— A Selection Guide for Hazardous Area Cable Glands
In explosive atmospheres such as oil, chemical, and gas facilities, cable glands are often overlooked, but they are a critical link in the explosion protection chain. A non‑certified or incorrectly selected cable gland can become a path for flammable gas to enter equipment, or even directly cause an explosion.
Core functions of a cable gland:
Securely fasten the cable to the equipment entry, preventing pull‑out
Seal the cable entry to prevent ingress of flammable gas, dust, and moisture
For armoured cables, provide reliable grounding of the armour
Maintain the flameproof integrity of Ex d equipment
Based on Anhui Tiankang (Group) Co., Ltd.’s nearly fifty years of experience in explosion‑protected electrical accessories, this article systematically explains the key points of selecting cable glands for hazardous areas, helping you ensure project safety and compliance.
1. Basic Types of Hazardous Area Cable Glands
Based on explosion protection principles and applicable scenarios, hazardous area cable glands are mainly classified as follows:
| Type | Explosion Protection Principle | Suitable Ex Method | Typical Application |
|---|---|---|---|
| Flameproof (Ex d) | If ignition occurs inside, flames are cooled and quenched through labyrinth gaps, not igniting the external atmosphere | Ex d | Ex d instruments, junction boxes, motors |
| Increased safety (Ex e) | Provides reliable electrical connections and sealing, preventing arcs/sparks | Ex e | Ex e junction boxes, lighting fixtures |
| Intrinsically safe (Ex i) | Used only for IS circuits; does not require flameproof construction, but must meet IP rating | Ex ia / ib | IS instruments, IS fieldbus |
| Encapsulated (Ex m) | Internal components encapsulated in compound to prevent spark propagation | Ex m | Special small equipment |
| Ex d e combination | Meets both Ex d and Ex e requirements | Ex d e | Often used for cable entry of junction boxes |
Additionally, based on cable type (armoured vs unarmoured), cable glands are divided into:
Unarmoured cable glands: For rubber/PVC/PE/LSZH sheathed cables
Armoured cable glands: For steel tape armoured (STA) or steel wire armoured (SWA) cables, capable of clamping the armour and providing grounding
2. Five‑Step Selection Process for Hazardous Area Cable Glands
Step 1: Determine Hazardous Area Classification and Ex Method
First identify the zone (Zone 0/1/2 or 20/21/22) and confirm the Ex method of the equipment (Ex d, Ex e, Ex i, etc.). The cable gland must match the equipment’s Ex method.
Ex d flameproof equipment → Must use Ex d certified cable gland
Ex e increased safety equipment → Must use Ex e certified cable gland
Ex i intrinsically safe equipment → Can use ordinary cable gland (IP sufficient); IS circuits do not require flameproof construction
Ex d e combination junction box → Must use Ex d e double‑certified gland
Key principle: The Ex marking of the cable gland must be at least equal to that of the equipment entry.
Step 2: Determine Cable Type (Armoured vs Unarmoured)
| Cable Type | Suitable Cable Gland |
|---|---|
| Unarmoured (PVC, LSZH, PE sheath) | Unarmoured cable gland (rubber seal + clamping) |
| Steel tape armoured (STA) | STA cable gland with steel tape clamping ring and grounding |
| Steel wire armoured (SWA) | SWA cable gland with wire braid clamping and grounding |
Tiankang note: Incorrect selection will fail to secure and ground the armour, losing mechanical protection and explosion performance. Always use a gland designed for the specific armour type and size.
Step 3: Confirm Cable Outer Diameter Range and Sealing Requirements
Each cable gland has a specified cable outer diameter range (e.g., 10–14 mm, 14–18 mm). Ensure your actual cable OD falls within that range; otherwise sealing fails.
For unarmoured cable: The seal bears directly on the cable sheath.
For armoured cable: The seal bears on the inner sheath (or core bedding), not on the armour. The armour is positioned between two seals and clamped.
Tiankang recommendation: Measure actual OD of multiple cables (including manufacturing tolerance) and choose a gland size that comfortably covers the range. Avoid using the extreme limits.
Step 4: Determine Thread Size and Match Equipment Entry
Cable glands are threaded into equipment or junction box entries. Common thread standards:
| Thread Standard | Code | Characteristics | Primary Region |
|---|---|---|---|
| Metric | M20×1.5, M25×1.5, M32×1.5, M40×1.5 | Fine pitch, good flameproof sealing, international | Europe, Asia, international projects |
| NPT | 1/2"NPT, 3/4"NPT, 1"NPT | Tapered thread, seals by thread itself | North America |
| PG | PG11, PG13.5, PG16, PG21 | Old European standard, gradually replaced by metric | Legacy equipment retrofits |
Selection points:
Thread size must exactly match equipment entry (including size and pitch)
Ex d flameproof glands typically require at least 5 full threads of engagement (metric) or 5 threads (NPT)
Do not force a metric thread into an NPT port; this will damage threads or destroy flameproof integrity
Tiankang note: Tiankang offers metric, NPT, and PG thread types to suit domestic and international equipment.
Step 5: Confirm Other Key Attributes
Ingress protection (IP) : Minimum IP66 (dust‑tight, protected against powerful water jets). Offshore or outdoor may require IP66/IP67 or even IP68 (immersion).
Temperature range : Gland materials must suit ambient temperature. Standard -40°C ~ +80°C; special high/low temperature projects require appropriate materials (e.g., silicone seals).
