Gravity Convection Dry Heat Sterilizer

What is the Gravity Convection Dry Heat Sterilizer?

A dry heat oven without a fan that relies on natural convection, operating from ambient to about 250 °C. It suits fine powders, oils and small instrument loads in laboratories where simplicity and low air movement are preferred.

Overview

The gravity convection sterilizer heats the chamber walls and relies on rising warm air to distribute heat. With no fan, there are no moving parts, noise is low and fine powders are not disturbed. Heat-up is slower and temperature gradients are larger than in forced-air units, often ±5 to 8 °C at 170 °C, so loads must be spaced and validated carefully. Chamber volumes range from 15 to 150 L. Stainless chambers and simple PID or analog thermostats control temperature, and an overtemperature limiter protects the unit. Because of its simplicity, cost is low and maintenance is limited to element and gasket checks. It is used in teaching, small clinics and for oils, powders and lightweight instrument loads in which airflow is undesirable.

How does it work?

Dry heat sterilization kills microorganisms by oxidation and protein denaturation in the absence of moisture. Because air conducts heat less efficiently than steam, higher temperatures and longer times are needed, for example 160 °C for 120 minutes, 170 °C for 60 minutes or 180 °C for 30 minutes. A heated chamber uses electric heating elements, and either natural gravity convection or a fan circulates air to equalize temperature. Fan-forced models reduce gradients and speed heat-up. A controller reads a platinum resistance or thermocouple sensor, and an independent overtemperature cut-out protects the unit. Timing begins when the coldest point in the load reaches the set temperature. Depyrogenation ovens run at 250 to 350 °C to destroy endotoxin, often with HEPA-filtered air supply. Insulated walls and a sealed door limit heat loss.

What are the key features?

• No fan, so no moving parts and low noise.
• Fine powders are not disturbed by airflow.
• Stainless steel chamber of 15 to 150 L.
• Simple PID or analog thermostat control.
• Independent overtemperature limiter for safety.
• Low purchase price and limited maintenance.

What are the technical specifications?

A typical gravity convection dry heat sterilizer configuration offers temperature range of Ambient +10 to 250 °C, chamber volume of 15-150 L, temperature uniformity of ±5-8 °C at 170 °C, heat-up time to 170 °C of Approx. 60-100 min, air movement of Natural convection and chamber material of SUS304 stainless steel. Values are indicative of the product class; the exact figures for each configuration are confirmed on the quotation and the calibration documents supplied with the instrument.

Which applications is it used for?

The Gravity Convection Dry Heat Sterilizer is used in fine powder sterilization, oil sterilization, small instrument loads and teaching laboratories. Across the wider Dry Heat Sterilizers class, laboratories also deploy it for glassware sterilization, metal instrument sterilization and depyrogenation of vials and glassware.

Which standards and certifications apply?

Relevant standards and methods include USP <1211>, Ph. Eur. 5.1.1, USP <1228.1> Dry heat depyrogenation, ISO 20857, EN 61010-2-010, GB/T 30690 and EN 13060. Certification candidates for this model are CE, ISO 9001 manufacturing and RoHS; each is to be confirmed for the specific configuration before shipment, and certificates are supplied only where they have been issued.

Place the sterilizer on a non-combustible surface with clearance for ventilation and keep flammable materials away. Use a dedicated electrical circuit sized for the heater. Load items in racks so air can circulate, and do not overfill. Wrap or cover items with aluminum foil or place them in metal or borosilicate containers that tolerate the temperature. Start timing at the set temperature for the coldest point, which is verified with thermocouples during validation. Use chemical indicators or biological indicators such as Bacillus atrophaeus spores to verify cycles. Allow the load to cool before opening, since glass can crack with thermal shock. Calibrate the temperature sensor annually and check door seals and fans regularly. Follow burn-safety rules when unloading.

How do I select the right Gravity Convection Dry Heat Sterilizer?

Select a gravity convection unit for powders, oils and small loads where low airflow and low cost matter. Forced-air ovens give better uniformity for racks of glassware. Specify chamber volume, temperature limit, control type and whether mapping data is needed.

How does it compare with other Dry Heat Sterilizers variants?

Decide first whether you need sterilization, which runs at 160 to 180 °C, or depyrogenation, which needs 250 °C or above. Then choose between gravity convection, which is simple and gentle on powders, and forced-air models, which give tighter uniformity and faster cycles. Size the chamber for the largest racks or trays and allow space between items for airflow. Check temperature range, uniformity across the chamber, programmable cycles and cooling rate. Regulated laboratories need data logging, validated load mapping and, for pharmaceutical use, HEPA filtration and double-door configurations. Confirm that the materials to be processed tolerate the temperature. Plastics, rubber, liquids, and most textiles are unsuitable, and sharp instruments may lose temper at higher temperatures.