Bronze as an alloy is one of the most versatile and commonly used materials for flanged bronze bushings because it comes in a plethora of alloys and compositions. Apart from being just versatile, bronze and its alloys are extremely durable, sturdy, ductile, and a lot less brittle than tough elements such as cast iron making them the most suitable candidate to be used in the manufacturing of machinery parts, used directly in machinery such as diesel engines, food processing, pumps, etc. As an alloy, bronze is not directly used in its natural form, but rather in the form of certain structures known as bronze sleeve bearings.
Being so versatile and displaying a wide variety of properties, selecting the right kind of bronze to suit your needs involves ensuring the following factors-
A good design for bronze bearings is substantially comprised of 3 primary factors- the environment, proper lubrication, and the best material suited for it. The environment of any 2 industries cannot be completely alike in any manner and creating the right lubrication cycle for the bearings cannot be completely overemphasized, which means that for different sets of jobs, a different type of bearing has to be used. For example, in propeller shafts, brass flange bushings are used simply because they don’t rust, in powder metallurgy, high and low-temperature machinery, food-grade applications, solid bronze bearings are used.
- Bushing clearance
Bearings and bushings are subject to a lot of expansions, compressions, and interference; and due to the radial motion of the shaft inside the bearings, there has to be maintained a safe distance between them both so that the motion of the shaft does not lead to situations where it starts getting in contact to an already dynamic bearing. This safe distance between the two is what is known as bushing clearance and is a factor that bronze bearing manufacturers have to pay a lot of attention and detail.
Yet another important factor to keep in mind is how much weight and stress shall the bearing be subjected to. Maximum load on a bearing is industrially counted in psi (pounds per square inch) and for a rough approximation, it is close to 1/3rd of the compression limit of the bearing material.
- PV value
The name may not signify much, but PV value is without a shadow of a doubt the most important factor that both manufacturers, as well as buyers, look into before making a purchase. It is the indication of how much return can be or would be returned on the money invested and is also the detrimental factor in the service life of the bearings.
The PV value is simply a product of the specific load (P) and the sliding speed (V) of the bearing. A lower PV value is an indication of a long life and vice versa.
- The sliding speed (V) is calculated as- (0.262 (pi/12) x RPM x shaft diameter)
- The specific load (P) is calculated as- (total load / projected area)
Multiplying the values obtained from the above formulae gives the PV value of your bearing in question. For example, bronze flanged sleeve bearings are made out of Cast Bronze C93200 and has a PV value of 75,000- the best number ever punched in the industry.
What is Plain Bearing?
A plain bearing is a mechanical part that is charged for bearing loads and allows rotational or sliding moments between two machine parts. It is also called a plain bearing bushing. It is a cylindrical sleeve used to bear loads of light to moderate intensity. Over a shaft, it can slide axially or radially allowing linear or rotary motion between shafts. The main purpose of using plain bearing and sleeve bearing is that the point of support should be free from any wear and tear while the shaft is directly rolled to the machine structure. Plain bearing material is very durable and is composed of only two parts in which the first one is a fixed part where the support is and the second one is in contact with the bush which is the moving part. The support is the main point of load-bearing while the bush part gets worn out due to the frequent motion.
What are its types?
- Sleeve Bearing – This is the most commonly used plain bearing which supports linear shafts, rotating shafts and oscillating shafts and functions through a sliding action.
- Mounted Bearing – It is specially designed according to the specs to get an ideal fit. If there is a loose fit, then creep or slippage can happen in mounted bearings and if there is a very tight fit, then it will affect the free movement of the shaft.
- Spherical Bearings – It allows angular motion between the control arms and linkages. It rotates in two directions to compensate for any misalignment of the shafts.
- Flange Bearings – This bearing supports a shaft running perpendicularly to the mounting surface of the bearing. The flange is also known as the rim of the bearing and is used as the locating medium to hold down the position of the sleeve bearing in its place.
- Thrust Bearings – It is used to prevent any metal to metal contacts in the application of thrust loads. These are very thin and easy to install on a shaft mechanism. It is a self-lubricating type to reduce any extra maintenance expenses.
What are its Advantages and Disadvantages?
The plain bearing design is very basic and it possesses numerous numbers of advantages with a few disadvantages.
- Low cost
- Produces less noise than other bearings
- Simple installation
- High shock resistance, providing better durability
- Allows high rotational speeds
- Plain bearing lubrication not required when using self-lubricating bearings
- High friction during the start-up process
- Requires large axial space
- Friction resisting materials used by plain bearing manufacturers are indispensable
- High wear in comparison with roller bearings
Plain bearing bushing relies on full fluid lubrication which is theoretically capable of working indefinitely. It is used in very critical applications where the failure of bearings can lead to a massive failure of the whole mechanism and can’t be sustained. Generally, it is mostly used in engines and turbomachines like steam turbines of power plants, ship propeller shafts, compressors in pipeline operations and many more types of machinery for aerospace and automobile industries. Plain bearing manufacturers even make bearings for special purposes with different specifications too.