Brass Glands for Armored Cables: SWA vs. STA Selection Guide

Introduction

Choosing the wrong gland for your armored cable isn’t just an inconvenience—it’s a safety hazard. I’ve seen installations where steel wire armored (SWA) cables were terminated with standard compression glands, leaving the armor floating without proper earthing. The result? Failed electrical inspections, compromised fault protection, and expensive rework.

Brass glands for armored cables are specialized termination devices designed to mechanically secure and electrically bond either Steel Wire Armored (SWA) or Steel Tape Armored (STA) cables—and selecting the correct type based on your armor construction is critical for safety, compliance, and long-term reliability.

I’m Samuel, Sales Director at Bepto Connector, and over the past decade, I’ve helped engineers across mining, petrochemical, and industrial sectors navigate the complexities of armored cable termination. Whether you’re installing power distribution in hazardous areas or running control cables through harsh outdoor environments, understanding the differences between SWA and STA glands will save you time, money, and potential safety incidents. Let me walk you through everything you need to know.

Table of Contents

• What Are SWA and STA Cables and Why Do They Need Specialized Glands?
• How Do SWA and STA Brass Glands Differ in Design and Function?
• How to Select Between SWA and STA Glands for Your Application?
• What Are the Critical Installation Steps for Armored Cable Glands?

What Are SWA and STA Cables and Why Do They Need Specialized Glands?

Armored cables incorporate metallic protective layers that provide mechanical protection and serve as the circuit protective conductor (CPC)¹ for fault current return paths—but only when properly terminated with compatible glands.

Understanding SWA (Steel Wire Armored) Cables

SWA cables feature a layer of galvanized steel wires wound helically around the cable core. This armor construction provides:

Mechanical protection advantages:

• High crush resistance (>1,000N per 100mm for typical constructions)
• Excellent resistance to impact damage during installation
• Protection against rodent damage in underground installations
• Suitable for direct burial² applications

Electrical characteristics:

• Armor acts as CPC with typical resistance of 1-3 Ω/km depending on wire gauge
• Provides electromagnetic shielding³ for sensitive circuits
• Must be bonded at both ends for effective fault protection
• Common in BS 5467 and BS 6724 cable standards

Typical constructions:

• Single-layer armor: 0.9mm, 1.25mm, or 1.6mm wire diameter
• Double-layer armor: For cables requiring enhanced mechanical protection
• Wire pitch: Typically 30-45mm depending on cable diameter

Understanding STA (Steel Tape Armored) Cables

STA cables use flat steel tape wrapped around the cable core, offering different performance characteristics:

Mechanical protection advantages:

• Excellent flexibility compared to SWA (30-40% smaller bending radius)
• Lighter weight for equivalent protection levels
• Easier installation in confined spaces or complex cable routes
• Preferred for indoor industrial installations

Electrical characteristics:

• Tape armor provides lower DC resistance than equivalent SWA (0.5-1.5 Ω/km)
• Superior longitudinal water barrier due to overlapping tape construction
• Effective EMC shielding with proper bonding
• Common in BS 5467 and IEC 60502 standards

Typical constructions:

• Single tape: 0.2mm or 0.5mm thickness, 20-50mm width
• Double tape: Overlapping layers for enhanced protection
• Tape overlap: Typically 15-25% for water ingress prevention

Hassan, a quality manager from a Dubai power distribution project, initially specified SWA cables for all applications. However, his installation team struggled with the tight bending radii required in crowded electrical rooms. After we recommended STA cables for indoor runs (reserving SWA for outdoor and underground sections), his installation time dropped by 35% and cable damage incidents disappeared.

Why Standard Glands Fail with Armored Cables

Attempting to terminate armored cables with standard compression glands creates three critical failures:

1. No armor termination: The steel armor floats freely, providing no mechanical retention or electrical continuity
2. Safety code violations: UK BS 7671, IEC 60364, and NEC require armor bonding for fault protection
3. Accelerated cable failure: Unsecured armor wires can fray, puncture the outer sheath, and cause short circuits

Specialized armored cable glands solve these problems through integrated clamping mechanisms that grip the armor while maintaining IP-rated sealing on the outer sheath.

How Do SWA and STA Brass Glands Differ in Design and Function?

