2026-07-30 8 min

PV Value Calculator

Calculate PV (pressure × velocity) value for bearing materials. The PV limit determines the maximum operating condition for sleeve bearings and thrust washers before thermal failure.

Calculator

Unit System

Bearing Material

Contact Pressure p (MPa)

Load ÷ projected bearing area

Sliding Velocity V (m/s)

Operating Temperature (°C)

Results

Critical

PV Value

5.0000MPa·m/s

Product of contact pressure and sliding velocity

PV Limit

0.3500MPa·m/s

Maximum allowable PV for selected material

Safety Factor

0.0700-

Ratio of PV limit to actual PV value

Power Loss

250000.0000W

Estimated frictional power loss at the bearing interface

Temperature Rise Estimate

40.0000°C

Estimated temperature increase above ambient

Status

Exceeded-

Operating condition relative to material PV limit

Visualizations

Results Overview

5MPa·m/sPV Value

0.4MPa·m/sPV Limit

0.1MPa·m/sSafety Factor

250,000MPa·m/sPower Loss

40MPa·m/sTemperature Rise Estimate

Formula

The PV value is the product of contact pressure and sliding velocity. If PV exceeds the material limit, thermal failure occurs.

PV = p × V (MPa·m/s)

Alternative Form

PV_limit = material-specific constant (MPa·m/s)

Variables

Symbol	Name	Unit	Description
PV	PV Value	MPa·m/s	Product of nominal bearing pressure and sliding velocity
p	Contact Pressure	MPa	Nominal bearing pressure (load / projected area)
V	Sliding Velocity	m/s	Relative speed between contacting surfaces
PV_limit	PV Limit	MPa·m/s	Material-specific maximum allowable PV before thermal failure

Explanation

The PV limit represents the maximum frictional heat generation rate a bearing material can dissipate without exceeding its thermal limit. Exceeding the PV limit causes rapid temperature rise, material softening, and catastrophic failure. The PV concept is widely used for sleeve bearing and thrust washer material selection.

Derivation

PV = p × V where p = F/A (load/projected area) and V = πDN/60 (for rotating shafts). The power loss per unit area = μ × p × V = μ × PV. The material PV limit is determined experimentally by increasing p and V until the temperature rise exceeds acceptable limits (typically 50-100°C above ambient).

Step-by-Step Calculation

Follow each step to understand how the result is calculated from your inputs.

Step 1

Select the bearing material to determine its specific PV limit from the database.

Material:PTFE

PV Limit:0.3500 MPa·m/s

Result: PTFE: 0.3500 MPa·m/s

Step 2

Calculate the PV value from the operating pressure and sliding velocity.

PV = p × V

Pressure p:5.0000 MPa

Velocity V:1.0000 m/s

Intermediate: PV = 5.0000 × 1.0000

Result: PV = 5.0000 MPa·m/s

Step 3

Compare calculated PV to material limit and evaluate status.

PV Value:5.0000 MPa·m/s

PV Limit:0.3500 MPa·m/s

Safety Factor:0.0700

Intermediate: Safety Factor = 0.3500 / 5.0000 = 0.0700

Result: Status: Exceeded

Final Answer

5.0000

Worked Examples

See how the calculator works with different scenarios.

Scenario

A PTFE thrust washer in a gear pump operates at 2 MPa pressure and 0.5 m/s sliding velocity at 60°C. Check if operating condition is safe.

Inputs

Material:PTFE

Pressure:2 MPa

Velocity:0.5 m/s

Temperature:60°C

Calculation

PV = 2 × 0.5 = 1.0 MPa·m/s PTFE PV limit = 0.35 MPa·m/s Safety Factor = 0.35 / 1.0 = 0.35 Status: EXCEEDED

Result

PV = 1.0 MPa·m/s, Exceeded (limit 0.35)

Interpretation

The operating condition exceeds the PTFE PV limit. Options: reduce pressure or velocity, switch to PTFE/bronze composite (limit 0.65), or consider PEEK (limit 0.70) for better performance.

