Factors which help to select the right bronze bearings

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-

 

  • Design

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.

 

 

  • Loading

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.

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