Are you struggling to choose between single and double compression cable glands for your electrical project? Not sure what the key differences are and which type is right for your specific application? In this article, we’ll break down the distinctions between these two common types of cable glands to help you make an informed decision.
What is a Single Compression Cable Gland?
A single compression cable gland is an electrical fitting used to terminate and seal cables where they enter equipment enclosures, such as control panels, machines, or appliances. It provides a secure, waterproof, and dustproof connection point for the cable.
To install a single compression gland, the cable is inserted through the fitting, and the dome nut is tightened. This action compresses the sealing ring around the cable, forming a robust seal that prevents ingress of moisture, dust, or other contaminants into the enclosure.
Parts of a Single Compression Cable Gland
A single compression cable gland typically consists of three main components:
- Sealing Ring: The sealing ring, usually made of elastomeric material like rubber or neoprene, is responsible for creating a watertight and dustproof seal around the cable. When compressed, it conforms to the shape of the cable, filling any gaps and preventing the ingress of contaminants.
- Compression Ring: The compression ring, also known as the clamping ring, is a cylindrical component that sits inside the cable gland body. Its purpose is to apply pressure on the sealing ring when the dome nut is tightened, ensuring a secure and reliable seal around the cable.
- Dome Nut: The dome nut, located at the outer end of the cable gland, is used to compress the sealing ring and compression ring onto the cable. As the dome nut is tightened, it forces the compression ring to press against the sealing ring, creating a tight seal and providing strain relief for the cable.
The cable is inserted through the dome nut, compression ring, and sealing ring before the gland is tightened. The cable gland body is then secured to the enclosure via a locknut or thread, depending on the specific design.
What is a Double Compression Cable Gland
A double compression cable gland is an enhanced version of the single compression design, offering a superior level of sealing and mechanical protection for cables in demanding applications. It features additional sealing and clamping elements compared to its single compression counterpart.
The double compression gland secures and seals the cable at two distinct points:
- Inner seal: Compresses onto the cable inner sheath to create a watertight barrier
- Outer seal and clamp: Grips the cable outer sheath or armor to provide a second layer of sealing and strain relief
This dual compression mechanism ensures a high degree of ingress protection, preventing liquids, dust, and gases from penetrating the enclosure along the cable path. The outer clamping also enhances the cable’s resistance to mechanical stresses, such as pulling, twisting, or bending forces.
Parts of a Double Compression Cable Gland
A double compression cable gland consists of several key components:
- Inner Sealing Ring: Similar to the sealing ring in a single compression gland, the inner sealing ring creates a watertight and dustproof seal around the inner sheath of the cable. It is compressed onto the cable by tightening the inner dome nut.
- Outer Sealing Ring: The outer sealing ring is an additional seal that compresses onto the outer sheath or armor of the cable. This second sealing point provides an extra layer of protection against ingress and enhances the overall sealing performance of the gland.
- Inner Compression Ring: The inner compression ring applies pressure on the inner sealing ring when the inner dome nut is tightened. It ensures a secure and reliable seal around the inner cable sheath.
- Outer Compression Ring: The outer compression ring serves to compress the outer sealing ring onto the cable armor or outer sheath. It also provides additional strain relief and mechanical protection for the cable.
- Inner Dome Nut: The inner dome nut is responsible for compressing the inner sealing ring and inner compression ring onto the cable’s inner sheath. It is tightened first during installation.
- Outer Dome Nut: The outer dome nut compresses the outer sealing ring and outer compression ring onto the cable’s armor or outer sheath. It is tightened after the inner dome nut to complete the double compression sealing.
The cable is inserted through the gland components in the correct order, and the gland body is then secured to the enclosure. The inner and outer dome nuts are tightened to their specified torque values to ensure proper compression and sealing.
Difference Between Single and Double Compression Cable Glands
Cable Type Suitability
Single compression cable glands are versatile and can accommodate a wide range of cable types, including unarmored and armored cables.
Double compression cable glands are particularly well-suited for armored cables, as the outer clamping mechanism can securely grip the cable’s armor layer. However, double compression glands may not be necessary for smaller, unarmored cables where a single compression design would suffice.
Installation
Installing a double compression cable gland is generally more complex and time-consuming compared to a single compression design. The additional components and the need to secure both the inner and outer seals require extra attention during installation.
Cost
Due to their additional components and more complex construction, double compression cable glands are typically more expensive than single compression designs.
Size
Double compression cable glands are generally larger in size compared to single compression designs. The extra components, such as the outer sealing ring and armor clamping mechanism, contribute to the increased size.
Applications
Single compression cable glands are suitable for a wide range of general-purpose applications across various industries. They are commonly used in indoor, low-risk environments where a basic level of sealing and strain relief is sufficient.
Double compression cable glands are ideal for demanding applications in harsh industrial environments. They are extensively used in sectors such as oil and gas, mining, chemical processing, and marine, where equipment is exposed to extreme conditions, high levels of moisture, dust, and mechanical stress.