Understanding Your Result

Your Result: PV Value: 5.0000 MPa·m/s

Typical range: PTFE: 0.04-0.35 MPa·m/s. Acetal: 0.05-0.12. Nylon: 0.05-0.10. Bronze: 0.15-0.50. Carbon-Graphite: 0.20-0.55. PTFE/Bronze: 0.20-0.65. PEEK: 0.30-0.70. UHMWPE: 0.03-0.08.

What This Means

The PV value represents the frictional power intensity at the bearing interface. Higher PV means more heat generation per unit area, requiring better heat dissipation or more thermally capable materials.

Why It Matters

Exceeding the PV limit causes rapid temperature rise, material degradation, and bearing failure. Proper PV analysis ensures bearing material selection matches the operating conditions for reliable long-term performance.

Professional Interpretation

PV limits are approximate values for dry running at room temperature. Actual allowable PV depends on heat dissipation, shaft material and finish, operating temperature, and whether lubrication is present. For critical applications, consult manufacturer data and conduct prototype testing.

Recommendations

•For dry running: stay below 80% of the PV limit to allow margin for start-up and transient conditions
•For lubricated bearings: PV limits can be 3-10× higher than dry values
•Consider heat dissipation: higher PV is possible with effective cooling (fins, circulating oil)
•Reduce PV by increasing bearing area (lower pressure) or reducing speed (lower velocity)

Educational Content

Introduction

The PV (pressure × velocity) value is a key parameter for evaluating bearing material performance in sliding contacts. It represents the combined effect of mechanical load and sliding speed on frictional heat generation at the bearing interface.

Concept Explanation

When a bearing operates, friction generates heat proportional to the product of contact pressure and sliding velocity: Q = μ × p × V × A. The material's PV limit represents the maximum heat flux it can dissipate without exceeding its maximum service temperature. Exceeding the PV limit causes a thermal runaway: higher temperature → material softening → increased friction → more heat → catastrophic failure.

Applications

▸Thrust washer material selection and design

▸Sleeve bearing for conveyor and material handling systems

▸Pump bearings (especially for chemical and food processing)

▸Automotive accessory bearings (alternator, water pump)

▸Home appliance bearings (washing machines, dishwashers)

▸Office equipment bearings (printers, copiers)

▸Aerospace bearings (control surfaces, landing gear)

Benefits

•Simplifies material selection with single combined parameter
•Relates directly to heat generation and thermal limitations
•Well-established for common bearing materials with published limits
•Allows quick feasibility assessment of bearing designs
•Guides optimization between pressure and velocity trade-offs

Limitations

•PV limits are approximate and vary between manufacturers
•Does not account for lubrication effects directly
•Static PV limit ignores dynamic loading conditions
•Heat dissipation (bearing housing, airflow) affects actual capability

Best Practices

•Always use safety factors: minimum 1.5 for continuous duty, 2-3 for critical applications
•Consider transient conditions: start-up, shutdown, and overloads
•Account for temperature derating: PV limits decrease at elevated temperatures
•Match shaft surface finish: Ra 0.1-0.4 μm for polymer bearings
•Provide adequate heat dissipation path through bearing housing

Common Misconceptions

Myth: PV limit is a material constant.

Truth: PV limits vary significantly between manufacturers, with surface finish, with temperature, and with lubrication. They are guidelines, not guaranteed material properties.

Myth: All bearing materials can be used at their full PV limit.

Truth: PV limits are typically based on continuous operation at room temperature. Intermittent duty, elevated temperature, or poor heat dissipation may require significant derating.

Myth: Higher PV limit always means better bearing material.

Truth: Higher PV materials (like bronze) often have higher friction coefficients and may require lubrication. PTFE has a low PV limit but very low friction, making it ideal for dry, low-speed applications.

