English 
A vacuum drying oven, as a type of constant temperature drying oven, is particularly suitable for drying heat-sensitive, easily decomposed, and oxidation-prone samples, as well as complex and precise mechanical parts and porous samples after cleaning. The principle behind its operation is that water or solvents have a lower boiling point under negative pressure, allowing moisture to evaporate at low temperatures, achieving the drying purpose.
Therefore, vacuum drying ovens have advantages that ordinary drying ovens do not: they can rapidly dry hard-to-dry samples, eliminate the risk of oxidation or explosion under vacuum or inert gas conditions, and prevent loss of powder samples during the drying process.
A vacuum drying oven does not use a motorized blower. The heating method is to heat the inner oven, using radiant heat to bake the items inside. The intensity of radiant heat decreases with distance, making it essential to ensure uniform temperature distribution inside the vacuum drying oven. Kenton’s KZ lab vacuum drying ovens feature an innovative preheating chamber technology and heat transfer technology with partition plates, increasing the contact area between the partition and the preheating chamber, ensuring consistent temperature throughout.
A vacuum drying oven must be paired with a vacuum pump. There are two main types of small vacuum pumps: oil-lubricated and oil-free, with options of 1L, 2L, or 4L. It is generally recommended to choose an oil-free vacuum pump. When using an oil-lubricated pump, it is essential to first close the vacuum valve on the oven before shutting off the pump motor to prevent oil from flowing back into the oven. To extend the lifespan of the vacuum pump and prevent solvents from corroding its internal parts, it is advisable to install an adsorption filter device between the oven and the pump.
There are several important points to note during the operation of a vacuum drying oven:
Always evacuate the air before heating to avoid starting the vacuum pump before heating. Once the set temperature is reached, if a decrease in vacuum level is noticed, you can appropriately re-evacuate.
After the experiment is complete, close the vacuum valve first, then turn off the vacuum pump motor, and finally shut off the temperature control switch.
After use, the oven should be vented to release pressure, otherwise, the door cannot be opened.
Samples should be promptly removed to prevent condensation on the oven walls from contaminating the samples again.
When selecting a vacuum drying oven, the first consideration should be its sealing capability. According to the GB/T 29251-2012 standard, for vacuum drying ovens with a working chamber volume of 0.1m³ or above, the ultimate pressure should not exceed 8kPa after being held at 0.3kPa for 24 hours at room temperature. The second factor is the thickness of the materials used. Due to the vacuum environment inside the oven, the outer shell must be thicker than that of an air-blower drying oven to withstand atmospheric pressure, typically with thicker steel for better quality and longer service life. The size and material of the accessories should also be selected based on the intended use. Different types of vacuum drying ovens have varying prices, with smaller tabletop models costing several thousand yuan, suitable for laboratory use. For the food and pharmaceutical industries, low-temperature vacuum drying ovens are more expensive, depending on size and material requirements.
Lastly, it is important to note that vacuum drying ovens do not have a temperature uniformity value parameter like ordinary electric constant temperature drying ovens. The temperature displayed and set on the vacuum drying oven controller refers to the temperature of the heated inner chamber wall, which is not the actual temperature inside the oven.
