Meta-aramid/Nomex filter bags are a strong option at high temperature, but should not be selected automatically without evaluating acidic moisture and chemical gases.
What Is a Meta-Aramid / Nomex Filter Bag?
Meta-aramid filter bags, also known in the market by the name Nomex, are a high-temperature-resistant media family. They are considered for asphalt, hot mineral processes, certain cement/lime points and hot gas filtration.
Temperature and Chemistry
As a general preliminary selection, 180-200°C operation with a 220°C short peak can be discussed; however, an acidic moisture environment poses a serious risk for aramid. A definitive selection cannot be made without SOx/SO3, NOx/NO2, HCl/HF, moisture, and dew point information.
| Condition | Aramid comment | Control |
|---|---|---|
| High-temperature dry gas | Strong candidate | Peak Temperature |
| Acidic humidity | At risk | SOx/gender/dew point |
| Corrosive dust | Mechanical inspection is required | Inlet distribution/cage |
Aramid, PPS, or P84?
Aramid is mechanically strong at high temperatures; PPS can be advantageous under certain chemical/moisture conditions; and P84 can be considered for high-temperature and fine-dust performance. The selection should never be made from a temperature table alone.
When Should I Choose Aramid?
Example
Example
- Process
- Asphalt plant filter
- Heat
- 170-200°C
- Risk
- Hot peaks and oily/acidic components
- Approaches
- Aramid + surface finish + chemistry check
Information for Bid
For an aramid quote, we request temperature trend, fuel/process type, acid/moisture data, bag dimensions, cage, snap-band, pulse pressure, and damage history. You can submit this data through the quote form. It can be compared with the PPS guide and the P84 guide.
Frequently Asked Questions
Are Nomex and meta-aramid the same?
Nomex is a common brand/trade name; technically it falls within the meta-aramid media family.
Is aramid suitable in acidic gas?
Acidic moisture is a risk factor; selection should not be made without verifying gas chemistry and dew point.
Engineering Selection Parameters: Media Name Alone Is Not Enough
When selecting a filter bag, the media name is only a starting point. The same meta-aramid / Nomex filter bag can run stably under a low A/C ratio, dry dust, and a properly functioning pulse system, but under high airflow, a damp cake, a poor cage, or an incorrect snap-band size, it can develop a dP or emission problem within a short time. That is why, in Hantech's evaluation, the bag is read together with the fan, filter area, cage, cell plate, pulse valve, and hopper behavior.
| Parameter | - why it is critical | Data requested for the quote |
|---|---|---|
| Normal / peak temperature | Media aging, shrinkage, and seam strength | Shift records, alarm history |
| Moisture and dew point | Sticky cake, hydrolysis, or chemical aging | Gas moisture, insulation, start-stop behavior |
| Gas chemistry | SOx/SO3, NOx/NO2, HCl, HF, O2, and an alkaline environment change media life | Gas analysis or process recipe |
| Powder micron distribution | 1-3 µm dust embeds into the felt; coarse abrasive dust wears down the housing | Particle analysis or site observation |
| A/C ratio | High filtration velocity causes rising dP and short bag life | Flow rate, bag diameter-length-count |
| dP trend | Indicates blinding, leaks, or inadequate cleaning | Pa/mmWG chart after new bags |
| Cage outer diameter and surface | Incorrect OD, burrs, or rust mechanically abrade the bag | Cage photo, OD, wire count |
| Snap-band / cell plate | Mouth leakage produces low dP + high emissions | Hole diameter, sheet thickness, bead detail |
This approach is especially important for meta-aramid / Nomex filter bag, because in the field the problem often appears to be 'bad media,' but the root cause may be the A/C ratio, pulse energy, moisture, cage surface, or cuff sealing.