The fundamental difference between SWA and STA glands lies in their armor clamping mechanisms—each engineered specifically for wire or tape armor geometry.

SWA Gland Design and Components

SWA glands use a cone-and-compression system to grip individual steel wires:

Key components:

1. Gland body: Nickel-plated brass⁴ with metric or PG threads, provides electrical bonding to enclosure
2. Armor cone: Tapered brass cone that wedges between individual armor wires
3. Compression ring: Tightens around the cone, forcing wires radially inward for mechanical grip
4. Inner seal: Seals against the cable’s inner sheath (beneath armor layer)
5. Outer seal: Seals against the cable’s outer sheath (above armor layer)
6. Locknut and washer: Secures gland to panel and ensures electrical continuity

Operating principle:
As you tighten the compression ring, the armor cone wedges deeper between the steel wires. This creates two critical functions simultaneously:

• Mechanical grip: 80-150N pull-out resistance depending on cable size
• Electrical bonding: Low-resistance path (<0.1Ω) from armor through gland body to enclosure earth

STA Gland Design and Components

STA glands use a different approach optimized for flat tape armor:

Key components:

1. Gland body: Similar brass construction with earthing continuity
2. Armor clamp ring: Flat clamping surface that grips the tape armor circumferentially
3. Compression gland: Separate compression mechanism for the outer sheath seal
4. Inner seal: Seals beneath the tape armor
5. Earthing tag or screw: Some designs include dedicated earthing connections for tape armor
6. Locknut and washer: Panel mounting and earth bonding

Operating principle:
The armor clamp ring compresses the tape armor against the gland body, creating friction-based retention and electrical contact. Because tape armor has larger surface area contact, STA glands often achieve lower contact resistance (<0.05Ω) than equivalent SWA glands.

Performance Comparison: SWA vs. STA Glands

Feature	SWA Glands	STA Glands	Critical Difference
Armor grip mechanism	Cone wedges between wires	Clamp compresses flat tape	SWA requires precise cone sizing
Typical pull-out force	80-150N	100-180N	STA provides superior mechanical retention
Electrical resistance	0.08-0.15Ω	0.04-0.08Ω	STA offers better earthing continuity
Installation complexity	Moderate—requires armor preparation	Easier—tape doesn’t fray	STA reduces installation time by 20-30%
IP rating capability	IP66-IP68	IP66-IP68	Equivalent when properly installed
Bending radius at gland	6× cable OD	4× cable OD	STA allows tighter installations
Cost differential	Baseline	+10-15%	STA premium reflects specialized design
Interchangeability	NOT compatible with STA cables	NOT compatible with SWA cables	Critical—never mix types

Why Material Choice Matters: Brass vs. Alternatives

Nickel-plated brass dominates armored cable gland applications for specific technical reasons:

Electrical conductivity: Brass provides 15-20% IACS (International Annealed Copper Standard) conductivity—sufficient for CPC bonding while maintaining mechanical strength.

Corrosion resistance: The nickel plating (typically 5-10 microns) protects against galvanic corrosion when brass contacts steel armor. Without plating, dissimilar metal corrosion can increase contact resistance by 10× within 2-3 years in humid environments.

Machinability: CW617N brass allows precision threading and cone geometry that’s difficult to achieve with stainless steel at comparable cost.

EMC performance: Brass glands provide 360° electromagnetic continuity when properly bonded—critical for shielded cable applications in industrial automation and instrumentation.

David, a procurement manager from a UK chemical plant, initially questioned the 40% price premium for nickel-plated brass SWA glands over aluminum alternatives. However, after his maintenance team discovered corroded aluminum glands during a routine inspection (just 18 months after installation in a mildly corrosive environment), the value became clear. The replacement project cost 8× the original price difference, not including production downtime.

How to Select Between SWA and STA Glands for Your Application?

Selecting the correct armored cable gland requires matching cable construction, environmental conditions, and installation constraints to gland specifications.

Step 1: Identify Your Cable Armor Type

This seems obvious, but misidentification is surprisingly common, especially with cables from different standards regions.

