Explosion-Proof Cable Glands: Complete Guide to Selection and Installation
Explosion-proof cable gland is a specialized device designed for the sealed, mechanically strong, and explosion-safe entry of a cable or group of cables into the enclosure of electrical equipment installed in hazardous areas. Its main task is to maintain the integrity of the equipment’s explosion protection level (usually “flameproof enclosure — Ex d”), preventing the transmission of an explosion from the internal volume to the outside and protecting against the ingress of dust, moisture, and external influences. These components are critically important safety elements in the oil and gas, chemical, mining, and other hazardous industries.
1. Main Tasks and Application Areas
Explosion-proof cable glands are used to create a reliable and safe connection between the cable line and electrical equipment in hazardous areas. Main application areas:
- Oil and Gas Industry: Connecting cables to pumps, valves, instrumentation and automation devices, fire extinguishing and control systems on drilling platforms, refineries, and storage facilities.
- Chemical and Petrochemical Industry: Installation of electrical equipment in workshops where explosive vapors, gases, and aerosols are present.
- Coal and Mining Industry: Ensuring safe connection of equipment in mines where explosive coal dust and methane may form.
- Flour Milling and Food Production: Protection in areas where the air may contain explosive flour dust, sugar dust, or other organic dust.
- Flammable Liquid and Fuel Storage Warehouses: Connecting lighting, ventilation, alarm and monitoring systems in storage areas for flammable liquids and gases.
- General Industrial Application: Any equipment with Ex d, Ex e, Ex de explosion protection markings installed in zones of classes 1, 2, 21, 22.
2. Classification, Construction, and Materials
The construction of an explosion-proof cable gland is optimized to ensure mechanical strength, tightness, and preservation of the explosion protection level. Main elements:
| Construction Element | Materials and Options | Purpose and Influence on Properties |
| Body (Metal Part) | Brass (most common, corrosion-resistant), stainless steel (AISI 316/316L for aggressive environments), galvanized steel. Has a thread (usually metric or conduit) for mounting into the entry hole. | Provides mechanical strength and is the main load-bearing element. The material determines corrosion resistance and suitability for chemically active environments. The threaded connection ensures tight contact with the apparatus enclosure. |
| Sealing Elements (Glands, O-rings) | NBR rubber (nitrile-butadiene), EPDM (ethylene-propylene rubber), silicone, PTFE (Teflon) for chemical resistance. | Ensure sealing and protection against dust and moisture (ingress protection up to IP68/69K). Elastically compress around the cable, compensating for vibrations. The material is selected based on the temperature range and type of environment (oil, gasoline, UV). |
| Clamping Mechanism (Tapered Compression Nut) | Metal (brass, steel), often with internal serrations or segments. | When tightened, compresses the sealing elements around the cable, providing mechanical fixation (pull-out protection) and sealing. The tapered shape allows a single gland to accommodate a range of cable diameters. |
| Internal Sealing Plugs (for unused entries) | Brass or steel with a rubber seal. | Designed to hermetically seal unused entries in multi-entry glands, maintaining the integrity of the explosion-proof enclosure. |
| External Sealing Washer/Gasket | Rubber, paronite, copper ring. | Installed under the gland body during installation to ensure a tight seal between the gland flange and the equipment enclosure wall. |
3. Main Types and Series of Explosion-Proof Glands and Their Features
The marking and types of explosion-proof cable glands vary depending on the manufacturer and standards. Let’s consider the key types, including popular search queries.
| Gland Type / Series | Description and Construction | Key Characteristics and Application |
| KV (Gerda KV Series) | Kabelny Vvod (Cable Gland). Standard series with metric thread (M). May have 1, 2, or 3 entries for cables. Body material — brass or stainless steel. | Universal explosion-proof cable gland for most tasks. Used for introducing power, control, and signal cables into the enclosures of luminaires, starters, control cabinets. Explosion-proof cable gland of the KV series is a basic and widely used model. |
| Explosion-Proof Armored Cable Glands | Special construction with a reinforced clamping mechanism and tapered split cones (collets), often with a shear ring for the armor. | Specifically designed for fixing and sealing armored cables (types like AVBbShv, VBbShv, etc.). They securely compress and ground the armor tapes, providing mechanical fixation and maintaining explosion protection. Armored cable glands are mandatory when connecting power lines. |
| Glands with Conduit Thread (G, NPT) | The body has a cylindrical (G) or tapered (NPT) conduit thread. Often used in North American standards and for specific equipment. | Used for mounting on equipment that has corresponding threaded entries. May require additional sealing materials (PTFE tape, hemp) during installation. Provide a reliable connection in systems with vibration. |
| Multi-Entry and Combination Glands | Body with multiple holes (2, 3, 4 entries) for simultaneously introducing several cables of different diameters. | Allow reducing the number of entry holes in the apparatus enclosure, which increases the reliability of explosion protection. Saves space and installation time. Unused entries are sealed with plugs. |
| Glands for Flexible Cables and Cables with PVC Sheath | Equipped with special soft sealing grommets with a wide compression range. | Prevent damage and flattening of the unarmored or flexible cable (e.g., KG) sheath during tightening, maintaining sealing and insulation. |
The requirements for explosion-proof cable glands are regulated by the standards series GOST IEC 60079-0 and GOST IEC 60079-1 (for Ex d protection type), as well as international directives ATEX and IECEx.
