A used dryer fabric's field CFM reading is not, by itself, a specification for its replacement. Before comparing it with a new fabric's published value, confirm how both figures were measured and what condition each fabric was in. If those details are missing, keep the readings as separate observations rather than treating their numerical difference as a design target.
Start with the question behind the measurement
A mill may measure permeability because drying has become uneven, a fabric appears contaminated, or a replacement is being planned. Record the dryer group and position, the reason for measuring, and whether the fabric was running, cleaned, or removed when it was tested.
The measurement can help describe the condition of the fabric in service. It does not independently identify the construction, material, seam, or permeability that the next fabric should have. The dryer-fabric selection guide covers those position-specific design questions; this article focuses on whether the numbers being compared mean the same thing.
Check whether two readings are comparable
Use the original reports, not just two CFM numbers, to complete this record:
| Check | Current fabric: original specification | Used fabric: field reading | Proposed new fabric |
|---|---|---|---|
| Fabric identification and dryer position | Record from data sheet | Confirm it is the same fabric and position | Identify proposed construction |
| Test method and instrument | Record if stated | Record | Record if stated |
| Pressure differential | Record if stated | Record | Record if stated |
| Reported unit and area basis | Copy exactly as written | Copy exactly as written | Copy exactly as written |
| Measurement date and fabric condition | New-fabric condition | Age, cleaning and operating condition | New-fabric condition |
| Measurement locations | Record if stated | Record locations across the width | Record if stated |
If the method, pressure differential, or unit basis cannot be confirmed, do not calculate a percentage change between the readings. ISO 9237 describes a method for measuring fabric air permeability; citing the standard does not establish that any particular PAPTEX model or field reading was tested under it.
Even where the methods match, a used-fabric measurement describes a fabric after service. The original specification and the proposed new-fabric value describe different states. Review them alongside the actual dryer-position record before deciding whether any design change is warranted. A numerical difference is a question to investigate, not a replacement recommendation.
Look beyond one spot reading
A single reading may miss a local restriction. In its dryer-fabrics technical paper, Valmet explains that a small number of spot checks may not show the full permeability profile and discusses measurements across the fabric width. That is industry evidence for checking the pattern of readings; it is not a PAPTEX test result.
If readings differ across the width, record their locations and inspect the corresponding fabric and operating conditions. Contamination or wear may be relevant, but the readings alone do not establish the cause or prove that a different new-fabric CFM will correct it. Keep any cleaning history and dated inspection photographs alongside the readings.
How to read PAPTEX model ranges
PAPTEX's 2026 product parameter sheet records 600–709 CFM for GW22504 and 500–600 CFM for GW24504. The sheet does not state the test method, pressure differential, area basis, or a batch inspection result for those ranges. Treat them as values recorded in the product parameter sheet, not as directly comparable targets for a used fabric measured by an undocumented field method.
The sheet also does not establish the material or seam for these two models. Those details must be confirmed for the proposed construction and order; they should not be inferred from a similarly named model. In particular, the separately documented GW22504K is not the same model as GW22504.
What to send for a useful replacement review
Send the current fabric's identification and original data sheet if available, the dated field readings with their test conditions and locations, and the observation that prompted the review. Identify the exact dryer position and include relevant cleaning and operating records. Mark unknown fields as unknown.
That gives the mill and supplier a defensible starting point: they can distinguish a measurement issue, a fabric-condition issue, and a proposed specification change before approving a replacement.
For dimensions, installation constraints and the broader order package, use the existing replacement dryer-fabric checklist. To review a specific position and its available readings, contact PAPTEX.
Source boundary: The model ranges above come only from PAPTEX's 2026 product parameter sheet; the sheet omits the named test conditions. ISO describes a testing method, and Valmet discusses permeability-profile measurement. Neither source verifies PAPTEX's model-specific material, seam, test method, batch record, or performance on a particular paper machine.
