Horizontal Flow Workbench Core Component Replacement Judgment Guide: From Inspection Standards to Practical Operation Methods
The core components of the horizontal flow workbench (HEPA/ULPA filters, fans, control panels, workbenches and seals) directly determine the purification effect and operational stability. Their replacement should be comprehensively judged based on performance test data, aging performance and industry standards, rather than simply relying on the service life. The following are the specific judgment methods, testing standards and replacement thresholds for each core component, taking into account both professionalism and practicality:
I. Judgment Criteria for Core Component Replacement (Sorted by Priority)
HEPA/ULPA filter (purification core, highest priority)
As a key component for ensuring cleanliness, the failure of the filter directly leads to the equipment’s inability to meet the usage requirements. The following judgment criteria should be given special attention:
(1) Performance testing and judgment (quantitative standards
Wind speed detection: Use a hot sphere anemometer to evenly take 5 to 9 measurement points on the working surface of the workbench (in accordance with ISO 14644-3 standard). If the average wind speed is ≤0.25m/s (the normal working wind speed range is 0.3-0.5m/s), and it still cannot be restored after cleaning the pre-filter and adjusting the fan speed, it indicates that the filter is clogged and needs to be replaced.
PAO leak detection test: A PAO aerosol generator is used for integrity testing. If the particle concentration downstream of the filter is greater than 0.01μm and the number of particles is ≥3520 particles /m³ (corresponding to ISO Level 5 cleanliness requirements), or the leakage rate is greater than 0.01%, it is determined that the filter is damaged and needs to be replaced immediately.
Resistance monitoring: If the initial resistance of the filter (for new equipment) is 200-300Pa and rises to 600-800Pa after use (more than twice the initial resistance), the fan load is too large and it needs to be replaced to prevent the fan from burning out.
(2) Intuitive performance judgment
There is obvious dust rising inside the workbench. Even after cleaning the countertop, there is still floating dust.
If the contamination rate of the product increases during the experimental/production process (such as cell culture contamination or excessive dust from electronic components), it can be determined that the filter has failed after excluding other factors.
Replacement threshold: Replace immediately if any of the above conditions are met (it is recommended to choose the original factory filter of the same specification, with a filtration efficiency of ≥99.99%@0.3μm, and ULPA filter ≥99.999%@0.12μm).
2. Centrifugal fan (Power core)
The fan provides a stable airflow. Its aging or malfunction can lead to uneven wind speed and increased noise. The basis for judgment is as follows:
(1) Performance and operational status judgment
Wind speed stability: If the wind speed fluctuation at the same measurement point is greater than ±20% after continuous monitoring for 10 minutes, or the wind speed deviation at different measurement points is greater than 30% (for example, the wind speed in some areas is 0.2m/s, and in some areas it is 0.4m/s), it indicates that the air volume output of the fan is unstable.
Noise and vibration: If the noise during operation is greater than 60dB (normally it should be ≤55dB), accompanied by obvious vibration of the machine body (the vibration acceleration detected by a vibration meter is greater than 2.8mm/s²), it may be due to wear of the fan bearings or dust accumulation and imbalance of the impeller.
Operational failure: The fan has difficulty starting, trips frequently, or suddenly stops during operation. After checking the circuit and finding no issues, it is determined that the fan motor is aging or the coil is burned out.
(2) Reference for service life
For fans that operate continuously for 5 to 8 years and intermittently for 8 to 10 years, even if there are no obvious faults, it is recommended to conduct preventive inspections (such as disassembling to check bearing wear and coil insulation).
Replacement threshold: If the maintenance cost of the fan exceeds 30% of the original value of the equipment, or if there are ≥2 faults within 3 consecutive months, the fan assembly should be directly replaced (EBM, NMB and other brand fans are preferred to ensure that the air volume and noise meet the standards).
3. Control Panel and Circuit System (Control Core)
The circuit system is responsible for functions such as equipment start-up and shutdown, and wind speed regulation. After aging, it is prone to cause safety hazards. The basis for judgment is as follows:
(1) Intuitive fault manifestation
Key malfunctions (such as the wind speed adjustment key or power key not responding), the display screen flickers/goes black, or the parameter display is abnormal (such as the wind speed showing 0 but the fan is running);
The equipment trips frequently or cuts off power immediately after startup. After checking that there is no problem with the power line, it is determined that the control module or circuit is aging.
The terminal blocks are oxidized or loose, or the insulation layer of the wires is cracked or discolored (posing a risk of short circuit).
