Can ULPA be used in high temperature environments?

This question cannot be answered simply by 'can' or 'can't'. The filtration mechanism of ULPA is the same as that of the normal temperature version, relying on filter materials to intercept particles. The difference is that when the temperature rises to a certain level, each component in the material system—filter material, colloid, sealing gasket, and outer frame—faces its own temperature resistance boundary.

The grade does not indicate temperature resistance. U15 and U16 describe filtration efficiency and are not directly related to temperature. One U16 may be able to withstand temperatures of 200°C, while another U16 may not even be able to withstand 80°C. Determining whether it can be used in high temperature environments depends on the material configuration and verification conditions of the specific model.

The temperature working conditions must be written completely

The word 'high temperature' is too general. Before selecting a model, first disassemble the temperature working conditions.

What is the continuous operating temperature. This is the temperature that the filter element needs to withstand for a long time. The aging speed, strength and sealing performance of the material at this temperature are the core basis for selection.

Are there any short-term peaks? The temperature may temporarily exceed the normal operating value during equipment startup and shutdown, process switching, or abnormal conditions. What the peak temperature is, how long it lasts, and how often it occurs determines whether the material can withstand it.

Heating and cooling rate. Rapid heating or cooling can cause thermal stress between different materials. The expansion coefficients of the outer frame and the filter material are different, and the colloid may bear additional shear forces during temperature changes. The faster the temperature rise and fall rate, the greater this stress.

What is the environmental medium. Is there water vapor, acidic gas or organic solvent in the high temperature air? Temperature plus chemical media make the test of materials more complicated than high temperature alone. Please refer to the relevant instructions for the material selection method for specific corrosive environments.

Only after understanding these four items can you proceed to material selection. The supplier only gives a requirement of 'temperature resistance', and the supplier cannot configure it accurately. For specific technical agreement agreement methods, please refer to the relevant instructions on ULPA efficiency requirements.

Temperature resistance boundary of filter material

Different filter materials have different temperature resistance capabilities.

Glass fiber filter material usually has better temperature resistance and is a common choice for high-temperature working conditions. But the specific upper limit depends on the composition and surface treatment of the glass fiber. Ordinary glass fiber and high-temperature glass fiber have different temperature resistance ranges and cannot be mixed.

PTFE filter material also has a wide temperature resistance range, but it should be noted that PTFE may produce trace amounts of outgassing at high temperatures, which may have an impact on certain processes. If the project has both resistance and low outgassing requirements, the outgassing performance of PTFE at the target temperature needs to be confirmed. For specific outgassing verification methods, please refer to the relevant instructions on low outgassing.

The temperature resistance data of the filter material should be viewed together with the entire product. Just because the filter material itself can withstand 200°C, it does not mean that the made filter element can also operate at 200°C for a long time. Gels and seals may have lower upper temperature limits. involving When selecting the ULPA ultra-high efficiency filter , the temperature resistance parameters should cover the entire configuration.

Glues and seals are often the weak link

Under high temperature conditions, the failure of colloids and seals often occurs earlier than that of filter media.

The temperature resistance of the edge sealing glue determines whether the bonding between the filter material and the frame is reliable at high temperatures. Ordinary colloids may soften, age or crack under high temperatures. Once the glue seam fails, air bypasses the filter, causing problems with both efficiency and sealing. For specific colloid selection methods, please refer to the relevant instructions on selecting sealants according to working conditions.

The material of the gasket also has a temperature resistance limit. Silicone, fluororubber, EPDM and other materials have different applicable temperature ranges. At high temperatures, the sealing gasket may harden and lose its resilience, resulting in a decrease in the pressing force and gaps in the sealing surface.

the outer frame also needs to be considered. Thermal expansion of The metal frame will expand at high temperatures, and dimensional changes may affect the fit with the mounting frame. If the expansion coefficients of the outer frame and other components of the filter element are significantly different, structural stresses may occur during temperature cycles. For specific frame material selection, please refer to the relevant instructions on the comparison between aluminum alloy and stainless steel.

