What should I check if the pressure difference of the high-efficiency filter suddenly drops?

The slowly increasing pressure difference is a sign of dust accumulation and can be judged based on the trend. A sudden drop in pressure difference is another thing - it's not that 'the filter has become clean', but that something in the system has changed.

The change may be on the measurement side or on the filtering side, and the two types of causes are handled differently. When troubleshooting, first eliminate measurement problems, and then check the filtering path. Do not reverse the order.

Troubleshoot measurement problems first

If the differential pressure gauge reading is zero or significantly low, first confirm whether the gauge itself is working properly.

Zero point of differential pressure gauge : After long-term use, it may drift and the reading will be low. You can use a standard instrument for comparison, or check the zero point status according to the instructions.

Pressure tapping port and pressure guiding tube : blockage, bending, or falling off will cause the reading to deviate. This is one of the most common causes of a sudden drop in pressure differential. Check whether the two pressure-conducting pipes are firmly connected and whether the pipes are pressed or disconnected.

Fan status : The fan stops, the damper is closed or the speed decreases, which will reduce the pressure difference on both sides of the filter. This situation should be compared with the operating records - whether the fan really stopped or slowed down.

Sensor failure : If it is a differential pressure sensor with signal output, also confirm whether the signal transmission and display are normal. If a certain unit in the group control system communicates abnormally, the readings displayed on the panel may not reflect the actual status.

Check the filter path again

If the measuring side is normal, check the filter and installation structure.

Damage to the filter material : The filter paper has holes or tears, air passes through the damaged area in a short circuit, and the resistance decreases. This situation manifests itself in a sudden drop in pressure differential.

Failure of the edge sealing or sealing surface : cracking of the glue, displacement of the sealing pad, and loosening of the pressing parts will allow air to bypass part of the filter material. The larger the bypass area, the more obvious the pressure drop will be.

Box or frame problems : cracked box seams, loose access doors, and deformed frames can also cause bypass. These locations are often not covered by filter material testing and require on-site inspection and confirmation. When it comes to the sealing structure of the liquid tank, the matching state of the knife edge and the tank body is the focus of investigation. Please refer to the relevant interface instructions.

Combine with other data to determine direction

It is difficult to determine the cause simply by looking at the drop in pressure differential. Combined with other operating data, the direction will be much clearer.

The air volume decreases at the same time : Prioritize checking the fan, damper and control status. The decrease in fan capacity will reduce the pressure difference on both sides of the filter and has nothing to do with the filter element itself.

The air volume remains unchanged but the particle monitoring is abnormal : the main suspicion is bypass air leakage. As the air bypasses the filter material, the air supply volume may not change significantly, but the quality of the air sent out has changed.

The drop in pressure difference is accompanied by a change in noise : it may be a change in the status of the fan or damper, or a loose structural part.

The pressure differential drops after maintenance operations : Check whether the filter element has been replaced, the damper has been adjusted, or the box has been inspected recently. The changes that occur after the operation are often related to the operation itself. For matching For the FFU fan filter unit system, whether the wind speed distribution inside the unit changes synchronously can also be used as a reference for judgment.

Establish a new baseline after exception recovery

After troubleshooting and restoring the target air volume, record the pressure difference and air volume.

Do not take low readings during abnormal periods as the initial resistance of the new filter element. This set of data reflects fault conditions, not normal operating conditions. Nor should a drop in pressure differential alone mean that the cleaning effect has improved - on the contrary, a drop in pressure differential may mean that the filtration effect has deteriorated.

After the treatment is completed, arrange air volume measurement and on-site leak detection according to project requirements to confirm that the system has returned to normal status. Newly created data must be marked with date and processing measures to distinguish it from previous records. involving For products of different grades of HEPA/ULPA air filters , the testing requirements after restoration shall be carried out in accordance with corresponding standards.

Two types of reasons, two treatment directions

To summarize the troubleshooting ideas:

Reasons on the measurement side : differential pressure gauge failure, pressure guide tube problem, sensor abnormality. The treatment direction is to repair or replace the measurement components, and there is no problem with the system itself.

Reasons on the filter side : damaged filter material, seal failure, and box bypass. The treatment direction is to repair the seal or replace the filter element. Specific measures need to be determined based on the on-site leak detection results.

Reasons on the fan side : the speed drops and the air valve is closed. The solution is to restore the fan to operating status and then re-measure the pressure difference.

Among the three types of reasons, problems on the fan side and measurement side are easy to solve; problems on the filter side require on-site leak detection to locate the specific leak point. Device-side applications such as The internal space of the EFU equipment-side fan filter unit is limited, and the accessibility of the leak detection path needs to be planned in advance.

About Aili Industrial’s cooperation in abnormal investigation

Aili Industrial can assist in checking the filter element resistance, fan operating point and spare parts specifications. filter with FFU fan filter unit、The fan filter unit at the EFU equipment end is matched in the same manufacturing system. The filter element resistance and fan working point can be confirmed together during the planning stage to facilitate comparison and judgment during operation.

Provides initial pressure difference, current air volume and operation records, which can help troubleshoot equipment problems in a more targeted manner. The specific handling method shall be subject to on-site inspection results and project maintenance requirements.