A Complete Guide to Selecting the Right Cable Gland for Wolong Nanyang Explosion-Proof Motors
Published by exmotorchina.com | Wolong Nanyang Explosion-Proof Electric Motor
What Is a Cable Gland — and Why Does It Matter?
When it comes to explosion-proof motor installations, most attention naturally falls on the motor itself. But there is one small component that plays an equally critical role in maintaining the integrity of the entire hazardous area installation: the cable gland — also known as a cable entry device, cable fitting, or in explosion-proof terminology, an Ex cable sealing fitting.
A cable gland performs two fundamental functions:
Mechanical retention — gripping the cable to prevent axial movement and radial rotation at the point of entry into the motor terminal box
Environmental sealing — maintaining the IP protection rating of the enclosure against dust and moisture ingress
In an explosion-proof installation, the cable gland takes on a third and equally important function: maintaining explosion-proof integrity at the cable entry point. When a cable enters the terminal box of an Ex motor, the gland must ensure that neither sparks nor thermal energy can escape through the cable entry — and that the cable entry point does not compromise the overall certified protection level of the motor enclosure.
A motor with a correctly specified and certified cable gland is safe. A motor with the wrong gland — or a non-certified gland — is not, regardless of how well the motor itself is designed and built.
Classification of Explosion-Proof Cable Glands
1. By Cable Type: Armoured vs. Non-Armoured
The most fundamental selection criterion is the type of cable being terminated.
Non-Armoured Cable Glands
| Attribute | Detail |
|---|---|
| Cable type | Non-armoured cables (rubber-sheathed, PVC-sheathed) |
| Sealing method | Compression seal ring and packing |
| Installation | Simple — no armour layer processing required |
| Relative cost | Lower |
Armoured Cable Glands
| Attribute | Detail |
|---|---|
| Cable type | Armoured cables (steel wire or steel tape armour) |
| Sealing method | Armour cone ring and metal compression gland |
| Installation | Requires armour layer stripping and earthing/grounding |
| Relative cost | Higher |
The rule is straightforward: armoured cables must use armoured cable glands. Non-armoured cables use non-armoured glands. The armour layer of an armoured cable must be terminated and grounded inside the cable gland body, and the components that retain the armour layer must not be releasable by hand without the use of a tool.
2. By Explosion-Proof Type: Ex d vs. Ex e
This classification is critical and non-negotiable in explosion-proof installations.
Flameproof Type (Ex d)
The Ex d cable gland forms part of the flameproof enclosure itself. Flame suppression is achieved through the precision thread engagement length and gap dimensions, which create a flame quench path that cools any escaping combustion gases below the ignition temperature of the surrounding atmosphere before they exit the enclosure. The gland must comply with IEC 60079-1 / GB/T 3836.2 requirements for flameproof enclosures.
Increased Safety Type (Ex e)
The Ex e cable gland achieves protection by compressing a sealing element tightly around the cable, preventing external flammable gases from entering the terminal box interior and preventing any sparks generated inside from reaching the external atmosphere through the cable entry point.
The matching rule — and why it matters:
The protection type of the cable gland must match the protection type of the motor terminal box:
Ex e motor terminal box → Ex e cable gland
Ex d motor terminal box → Ex d cable gland
Never install an Ex e cable gland on an Ex d (flameproof) enclosure. An Ex e gland does not provide the flameproof joint geometry required to form part of a flameproof enclosure — using it on a flameproof terminal box defeats the entire protection concept and renders the installation non-compliant and unsafe.
3. By Material
Material selection determines corrosion resistance and service life in the installation environment.
| Material | Properties | Recommended Environment |
|---|---|---|
| Zinc-plated carbon steel | Low cost, basic corrosion resistance | General indoor installations, dry environments |
| Nickel-plated brass | Good conductivity and corrosion resistance, cost-effective | Standard industrial environments, most factory and plant locations |
| Stainless steel 304 | Excellent corrosion resistance and mechanical strength | Outdoor, high-humidity, moderately corrosive environments |
| Stainless steel 316 | Superior corrosion resistance (Mo-bearing, chloride resistant) | Chemical plants, refineries, coastal and offshore installations |
| Pure copper | Highest conductivity and corrosion performance | High-specification applications where cost is secondary to performance |
The selection principle is simple: choose the right material, not the most expensive one. For most general industrial and plant environments, nickel-plated brass offers the best balance of performance and cost. For chemical processing, refining, tobacco, and other aggressive or dusty environments, stainless steel is the correct choice.
