Weighing hood, also known as negative pressure weighing hood or weighing chamberIt mainly includes two types: negative pressure weighing hood and activated carbon weighing hood. The negative pressure weighing hood is mainly used as a local purification equipment for pharmaceutical, microbiological research, and scientific experiments, while the activated carbon weighing hood is mainly used as a local purification equipment for activated carbon weighing in the water needle workshop. The weighing hood can provide a vertical unidirectional airflow, with some clean air circulating in the work area and some discharged to nearby areas, creating negative pressure in the work area and preventing cross contamination. It can control the dust and dirt in the work area from spreading outside the operation area, ensuring that operators do not inhale the items being operated and maintaining a high cleanliness environment in the work area.
The weighing operation area is protected by Class 100 vertical laminar flow ISO 5 (NF, EN, ISO14644-1) and designed in accordance with the requirements of FDA, EU GMP, and Chinese GMP.

Working principle of weighing hood:
The indoor air is weighed and filtered through a primary filter, then compressed into a static pressure box by a centrifugal fan. After passing through an efficient filter, it is blown out from the air outlet of the air diffusion and supply unit. Clean air flows through the work area at a uniform cross-sectional wind speed, forming a highly clean working environment. The operating area of the central weighing hood is maintained in a negative pressure state, and 10% of the circulating air is discharged. The air in the central weighing chamber is self circulated through a two-stage filtration system (high-efficiency filter to remove 99.99% of particles ≥ 0.3 μ m and all dust), designed to meet the GMP requirements of pharmaceutical factories.

Usage of weighing cover:
Dust and reagent weighing and packaging can be carried out in the weighing hood equipment, which can control the overflow and upward movement of dust and reagents, prevent the inhalation hazards of dust and reagents to the human body, and also avoid cross contamination of dust and reagents, protecting the safety of the external environment and indoor personnel.

Weighing hood structure:

The weighing cover is made of 304 stainless steel, and the working area wall panel is made of stainless steel 304 (1.2mm thick, oil brushed short wire, connected by internal circular arc angles, without dead corners, ensuring the sealing and cleanliness of the working area.

The negative pressure weighing cover adopts a modular design, which is easy to assemble and disassemble on site. Composed of initial effect, high-efficiency filter in fan case, and uniform flow film.
The weighing hood is assembled from several parts, including the workspace, return air box, fan box, outlet box, and outer box. The control panel is located on the front of the working area inside the equipment. The control panel adopts Siemens touch screen frequency converter control system, which can control the start and stop of the fan, adjust the fan frequency, and adjust the required wind speed in the working area (after the equipment is installed and used, specialized personnel need to adjust the frequency).

Weigh the hood and display the pressure difference, wind speed, and temperature and humidity of the primary filter, high-efficiency filter, and uniform flow membrane. In addition, install a dust particle monitoring system to monitor the dynamic cleanliness in real time, serving as a reference for cleanliness. At the same time, it also alerts for abnormal conditions such as wind speed, pressure difference, and cleanliness. A differential pressure gauge is used to measure the pressure of a filter at different times, providing a persistent performance indicator for the weighing hood.

The initial effect requires regular cleaning based on usage. There are four differential pressure sensors installed in the return air duct, corresponding to the resistance of specialized flow equalization membranes, initial and high-efficiency filters, and displayed on the touch screen. When the pressure difference of the filter exceeds the range, there will be an alarm displayed on the touch screen and an audible alarm on the automatic control box.

Optional functions of weighing hood/weighing room:
The distribution cabinet is set up separately;

LCD screen/touch screen control;

Equipped with low wind speed alarm, overpressure difference, and over temperature and humidity alarm functions;

Equipped with USB interface, data can be exported and printed;

Add temperature and humidity adjustment function to regulate temperature and humidity;

Equipped with dust particle and planktonic bacteria detection functions;

Adopting PLC control system, the wind speed is automatically constant, with wind speed

Differential pressure, temperature and humidity display;

Weighing hood/weighing room product model (GZZJ-CS1200)
Dimensions (mm): W1300xL1500xH2450;

Internal dimensions (mm): W1200xL1000xH1950;

Overall material of outer box: SUS304 stainless steel plate;

High efficiency filter: H14 grade aluminum frame liquid tank high-efficiency filter, 1220 * 610 * 69mm;;

Purification level: CLASS 100@0.5UM ；

Control mode: manual switch control/touch screen fully automatic control;

Rated wind speed: 0.36-0.51M/s (GMP standard);

Cleanliness level: Level 100;

Rated power: 0.65KW;

Average illuminance: ＞ 400LUX;

Imported frequency converter: speed regulation (frequency adjustment);

Weighing hood/weighing room protection object:

Protecting drugs

Protect operators

protect the environment

Note: Non standard products can be made according to customer requirements.
Optional accessories: 1. Wind speed sensor; 2. Differential pressure sensor; 3. Frequency converter; 4. Touch screen; 5. PLC control; 6. Polymer uniform flow membrane.