4. Criteria for Selecting an Explosion-Proof Cable Gland
Choosing the specific type and size is a key stage in ensuring the safety and reliability of a system in a hazardous area.
| Selection Criterion | What to Consider and Check | Practical Recommendations |
| Cable Diameter(s) | Outer diameter of the cable in millimeters (considering sheath, armor). Diameter of each cable for group entry. | This is the primary parameter. Select the gland so that the cable’s operational diameter falls in the middle of the range specified for the sealing grommet. Do not use a cable at the extreme end of the range. |
| Cable Type | Armored (armor made of steel tapes/wires) or unarmored. Flexible (KG) or rigid. | For armored cables, use only specialized explosion-proof armored cable glands with a grounding tag for the armor. For flexible cables, use glands with soft grommets. |
| Entry Hole Thread | Type (metric M, conduit G/NPT), diameter, and thread pitch on the equipment enclosure. | Must match exactly. Transitions using adapters are possible but must be certified as part of an explosion-proof assembly. The most common type is metric thread (M). |
| Climatic and Chemical Conditions | Ambient temperature, presence of oils, solvents, UV radiation, seawater. | Body material: for aggressive environments — AISI 316 stainless steel. Seal material: NBR for oils, EPDM for steam/UV, PTFE for chemicals. Check the temperature range of the seals. |
| Ingress Protection (IP) Rating and Explosion Protection Level | Required dust and moisture protection (IP66, IP68). Explosion protection marking (Ex d IIC T6, Ex d IIB T4, etc.) | The gland must provide at least the same IP rating as the apparatus enclosure. The explosion protection level of the gland must correspond to or exceed the zone level and the explosive mixture group. |
| Mechanical Loads | Cable weight, vibration, risk of accidental pulling out. | For heavy cables and vibration loads, choose glands with a reinforced clamping mechanism and an additional lock nut. Always check the certified pull-out force. |
When analyzing queries like “explosion-proof cable gland for cable“, it is important to remember that correct selection based on cable diameter and type is not a recommendation but a mandatory requirement for maintaining the explosion-proof certification of the entire equipment.
5. Features of Installation and Connection
- Cable Preparation: Carefully strip the cable to a length sufficient for connection inside the apparatus. For armored cables, leave the armor to a length necessary for contact with the grounding tag inside the gland. The armor must be cleaned and compressed.
- Assembly Order: Slide all gland elements onto the cable in the correct sequence (nut, clamping cone, sealing grommets) before inserting the cable into the gland body.
- Armor Grounding: In armored cable glands, ensure that the grounding tag (leaf spring clamp) makes reliable contact with the cleaned armor tape. This is critically important for electrical safety.
- Tightening: Tighten the compression nut evenly, with the recommended torque (if specified). Do not apply excessive force to avoid damaging the cable or stripping the thread. Achieve tightness and reliable pull-out protection.
- Thread Sealing: When installing the gland into the equipment enclosure, use the provided gasket. For threaded connections like NPT, a sealant approved for hazardous areas may be required.
- Visual Inspection: After installation, check that the cable sheath is not deformed, all seals are properly seated, and there is no misalignment.
6. Conclusion
Choosing the correct explosion-proof cable gland is not just an installation procedure, but a mandatory condition for maintaining the explosion protection level of the entire electrical equipment. The safety of people, facilities, and the continuity of technological processes in hazardous industries depend on its correct selection and installation. Using specialized types, such as the universal KV series cable gland for standard tasks or explosion-proof armored cable glands for power lines, in strict accordance with cable parameters and operating conditions, is the key to long-term and safe operation.
Purchasing high-quality, certified cable glands from trusted manufacturers, such as JSC “Kazenergokabel”, guarantees full compliance with GOST, IECEx, and ATEX standards, eliminating risks during audits and ensuring trouble-free operation. The company offers a full range of cable and wire products and accessories for facilities of any complexity.
