What should be noted for the daily maintenance of a negative pressure weighing chamber?

The daily maintenance of the negative pressure weighing chamber is the key to ensuring its stable performance, extending its service life, and guaranteeing operational safety. It should focus on core aspects such as the filtration system, negative pressure control, cleanliness maintenance, and equipment components. The following are the detailed maintenance points:
I. Maintenance of the Filtration System (Core Focus)
The filtration system is the key to blocking the spread of pollutants and needs to be inspected and replaced regularly to avoid pollution risks caused by filtration failure.
Primary filter
Inspection frequency: At least once a week (which can be judged by observing the accumulation of dust on the surface of the filter).
Maintenance content
If it is a washable type (such as nylon mesh), it can be rinsed with water or neutral detergent, dried, and then reinstalled.
If it is disposable (such as non-woven fabric), replace it immediately when the surface is obviously covered with dust and the resistance increases (such as more than 1.5 times the initial resistance).
Note: When replacing, the power of the equipment must be turned off. Avoid touching the filter material with your hands to prevent secondary pollution.
High-efficiency filters (HEPA/ULPA
Inspection frequency: Resistance monitoring is conducted once a month (through the built-in differential pressure gauge of the equipment), and integrity testing (such as PAO leak detection test) is carried out every 6 to 12 months.
Maintenance content
When the resistance exceeds the rated final resistance (usually 2 to 3 times the initial resistance) or when leakage is found during leak detection, replacement must be carried out.
When replacing, strictly follow the clean operation specifications (such as wearing clean suits and sealing the frame with sealant) to ensure there is no leakage after installation.
Record: Make detailed records of the replacement time, filter model, and leak detection results, and form a traceability file.
Ii. Maintenance of Negative Pressure and Airflow Systems
Negative pressure stability directly affects the control effect of pollutants, and special attention should be paid to airflow balance and pressure parameters.
Negative pressure value monitoring
Before starting up every day, confirm through the pressure display screen whether the negative pressure value is within the set range (usually 5Pa to 15Pa). If it deviates, the cause needs to be investigated.
Exception handling
If the negative pressure is too high (with an absolute value that is too high), it may be due to excessive exhaust air volume or insufficient intake air. Check whether the air valve is stuck and whether the air inlet is blocked.
If the negative pressure is too small or positive, it may be due to a clogged high-efficiency filter, fan failure, or poor sealing. Each one needs to be checked one by one.
Maintenance of fans and dampers
Fan: Check monthly for smooth operation and any abnormal noise or vibration (which may be caused by bearing wear or dust accumulation on the impeller). Clean the dust on the impeller surface every six months and inspect the motor lubrication condition annually.
Air valve: Manually or automatically test the adjustment function every month to ensure smooth operation without jamming and prevent air volume imbalance caused by air valve failure.
Air flow organization inspection
Observe the airflow direction in the operation area every quarter using a smoke test (such as a smoke pen)
Ensure that the airflow covers the entire weighing platform surface without obvious vortices or dead corners.
Check whether the airflow at the door gap, operation port, and other places is "drawn in inward" (reflecting the negative pressure effect). If there is air leakage outward, the seal needs to be repaired or the negative pressure adjusted.
Iii. Cleanliness and Surface Maintenance
Keeping the interior of the equipment clean can prevent material residue and cross-contamination, and at the same time reduce the burden on the filter.
Daily cleaning (after each use)
Wipe the internal surfaces (countertop, side walls, observation window) with 75% alcohol or a disinfectant that meets industry standards, with a focus on removing the dust and material traces remaining from weighing.
Cleaning tools should be dedicated (such as clean cloths that do not shed debris) to avoid introducing external contaminants.
Regular deep cleaning (once a week)
Disassemble the detachable parts (such as weighing platforms and guardrails), thoroughly clean them, and then disinfect.
Clean the air intake and return grilles and remove the accumulated dust (to avoid blockage and affect air volume).
Material protection
The inner walls are mostly made of stainless steel. Avoid using hard tools to scratch the surface to prevent rust.
If there are stains on the window glass, you can wipe them with a special glass cleaner. Avoid using corrosive solvents.
Iv. Maintenance of Auxiliary Components and Safety Functions
Operation interface and sensor
Check every month whether the buttons on the control panel and the display screen are functioning properly and whether the parameter Settings are saved intact.
The pressure sensor and temperature and humidity sensor (if any) should be calibrated once every quarter to ensure the accuracy of the monitoring data.
Safety device
Ultraviolet disinfection lamp (if any): Check whether the lamp tube is lit normally every week. Replace it when the cumulative usage time reaches 800-1000 hours (about one year) to avoid a decline in disinfection effect.
Interlocking device (such as door and fan linkage): Conduct monthly tests to ensure that the fan automatically stops or maintains negative pressure when the door is opened, preventing contaminants from overflowing when the door is opened.
Electrical system
Check every six months whether the power cord, plug, and grounding are in good condition, and whether they are worn or loose.
The interior of the distribution box should be kept dry and free of dust to avoid the risk of short circuits.
V. Maintenance Records and Contingency Plans
Establish maintenance files: Record in detail the time, content, model of replaced parts, abnormal conditions, and handling results of each maintenance, facilitating the traceability and prediction of faults.
Formulate emergency response plans: Develop handling procedures for common faults (such as sudden drops in negative pressure and filter leakage) to ensure rapid shutdown, isolation of contamination, and contact of professional personnel for maintenance in emergencies.
Summary
The core of maintaining a negative pressure weighing chamber is "effective filtration, stable negative pressure, cleanliness meeting standards, and safe operation". The maintenance cycle should be adjusted in combination with the usage frequency and material characteristics (for example, when handling highly toxic materials, the inspection of the filtration system needs to be more frequent). Regular maintenance not only ensures that the equipment complies with industry standards such as GMP and FDA, but also fundamentally reduces the risk of pollution during production.