CW-4 Tape Validation: Line & Interface

Qualify semi conductive non woven tape by line and interface. Buyers should choose the grade by its position and duty in the cable, not by black color or a generic material name. For use inside the metal-jacket region or another drawing-defined location, connect the grade-specific electrical and mechanical data with roll quality, wrapping behavior and evidence from a controlled cable-line trial.

Conceptual industrial scene; it does not show a Chaowang production line, customer cable or approved test result.

Where Semi Conductive Non Woven Tape Fits

Jiangsu Chaowang New Material describes CW-4 Semi-Conductive Non Woven Tape as polyester fiber combined with semi-conductive adhesive, intended for cushioning and water-blocking service inside the metal jacket of extra-high-voltage power cable. Confirm that duty against the layer drawing and cable specification.

The public BWFD20 listing gives 0.20 ± 0.02 mm thickness, 100 ± 10 g/m² mass per unit area, tensile strength of at least 60 N/cm, elongation of at least 12% and surface resistance below 150 Ω. The page labels another field “Volume Resistance” and reports below 1 × 10^5 Ω·cm. Because Ω·cm is a resistivity unit, confirm whether the current datasheet means volume resistivity and verify the method. It also lists instantaneous and long-term thermal-stability values of 230°C and 90°C. These product-page values do not replace the current datasheet, test methods, certificate of analysis or cable-design approval.

Keep the quantities separate in an RFQ. Thickness is a dimensional value; g/m² is mass per unit area. If buyer and supplier use ISO references, ISO 9073-1 addresses mass per unit area, ISO 9073-2 addresses nonwoven thickness under specified pressure, and ISO 9073-3 addresses tensile strength and elongation by a strip method. Confirm the agreed edition and procedure rather than comparing numbers generated under different conditions.

Separate CW-4 from Binding and Swellable Grades

“Nonwoven cable tape” describes a broad material family, not one interchangeable function. The CW-1 nonwoven binding tape is positioned for binding and wrapping. The CW-5 water-blocking tape uses superabsorbent polymer for a swelling function, but its public page does not identify it as a semi-conductive grade. Neither product should be approved as a CW-4 substitute from appearance alone.

Likewise, CW-4 is not the same product as CW-8. The published CW-8 semi-conductive water-blocking tape construction includes superabsorbent polymer and lists swelling data. The public CW-4 page does not list SAP, expansion height or expansion rate. If a cable layer requires both a semi-conductive interface and a defined swellable response, write both requirements into the specification and review the appropriate grade instead of assuming every black tape will swell.

The broader Chaowang non-woven cable tape range helps buyers compare functional families. The final selection should follow the cable drawing, electrical duty, mechanical duty and required water-blocking mechanism.

Control Roll Geometry and Line Handling

Laboratory data cannot compensate for a roll that tracks poorly. Before ordering production quantity, define slit width and tolerance, core inside diameter, maximum roll outside diameter, winding format, usable length, splice rules, edge quality and packaging. Ask Chaowang to confirm the current converted-roll capability for the requested format; do not copy another supplier’s pad or spool dimensions into the purchase order.

During a representative trial, start from recorded baseline settings and change one variable at a time. Observe:

• Unwind behavior: stable tension, no telescoping, blocking or sudden release.
• Guiding and tracking: centered travel through guides without edge fold or lateral drift.
• Overlap: consistent helical coverage at the specified tape angle and line speed.
• Surface condition: no unacceptable shedding, contamination, wrinkles or exposed gaps.
• Finished build: acceptable diameter, roundness and compatibility with the next process step.

Conceptual overlap detail; actual coverage, tension and acceptance limits must follow the approved cable construction.

Record roll identity, tape width, overlap, line speed, pay-off tension, guide arrangement and observations. A vague note that the tape “ran well” is difficult to reproduce. If the edge lifts or the tape wrinkles, isolate whether the cause is the roll, alignment, tension, overlap or the underlying cable surface before changing several settings together.

Verify Electrical-Property Retention at the Interface

Surface resistance and volume resistance are different properties, and both depend on the stated method, specimen conditioning, electrode arrangement and units. Where the parties agree they are appropriate, IEC 62631-3-1 and IEC 62631-3-2 provide separate DC-method references for volume and surface resistive properties. Citing them here does not claim that Chaowang uses these methods or that CW-4 is certified to them.

A practical approval sequence has three levels:

1. Incoming material: confirm identity, dimensions, mechanical data, separately defined electrical properties and roll condition against the approved grade and methods.
2. Wrapped layer: inspect overlap, contact, surface damage and process consistency, then test agreed electrical characteristics on a defined specimen or trial construction.
3. Finished cable: complete the electrical, mechanical and water-related tests required by the cable design and customer specification.

Conceptual validation scene; no displayed instrument value or production release is implied.

Retain the trial record and agreed sample. If an electrical result or processing behavior changes after wrapping, investigate conditioning, abrasion, compression, contamination and specimen preparation before assigning a cause. Material-page data alone cannot prove performance in every cable geometry.

Frequently Asked Questions

Is every black nonwoven cable tape semi-conductive?

No. Black may be a useful visual identifier within an approved system, but color is not electrical acceptance evidence. Require the exact grade, surface and volume resistance values, units, test method, conditioning and lot documentation.

Is CW-4 a swellable water-blocking tape?

The public CW-4 page mentions cushioning and water-blocking service but does not publish SAP or swelling-response data. Do not describe it as swellable without grade-specific documentation. If expansion is required, state the test liquid, time, method and acceptance value in the RFQ.

When should CW-8 be considered instead?

Consider CW-8 when the layer specification requires a semi-conductive tape with a defined superabsorbent-polymer construction and swelling response. It is not an automatic replacement for CW-4: confirm the cable layer, thickness, electrical, mechanical and water-blocking requirements before choosing a grade.

Can surface resistance replace a volume resistivity requirement in an RFQ?

No. They describe different measurement paths and should not be treated as alternative labels for one result. Because the CW-4 page uses “Volume Resistance” beside an Ω·cm value, confirm the intended property, then state units, method, conditioning, electrode arrangement and acceptance limit.

Which line conditions should remain fixed during a CW-4 trial?

Fix and record the cable build, tape width, roll identity, overlap target, line speed, pay-off tension, guide arrangement and downstream process. Change one variable at a time so a tracking, wrinkle or electrical-result change can be investigated against a stable baseline.

How should electrical results before and after wrapping be compared?

Use agreed specimen definitions, conditioning, electrodes, units and test methods at both stages. Record the applied tension, overlap and sampling position. A change is meaningful only when the comparison conditions are controlled; the acceptance limit must come from the cable specification or approval plan.

To qualify semi conductive non woven tape for a new power-cable construction, contact Jiangsu Chaowang New Material with the layer drawing, electrical requirements, roll geometry, test methods and trial conditions. Request the current CW-4 datasheet and a representative sample before approving production volume.