1、 Corresponding relationship between vacuum level and series

The vacuum level of diaphragm pumps is usually divided into first, second, third, and fourth stages, which achieve step-by-step compression by connecting multiple pump heads in series to obtain lower ultimate pressure.

2、 How does the level affect the vacuum degree?

The vacuum level of a diaphragm pump is not simply a combination of numbers, but is achieved by connecting pump heads in series. Its working principle can be understood as:

1. The limitation of single-stage compression: At the end of the exhaust stroke, a small amount of compressed gas that cannot be discharged will always remain in the pump chamber of a single-stage diaphragm pump, and this space is called the "dead chamber". In the next suction stroke, this portion of gas will re expand, occupying a portion of the pump chamber's volume, thereby limiting the maximum low pressure that the pump can achieve.

2. The advantage of multi-stage series connection: multi-stage pumps work by connecting two or more pump heads in series. After the first stage pump compresses the gas, it is not directly discharged into the atmosphere, but into the inlet of the second stage pump. In this way, the back pressure (outlet pressure) that the first stage pump needs to overcome during operation is greatly reduced, allowing it to achieve lower inlet pressure than when working alone. The second stage pump further compresses the gas discharged from the first stage pump, and so on, gradually reducing the pressure to ultimately achieve a higher ultimate vacuum degree.

3、 How to choose a diaphragm pump based on the vacuum level?

When choosing a diaphragm pump, the principle of "the maximum vacuum degree of the equipment should be one order of magnitude higher than the required vacuum degree for operation" should be followed to ensure that the pump can work stably and efficiently.

-First stage pump: suitable for applications that do not require high vacuum degree, such as vacuum filtration, simple vacuum drying, and degassing.

-Secondary pump: It is the "golden oil" of the laboratory, which can meet the needs of most conventional experiments such as rotary evaporator, vacuum drying oven, solid phase extraction, etc.

-Third/Fourth Stage Pump: Suitable for precision experiments that require high vacuum levels, such as providing pre vacuum for high vacuum equipment such as mass spectrometers and scanning electron microscopes, or for special processes such as molecular distillation.

Important reminder: In addition to vacuum degree, when choosing a diaphragm pump, factors such as pumping rate (flow rate), chemical properties of the pumped medium (to choose corrosion-resistant materials such as PTFE coating), and noise and vibration levels should also be considered.