Material selection :
Brass nickel‑plated : Most common; corrosion resistant, high mechanical strength, good value – suitable for oil & gas, chemical
Stainless steel 304/316 : For highly corrosive environments (offshore, seawater, acids/alkalis)
Aluminium / nylon : For weight‑sensitive or non‑corrosive light industry (generally not for hazardous areas)
Armour grounding : Armoured cable glands must provide a grounding lug or terminal to ensure armour continuity and connection to the earth system.
Double sealing : For Ex d e combination or high sealing requirements, choose glands with both inner and outer seals.
Accessories : Blanking plugs, reducers, adaptors, locknuts as needed.
3. Selection Decision Flowchart
1. Equipment Ex method? → Ex d → choose Ex d gland Ex e → choose Ex e gland Ex i → ordinary gland (IP sufficient) 2. Cable type? → Unarmoured → unarmoured gland Steel tape armour → STA gland Steel wire armour → SWA gland 3. Cable OD? → Measure actual OD → select gland covering the range 4. Equipment thread? → M20/M25/M32/NPT1/2" etc. → match thread 5. Environmental requirements? → IP66/IP67, material (brass/SS), temperature range
4. Common Mistakes and Risks
| Mistake | Consequence |
|---|---|
| Using ordinary non‑Ex gland in hazardous area | Loss of flameproof/increased safety; explosion risk |
| Thread mismatch | Cannot tighten; gap leakage; or thread damage |
| Ignoring armour clamping and grounding | Armour can pull out or become floating; risk of sparking |
| Cable OD out of sealing range | Seal failure; gas/moisture ingress |
| Using unarmoured gland on armoured cable | Armour not secured; pull‑out; seal failure |
| Plastic/rubber parts beyond temperature range | Aging, cracking, seal failure |
5. Tiankang Hazardous Area Cable Gland Product Range
Anhui Tiankang Group, as a leading supplier of explosion‑protected electrical accessories in China, offers a full range of ATEX / IECEx / CCC certified cable glands for oil & gas, chemical, pharmaceutical, power, and other industries.
Product Overview
| Series | Certification | Cable Type | Material | IP Rating |
|---|---|---|---|---|
| Ex d unarmoured | Ex d IIC Gb | Unarmoured | Brass Ni / SS | IP66/IP67 |
| Ex d STA (steel tape) | Ex d IIC Gb | Steel tape armoured | Brass Ni / SS | IP66/IP67 |
| Ex d SWA (steel wire) | Ex d IIC Gb | Steel wire armoured | Brass Ni / SS | IP66/IP67 |
| Ex e unarmoured | Ex e IIC Gb | Unarmoured | Brass Ni / Nylon | IP66/IP67 |
| Ex e armoured | Ex e IIC Gb | Steel tape/wire | Brass Ni | IP66/IP67 |
| Ex d e double seal | Ex d e IIC Gb | Unarmoured/armoured | Brass Ni | IP66/IP67 |
Core Advantages
National Ex certification (CCC) and international ATEX, IECEx
Flamepath dimensions and thread engagement strictly per standards, verified by flameproof tests
Thread options: Metric M16~M75, NPT 1/2"~3", PG series
Seal materials: Oil‑resistant NBR, silicone (Si), Viton (FKM) for different temperatures and media
Nickel‑plated brass for excellent corrosion resistance; stainless steel for extreme environments
Accessories: extended seals, locknuts, blanking plugs, reducers
Perfectly matched with Tiankang armoured cables – one‑stop supply
6. Selection Example
Example: An offshore platform, Zone 1 hazardous area. Equipment is an Ex d flameproof junction box with M25×1.5 thread. Incoming cable is steel tape armoured instrumentation cable, inner sheath OD 12 mm. Environment is salt‑spray corrosive; IP67 required.
Selected gland:
Type: Ex d flameproof steel tape armoured cable gland
Thread: M25×1.5
Material: Stainless steel 316L (salt‑spray resistant)
Sealing range: suitable for 12 mm inner sheath
IP rating: IP67
Certification: ATEX / IECEx / CCC
Tiankang model reference: TG-Ex-d-STA-M25-316L (example – consult factory)
7. Installation Notes
Clean threads : Remove oil, dirt, rust from equipment entry and gland threads before installation.
Use sealing gaskets/compounds : Per equipment requirements, may need flat gasket or sealant.
Torque : Use torque wrench per product manual. Do not overtighten (deformation) or undertighten (seal failure).
Armour grounding : Ensure armour is positively clamped by the gland’s clamping ring and connected via grounding lug to equipment earth terminal.
Seal unused entries : Unused openings must be closed with Ex certified blanking plugs to maintain IP and Ex rating.
8. Conclusion
Cable glands in hazardous areas are not ordinary hardware – they are critical safety components. Selection must consider Ex method, cable type, outer diameter range, thread size, environmental conditions, and more. A correctly selected and installed cable gland effectively prevents explosion propagation and protects personnel and equipment.
Anhui Tiankang (Group) Co., Ltd. provides one‑stop explosion‑protected electrical supply from cables to glands. All products are rigorously certified and tested, and we offer project‑level technical support.
Contact Us
For hazardous area cable gland selection advice, certification verification, or quotations, please contact:
Yin Shuangjie
📧 Email: [email protected]
📱 WhatsApp / Zalo: +86 17856068126
🌐 Website: http://www.tiankang-global.com/
Anhui Tiankang (Group) Co., Ltd. – providing safe, reliable cable connection solutions for your hazardous area applications.
