Types of cable glands
By cable type
Cable glands are classified by cable type to ensure proper sealing, mechanical retention, and electrical continuity tailored to the cable's construction, primarily following the BS 6121 standard.[22] This classification addresses variations in armor, sheath, or flexibility, preventing issues like moisture ingress or strain failure.
For unarmored cables, such as single-core or multi-core cables with only an outer elastomeric or plastic sheath, glands provide sealing directly on the outer sheath without armor clamping. Designated as Type A under BS 6121, these include subtypes like A1 for basic sealing (IP66 with thread sealant) and A2 for enhanced environmental protection (IP66, up to IP68 in deluge-rated variants).[23] Type A3 adds an electrical bond for metallic inner screens, while A4 combines A2 sealing with bonding. The design emphasizes compression of the sheath for strain relief and watertight entry, suitable for indoor or low-moisture outdoor applications.[22]
Armored cable glands accommodate cables with protective layers like steel wire armor (SWA) or wire braiding, incorporating inner displacement seals for armor clamping alongside outer sheath seals. For SWA cables, Type B provides mechanical retention and electrical continuity via armor wire clamping without a dedicated seal, while Type BW offers no seal and Type CW includes a single outer seal for better protection.[22] Double-seal variants like E1W ensure both inner armor and outer sheath sealing, achieving IP66 or higher ratings and earth bonding. For braided wire cables, Type C focuses on braid clamping with a single outer seal, and E1X provides double sealing for enhanced durability in flexible armored setups. These glands differ from unarmored types by prioritizing armor retention for grounding and mechanical strength, often using suffixes like W for SWA or X for braiding per BS 6121.[23]
Glands for flexible conduits or hoses are designed to handle bendable protective tubing, often enclosing unarmored or braided cables, with features for additional flexibility and strain relief. Types like A2FFC support rigid or flexible conduits, providing sealing on the conduit outer layer while allowing angular movement without compromising integrity, typically rated IP68 and compliant with BS 6121 and IEC 62444. These differ from standard armored glands by focusing on conduit compression rather than wire armor, offering bend protection in dynamic installations like machinery.[24]
By design and compression
Cable glands are classified by their design and compression mechanisms, which determine how they secure and seal cables against environmental factors. These designs primarily revolve around the number of compression points and the type of threading used for installation, ensuring compatibility with various enclosures and cable sizes. Single and double compression types represent the core variations, while thread standards like PG, Metric, and NPT influence mounting and regional applicability.[25]
Single-compression glands provide sealing solely on the outer sheath of the cable, compressing it via a single ring or seal to prevent basic ingress of dust and moisture. This design is suitable for light-duty, non-hazardous applications, such as indoor electrical enclosures or general-purpose wiring in mild environments. They are simpler in construction, typically consisting of a body, seal, and locknut, which makes them more cost-effective and easier to install compared to multi-seal variants.[26][27]
In contrast, double-compression glands employ two independent seals: one for the outer sheath and another for the inner conductors, braid, or bedding layer, offering enhanced protection against moisture ingress, gas migration, and mechanical stresses like vibration or pulling forces. This dual-sealing approach is ideal for demanding outdoor or industrial settings where superior strain relief and environmental resistance are required. The additional components, such as inner compression nuts and cones, contribute to higher integrity but increase complexity and cost.[26][27][28]
Thread types on cable glands ensure secure attachment to enclosures and are standardized for interoperability. PG (Panzer-Gewinde) threads, originating from Germany, feature straight threads with an 80° flank angle and are common in European installations for their robust sealing in harsh conditions; for example, a PG9 thread accommodates cables with diameters of 4–8 mm. Metric threads, based on the ISO system, use straight threads with a 60° flank angle and specified pitches (e.g., M20 x 1.5), prevalent in international and IEC-compliant setups for precise fitting. NPT (National Pipe Taper) threads, standard in the U.S., are tapered with a 60° angle and 1/16-inch taper per foot, providing self-sealing through wedging action, though they require careful compatibility checks to avoid cross-threading. Selection depends on regional standards and enclosure entry sizes, with adapters available for mismatches.[29]
Design variations further differentiate basic from advanced glands, particularly in sealing sophistication. Stuffing glands, often designated as A-type, focus on fundamental cable retention and outer sheath sealing using displacement seals for IP66 to IP68 protection, making them suitable for unarmored or braided cables in standard industrial applications without additional environmental extremes. Advanced designs build on this by incorporating deluge protection, such as enhanced seals tested to withstand high-pressure water jets (e.g., DTS01 standards), providing superior resistance to flooding or washdown conditions while maintaining basic retention functions. These variations can be adapted for armored cables to ensure overall system integrity.[25][30]
