Comprehensive Guide to Cable and Duct Sealing Terminology
Duct Sealing Terminology Intro
Sealing cable ducts and penetrations is essential in preventing moisture accumulation and stopping the passage of water, gases, vapours, and flames through ducts or conduits into other parts of an electrical installation. However, the terminology surrounding these sealing solutions can be confusing due to the variety of names and crossover into industries like HVAC. This guide aims to clarify these terms, helping you select and use the right duct sealing system for your needs.
Cable Duct Sealing System or Kit
A Cable Duct Sealing System or Kit comprises components designed to seal cables within a cable duct. The technology utilised can vary, including sealing compounds, mechanical seals, or expanding polyurethane foam. It’s important to note that expanding polyurethane is notorious for failures and is generally not recommended. When selecting a duct sealing system, ensure it provides a watertight seal and offers chemical resistance, especially when installed in environments exposed to aggressive agents or running water.
Duct Seal
Duct Seal is a common term associated with the action of sealing a duct. At AC Cable Solutions, we brand our products as DuctSeal LG, DuctSeal HG, and DuctSeal FR. These products offer excellent adhesion and are designed for quick and easy installation, ensuring a secure seal against water and gas ingress. In the HVAC industry, duct seal or duct sealing refers to using sealants to seal pipework joints and ends to prevent air leaks.
Conduit Seal
In the USA, Conduit Seal is a popular term used to describe components that seal circular entries like conduits or ducts. The technologies commonly associated with this term are expanding polyurethane (which is advisable to avoid) and mechanical duct seals. Mechanical seals provide better protection, especially against chemical agents and pressing water, and are suitable for compliance with standards.
Duct Sealants
The term Duct Sealants can mean different things across industries. In electrical installations, it refers to products used to seal cables within a duct or penetration, offering protection against water and gas. In the HVAC industry, it describes sealants applied to pipe joints and ends to prevent air leaks. At AC Cable Solutions, our duct sealants provide excellent chemical resistance and are designed for both indoor and outdoor applications, including hazardous EX zones.
Re-Enterable Duct Sealing System
A term highly used in the UK, a Re-Enterable Duct Sealing System allows for easy re-entry or removal in the future to add or remove cables. This flexibility saves time and costs when upgrading cable infrastructures and enables engineers to modify cable configurations quickly. Industries like water utilities, including Severn Trent Water, and fuel filling stations frequently use this system due to its adaptability and ease of installation.
Cable Transit
The term Cable Transit originated in the early 1950s when the Swedish company MCT Brattberg introduced their innovative sealing system for cables passing through penetrations in structures like ship bulkheads and decks. Since then, it has become a generic term for various sealing technologies used when sealing cables through penetrations of any size or shape.
Multi Cable Transit
Building on the concept of Cable Transit, Multi Cable Transit (MCT) refers to a sealing system capable of handling multiple cables or pipes through a penetration, commonly used in ship bulkheads and decks. These systems are designed to withstand high pressure and provide a watertight seal, making them suitable for complex installations where multiple cables are present.
Circular Cable Transit
A more specific term, Circular Cable Transit, refers to mechanical sealing solutions for sealing single or multiple cables through a circular penetration. These systems typically use mechanical seals that provide excellent adhesion and are suitable for applications exposed to chemical agents and various gases.
Mechanical Duct Seal
As the name suggests, a Mechanical Duct Seal uses a mechanical method to seal cable ducts. This typically involves specially modified rubber sandwiched between V2 stainless steel plates, with multiple entries for cables and pipes. The seal mechanically pressure-fits around the cables or pipes, providing protection against gases, vapours, and water. This type of seal offers chemical resistance and is often used in critical installations requiring compliance with standards.
Ring Seal
A Ring Seal is used to mechanically seal a single cable or pipe through a penetration. It is commonly used in the oil and gas industry and is now gaining popularity in the heat pumps industry for sealing pipework, typically PE sheathed cables and pre-insulated pipes. Ring seals provide strong protection against both water ingress and chemical exposure.
