clothing
- Porous and hollow materials
- Waste Sterilization
- A notable and increasingly popular use of autoclaves is pre-treatment of waste, such as medical waste, laboratory waste, and pathogenic materials.
- Autoclaves in this category function similarly to pressure cookers, aiming to neutralize potential infectious agents under high temperature and pressure, such as bacteria, viruses, and pathogens in cultures.
- Additional Features
- Countdown timer and end-of-sterilization alarm.
- Anti-opening mechanism when the temperature is above 80°C.
- Overheat and overpressure protection in the sterilization chamber, electric leakage protection, external chamber overheat protection.
- Water level warning.
- Automatic drying, rapid cooling, vacuum drying.
III. STERILIZATION METHOD
Steam Sterilization (Steam Sterilization) uses saturated steam at high temperature and pressure to compress and increase impact on bacteria and viruses, aiming to destroy them quickly.
The steam sterilization method utilizes an autoclave to create an environment with temperatures ranging from 115°C to 135°C with an overpressure of 0.5 to 2.0 bar.
Steam sterilization using an autoclave is the most advantageous method, including high sterilization efficiency, low cost, minimal destruction of sterilized samples, and short sterilization time (about 4-15 minutes from reaching sterilization temperature) as steam transfers heat much better than hot air.
- Autoclave with Internal Steam Supply
a) Direct Heating by Electric Resistance Usually made of heating wires covered by an insulating and heat-resistant layer. The outermost layer is made of chrome-plated copper or stainless steel. This component frequently contacts water and chemicals, so it must be cleaned regularly to avoid damage. The resistance is protected through temperature and water level sensors in the chamber.
- Simple, easy to maintain and replace.
- Does not require much technical expertise, less costly.
- Slower heating time compared to autoclaves supplied with steam from a steam generator.
- Longer cooling time as it waits for water in the chamber to cool down. Some other autoclaves can drain water immediately after the process, allowing the resistance to cool down faster.
b) Steam Supply from Outer Chamber Layer Some autoclaves have an additional outer layer surrounding the main sterilization chamber. Here, steam or water is heated to supply steam to the chamber or cool the sterilization chamber.
- Faster heating and cooling time, saving operational time.
- Limits steam condensation on samples during heating and drying, suitable for sterilizing porous materials or fabrics requiring a certain dryness level.
- More complex and costly technique, requires regular maintenance.
- Consumes more water and electricity.
c) Steam Supply from Integrated Steam Boiler
- Faster heating time as high-temperature steam is generated when the power switch is turned on.
- Better steam circulation and penetration as steam is only pumped into the chamber when reaching a certain pressure.
- Faster cooling compared to resistance heating.
- Requires high technical expertise, higher cost. Requires an integrated steam boiler for stable steam supply. Some autoclaves are equipped with backup batteries to maintain chamber temperature during power outages or condensation devices to dry steam before entering the chamber, along with accompanying pressure control valves.
- Autoclave with External Steam Supply Saturated steam is supplied from an independent external source, directed into the autoclave. This equipment is suitable for large-capacity autoclaves with front-loading doors, capable of integrating automatic door opening/closing or sample lifting devices. Commonly used in factories, production facilities, or hospitals with central steam boiler systems.
- These machines generate hot steam using available fuel sources to create steam, such as electricity or gas.
- These machines are expensive, with high maintenance and operational costs. For small autoclaves, using these machines can be nearly or more expensive than the autoclave itself.
- Additional systems for water treatment and drainage or other auxiliary equipment are needed, increasing costs.
IV. INSTALLATION LOCATION
- Installation area for the autoclave.
- Which room to install?
- Room size?
- Ground floor or upper floor?
- Transportation method?
- Floor load capacity?
- Distance from the autoclave to the walls: 30-40 cm from the back, 90-100 cm from the sides, 100-200 cm from the front (if the autoclave has a sample cart, space for pulling out samples is needed).
V. MANDATORY REQUIREMENTS
- Power Supply:
- Single-phase: for small autoclaves <100L. Some 100-200L autoclaves cannot be heated with a single-phase power supply.
- Three-phase: for large autoclaves >100L or autoclaves with additional drying functions.
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Water Supply: RO water or distilled water.
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Drainage: made of heat-resistant material (134℃), may include a condenser to cool water before discharge. Diameter over 1.5 inches for better ventilation.
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Steam: (for autoclaves requiring an external steam generator).
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Pressure: supply pressure must be greater than 1 bar compared to the autoclave’s operating pressure to ensure safety.
VI. PROCESS MONITORING
- Integrated Data Printer
- Less costly and uses the same sensors as the autoclave. Some printers use thermal printing, which can be faster and quieter than other systems but the paper can be affected by heat. Care must be taken with handling and storing thermal paper records in the hot environment around the autoclave.
- Less common compared to modern control systems, if there’s a fault in the control system, it can cause inaccurate prints leading to sample damage. However, today’s manufacturers have created more reliable modern microprocessor systems capable of self-checking and fault detection.
- Cycle Log Recording System
- Some modern automatic microprocessor control systems can store cycle logs.
- More versatile with integrated data storage, USB export, and barcode printing capabilities, better serving modern data storage.
- Higher cost.
VII. MAINTENANCE AND MAINTENANCE COST
- Sterilization Chamber
- Non-corrosive materials: Stainless steel, aluminum, copper.
- Smooth, seamless construction: For easier cleaning and avoiding contaminants.
- Pressure-resistant design: Thick, rigid materials, no deformations.
- Control System
- Display: Clear, easy-to-read.
- User-friendly interface: Simple and intuitive.
- Automatic control: Microprocessor system with fault detection.
- Safety features: Temperature, pressure, water level sensors, and emergency stop.
- Serviceability
- Ease of access for maintenance: Panels and parts designed for easy access.
- Availability of replacement parts: Ensure parts are readily available.
- Manufacturer support: Availability of technical support and service.
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
Fax: 028 3762 8043
Email: ducduong@ducduongco.com
Website: www.ducduongco.com