Multi-entry cable glands are designed to accommodate multiple individual wires through a single entry point, providing individual sealing and strain relief for applications requiring high-density cable routing. These include multi-hole glands with fixed inserts featuring replaceable rubber or plastic grommets with multiple holes (typically 6 or more, sized 4–7 mm), suitable for wires such as #8 AWG (outer diameter approximately 5.4–5.5 mm for THHN/THWN insulation), achieving IP67 or IP68 sealing ratings. Gel-filled multi-entry glands utilize compressible gel inserts that seal around multiple unmated cables of varying sizes without predefined holes, facilitating easy insertion and suitable for high-density setups. Modular block systems incorporate peelable layers or adaptable modules within a frame to seal numerous cables, often used in heavier-duty or hazardous location applications and capable of handling 6 or more #8 AWG wires. These glands are available from electrical suppliers in NPT or metric threads, with selection requiring verification of hole diameters or clamping ranges against wire outer dimensions and applicable ratings such as NEMA or IP.[31][32][33]
Special purpose glands
Special purpose cable glands are engineered for specific environmental challenges or operational requirements beyond standard applications, such as handling pre-terminated cables, ensuring electromagnetic shielding, containing explosions in hazardous zones, or providing superior water resistance for submersion. These designs incorporate specialized features like split bodies, conductive contacts, flameproof barriers, or enhanced sealing materials to meet niche demands in industries including automation, telecommunications, oil and gas, and marine operations.[34][35][36]
Split glands facilitate the installation of pre-terminated cables with connectors, allowing them to be routed into enclosures or panels without disconnection or reconfiguration. These glands feature a divisible body that opens to accommodate the cable assembly, then closes to form a secure seal and provide strain relief. Suitable for cable diameters ranging from 1 to 35 mm, they support quick assembly, often tool-free, and achieve IP ratings up to IP68 for dust and water protection. Examples include the KVT series, which integrates cord grips for added mechanical stability in dynamic environments.[34]
EMC glands ensure electromagnetic compatibility by establishing a low-impedance, 360-degree electrical contact with the cable's metal braiding or shielding layer, effectively attenuating interference signals. This contact, typically via spring or cone mechanisms, maintains shielding integrity across a broad frequency range, with attenuation levels from 40 dB to over 100 dB depending on the design and test conditions like the triaxial method per IEC 62153-4-10. Such glands are essential in sensitive electronic systems, such as automation controls or e-mobility applications, where they prevent electromagnetic radiation from disrupting operations. The TRI spring design, for instance, offers vibration resistance and high current-carrying capacity for reliable performance.[35]
Explosion-proof glands are critical for use in hazardous areas where flammable gases, vapors, or dusts may be present, incorporating protection types like Ex d (flameproof) or Ex e (increased safety) to contain internal ignitions and prevent external propagation. Ex d variants feature robust enclosures that withstand explosions without rupture, while Ex e designs emphasize secure sealing to avoid sparks or excessive temperatures. Constructed from materials such as nickel-plated brass, aluminum, or stainless steel, these glands support temperature ranges from -60°C to +130°C and are certified under ATEX and IECEx standards for global hazardous location compliance. They often include displacement seals for armored or unarmored cables, ensuring IP66 to IP68 ingress protection alongside deluge resistance.[37][36]
Waterproof and submersible glands provide enhanced sealing for applications requiring protection against water ingress, including outdoor exposure and prolonged immersion. Weatherproof cable glands (also known as waterproof cord grips or strain relief connectors) are the standard fittings for running electrical wires through metal walls in outdoor settings. These glands are installed by drilling a hole in the metal wall, inserting the gland body, securing it with a locknut on the opposite side to capture the wall, threading the cable through, and tightening the compression nut to create a watertight seal around the cable, preventing water ingress while providing strain relief. They are available in materials such as nylon, brass, or stainless steel, with IP67/IP68 or NEMA 4X/6P ratings suitable for wet and outdoor locations. For prolonged submersion, these glands achieve IP68 ratings that withstand immersion up to 10 meters for durations such as 30 minutes under 1 bar pressure. They use high-elasticity seals and corrosion-resistant materials like nylon PA66 to maintain integrity in wet environments, with some variants offering heat resistance up to 200°C for applications near heat sources. Commonly applied in marine, outdoor, or underwater installations, they ensure reliable cable entry without water ingress, supporting operational continuity in demanding conditions.[38][39]