Which Field Symptom Changes Which Decision?
| Site indication | Possible root cause | Hantech approach |
|---|---|---|
| dP rises above 1800-2200 Pa after new bags | High A/C, fine dust penetration, moist cake, or weak pulsing | Surface treatment/membrane need and filter area are checked together |
| Low dP but dust at the stack | Filter bag tear, snap-band leakage, or bypass | Cell plate, collar detail, and cage contact marks are checked |
| Vertical wear on the filter bag body | Cage burrs, incorrect OD, or bag chafing | Bag performance cannot be upgraded without replacing the cage surface and wires/rings |
| Dust traces at the filter bag top | Snap-band isn't seating properly, or sheet thickness is wrong | Double cord, band size, and hole tolerance are re-measured |
| dP increases on humid days | Dew point, condensation, or sticky cake | Thermal insulation, hydrophobic surface, and process control are evaluated together |
This table is used at the quoting stage to avoid selling the customer an unnecessary premium media. If the symptom stems from a mechanical or process issue, choosing a more expensive bag will not be a lasting solution.
Comparison with Alternative Media
Aramid is compared against PPS, P84, and fiberglass/PTFE options specifically in terms of the balance between temperature, chemistry, and mechanical strength. Hantech's approach is not to push a single brand or the most expensive option, but to balance the most economical, sufficiently safe solution against process risk.
| Comparison criterion | Comment for this media | Alternative decision |
|---|---|---|
| Heat | 180-200°C operation with a 220°C short-term peak basis may be possible; acid/moisture content can limit this. | If the limit is exceeded, a higher-grade media is considered |
| Fine dust / low emission | A need for surface treatment or a membrane can arise | ePTFE membrane, P84, or PTFE is compared |
| Moisture / acid | Media chemical resistance is not read on its own -- it's assessed together with dew point | Options such as PPS/PTFE/fiberglass PTFE may be required |
| Mechanical risk | Cage and installation errors can ruin even good filter media | The cage/snap-band/pulse system is corrected first |
| Expense | Premium media is selected only when there is a real risk or target | Adequate candidates such as PES/PPS/Aramid are not ruled out |
Under These Conditions, I Would Not Choose Meta-Aramid / Nomex Filter Bag
Worked Example: Aramid Filter Bag Selection for an Asphalt Plant
Sample account and comment
- Flow Rate
- 60,000 m³/h
- Bag size
- Ø160 x 6,000 mm
- Number OF bags
- 240
- One bag area
- π x 0.16 x 6.0 = 3.02 m²
- Total Area
- 240 x 3.02 = 724.8 m²
- Gross A/C
- 60,000 / 60 / 724.8 = 1.38 m/min
- First decision
- Meta-aramid / Nomex filter bags are evaluated based on dust particle size, moisture, and dP trend
This example value is not good or bad on its own. 1.38 m/min may look acceptable for dry, medium-grain mineral dust, but risky for fine (1-3 µm), sticky, or moist dust. If dP rises quickly after a new bag is installed, the surface finish, pulse energy, filter area, and inlet distribution should be reviewed together, not just the media.
Aramid is a strong candidate for mechanical strength at high temperature; the decision may change if acidic moisture is present. However, this choice should not be finalized into a firm quote without first verifying cage surface condition and snap-band fit.
RFQ / Quotation Checklist
Size and quantity alone are not enough for a sound meta-aramid / Nomex filter bag quote. The minimum data set is: bag diameter, bag length, quantity, top attachment type, bottom cap detail, current media and weight, surface treatment, normal/peak temperature, moisture or dew point risk, gas chemistry, dust type, micron distribution, dP trend, target emission, cage outer diameter, cell plate hole size, sheet thickness, pulse pressure, and photos of the current bag/cage.
Once this information is available, Hantech evaluates filter bags, filter cages, pulse-jet valves, and if needed performance measurement together. You can submit the data via the quote form.
Technical Review Note
Technical review: Doğuhan Kırmacı — industrial filtration, dust collection systems and filter bag selection applications.
This content has been prepared by comparing process data, manufacturer technical limits, field failure behavior, and bag-cage-pulse compatibility. The values here are for preliminary selection; the final selection must be verified against the manufacturer's datasheet, site measurements, and process conditions.