IS (Intrinsically Safe) vs. NIS (Non-Intrinsically Safe) Cables: Comparison and Selection Guide
This guide provides a detailed comparison of IS (Intrinsically Safe) and NIS (Non-Intrinsically Safe) cables, covering their core differences, applicable scenarios, and selection criteria. Aligned with international standards (IEC, ATEX) and Chinese regulations (GB 3836, GB/T 19666), it helps engineers optimize cable selection for safety-critical environments.
1. Core Differences: Safety Design and Applications
| Feature | IS Cables | NIS Cables |
|---|---|---|
| Explosion Protection | Limits circuit energy (current/voltage) to prevent sparks | No energy limitation design |
| Applicable Environment | Hazardous areas (e.g., oil, chemical, mining) | Non-hazardous industrial/commercial areas |
| International Standards | IEC 60079-11, ATEX | IEC 60227, IEC 60502 |
| Chinese Standards | GB 3836.4, GB 3836.15 | GB/T 19666 (flame retardancy) |
| Structural Requirements | Compact filling, optional shielding/armor | Standard construction |
2. Key Selection Criteria: 5 Optimization Principles
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Risk Assessment
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IS Cables: Mandatory for Zone 0/1/2 (flammable gases/dust).
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NIS Cables: Restricted to non-hazardous areas (e.g., factories, offices).
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Structural Design
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Compactness: Hazardous areas require circular, densely filled cables (core-to-sheath and core-to-core compaction) to prevent gas infiltration via "thermal pumping effects" (per GB 3836.15).
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Shielding & Grounding:
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Shielded cables require single-end grounding (equipment side) with resistance ≤4Ω.
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Armored cables (e.g., IA-DJYPVP22) need armor-clamping devices for reliable grounding.
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Material & Certification
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IS Cables: Require IS parameter test reports (max current, voltage, capacitance, inductance) and system certifications (e.g., ATEX, IECEx).
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NIS Cables: Must comply with flame retardancy (e.g., ZC class, GB/T 19666-2019) and general electrical standards.
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Compatibility Verification
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IS cables must match device parameters (e.g., capacitance ≤ device tolerance) to avoid energy overload.
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Cost & Maintenance
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IS Cables: Higher upfront cost but lower maintenance (safety prioritized).
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NIS Cables: Cost-effective for non-explosive environments.
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3. International Client Needs: Certifications & Documentation
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Quotation Requirements: Specify cable type (IS/NIS), specs (cross-section, voltage, shielding/armor), length, and standards (e.g., IEC, NEC).
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Certification Documents:
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IS Cables: Provide system-level explosion-proof certifications (ATEX/IECEx) and IS parameter test reports.
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NIS Cables: Submit flame retardancy test reports (GB/T 19666) or IEC compliance declarations.
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Technical Support: Customized bilingual documents (datasheets, installation guides).
4. FAQs
Q1: Do IS cables require shielding?
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Shielding is optional but recommended for high EMI environments (e.g., near inverters). Ensure single-end grounding.
Q2: How to validate IS system safety?
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Submit IS parameter test reports (issued by CMA/CNAS-accredited labs) to confirm cable-device compatibility.
Q3: Can NIS cables be used near chemical plants?
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Only in non-hazardous zones (e.g., control rooms). Hazardous areas mandate IS cables.
5. Summary & Recommendations
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Choose IS Cables: High-risk explosive environments, ATEX/IECEx-certified projects.
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Choose NIS Cables: General industrial/commercial setups with no explosion risks.
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Certification Bodies: National Supervision and Inspection Center for Explosion Protection Equipment (China), TÜV Rheinland, SGS.