Pressing Water Seal
Originating from Germany, Pressing Water Seal refers to a sealing system that can resist water pressure pressing up against the seal installed in the duct or conduit. Any sealing system installed should withstand pressing water. The performance varies based on the type of seal, with mechanical seals generally outperforming sealing compounds due to their superior durability and resistance.
Additional Cable Gland Terminology
CW & BW Cable Glands
BW cable glands are typically used for Steel Wire Armoured (SWA) cables in indoor applications where a waterproof seal on the outer sheath is not required. They provide mechanical retention and earth continuity between the armour and the gland body.
CW cable glands are designed for outdoor use on both armoured and unarmoured cables. They include an additional sealing element to protect against water and dust ingress (commonly rated IP66 or higher). These glands maintain enclosure integrity and are suitable for harsh or external environments.
The distinction between CW and BW glands is important when selecting the correct gland for your application — match the cable type (armoured or unarmoured), installation environment (indoor or outdoor), and sealing requirement.
Cable Glands & Cable Gland Kits
Cable glands are mechanical fittings that secure and terminate the end of an electrical cable to equipment or enclosures. They provide strain relief, environmental sealing, and maintain electrical continuity for armoured cables.
Cable gland kits include all the required components for quick installation, such as the gland body, locknut, earth tag, shroud, and washers. They are available in a range of materials, including brass, stainless steel, and nickel-plated brass, to suit various applications.
Armoured vs Unarmoured Cables
Armoured cables (SWA) have a steel wire armour layer for mechanical protection and require correct termination to maintain electrical bonding. Unarmoured cables lack this metallic layer and use glands designed for sealing and strain relief only.
Key Cable Gland Components
- Outer Sheath – The external protective layer of the cable that is sealed by the gland to prevent dust and moisture ingress.
- Sealing Ring – Provides the environmental seal between the gland and the outer sheath.
- Clamping Ring – Ensures secure mechanical retention of the cable and maintains strain relief.
- Earth Tag – Used with armoured cable glands to provide an electrical connection between the gland and the armour for earth continuity.
Ingress Protection & Ratings
Ingress Protection (IP) Ratings define how well a gland or fitting resists intrusion from dust and liquids. Common levels include IP66 (dust-tight, protected against high-pressure water jets) and IP68 (protected against continuous immersion).
Hazardous Area & ATEX/IECEx Glands
For hazardous areas where explosive gases or dust may be present, glands must comply with ATEX and IECEx standards. These glands are marked and certified to ensure they meet the necessary safety requirements for use in potentially explosive atmospheres.
Earthing & Continuity
For armoured cables, the gland provides a mechanical and electrical connection between the cable armour and the equipment earth. This continuity is critical for system safety and grounding integrity in electrical installations.
Installation & Selection
Choosing the correct cable gland depends on multiple factors — cable type, size, installation environment, sealing needs, and certification requirements. Always ensure glands are installed according to manufacturer instructions to maintain safety and compliance.
Conclusion
Understanding the terminology behind cable glands, duct sealing systems, and associated accessories is essential for selecting the right products for your installation. Whether you’re working with CW or BW cable glands, hazardous area equipment, or flexible conduit systems, knowing the correct terms ensures safe, compliant, and reliable performance.
At AC Cable Solutions, we supply a complete range of cable glands, duct sealing systems, transit seals, and industrial accessories — all designed to meet global standards including ATEX, IECEx, and WIMES compliance. Our products are manufactured for durability, safety, and ease of installation across industrial, commercial, and hazardous environments.
To learn more, browse our Cable Glands Collection or explore our Duct Sealing Systems.
For expert guidance, contact our technical team or submit an enquiry — we’re here to help you find the perfect solution for your next project.
Need More Information?
If you need help selecting the right products or have any questions, contact our expert team today. We’re here to support you in ensuring the success of your installations.