What is a Bushing Used For? And no, we're not talking about plants!
The guide to bushes, what they’re used for, and how they contribute to the modern manufacturing industry.
Have you ever come across the term "bushing"? Unless you have a background in mechanics or heavy industry, you might think a bushing is a shrub. But in the world of engineering, a bushing is a whole different concept - and one that keeps all kinds of machinery operating smoothly.
A bushing is a cylindrical lining designed to prevent wear to moving components. Bushings are often used as a casing on machinery with rotating or sliding shafts, pins, or hinges. They are also known as bushes, plain bearings or sleeve bearings.
Bushings are among the most versatile components in modern engineering, with a range of materials and sizes available. Read on to find out more about the humble bushing.
So, what is a bushing used for?
Bushings are compact and lightweight, and they possess high load-bearing capacities. They also are the least expensive type of bearing. Depending on the application, some bushings are available with supplemental lubrication or designed to run dry, with no additional lubrication.
Bushings are typically made from one or a combination of different materials, each with its own benefits and applications. Common types of bushes include:
Rubber Bushings: Softer than polyurethane, allowing it to dampen more vibrations. However, it can wear out when exposed continuously to stretching, heat, oil or chemicals.
Polyurethane Bushings: Firmer than rubber and handle more abrasion, but also require more frequent lubrication. This type of material may be moulded.
Bronze Bushings: Harder and less likely to break or deform than rubber or plastic. About 17 types of bronze are used in making bushings. Two of the most common are oilite, a self-lubricating material, and copper, which is bronze combined with tin, aluminium, or silicone.
Steel-backed/Babbit Bushings: A lower-cost material than bronze, offering excellent fatigue resistance and load-carrying capacity.
Cast-Iron Bushings: Used to support hardened steel shafts.
Neoprene Bushings: Looks and feels like rubber, but can withstand heat better and does not quickly deteriorate when exposed to oil or heat.
Nylon: Inhibits friction and requires no lubrication. It may also be moulded, cast or machined easily.
Delrin or Acetal: Useful in wet environments for their stability and resistance to wet abrasion.
Ultrahigh-Molecular-Weight Polyethylene (UHMWPE): Has a low friction surface and is used as an alternative to bushings made from acetal or nylon.
Carbon-Graphite: Self-lubricating and resistant to chemicals and solvents. Also suitable for exposure to low-viscosity or corrosive liquids.
Polyimide, Polysulfone, Polyphenylene Sulfide: Highly resistant to chemical burning.
Bushings are also characterised by key features, offering greater suitability to specific uses and environments.
Common features of bushings include:
Coatings: Some bushings use thermal spraying to provide an internal coating. This treatment reduces friction between the bushing's inner surface and the shaft that it supports. Common types of coating used include dry film lubricant, Teflon, or graphite.
Grooves: Grooves on bushings act as oil channels, allow lubricants to flow more easily across the bushing.
Indents: These are small pockets on the bushing surface that retain oil or other lubricants, reducing maintenance requirements.
What types of machinery can bushings be used in?
Bushings are extremely versatile, and they're vital to many modern-day applications. Used primarily in machinery used for power generation, marine, rail, mining, and oil and gas industries, bushings are a vital necessity in modern machinery.
Power Plant Steam Turbines
Power plant steam turbines generate a lot of heat that can eventually cause machine breakdown. Besides absorbing heat, bushings protect the machine components from vibration and wear. They also prevent steam leakage and other operational and maintenance issues.
Compressors
Bushings in air compressors create space between the moving parts. As bushings contain no rubbing metal parts, they provide little to no risk of decreased performance due to wear-and-tear. They are also pressure-lubricated, which helps boost the compressor's overall efficiency.
Cars
Car bushings are mounted on the suspension and steering joints to control the movement. They also absorb noise and vibration when you encounter bumps in the road, providing a smoother ride. Besides a car's steering and suspension system, bushings are also used in non-moving parts such as the body and strut mounts.
What does the bushing do?