Visual identification:

• SWA: Remove 50mm of outer sheath—you’ll see individual round wires wound helically
• STA: Remove outer sheath—you’ll see flat metallic tape wrapped around the core
• AWA (Aluminum Wire Armored): Similar to SWA but with aluminum wires (requires different gland specifications)

Check cable markings:

• BS 5467 cables typically specify “SWA” or “STA” in the designation
• IEC cables may use codes like “SWA” or “STA” in the construction description
• When in doubt, consult the cable manufacturer’s datasheet

Pro tip: Some cables use double armor (tape + wire). These require specialized glands—contact our technical team at Bepto for recommendations.

Step 2: Match Gland Size to Cable Dimensions

Armored cable glands require three critical measurements:

1. Cable outer diameter (over outer sheath):

• Measure with calipers at three points
• Use maximum reading for gland selection
• Typical range: 10-75mm for industrial power cables

2. Armor wire diameter (SWA) or tape thickness (STA):

• SWA: Measure individual wire diameter (common sizes: 0.9mm, 1.25mm, 1.6mm, 2.0mm)
• STA: Measure tape thickness with micrometer (common: 0.2mm, 0.5mm, 0.8mm)
• This determines the correct armor cone or clamp size

3. Inner sheath diameter (beneath armor):

• Determines inner seal sizing
• Critical for achieving IP68 rating

Step 3: Consider Environmental and Application Factors

Application Type	Recommended Gland Features	Typical Standards
Outdoor/Underground (SWA)	IP68-rated, extended threads for thick panels, stainless steel locknut	BS 6121, IEC 62444
Indoor Industrial (STA)	IP66-rated, standard threads, nickel-plated brass throughout	IEC 60423
Hazardous Areas (SWA/STA)	ATEX/IECEx certified, flameproof threads, increased creepage distances	IEC 60079-1
Marine/Offshore (SWA)	IP68/IP69K, stainless steel 316L option, salt spray tested (1000+ hours)	IEC 60092-352
High EMC Environments (STA)	360° shield continuity, low contact resistance (<0.05Ω), EMC gaskets	IEC 61000-5-2
Vibration-Prone (SWA)	Extended thread engagement, vibration-resistant locknuts, thread-locking compound	DIN 46320

Step 4: Verify Compliance Requirements

Different industries and regions impose specific requirements:

UK installations (BS 7671):

• Armor must be bonded at both ends for CPC function
• Gland must maintain IP rating of enclosure
• Minimum short-circuit current capacity must be verified

European installations (IEC 60364):

• Gland must provide <0.1Ω bonding resistance
• Fire performance requirements in public buildings
• RoHS and REACH compliance for materials

North American installations (NEC):

• Listed glands required for hazardous locations
• Specific torque requirements for compression components
• Grounding continuity must be verified and documented

Hazardous area installations (ATEX/IECEx):

• Certified glands mandatory (standard glands void area classification)
• Temperature class must match cable and equipment ratings
• Installation must follow manufacturer’s certified drawings exactly

Step 5: Calculate Required Quantity and Spare Strategy

Installation planning:

• Order 5-10% extra glands for installation damage/errors
• Stock spares of common sizes for maintenance (typically 2-5 per size)
• Consider standardizing on fewer gland sizes to simplify inventory

Long-term maintenance:

• Armored cable glands rarely fail if properly installed
• Keep replacement seals in stock (seals degrade before metal components)
• Document gland sizes and cable specifications for future expansions

What Are the Critical Installation Steps for Armored Cable Glands?

Proper installation of armored cable glands requires precision and attention to detail—shortcuts lead to safety hazards and premature failures.

Pre-Installation Preparation

Tools required:

• Cable stripping knife or armor stripper tool
• Hacksaw (for cutting armor wires/tape)
• File (for deburring cut armor ends)
• Torque wrench (for final tightening)
• Continuity tester (for verifying earth bonding)

Safety precautions:

• Wear cut-resistant gloves—armor wire ends are extremely sharp
• Ensure cable is de-energized and isolated
• Verify cable identification before cutting

Step-by-Step Installation for SWA Glands

1. Strip the outer sheath (50-75mm):

• Use a cable knife carefully to avoid damaging armor wires
• Remove sheath to expose clean armor wires
• Typical length: 60mm for M20-M32 glands, 80mm for M40-M63

2. Cut and prepare armor wires:

• Cut wires to required length (typically 40-50mm from sheath end)
• File wire ends to remove sharp burrs (critical safety step)
• Spread wires slightly to allow cone insertion
• Warning: Do NOT unwind wires—maintain helical structure

