In every industrial electrical installation — whether in an oil refinery, a chemical processing plant, an offshore platform, or a power generation facility — one small component plays a silent but absolutely critical role: the double compression brass cable gland. Choosing the wrong gland or installing it incorrectly can result in moisture ingress, insulation failure, electrical faults, or in worst-case scenarios, explosions and loss of life.
This guide provides the most comprehensive, authoritative, and up-to-date information on double compression cable glands — covering their design, working mechanism, technical specifications, installation best practices, compliance requirements, and selection criteria. We also explore why Cabex India has emerged as India’s most trusted manufacturer and global exporter of certified double compressor glands for over 30 years.
1. What Is a Double Compression Brass Cable Gland?
A double compression cable gland — also referred to as a double compressor gland or double seal cable gland — is a mechanical device used to secure, seal, and protect electrical cables at the point where they enter an enclosure, panel, or equipment housing.
The term “double compression” refers to its unique dual-sealing mechanism. Unlike a single compression gland that grips the cable at only one point (the armour layer), a double compression gland applies controlled mechanical pressure at two distinct points:
First Compression — Outer Armour
The outer seal grips the cable’s metallic armour (SWA or STA), providing mechanical retention and preventing the cable from being pulled out under tension or load.
Second Compression — Inner Sheath
The inner seal compresses firmly around the cable’s inner insulation sheath, creating a watertight and dustproof barrier that prevents moisture, gas, vapour, and contaminants from entering the enclosure.
Why Brass?
High-grade brass (CZ121 / CW617N alloy) offers excellent machinability, corrosion resistance, conductivity for earthing, and mechanical strength — making it the industry standard material for cable glands.
This dual-sealing action makes the double compression brass cable gland the preferred choice for armoured and unarmoured cables operating in hazardous, outdoor, high-vibration, or chemically aggressive environments. It meets and exceeds global standards including IECEx, ATEX, and IEC 62444.
2. Double Compression vs. Single Compression: Key Differences
Before selecting a cable gland for your project, understanding the fundamental difference between single and double compression glands is essential for both safety and compliance.
| Feature | Single Compression Gland | Double Compression Gland |
|---|---|---|
| Compression Points | One (at cable armour only) | Two (armour + inner sheath) |
| Sealing Level | Basic — moisture can seep in | Superior — dual barrier prevents ingress |
| Cable Type | Light to medium armoured cables | Heavy armoured & unarmoured cables |
| IP Rating | Typically IP54 – IP65 | IP66 – IP68 |
| Hazardous Areas | Not recommended | Fully suitable (with ATEX/IECEx cert.) |
| Outdoor / Wet Environments | Limited suitability | Highly suitable |
| Vibration Resistance | Moderate | High — dual lock prevents loosening |
| Typical Cost | Lower upfront | Moderate — far lower lifecycle cost |
| Industry Use Case | Indoor panels, light-duty commercial | Oil & gas, chemical, mining, marine, power |
Expert Tip: In sectors like oil & gas, chemical processing, and mining where hydrocarbons and explosive gases are present, double compression cable glands are not optional — they are mandated by safety regulations including ATEX Directive 2014/34/EU and IECEx standards.