4. By Thread Type and Size
Thread compatibility between the cable gland and the motor terminal box entry thread is non-negotiable — different thread systems cannot be mixed.
Common thread systems:
Metric (M series): M20×1.5, M25×1.5, M32×1.5, M40×1.5, M50×1.5, M63×1.5
British Standard Pipe (G series): G1/2, G3/4, G1
American NPT: 1/2" NPT, 3/4" NPT, 1" NPT
Common nominal sizes: DN15, DN20, DN25, DN32, DN40, DN50.
For Wolong Nanyang explosion-proof motors (YBX5 series), the cable entry thread specifications by frame size are as follows:
| Frame Size | Entry Thread |
|---|---|
| 80 – 100 | M25 × 1.5 |
| 112 – 132 | M32 × 1.5 |
| 160 – 180 | M40 × 1.5 |
| 200 – 225 | M50 × 1.5 |
| 250 – 280 | M63 × 1.5 |
Always verify the terminal box entry thread specification directly on the motor or in the motor documentation before ordering cable glands.
How to Select the Right Cable Gland: A Five-Step Process
Step 1 — Identify the Cable Type
Confirm whether the cable is armoured or non-armoured. This determines the fundamental gland type. For armoured cables, record both the outer diameter with armour and the outer diameter without armour, as both dimensions are needed for gland selection.
Step 2 — Determine the Thread Specification
Check the motor terminal box entry thread. Match the gland thread type (metric, BSP, NPT) and size to the motor entry thread. Do not mix thread systems.
Step 3 — Match the Cable Outer Diameter
Select a gland with a cable clamping range that matches the actual cable outer diameter. As a general rule, select a gland whose clamping range centre is approximately 10% above the actual cable diameter to ensure reliable sealing without over-compression of the seal element.
Step 4 — Select the Material
Match material to environment:
Indoor, dry, general industrial: zinc-plated carbon steel or nickel-plated brass
Outdoor or humid: nickel-plated brass or stainless steel 304
Chemical, refining, high-corrosion: stainless steel 304 or 316
High-specification: pure copper
Step 5 — Verify Certification and Standards Compliance
Explosion-proof cable glands must comply with GB 3836 (Chinese national standard) and/or IEC 60079 (international standard) and carry a valid Ex certification mark. The certification must be verified as current and applicable to the specific protection type and equipment group being installed.
Updated regulations require that Ex cable glands carry complete certification and integrate flame-isolating and sealing structures in a single certified assembly. Always use a certified gland with documentation — non-certified or sub-standard glands are not acceptable in any classified hazardous area installation, regardless of price.
The Core Principle to Remember
Explosion-proof installations are only as safe as their weakest compliant component. A correctly designed, certified, and installed Wolong Nanyang explosion-proof motor fitted with an incorrectly specified or non-certified cable gland is not a safe installation — the protection concept of the motor's terminal enclosure is compromised at the point of cable entry.
The cable gland is not a minor accessory. It is a certified component of the explosion-proof system.
Select every cable gland by matching five criteria without exception:
Protection type (Ex d or Ex e — must match the motor terminal box)
Cable type (armoured or non-armoured)
Thread specification (type and size — must match the motor entry thread)
Cable outer diameter (within the gland's certified clamping range)
Material (matched to the installation environment)
Get all five right, and the cable entry maintains the motor's certified protection level. Get any one wrong, and it doesn't.
About Wolong Nanyang Explosion-Proof Electric Motor
Wolong Nanyang Explosion-Proof Electric Motor is a specialized manufacturer of explosion-proof and industrial electric motors, with close to 70 years of manufacturing experience. Our product range covers more than 20 series of explosion-proof and non-explosion-proof motors, including medium and small explosion-proof motors, high-speed motors, and brake motors — all produced under a comprehensive quality management system with full in-house testing and verification capability.
We are committed to supporting our customers across global markets with reliable motor products, application engineering expertise, and professional after-sales service.
Explore our explosion-proof motor range at www.exmotorchina.com
