How to choose a replacement filter element after the old model HEPA is discontinued?

After the equipment has been used for several years, the original filter element is discontinued. This situation is not uncommon in the semiconductor, pharmaceutical and precision manufacturing industries.

A common way to find a replacement is to measure the length, width and thickness of the old filter element, and then find a source based on this size. The dimensions are correct, but when you put it in and find that the pressure is not tight, or the sealing surface does not meet, the problem is exposed. The difficulty in alternative selection is not the size, but the interface. The length, width and thickness are just the appearance. What really determines whether it can be used is the sealing structure, pressing method and installation direction.

First collect all the information about the old filter element

The original factory information may no longer be found, but the physical object is still there, which is the most direct source of information.

What needs to be recorded includes: the model, grade, and production information on the nameplate of the old filter element; the length, width, thickness, and material of the outer frame; the type and structure of the filter material; the sealing method, whether it is a gasket or a liquid tank; the air flow direction mark; and the interface size of the installation frame.

It’s also important to take photos and keep them. These photos of the installation frame, clamping parts, inspection openings, and filter elements after installation can save a lot of back and forth when communicating with the supplier. If the on-site air volume and pressure difference records are retained, they should also be compiled together, which can help determine the design working point of the original filter element.

When measuring the size, it is recommended to measure the old filter element and the installation frame at the same time. The old filter element may have been deformed, and it may not be appropriate to make a new product directly according to its size. The installation frame is the final partner. For matching FFU fan filter unit or For the fan filter unit at the EFU equipment end , the structure on the box side must also be measured because the sealing surface of the filter element matches the box.

Several key items to check for alternatives

Filter level. The grade of the original model must be confirmed clearly. The grade markings of discontinued products may use old standards. Substitutes need to correspond to current standards and check whether the testing requirements are consistent.

Rated air volume. The resistance of the replacement product at the target air volume should match the operating point of the original system fan. If the resistance of the replacement is significantly different, the actual air supply volume may deviate from the original design even if it is sized to fit. This is especially critical in device-side applications, please refer to HEPA/ULPA air filters . Product data check for

Sealed structure. This is the most problematic part. If the original box is sealed by a liquid tank, the replacement must have the corresponding liquid tank size; if it is pressed by a gasket, the position of the pressing surface and the specifications of the gasket must match. For the verification method of the liquid tank structure, please refer to the relevant instructions on the knife edge size verification.

Installation direction and disassembly path. The position of the protective net and sealing surface of the replacement product must be consistent with the original design direction, otherwise the risk of reverse installation increases. The disassembly and installation path must also be confirmed. Even if the new filter element can be installed, it must also be able to be taken out.

Non-standard alternative development process

For products whose old models have been discontinued, replacements often require customization.

The process is generally as follows: collect old samples and installation frame data, confirm technical conditions, develop according to the drawings by the supplier, make samples, trial assembly and verification, and mass production after confirmation.

This step of sample verification cannot be omitted. There may be differences between the dimensions on the drawing and the actual assembly state, especially the fit of the sealing surface, which can only be confirmed after installation. After trial installation, perform air volume measurement and installation leak detection according to project requirements, and record the results as the basis for mass production.

In this process, the management of drawing versions is very important. If there are any modifications after trial assembly, update the drawings and re-confirm to avoid inconsistency between batch goods and verified samples.

Choose a representative location for fitting

If there are multiple filter elements of the same specification on the same equipment, select a representative one during trial installation.

The so-called representative means that its installation box status, interface conditions, operating environment and other locations are similar. If there are differences in the installation frames at different locations, they need to be confirmed separately. After the trial installation, check the sealing status, compression effect and replacement path, and arrange the batch after confirming that it is feasible.

For equipment in operation, trial installation may require scheduled downtime windows. By clearly listing the inspection items and acceptance criteria for trial installation in advance, necessary verification can be completed within limited downtime and the impact on production can be reduced.

It is recommended to re-establish maintenance records after replacement.

Replacement filter elements may have different specifications than the original ones, and original maintenance records and replacement intervals may not apply.

It is recommended to re-establish a ledger and record the model, grade, supplier information, installation location and initial operating parameters of the new filter element. After running for a period of time, judge whether the replacement cycle needs to be adjusted based on the actual pressure difference and air volume data.

The advantage of this is that the next time you need to replace it, you will have complete data to check without having to collect the information again.

For occasions such as semiconductors and pharmaceuticals that have high requirements for particle control, it is recommended that the testing data of the replacement filter element and the installation leak detection records be filed together, so that the acceptance can be documented. involving the FFU fan filter unit , the fan parameters and filter element resistance data must also be saved accordingly. For the items supporting

About Aili Industrial’s alternative packages

Aili Industrial can help identify alternatives by combining the old filter element, installation frame and fan parameters. filter with FFU fan filter unit、The EFU equipment-end fan filter unit is matched in the same manufacturing system, and the interface size and sealing structure can be checked together during the planning stage.

When retrofitting an old system, it is advisable to trial-install and retest it before determining batch replacement specifications. It is recommended to provide the physical object or photo of the old filter element, the measured size of the installation frame, the original fan parameters and the target air volume to facilitate the judgment of alternatives. The specific plan shall be subject to trial installation testing and project confirmation documents.