A guide to pv calculations

Incorrect bearing specification is one of the main causes of plain bearing failure. PV calculation bearings provide a reliable method for selecting the ideal sliding bearing for your application by ensuring the operating conditions remain within the recommended bearing PV limit.

Let me help you get this right.

Why are PV calculations so important?

There are two reasons PV calculation bearings are a helpful guide when specifying plain bearings:

• Optimising performance – minimising wear, friction, and heat generation.
• Longer operational life – delivering longer Mean Time Between Failures, reducing maintenance costs, and minimising downtime.

PV Value: A Clear Definition

Put simply, the PV value bearings use to determine performance represents the bearing’s load-carrying capacity, expressed as pressure multiplied by velocity. When performing a pressure velocity calculation, P represents the pressure exerted on the bearing, while V represents the sliding velocity of the mating parts.

Here are the two calculations used to measure PV value:

Psi × ft/min

N/mm² × m/s

The higher the PV value, the greater the loads and sliding speeds the bearing can handle. Exceeding the recommended bearing PV limit for a particular material can lead to premature wear and eventual plain bearing failure.

Factors to Consider When Calculating PV Values

Bearings are not a one-size-fits-all solution, and there will always be application-specific factors that influence bearing performance. Here are the factors to consider when performing a pressure velocity calculation:

• Operating temperature – High temperatures can alter bearing material properties and reduce load-carrying capacity.
• Lubrication – Correct lubrication is critical to reducing friction and heat generation, improving bearing life.
• Bearing material – The bearing material PV rating varies considerably depending on the material selected, directly affecting load capacity and wear resistance.

How to Perform PV Calculations for Plain Bearings

Here are three simple steps for calculating PV value:

1. Confirm the applied load (pressure) on the bearing (P).
2. Calculate the sliding velocity of the mating parts (V).
3. Multiply the pressure (P) by the sliding velocity (V) to determine the PV value.

REMEMBER: Always compare your calculated PV value bearings with the recommended bearing material PV rating. If your result exceeds the specified bearing PV limit, the selected bearing is not suitable for your application.

HELP IS AVAILABLE: Consulting an expert is always the best practice when specifying bearings. We can help you perform PV calculation bearings, evaluate operating conditions, and recommend the right bearing material based on PV value and other critical application requirements.