While its primary function is to reduce friction and noise between two surfaces that rotate or slide against each other, a bushing also serves several additional purposes.
It serves as a guide for installing other elements in a system.
It may be inserted into a housing to limit the size of an opening or resist abrasion.
It functions as a lining through which a conductor passes, providing insulation and protection for the conductor.
It is an adapter for joining pipes of different sizes.
How does a bushing work?
Most bushings are manufactured in a cylindrical or conical shape, using wear-resistant and shock-absorbent materials. They are made to slide over rods or shafts, providing extremely low-friction motion and protecting more critical parts.
Where mechanical components inevitably deteriorate over time, it's cheaper and easier to replace a bushing than a complex piston suspension component. Bushings also work to minimise energy usage, reduce noise, absorb vibration, and protect the equipment from overall wear and tear.
Where is a bushing located?
A bushing's location depends on the application. Most of the time, bushes are mounted on parts where vibration and friction are common.
In cars, bushings are found on automotive suspension systems, sway bars, transmission gear sticks, doors and windshields. In steam turbines, bushings are installed in the valve components, such as the main stop valve, control valve, extraction valve and reheat stop valve. In air compressors, bushings connect the air compressor piping to threads.
What does a bushing help to achieve?
Bushes may be small, but they play a vital role in a machine's efficiency and longevity. They isolate noise, vibration and shock, allowing the moving components to operate smoothly while providing added resistance to abrasion and damage.
What is the difference between bearing and bushes?
Bearings and bushings are often used interchangeably, but it is important to note that they are two different components.
Bearings
'Bearings' is a general term that refers to any mechanical component designed to support a rotating body and reduce friction between moving parts. It facilitates high-speed movement while handling stress and ensuring rotation is accurate.
Technically, bushings or bushes can be considered a straightforward kind of bearing - also referred to as a 'plain bearing'.
Bearings are typically more complex in construction than bushings, typically consisting of several rollers or balls. Unlike bushings that need only a small amount of lubrication, bearings require constant lubricant supply to prevent damage and wear.
Bearings are divided into two main classes: journal bearings, where the load acts at right angles to the axis, and thrust bearings, where loads are parallel to the axis. In addition to plain bearings or bushings, common types of bearings include roller bearings, fluid bearings, magnetic bearings, flexure bearings and moulded plastic bearings.
Bushings
As mentioned, bushings are a specific subtype of bearing. They support a component in an assembly, ensuring smooth operation and reducing machine wear-and-tear. Unlike bearings composed of multiple parts, a bushing often comes as a single component. However, it can be equipped with rolling elements for sliding or support. Compared to bearings, bushings are more durable and require less maintenance because they have no moving parts.
Similarities between bushings and bearings
Both bearings and bushings reduce rolling friction between a shaft and an attached part. Hence, they both reduce friction energy losses, risk of wear-and-tear damage and repair and maintenance expenses.
Related Questions
What else is there to know about bushes in modern-day machinery?
Since bushings are used in machinery with a rotating or sliding shaft component, they can be found in almost every industrial application. Thanks to their excellent anti-friction and load-carrying capacities, bushings are vital in construction, mining, agriculture, forestry, transportation, hydropower generation, food processing, material handling and many more industry sectors.
How long have bushes been used in machinery?
The modern-day bushing was introduced in the 1930s by Frederick Zeder, the chief of engineering at Chrysler. Zeder came up with a new Plymouth model equipped with rubber mounts that allowed the engine to be isolated from the frame. Ultimately, this invention effectively cut down the vehicle's noise and vibration while being driven. This innovative feature became a game-changer in the automotive industry and led to increased car sales for Plymouth.
Where can I purchase bushes?
Because of their many uses, bushings are available for purchase through many online suppliers in addition to hardware stores and automotive stores. Many companies that supply equipment for specific industries - such as construction, plumbing, automotive, and agriculture - also have compatible bushings in their product catalogue. At Armstrong Energy, we supply a large range of standard bushes and can machine fully-customised bushes.