Practical Tips

•For PTFE bearings, never exceed PV = 0.1 MPa·m/s for continuous dry operation at 100°C
•PTFE/bronze composites combine the low friction of PTFE with the thermal conductivity of bronze for higher PV capability
•Carbon-graphite is self-lubricating with absorbed moisture — its PV limit drops significantly in dry environments
•PEEK maintains high PV capability at elevated temperatures (up to 250°C)
•UHMWPE has very low PV limit but excellent abrasion resistance for dirty environments
•Shaft hardness should be > 50 HRC for bronze bearings, > 30 HRC for polymer bearings
•Running-in at reduced PV (50% of design value) for 50-100 hours improves bearing life

Common Mistakes

Operating at PV limit without safety factor

Always apply a minimum safety factor of 1.5-2.0. PV limits are best-case values under ideal conditions. Real operating conditions (starts, stops, temperature variations) reduce the safe margin.

Ignoring temperature effects on PV capacity

Material PV limits decrease at elevated temperatures. Many polymers lose 50% of their PV capacity at 100°C. Check manufacturer derating curves for the actual operating temperature.

Using PV limits for lubricated bearings without adjustment

PV limits are typically for dry running. With adequate lubrication, PV limits can increase 3-10×. However, failure to account for this may overdesign (too large bearing) or underdesign (inadequate lubrication system).

Confusing PV value with PV limit

PV value = p × V (your operating condition). PV limit = maximum allowable for the material. A safety factor < 1 means the PV value exceeds the limit — the bearing will fail from overheating.

Assumptions

This calculator makes the following assumptions to provide estimates:

Steady-State Operation: PV limits assume steady-state continuous operation. Intermittent duty, cycling, or start-stop conditions may allow higher momentary PV values.

Room Temperature Baseline: Published PV limits are typically for 20-25°C ambient. Elevated operating temperatures reduce the effective PV limit.

Dry Running Condition: Standard PV limits are for dry (unlubricated) operation. Lubrication can significantly increase the allowable PV, but the specific value depends on lubricant type and supply method.

Smooth Shaft Surface: PV limits assume proper shaft surface finish (Ra 0.1-0.4 μm). Rougher surfaces increase friction and reduce effective PV capacity.

Limitations

Be aware of these limitations when using this calculator:

Empirical Values: PV limits are empirical values from standardized tests. Actual performance depends on geometry, heat dissipation, and operating conditions specific to each application.

No Dynamic Effects: The PV calculation assumes constant pressure and velocity. Impact loads, vibration, and oscillating motion produce different thermal conditions.

Material Quality Variation: PV limits vary between manufacturers, grades, and formulations. Always verify with specific material supplier data for critical applications.

Size Effect: Heat dissipation scales with bearing size. Small bearings have higher surface-to-volume ratio and may operate at higher PV than large bearings of the same material.

Frequently Asked Questions

Answers to common questions about this calculator.

What is PV value in bearings?

PV value is the product of contact pressure (P) and sliding velocity (V) at the bearing interface. It represents the frictional power intensity and determines whether a bearing material can operate without overheating.

How is PV value calculated?

PV = p × V where p is the nominal bearing pressure in MPa (load divided by projected area) and V is the sliding velocity in m/s. The result is expressed in units of MPa·m/s.

What is a good PV value?

There is no single good PV value — it depends on the material. For PTFE, PV < 0.1 is good. For carbon-graphite, PV < 0.4 is good. The key is that the PV value must be less than the material's PV limit with a safety factor of at least 1.5.

What determines the PV limit of a material?

The PV limit is determined by the material's thermal conductivity, maximum service temperature, friction coefficient, and wear resistance. Manufacturers determine PV limits through standardized thrust washer testing per ASTM D3702.

How does temperature affect PV capacity?

Most materials lose PV capacity at elevated temperatures. As a rule of thumb, derate the PV limit by 0.5-1% per °C above room temperature. Polymers are particularly sensitive — PEEK loses 30% capacity at 150°C.

What happens when PV exceeds the limit?

Exceeding the PV limit causes a thermal runaway: increased friction generates more heat, the material softens, friction increases further, and the bearing fails rapidly (often within minutes). The failure may involve melting, seizure, or complete material degradation.

What is the difference between PV and PV limit?