3. Components of a Double Compression Cable Gland
Understanding the anatomy of a double compression cable gland helps in correct selection, installation, and maintenance. A complete double compression gland assembly consists of the following parts:
| Component | Material | Function |
|---|---|---|
| Gland Body | Brass CZ121 / CW617N | Main housing; connects gland to the enclosure; provides structural integrity |
| Outer Compression Nut | Brass | Tightens outer seal ring against cable armour — provides armour grip and mechanical retention |
| Armour Clamp / Cone Ring | Brass | Grips and locks cable armour (SWA/STA) to ensure electrical continuity and strain relief |
| Inner Sealing Ring (Grommet) | Neoprene / EPDM / Nitrile / Viton | Compresses around cable inner sheath; creates watertight and dustproof inner seal |
| Outer Sealing Ring / Washer | Neoprene / EPDM | Seals the entry point at the enclosure face; prevents external moisture ingress |
| Locknut | Brass / Steel | Secures gland body to the enclosure panel; prevents vibration-induced loosening |
| Earth Tag (optional) | Brass / Copper | Provides earthing / grounding continuity from cable armour to enclosure |
| PVC Shroud (optional) | PVC | Additional weather protection; prevents UV degradation and corrosion on exposed gland bodies |
4. Technical Specifications & Size Chart
Correct sizing is one of the most critical factors in double compression cable gland selection. Using an incorrectly sized gland compromises the seal, rendering IP ratings void and potentially creating safety hazards. The table below covers standard metric sizing for double compression brass cable glands:
| Thread Size (Metric) | Cable OD Range (mm) | Armour OD Range (mm) | IP Rating | Typical Application |
|---|---|---|---|---|
| M20 | 7 – 13 | 10 – 15 | IP66/IP68 | Control cables, light power |
| M25 | 13 – 18 | 15 – 21 | IP66/IP68 | Medium power, instrumentation |
| M32 | 18 – 25 | 21 – 29 | IP66/IP68 | Power & process cables |
| M40 | 25 – 32 | 28 – 37 | IP66/IP68 | Heavy armoured industrial cables |
| M50 | 32 – 42 | 36 – 48 | IP66/IP68 | High-voltage, offshore, mining |
| M63 | 42 – 55 | 48 – 62 | IP66/IP68 | High-capacity power systems |
| M75 | 55 – 68 | 62 – 76 | IP66/IP68 | Large-bore armoured cables |
Sizing Rule: Always measure the actual outer diameter (OD) of your cable before selecting a gland. Verify against the manufacturer’s sizing chart — never estimate by eye. An undersized gland crushes the cable; an oversized one fails to seal.
Key Technical Properties
- Material: High-tensile brass (CZ121 / CW617N); optional nickel-plated finish for marine or corrosive environments
- Thread Options: Metric (M), BSP (G), NPT, PG
- IP Protection: IP66 (standard) to IP68 (premium — continuous immersion)
- Operating Temperature: −40°C to +120°C (Viton seals extend to +200°C)
- Standards Compliance: IEC 62444, BS 6121, EN 60529, ATEX 2014/34/EU, IECEx
- Surface Finish: Natural brass, nickel-plated, or hot-dip galvanised
5. Industrial Applications: Where Are Double Compression Glands Used?
The double compressor gland’s superior sealing capability, mechanical strength, and hazardous area certifications make it indispensable across a wide range of demanding industries:
Oil & Gas
Refineries, offshore platforms, LNG terminals — environments with explosive hydrocarbon atmospheres demand ATEX/IECEx-certified double compression glands at every cable entry point.
Chemical & Petrochemical
Chemical plants processing volatile solvents, acids, and caustic substances require glands with Viton seals and corrosion-resistant brass bodies to maintain enclosure integrity.
Power Generation
Thermal, hydro, solar, and wind power plants use double compression glands to protect high-voltage cable entries from moisture, vibration, and extreme temperatures.
Mining & Quarrying
Underground mining environments expose cables to rock dust, methane gas, and constant mechanical stress — making double compression glands a safety-critical requirement.
Marine & Offshore
Saltwater corrosion, wave impact, and continuous humidity demand nickel-plated double compression brass glands with IP68 certification for all marine cable entries.
Infrastructure & Construction
Tunnels, bridges, outdoor switchgear, and industrial buildings use double compression glands to maintain weatherproof cable entry points in all climate conditions.
6. Step-by-Step Installation Guide for Double Compression Cable Glands
Correct installation is just as important as selecting the right gland. Even a premium-grade double compression cable gland will underperform if installed incorrectly. Follow this installation best-practice guide from Cabex India’s technical team:
- Verify Compatibility: Confirm the gland thread size matches the enclosure entry hole. Check that the cable outer diameter falls within the gland’s specified range using the manufacturer’s sizing chart.
- Prepare the Cable: Strip the outer sheath carefully to expose the required length of armour (SWA/STA). Cut armour wires cleanly and evenly. Strip back the inner sheath to expose the conductors as required. Avoid nicking insulation.
- Disassemble the Gland: Lay out all components — locknut, sealing washer, gland body, armour cone/ring, outer compression nut, and inner sealing grommet — in installation order before starting.