3. Assemble gland components on cable:

• Slide locknut, washer, and gland body onto cable (before inserting cone)
• Insert armor cone between wires, ensuring even distribution
• Position cone so wires sit in the cone grooves

4. Strip inner sheath for inner seal:

• Remove additional 15-25mm of inner sheath (beneath armor)
• Ensure clean, undamaged surface for seal contact
• Check for any armor wire punctures in inner sheath

5. Install seals and tighten compression ring:

• Fit inner seal onto cable beneath armor
• Position outer seal on outer sheath
• Thread compression ring onto gland body
• Hand-tighten until resistance is felt
• Apply torque wrench: typically 15-25 Nm for M20-M32, 30-45 Nm for M40-M63

6. Mount to enclosure and verify:

• Thread gland through panel hole
• Install washer and locknut inside enclosure
• Tighten locknut to manufacturer’s specification (typically 20-35 Nm)
• Critical: Verify electrical continuity from armor through gland to enclosure earth (<0.1Ω)

Step-by-Step Installation for STA Glands

1. Strip outer sheath (40-60mm):

• Carefully remove outer sheath without damaging tape armor
• Expose clean tape armor surface
• Typical length: 50mm for standard glands

2. Prepare tape armor:

• Do NOT cut tape armor at this stage
• Ensure tape edges are smooth and not frayed
• Clean any adhesive residue from tape surface

3. Assemble gland components:

• Slide locknut, washer, gland body, and armor clamp ring onto cable
• Position armor clamp ring over tape armor section

4. Secure tape armor:

• Some designs require cutting tape after clamp positioning
• Others clamp over intact tape—follow manufacturer instructions
• Ensure clamp contacts tape over 360° circumference

5. Strip inner sheath and install seals:

• Remove inner sheath beneath tape armor (15-20mm)
• Install inner seal
• Position outer seal on outer sheath
• Tighten compression gland to specified torque (typically 12-20 Nm for M20-M32)

6. Final assembly and testing:

• Mount to enclosure panel
• Tighten locknut to specification
• Verify earth continuity (<0.1Ω)
• Perform IP rating test if required by installation standards

Common Installation Mistakes to Avoid

Mistake #1: Using SWA glands on STA cables (or vice versa)

• Consequence: Armor not properly secured, no electrical bonding, safety code violation
• Solution: Always verify cable type before ordering glands

Mistake #2: Over-tightening compression components

• Consequence: Crushed cable cores, damaged insulation, reduced current capacity
• Solution: Always use torque wrench to manufacturer specifications

Mistake #3: Inadequate armor wire preparation

• Consequence: Sharp wire ends puncture inner seal, causing IP rating failure
• Solution: Always file wire ends smooth and inspect before assembly

Mistake #4: Forgetting to thread components before cone insertion

• Consequence: Having to disassemble and restart installation
• Solution: Lay out all components in assembly order before starting

Mistake #5: Not verifying earth continuity

• Consequence: Ineffective fault protection, failed electrical inspection
• Solution: Test every gland with continuity meter before energizing

Conclusion

Selecting between SWA and STA brass glands isn’t just about matching armor type—it’s about ensuring safety, compliance, and long-term reliability in critical power and control installations. By understanding the mechanical and electrical differences between wire and tape armor terminations, you can specify the correct glands the first time and avoid costly rework or safety incidents.

At Bepto Connector, we manufacture the complete range of brass armored cable glands for both SWA and STA applications, with sizes from M20 to M75 and certifications including ATEX, IECEx, and marine approvals. Our engineering team provides free cable-to-gland matching consultations and can supply technical installation drawings for your specific project requirements. Contact us today for detailed selection guides, material certificates, and competitive factory-direct pricing on armored cable glands.

FAQs About SWA and STA Brass Glands

1. Learn about the role of a circuit protective conductor in ensuring electrical grounding and safety. ↩

2. Understand the regulations and technical requirements for the direct burial of electrical cables. ↩

3. Explore the principles of electromagnetic shielding to prevent interference in industrial cabling. ↩

4. Discover the benefits of nickel-plated brass for corrosion resistance in industrial cable terminations. ↩