PV value is your calculated operating condition (p × V). PV limit is a material property representing the maximum safe operating condition. The safety factor is PV limit ÷ PV value.

How does lubrication affect PV capacity?

Lubrication can increase effective PV capacity by 3-10× compared to dry operation. Oil lubrication provides the highest improvement, followed by grease, then solid lubricants. However, the PV limit for dry operation should always be checked as a baseline.

What is the PV limit of PTFE?

Unfilled PTFE has a PV limit of approximately 0.04-0.35 MPa·m/s for dry running at room temperature. The wide range reflects differences in test conditions and material grades. PTFE/bronze composites achieve 0.20-0.65 MPa·m/s.

What bearing material has the highest PV limit?

Among common materials, carbon-graphite (up to 0.55 MPa·m/s) and PEEK (up to 0.70 MPa·m/s) have the highest dry PV limits. Bronze with lubrication can exceed 1.7 MPa·m/s. Specialty materials like polyimide can reach 3.5 MPa·m/s.

How do I convert PV units?

1 MPa·m/s = 145 psi·ft/min. 1 psi·ft/min = 0.0069 MPa·m/s. Always verify units when checking manufacturer specifications, as some US suppliers use psi·ft/min while international standards use MPa·m/s.

What is the relationship between PV and bearing wear?

At PV below the limit, wear rate is typically mild and proportional to PV. At PV near or above the limit, wear rate increases dramatically as thermal effects degrade the material. Running at 80% of the PV limit typically provides acceptable wear life.

How does shaft hardness affect PV capability?

Harder shaft surfaces reduce abrasive wear of the bearing material and improve heat transfer. For bronze bearings, shaft hardness > 50 HRC is recommended. For polymer bearings, > 30 HRC is typically sufficient.

What is the PV limit of bronze bearings?

Dry bronze bearings have PV limit of 0.15-0.50 MPa·m/s. With proper oil lubrication, this can increase to 1.0-1.7 MPa·m/s. Leaded bronze (SAE 660) has better dry performance than aluminum bronze.

How does surface finish affect PV limit?

Smoother shaft surfaces (Ra < 0.2 μm) reduce friction and allow higher PV operation. Very smooth surfaces (Ra < 0.05 μm) may increase friction due to adhesion in polymer bearings. The optimal Ra is 0.1-0.4 μm for most bearing materials.

What is the role of heat dissipation in PV capability?

Heat dissipation is critical. A bearing in a massive metal housing can operate at higher PV than one in a plastic housing with poor thermal conductivity. Fins, airflow, and circulating lubricant all improve heat dissipation and effective PV capacity.

How does intermittent duty affect allowable PV?

Intermittent operation allows the bearing to cool between cycles. Momentary PV values 2-3× the continuous limit may be acceptable if the duty cycle is below 25% and adequate cooling occurs during the off period.

What is the significance of PV in thrust washers?

Thrust washers often operate at higher PV values than journal bearings because heat can dissipate from both sides. Thrust washer PV limits are typically 1.5-2× higher than sleeve bearing limits for the same material.

How do I increase PV capacity of a bearing?

Options include: increase bearing area (reduce pressure), reduce speed, select a higher PV material, add lubrication, improve cooling (fins, oil circulation), or use a harder shaft with better surface finish.

What is the PV limit of nylon bearings?

Nylon (PA6, PA66) has a dry PV limit of approximately 0.05-0.10 MPa·m/s. Oil-filled nylon grades can achieve 0.15-0.25 MPa·m/s. Nylon absorbs moisture, which affects dimensional stability and PV performance.

How does water absorption affect polymer PV limits?

Water absorption softens many polymers (nylon, acetal) and reduces their PV capacity. Nylon can absorb 2-8% water, reducing its PV limit by 30-50%. Use moisture-resistant grades for wet environments.

What is the PV limit of UHMWPE?

UHMWPE has a very low PV limit of 0.03-0.08 MPa·m/s, but it has excellent abrasion resistance and very low friction. It is ideal for low-speed, high-wear applications like conveyor guides and chute liners.

