Different types of cable bushings and their unique advantages
Cable bushings play a vital role in maintaining the integrity, safety, and performance of cable connections and systems. But what exactly are these components? Our guide is designed to give you a better understanding of cable bushings, what they’re used for, and which material you should consider. We’ll cover:
What are Cable Bushings?
Cable bushings, sometimes called cable bushes, are used in electrical installations to protect cables as they pass through walls, floors, or other barriers.
One of the key functions of cable bushings is to provide electrical insulation. Typically made of rubber or plastic, they create a barrier between the cable and the surrounding structure. This insulation prevents electrical contact, which could result in short circuits or other hazards.
Cable bushings also provide mechanical protection. They shield cables from physical damage caused by sharp edges, rough surfaces, or vibrations. By acting as a cushion or barrier, they minimise the risk of abrasion, puncture, or stress on the cable insulation. This is particularly important in areas where cables may be subject to movement or external forces.
Cable bushings play yet other roles by providing strain relief and environmental sealing. They create a seal around the cable – sometimes multiple cables – safeguarding it from humidity, dust, dirt, and other contaminants. This is particularly important in outdoor or harsh environments where cables are exposed to weather conditions or chemical substances.
You should also check out Guide to Cable Strain relief and Protection.
Cable Bushings vs. Grommets
The primary function of grommets – see the example shown here – is to protect wires and cables against abrasion. Grommets are used in non-electrical or low-voltage applications, or non-critical electrical applications, such as automotive to pass a cable from one panel hole to another.
While a cable bushing is sometimes called a cable bushing grommet, they’re not the same. Cable bushings are designed specifically for electrical applications.
Learn more in our Guide to Rubber Grommets.
Types of Cable Bushings
One of the most common applications for bushings are power transformers. Transformer bushings are paper-insulated bushings used in high-voltage applications. The main concern here is the entry of moisture, which is why resin-impregnated paper is used. Besides transformer bushings, what are the smaller types of cable bushings commonly used?
Understanding these different types of cable bushings and their applications allows you to make informed decisions for efficient cable routing and organisation. When installing a cable bushing, it’s important to make sure that the cable’s core insulation is not damaged during the process. The bushing should provide a smooth and rounded pathway for the cable to pass through, without causing any stress or abrasion on the core insulation.
Snap-Fit Bushings – Closed
The closed bushing design features multiple locks that allow the bushing to snap into common panel thicknesses. Installation is fast and easy, requiring only fingertip pressure to snap into place. Nylon 6/6 and Heat-Stabilised Nylon 6/6.
Use of cable bushings: Electrical and telecommunications cables, tubing, hose, rope, and utility lines.
Snap-Fit Bushings – Open/Close
Standard open bushings with an easy push-in design allows them to lock into place. The split design means they can be assembled into panel thicknesses that already contain a bundle. Nylon 6/6 and Heat Stabilised Nylon 6/6.
Use of cable bushings: Electrical enclosures – the open portion allows for easy cable insertion and routing, providing strain relief and organisation for cables.
All-Fit Bushings – Closed
The bushing body is made to fit various sized parts. The closed structure of these cable bushings ensures effective electrical insulation. Also called Universal bushings, they help to absorb shock and vibration. The bushing’s web or shutters provide a clean finished appearance. Nylon 6/6 and Heat Stabilised Nylon 6/6.
Use of cable bushings: Suitable for applications where a high degree of electrical insulation, shock absorption and vibration damping are required, such as heavy machinery.
Strain Relief Bushings
Cable strain relief bushings prevent excessive bending, pulling, or twisting of cables, which can lead to insulation damage, wire breakage, or disconnection. By absorbing the mechanical stress caused by movement, vibration, or tension, strain relief bushings help maintain the integrity of the installed cable system. Nylon 6/6.
You’ll need a tool for easy insertion and extraction, such as our ergonomic bushing installation tool.
Use of cable bushings: Consumer electronics and appliances – also suitable for medical devices.
Snub Bushings
The thick split opening of snub bushings close around a cable once it's snapped into place. This not only secures it, but ensures that the cable doesn’t move while providing solid insulation and strain relief. Nylon 6/6.
Use of cable bushings: Automotive wiring, machinery, and industrial equipment
Advantages and Disadvantages of Cable Bushings
Cable bushings offer several advantages and disadvantages, which you should consider when evaluating their use for your application.
Advantages:
- Electrical Insulation: prevents electrical contact between the cable and the surrounding structure
- Mechanical Protection: acts as a cushion or barrier, reducing the risk of abrasion, puncture, or stress on the cable insulation
- Environmental Sealing: provides a seal around the cable, protecting it from moisture, dust, dirt, or other contaminants
- Compliance with Regulations: approved cable bushings can ensure compliance with electrical and safety requirements, providing peace of mind and avoiding potential penalties or safety risks
Disadvantages:
- Installation Complexity: some cable bushings, such as cable strain relief bushings, may require additional effort and time for installation
- Space Constraints: cable bushings can occupy space within the installation, which may be a consideration in situations where space is limited, or the installation requires a high density of cables
- Limited Cable Adjustability: once cable installation with a cable bushing takes place, it may be challenging to make adjustments to the cable routing without removing and reinstalling the bushing. This can be an inconvenience where frequent changes or modifications to the cable layout are anticipated
Cable bushings: plastic vs. rubber
Materials are key factors when considering the pros and cons of cable bushings, which are typically made of rubber or plastic.
Plastic cable bushings
These cable bushings offer high mechanical strength, low friction, and good dimensional stability. They exhibit excellent resistance to chemicals, oils, and solvents. Nylon bushings also have a low coefficient of friction, which can help reduce wear and extend the lifespan of components.
Rubber cable bushings
These are excellent at vibration absorption, acting as a vibration isolator. Be aware, rubber cable bushings are susceptible to wearing out easily, especially when used in an environment where oils are present. Extreme temperatures can affect rubber cable bushings too.
Rubber bushings, commonly used in vehicle suspension systems, can potentially hurt vehicle performance, particularly handling during cornering and braking. Routine inspections should pay particular attention to rubber bushes for wear and tear.
Nylon and Rubber Cable Bushings: At a Glance
| Characteristic | Nylon 6/6 | Rubber |
|---|---|---|
| Vibration damping | Good | Better |
| High strength | Better | Good |
| Chemical resistance | Better | Variable |
| Wearability | Better | Fair to Good |
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