- Thread the Cable: Pass the cable through the locknut, outer sealing washer, and gland body in sequence. Fan out the armour wires over the cone ring to create a secure mechanical grip.
- Seat the Armour: Fold the armour wires back over the cone ring. Ensure all wires are evenly distributed and properly seated. This establishes electrical continuity and mechanical retention — the first compression point.
- Insert Inner Grommet: Slide the inner sealing grommet over the cable’s inner sheath. This is the second compression point and forms the watertight inner seal.
- Tighten to Specification: Use a calibrated torque wrench and tighten the gland body and outer compression nut to the manufacturer’s specified torque (typically 25–80 Nm depending on gland size). Over-tightening crushes the seal; under-tightening fails to seal.
- Mount and Secure: Thread the assembled gland into the enclosure entry. Tighten the locknut firmly. Attach an earth tag if required for armour continuity.
- Inspect & Test: Conduct a visual inspection of the installed gland. For hazardous area installations, perform an IP ingress test before energising the system. Log the gland’s batch certification number for compliance records.
Critical Reminder: Always use original cable gland accessories — shrouds, locknuts, and earth tags — from the same certified manufacturer. Mixing components from different suppliers can invalidate the gland’s IP and ATEX ratings, voiding compliance.
7. Compliance Standards & Certifications
For any industrial installation — and especially in hazardous areas — ensuring your double compression cable gland meets the relevant international and Indian standards is non-negotiable. Using uncertified glands can result in audit failures, project shutdowns, legal liability, and catastrophic safety incidents.
Key international and Indian certifications to verify include:
- ATEX (EU Directive 2014/34/EU): Mandatory for explosive atmosphere applications in Europe. Certifies glands as safe for use in Zone 1 and Zone 2 hazardous areas.
- IECEx: Internationally recognised across 50+ countries including India, Middle East, Australia, and Southeast Asia. Ensures consistent global compliance.
- CMRI (India): Central Mining Research Institute certification — mandatory for electrical equipment in Indian mining operations.
- ISI (BIS): Bureau of Indian Standards certification for domestic Indian market compliance.
- EN 60529 / IEC 60529: Defines IP (Ingress Protection) ratings from IP54 to IP68 for dust and water resistance.
- IEC 62444: Specifies cable retention, pull-out resistance, and performance requirements for cable glands.
- BS 6121: British standard for cable glands in electrical equipment — widely accepted in Middle East and African markets.
Why Industry Leaders Trust Cabex India
With over 30 years of engineering excellence, Cabex India manufactures and exports ATEX & IECEx certified double compression brass cable glands to clients across Europe, the UK, the Middle East, Australia, and Southeast Asia. Every gland carries full batch traceability, zero-defect manufacturing commitment, and internationally recognised certifications.Explore Cabex Double Compression Glands →
8. Why Choose Cabex India for Double Compression Cable Glands?
Not all cable glands are created equal. When safety, compliance, and long-term reliability are at stake, the manufacturer you choose matters enormously. Cabex India stands apart in the Indian and global cable gland market through a combination of proven manufacturing excellence, global certifications, and decades of customer trust.
ATEX Certified
IECEx Certified
CMRI Certified
ISI / BIS Marked
IP68 Rated
30+ Years Experience
Global Exporter
Zero-Defect Manufacturing
Cabex India’s Differentiating Strengths
1. Manufacturing Legacy & Engineering Depth: Founded with a commitment to industrial safety, Cabex India has spent over three decades mastering the science of cable termination. Their engineers understand exactly what it takes to build a gland that performs in the harshest environments on Earth — from offshore oil rigs to underground mines.
2. Full Certification & Batch Traceability: Every Cabex double compression cable gland is manufactured and certified with full batch-level traceability. This is critical for hazardous area audits where certification numbers must be logged and verifiable. Clients receive complete technical datasheets and test reports with every supply.
3. Precision-Grade Brass Manufacturing: Cabex India uses premium-grade brass alloy (CZ121 equivalent), precision-machined on CNC equipment to tight tolerances. The result is consistent thread quality, seal concentricity, and armour grip performance across every gland in every production batch.
4. Comprehensive Product Range: Cabex India offers the complete spectrum of cable gland solutions — from standard double compression brass glands to flameproof double compression glands, nickel-plated variants, stainless steel glands, and fully customised solutions engineered to client specifications.
