What wind speed should be selected for the  weighing room of a GMP pharmaceutical factory?

    What is a negative pressure weighing room? The negative pressure weighing room is a special local negative pressure clean equipment used for sampling and weighing in places such as pharmaceuticals, microbial research, and scientific experiments. The purpose is to reduce cross-infection and provide a clean environment area. Dust and reagents are collected in the equipment. Weighing and dispensing can control the spillage and rise of dust and reagents, prevent the inhalation harm of dust and reagents to the human body, avoid cross-contamination of dust and reagents, and protect the safety of the external environment and indoor personnel. Negative pressure weighing chambers often reach a cleanliness level of 100. It provides a vertical one-way airflow. Some clean air circulates in the work area and some is discharged to nearby areas to generate negative pressure in the work area and prevent cross-contamination. Ensure a high cleanliness environment in the work area.

    The working principle of the negative pressure weighing chamber is also known as its name. It generates a negative pressure area environment. The pretreated air passes through a high-efficiency filter under the pressure provided by the centrifugal fan, making it meet the dynamic class A requirements. The clean air flow is sent to the air supply box. About 85% of the air passes through the uniform air supply screen to form a uniform vertical air supply airflow. In addition, about 20% of the air is discharged from the equipment through the air volume adjustment plate. All air flows are processed through high-efficiency filters, so there is no residual powder in the air supply and exhaust, which can effectively avoid secondary pollution and form a stable one-way flow in the work area. The dust emitted in this area will be in the one-way airflow. Under the influence of the flow lines, it is captured by the primary and medium-efficiency filters, and the weighing room equipment carries 10%-15% of the wind, thus forming a negative pressure state relative to the external environment.

    So how to calculate the wind speed and volume of the negative pressure weighing room? Generally speaking, the calculation method of the air supply air volume of the fan is relatively simple. Normally, when selecting the fan, the U of the domestic fan is 0.6-0.7m/s, and the U of the imported fan is 0.5m/s. The formula for calculating the air volume is L =1.1*360OUF, in the formula, L represents the air supply volume of the negative pressure weighing room in m³/h, F is the measured cross-sectional area of the negative pressure weighing room m2, and U represents the cross-sectional average wind speed of the negative pressure weighing room. m/s is what we call the supply air speed, and 1.1 represents the universal safety factor index. Based on the above formula, we can generally calculate the wind speed between regions.

    The operating area of ​​the negative pressure weighing room is protected by Class 100 vertical laminar flow ISO5 (NF, EN, ISO14644-1). It is designed according to the requirements of the FDA, EU GMP, and my country's GMP. Generally, pharmaceutical factories can only produce if they meet relevant standards. According to GMP standards, the rated wind speed of the negative pressure weighing room is 0.36-0.51m/s. The air in the negative pressure weighing room passes through a three-stage filtration system (high-efficiency filter removes 99.99% of particles ≥0.3μm and above). ) performs self-circulation, and the design complies with the GMP requirements of pharmaceutical manufacturers.

    According to the specific requirements for the use of negative pressure weighing rooms, they are related to the cleanliness level. If the materials to be weighed require a sterile environment, then a Class A weighing cover under a Class B background is required, and the wind speed requirement is 0.36-0.54m/ s, GMP production of sterile pharmaceutical products. For high-risk operating areas, such as filling areas, areas where rubber stopper barrels and open packaging containers are in direct contact with sterile preparations, and areas where aseptic assembly or connection operations are performed, a one-way flow operating table (cover) should be used Maintain the environmental status of the area. The one-way flow system must supply air evenly in its working area, and the wind speed control guideline value is 0.36~0.54m/s, there should be data to prove the status of the one-way flow and have been verified.

    For wind speed control, we generally need to pay special attention to the wind speed sensor, and changes in wind speed are also affected by the cleanliness of the filter. The wind-speed air in the negative pressure weighing room passes through the primary effect filter and the medium effect filter and is pressed into the static pressure box by the centrifugal fan. After passing through the high-efficiency filter, it is blown out from the air outlet surface of the air diffusion air supply unit. The clean air is uniformly distributed. The cross-sectional wind speed flows through the work area, thus forming a highly clean working environment. The operating area of the central weighing hood is maintained at negative pressure and 10% of the circulating air is exhausted. Therefore, we should also pay attention to the changes in the filter corresponding to the pressure difference gauge and whether the flow equalization membrane is clogged and replace it.