What is the reason for the sudden increase in ULPA pressure difference?

The pressure difference gradually rises, usually due to dust accumulation. A sudden jump in pressure difference is of a different nature - it may come from a pollution incident, moisture, channel blockage or instrument abnormality, or it may just be a change in working conditions.

The order of judgment is very important: first check whether the air volume has been changed at the same time, then check the upstream pollution events, and finally check the measurement link. After completing these three steps, most anomalies can be located.

First check whether the air volume has been changed at the same time

This is where things tend to go wrong the most.

Increasing the fan speed, changing the valve opening, and switching the system mode will all cause the pressure difference reading to change. Even if the filter element itself does not accumulate dust, the pressure difference may increase significantly when the air volume increases. This is related to the resistance characteristics of ULPA: the higher the air volume, the greater the pressure difference on both sides of the filter element.

The judgment method is: call up the air volume, fan gear or speed records at that time. If the pressure difference jumps and the air volume also changes, then the priority is to investigate the change in working conditions instead of directly suspecting that the filter element is clogged.

Do not misjudge changes in operating conditions as blockage. In matching In the FFU fan filter unit system, if the group control system automatically adjusts the gear, the pressure difference of a single FFU may change collectively. Device-side applications such as EFU equipment end fan filter unit , equipment operating mode switching may also affect the air supply volume, thereby affecting the pressure difference reading. For specific troubleshooting methods, please refer to the relevant instructions of the pressure difference measuring point.

How to investigate upstream pollution incidents

If the air volume does not change significantly and the pressure difference does jump in a short period of time, the next step is to check whether there is sudden pollution upstream.

Whether the pre-filter is invalid or damaged. If the primary and medium-efficiency filters are damaged or have not been replaced for a long time, a large amount of dust will directly impact the terminal ULPA. In this case, the terminal pressure difference will increase significantly in a short period of time. For specific configuration ideas, please refer to the instructions related to pre-filtering.

Construction or maintenance dust. If there is grinding, welding or cleaning work near the equipment, dust may enter the system through the air inlet. This type of event usually has a time node that corresponds to the time when the pressure difference jumps.

Process changes or abnormal emissions. If a new dust-generating process is added to the production line, or a certain piece of equipment has abnormal emissions, it may also cause a sudden increase in end load.

Moisture or condensation. In a high-humidity environment, the resistance of the filter material may change after absorbing moisture. If the system is restarted after shutdown, or the ambient temperature and humidity fluctuate greatly, condensation may form on the surface of the filter material, causing abnormal pressure differential readings. This type of problem is more common in high-humidity seasons. For specific symptoms, please refer to the relevant instructions for high-humidity environments.

The solution is not to just replace the end filter element. If the upstream pollution source is not resolved, the same problem will recur when a new filter element is installed. The source of pollution must be dealt with first, and then the final filter element needs to be replaced.

The measurement link must also be checked

When field data is abnormal, there may also be problems with the measurement process itself.

Is the pressure tube blocked or bent? If the pressure guide pipe is blocked by dust, pressed down, or has water accumulation, the differential pressure reading may deviate from the actual value. Check whether the pipeline is smooth and whether the connection is firm.

Is the zero point of the differential pressure gauge drifting? After long-term use, the zero point of the instrument may change. Compare with a standard instrument or check the zero point status according to the instructions.

Is the sensor signal normal? If you are using a differential pressure sensor with signal output, make sure 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.

Whether the measuring point position changes. If the tap location or pipe routing has been recently adjusted, the reading will also change. Confirm that the measuring point has not changed, or record the new measuring point position as a baseline. involving For HEPA/ULPA air filter products of different grades, the measurement link inspection methods are the same.

Project judgment example

While a certain semiconductor equipment was running, the ULPA differential pressure meter reading suddenly jumped from 180 Pa to 320 Pa.

When troubleshooting, first call up the operation record: at the same time, the fan gear of the equipment was adjusted from 60% to 80%. After the air volume increases, the pressure difference rises, which is normal and does not mean that the filter element is clogged.

Return the gear position to the original 60%, and the pressure difference returns to about 185 Pa, which is basically the same as before adjustment. This shows that there is no abnormality in the status of the filter element, and the problem lies in changes in working conditions.

The key to this case is: look at the working conditions first, then look at the filter element. If you directly change the filter element or increase the speed at that time, not only will it not solve the problem, but it may also cover up the real changes in operating parameters. involving ULPA ultra high efficiency filter or The resistance of HEPA high-efficiency filter must be judged together with the air volume.

Selection and Acceptance Checklist

About Aili Industrial’s pressure difference investigation cooperation

To troubleshoot abnormal pressure differences, operating data, product parameters and system conditions need to be looked at together.

Aili Industrial's manufacturing system covers filters, motors, fans, control systems and complete machine assembly, and can provide HEPA/ULPA products of different grades and supporting air supply equipment. filter with FFU fan filter unit、When the EFU equipment-end fan filter unit is matched in the same system, the filter element resistance and fan operating point can be calculated together in the planning stage to facilitate comparison and judgment during operation.

When the pressure difference suddenly rises on site, it is recommended to record the air volume, rotation speed and pressure difference readings first, and then contact the supplier to check the product curve. The specific handling method shall be subject to on-site inspection results and project maintenance requirements.