5. Global Reach, Local Support: With established export credentials in Europe, the UK, Australia, the Middle East, and the Far East, Cabex India combines global quality standards with responsive local support — making them equally trusted by multinational EPC contractors and domestic industrial buyers.
6. Accessories Ecosystem: Every Cabex gland is supported by a complete range of hazardous area cable gland accessories — PVC shrouds, locknuts, earth tags, adapters, and reducers — all sourced from the same certified manufacturer to ensure compatibility and compliance.
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9. Selection Checklist: Choosing the Right Double Compression Gland
Before placing an order for your double compression cable gland, work through this checklist to ensure you select the right product for your specific application:
- ☑️ Cable type: Armoured (SWA/STA) or unarmoured?
- ☑️ Cable outer diameter: Measure accurately and match to gland size chart
- ☑️ Thread type: Metric / BSP / NPT / PG — verify enclosure entry thread
- ☑️ IP rating required: IP66 for weather protection; IP68 for immersion environments
- ☑️ Hazardous area classification: Zone 0/1/2 (Gas) or Zone 21/22 (Dust) — verify ATEX/IECEx cert. accordingly
- ☑️ Material: Standard brass; nickel-plated brass for corrosive/marine; stainless steel for offshore
- ☑️ Temperature range: Confirm seal material (Neoprene, EPDM, or Viton) suits operating temperature
- ☑️ Certifications: Request ATEX/IECEx/CMRI certificates and batch test reports from supplier
- ☑️ Accessories: Confirm availability of matching shrouds, locknuts, and earth tags from same certified source
10. Frequently Asked Questions (FAQ)
What is a double compression brass cable gland?
A double compression brass cable gland is a precision-engineered mechanical fitting that secures and seals electrical cables at their entry point into enclosures or electrical equipment. It applies compression at two distinct points — at the cable armour and at the inner cable sheath — creating a dual barrier against moisture, dust, gas, and mechanical stress. Manufactured from high-grade brass, it is the standard choice for demanding industrial, hazardous, and outdoor applications.
What is the difference between single and double compression cable glands?
A single compression gland applies sealing pressure at only one point — the cable armour — making it suitable for light-duty indoor applications. A double compression cable gland seals at both the armour and the inner sheath, providing significantly superior protection against moisture ingress, corrosive vapour, and mechanical pull-out. Double compression glands are mandatory for hazardous areas, outdoor environments, and heavy armoured cable installations.
What IP rating does a double compression cable gland have?
High-quality double compression cable glands achieve IP66 (protection against powerful water jets) or IP68 (protection against continuous water immersion up to 1.5 metres for 30 minutes or more). Cabex India’s double compression glands are certified to IP68, making them suitable for the most demanding wet, outdoor, and submerged applications.
Can a double compressor gland be used for unarmoured cables?
Yes. While double compression glands are primarily designed and optimised for armoured cables (SWA/STA), they can also be used with unarmoured cables in applications where enhanced sealing, superior ingress protection, and additional strain relief are required — for example, in wet, dusty, or chemically aggressive environments.
What certifications are required for double compression cable glands in hazardous areas?
For hazardous area installations, your double compression cable gland must carry ATEX certification (for European Zone 1/2 applications) and/or IECEx certification (internationally recognised). In India, CMRI certification is required for mining applications, while ISI/BIS marking applies for domestic industrial use. Always request complete certification documents and batch-level test reports from your supplier — never rely solely on product brochures or catalogue claims.
What thread types are available in double compression brass cable glands?
Double compression brass cable glands are available with Metric (M) threads (M16 to M75+), BSP/G threads, NPT (American National Pipe Thread), and PG threads. The correct thread type depends on your enclosure’s entry configuration and the installation standard applicable in your region. Cabex India supplies all four thread types and can also manufacture custom thread configurations.
How often should double compression cable glands be inspected?
For hazardous area installations, visual and torque inspections should be conducted at least annually. Replace any gland showing signs of corrosion, cracked seals, pitting, or compromised insulation immediately. Maintain a logbook recording each gland’s ATEX/IECEx batch certification number and installation date — this is mandatory for compliance audits in most regulated industries.