(2) Safety and performance requirements
For equipment used in scenarios such as biosafety and medical care, the circuit system must comply with the IEC 61010 safety standard. If the insulation resistance is detected to be less than 2MΩ, the control module should be repaired or replaced immediately.
Replacement threshold: If the control module failure cannot be repaired or the circuit aging range is wide (such as damage to the insulation layer of multiple sets of lines), it is recommended to replace the control panel assembly to avoid safety accidents.
4. Worktable surface and seals (Protective and sealing core
The countertop and seals ensure the cleanliness of the operating space and the airtightness of the airflow. The basis for judgment is as follows:
(1) Workbench surface (stainless steel 304/316 material)
The countertop shows severe corrosion (such as pitting, large areas of rust spots), deformation (flatness deviation > 2mm/m), or cracking of the sealant at the edge of the countertop, resulting in air leakage.
The countertop has deep scratches (> 1mm), which cannot be cleaned thoroughly and is prone to bacterial growth (in biological laboratory scenarios) or residual dust (in electronic industry scenarios).
(2) Seals (such as sealing strips on the workbench frame, sealing gaskets at the connection between the filter and the chassis)
The sealing strip ages, hardens or falls off, or the sealing gasket cracks. When tested with a smoke generator, there is obvious air leakage (smoke overflow) at the edge of the workbench.
Sealing failure leads to substandard cleanliness (such as excessive leakage rate in the frame area during PAO leak detection).
Replacement threshold: If the countertop is corroded or deformed, affecting its use, or if the seal fails and causes air leakage that cannot be repaired, replace the countertop or seal. If the connection between the countertop and the chassis is deformed, the overall structural stability should be evaluated. If necessary, the entire equipment should be refurbished.
5. Auxiliary components (pre-filter, ultraviolet lamp, etc.)
Pre-filter (coarse/medium efficiency)
Appearance judgment: The surface of the filter cotton is severely dusted, the color has turned black, or the usage time has exceeded 6-12 months (adjust according to the dust concentration of the usage environment).
Resistance judgment: If the resistance of the pre-filter is greater than 100Pa, it needs to be replaced in time (to avoid clogging the HEPA filter).
(2) Ultraviolet germicidal lamp (if equipped
If the usage time exceeds 8,000 hours (approximately one year), or the ultraviolet light intensity is less than 70μW/cm² (detected by a UV radiometer), the sterilization effect will decline and the lamp tube needs to be replaced.
Ii. The “Priority Principle” for Core Component Replacement
Safety first: If there are potential safety hazards in the fan or circuit system (such as motor overheating or short circuit), stop the machine immediately for replacement to prevent fire or electric shock accidents.
Effect first: If the HEPA/ULPA filter fails and fails to meet the cleanliness standards, it should be replaced first to avoid affecting product quality or experimental results.
Cost priority: If the maintenance cost of a single component exceeds 30% of the original value of the equipment, or if multiple core components age simultaneously (such as the fan + filter + circuit all need to be replaced), it is recommended to directly replace the equipment, which offers a higher cost performance.
Iii. Practical Testing Tools and Frequency Suggestions
Essential testing tools
Hot sphere anemometer (accuracy ±0.01m/s) : Detects wind speed;
PAO aerosol generator + particle counter: Detect filter integrity;
Noise meter (accuracy ±1dB) : Detects the noise of the fan;
Vibration meter: Detects the vibration of fans;
Ultraviolet radiometer: Detects the intensity of ultraviolet lamps.
2. Suggested detection frequency
Daily inspection: Observe the operating status of the equipment every day (noise, display screen, tabletop cleanliness);
Monthly inspection: Wind speed, countertop sealing performance (simple smoke test);
Quarterly inspection: Pre-filter cleaning/replacement, circuit wiring inspection;
Annual inspection: Comprehensive inspection of PAO leakage, noise, vibration and ultraviolet intensity (the inspection report is issued by a third-party institution, meeting the requirements of GMP, ISO 14644 and other standards).
الملخص
To determine whether the core components of a horizontal flow workbench need to be replaced, the principle of “data quantification as the main approach, intuitive presentation as a supplement, and industry standards as the guideline” should be followed: first, determine the component status through professional detection data (such as wind speed, leakage rate, and noise), and then decide whether to replace them in combination with the strict requirements of the usage scenarios (such as biosafety and semiconductor manufacturing). Regular inspection and preventive maintenance can not only avoid production/experimental losses caused by component failure, but also maximize the service life of equipment and reduce the overall cost.