How does the coefficient of friction affect PV capability?

PV = p × V represents the load-speed product. The actual heat generation is Q = μ × PV × A. Materials with lower μ generate less heat at the same PV, effectively having higher thermal PV capacity. This is why PTFE (μ = 0.04) outperforms acetal (μ = 0.3) despite lower mechanical strength.

What is the significance of PV in gear design?

Gear tooth contacts experience high instantaneous PV values during sliding at the pitch line. PV analysis helps evaluate scuffing risk — the welding of gear tooth surfaces due to excessive frictional heating.

How do I select a bearing material based on PV?

Calculate the required PV from your operating conditions. Select materials with PV limit 1.5-2× the required PV. Consider temperature, lubrication, shaft hardness, and FDA/chemical compatibility requirements. Match the material to the specific application constraints.

What is the PV limit of acetal (POM)?

Acetal has a dry PV limit of 0.05-0.12 MPa·m/s. It performs well in moisture and chemical environments but has limited thermal capability (max 90°C). Acetal is commonly used for low-load, low-speed applications like plumbing fittings and consumer products.

How does running-in affect PV capability?

Running-in at reduced PV (50% of design value) for 50-100 hours allows the bearing surface to conform to the shaft. This can increase the effective PV limit by 20-30% compared to starting at full load.

What is the effect of edge loading on PV?

Edge loading concentrates pressure at the bearing edge, locally increasing PV and causing premature failure. Proper alignment, crowning, and edge relief are essential for achieving the full PV capability of the material.

How do fillers and reinforcements affect PV limits?

Fillers like glass fiber, carbon fiber, and PTFE can increase PV limits by 2-5× compared to unfilled polymers. However, some fillers increase shaft wear. Compromise between PV capability and counterface wear must be considered.

What is the future of PV analysis in bearing design?

Advanced thermal modeling and computational tribology are supplementing traditional PV analysis. However, PV remains the standard first-pass screening tool for bearing material selection due to its simplicity and well-established material database.

Related Calculators

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Related Guides

Deepen your understanding with these educational resources.

Bearing Material PV Rating Guide

Machine Design guide to bearing materials

ASTM D3702 Test Method

Standard for wear and friction testing

PV Limits for Bearing Materials

Engineering Toolbox reference data

Glossary

Technical terms used in mortgage calculations explained in plain language.

Bearing Pressure: Nominal contact pressure calculated as load divided by projected bearing area (F/A).
Frictional Power: Heat generated per unit time at the bearing interface, proportional to μ × p × V × A.
PV Limit: Maximum product of pressure and velocity a bearing material can sustain without thermal failure.
PV Value: Product of bearing pressure and sliding velocity (p × V), expressed in MPa·m/s.
Safety Factor: Ratio of PV limit to actual PV value. A factor > 1 indicates safe operation.
Sliding Velocity: Relative tangential speed between the bearing and shaft surfaces.
Thermal Failure: Catastrophic bearing failure caused by excessive frictional heat generation exceeding material thermal limits.
Thermal Runaway: Self-accelerating failure process where increased friction generates more heat, further degrading material properties.
Thrust Washer: Bearing component that supports axial (thrust) loads in rotating machinery.
Wear Rate: Volume or thickness of material removed per unit sliding distance, proportional to PV below the material limit.

Authoritative References

Trusted sources and standards referenced by this calculator.

ASTM D3702 - Standard Test Method for Wear Rate and Coefficient of Friction of Materials in Self-Lubricated Rubbing Contact Machine Design - Bearing Material PV Ratings Tribology Data Handbook (CRC Press) - PV Limits of Bearing Materials SKF Bearing Design Guide - PV Value Analysis Engineering Toolbox - PV Values for Bearing Materials ISO 7148 - Plain Bearings — Testing of the Tribological Behaviour of Bearing Materials

Applicable Standards

ASTM D3702ASTM G99ISO 7148ISO 281DIN 50324ASME B106.1M

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Last Updated:

2026-07-30

Version:

2.0.0

References:

License:

Free to use for educational and professional purposes.