When selecting the model, the overall upper temperature resistance limit should be determined based on the lowest item. The filter material is resistant to 200°C, but the colloid is only resistant to 150°C. The continuous operating temperature of the entire product cannot exceed 150°C.

Thermal state detection cannot copy the normal temperature solution

The detection under high temperature working conditions is different from that under normal temperature.

Efficiency testing should indicate the temperature conditions. Efficiency data measured at room temperature cannot directly represent performance at high temperatures. Temperature changes will affect gas density and viscosity, which in turn affects the flow rate through the filter material and filtration efficiency. If the project requires verification of efficiency at high temperatures, the testing conditions and judgment standards must be agreed separately. For specific testing items, please refer to the relevant instructions for factory testing.

The conditions for leak detection must also be confirmed. It needs to be verified whether the aerosols and instruments used for leak detection at room temperature are suitable for use at high temperatures. The conditions and methods of hot leak detection should be implemented according to the project plan and cannot be directly replaced by the normal temperature plan.

The calculation of pressure difference and air volume should be based on thermal conditions. At high temperatures, the gas density decreases, and the relationship between the mass flow rate and the volume flow rate of the fan will change. If the fan selection is based on normal temperature data, the actual air volume may deviate from expectations under high-temperature operation. Supporting FFU fan filter unit or The system, fan and control parameters of the fan filter unit at the EFU equipment end must also be checked according to the hot working conditions.

How to determine status during operation

In high-temperature environments, the status monitoring of filter elements needs to be combined with temperature data.

Differential pressure records should be marked with temperature. The same filter element may have different differential pressure readings at different temperatures. Only by recording the pressure difference and the corresponding temperature together can we determine whether the change comes from dust accumulation or temperature fluctuations.

The aging of seals requires regular inspection. High temperatures will accelerate the aging of seals and colloids. When replacing the filter element, check the condition of the gasket. If it has hardened or cracked, it is recommended to replace it instead of continuing to use it. For specific seal inspection methods, please refer to the instructions related to glue seam cracking.

The operating temperature curve should be retained. The temperature change range, peak duration and number of cycles in actual operation are important basis for judging whether the filter element is working within the design range. This data can be used for subsequent replacement or troubleshooting.

Project judgment example

A certain piece of equipment needs to operate at a higher temperature. The original filter is a room-temperature type H14, and the replacement cycle is very short. The project is considering switching to ULPA and hopes to solve the temperature resistance problem.

The investigation found that the colloid of the original filter element had softened at the operating temperature, and the glue seams were slightly deformed. The filter material itself is in normal condition, but the temperature resistance of the colloid is insufficient.

Processing direction: First confirm the operating temperature and peak conditions, and then select a colloid and seal solution that matches the temperature. In terms of filter material, the glass fiber solution may be more suitable for this working condition, but the temperature resistance of the edge sealing glue and outer frame treatment needs to be confirmed. At the same time, the thermal operating point of the fan needs to be recalculated to avoid insufficient air volume at high temperatures. involving HEPA/ULPA air filters should be written into the technical agreement. The selection and temperature resistance requirements of

The key to this case is: the temperature resistance problem is often not in the filter material, but in the colloid and seals. When selecting, check the entire configuration, rather than just looking at the temperature resistance data of the filter material.

Selection and Acceptance Checklist

About Aili Industrial’s high-temperature working condition supporting equipment

The core of ULPA selection for high-temperature working conditions is to match the temperature conditions, material resistance and overall configuration. If any one of these links is missing, the plan may not work.

Aili Industry has independent manufacturing capabilities in filters, fans, control systems and sheet metal processing, and can provide ULPA ultra high efficiency filter、HEPA high-efficiency filter and supporting air supply equipment. For high-temperature working conditions projects, continuous temperature, peak conditions, media environment and installation space can be combined to assist in checking the filter material type, colloid scheme and outer frame treatment method. When the filter is matched with equipment such as FFU and EFU, the working point of the fan under thermal conditions can also be calculated together in the planning stage.

Provide complete temperature operating conditions, medium conditions and verification requirements when enquiring, which will help confirm the appropriate high-temperature configuration plan. The specific selection is subject to the technical documents and test results confirmed by the project.