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Summary

Combination Gears for High Gear Ratio Applications

Gearbox: Combination Gear vs. Worm Gear

Two-stage gearboxes that are a more efficient alternative speed reducer to worm gears in applications with high gear ratios

Synopsis:

Worm gears are widely used in packaging machinery, conveyors, materials-handling applications, and in pharmaceutical and food processing plants. Huge numbers of right-angle worm gear motors are in use. Worm gears are specified because they have a low initial cost, are compact, deliver high speed reductions, offer fine speed control with a long service life, feature quiet operation, and can withstand high overloads. However, worm gears have low efficiencies at high gear ratios and are not the best choice from an energy efficiency standpoint.

Worm gears may have efficiencies of 55% to 75% at high gear ratios. Available helical/bevel gears are about 95% efficient. Combination gears (two-stage gearboxes) achieve a high gear ratio while maintaining an efficiency of about 90%. Improving gear efficiency from 80% to 95% results in a15.8% reduction in baseline energy use.

High-efficiency gear reducers should be specified for new projects or existing process retrofits. In-service worm gear replacements are difficult to accomplish because product familiarity is needed to identify worm gear drives. Physical constraints can present obstacles, such as mounting configurations, couplings, shaft size, and gear reducer centerline-to-centerline distances. Retrofits should focus on applications with high gear ratios. In some cases, a gearbox can be replaced.  In other cases, an integral right-angle gear drive motor is recommended.  Increasing the gear reducer efficiency may provide an opportunity to downsize the replacement motor. Additional energy savings are obtained when an old standard efficiency motor is replaced with aPremium Efficiency model. .  

Energy Savings: 17%
Energy Savings Rating: Extensive Assessment  What's this?
LevelStatusDescription
1Concept not validatedClaims of energy savings may not be credible due to lack of documentation or validation by unbiased experts.
2Concept validated:An unbiased expert has validated efficiency concepts through technical review and calculations based on engineering principles.
3Limited assessmentAn unbiased expert has measured technology characteristics and factors of energy use through one or more tests in typical applications with a clear baseline.
4Extensive assessmentAdditional testing in relevant applications and environments has increased knowledge of performance across a broad range of products, applications, and system conditions.
5Comprehensive analysisResults of lab and field tests have been used to develop methods for reliable prediction of performance across the range of intended applications.
6Approved measureProtocols for technology application are established and approved.

Status:

Details

Combination Gears for High Gear Ratio Applications

Gearbox: Combination Gear vs. Worm Gear

Two-stage gearboxes that are a more efficient alternative speed reducer to worm gears in applications with high gear ratios
Item ID: 435
Sector: Industrial, Agricultural
Energy System: Motors & Drives--Drives

Synopsis:

Worm gears are widely used in packaging machinery, conveyors, materials-handling applications, and in pharmaceutical and food processing plants. Huge numbers of right-angle worm gear motors are in use. Worm gears are specified because they have a low initial cost, are compact, deliver high speed reductions, offer fine speed control with a long service life, feature quiet operation, and can withstand high overloads. However, worm gears have low efficiencies at high gear ratios and are not the best choice from an energy efficiency standpoint.

Worm gears may have efficiencies of 55% to 75% at high gear ratios. Available helical/bevel gears are about 95% efficient. Combination gears (two-stage gearboxes) achieve a high gear ratio while maintaining an efficiency of about 90%. Improving gear efficiency from 80% to 95% results in a15.8% reduction in baseline energy use.

High-efficiency gear reducers should be specified for new projects or existing process retrofits. In-service worm gear replacements are difficult to accomplish because product familiarity is needed to identify worm gear drives. Physical constraints can present obstacles, such as mounting configurations, couplings, shaft size, and gear reducer centerline-to-centerline distances. Retrofits should focus on applications with high gear ratios. In some cases, a gearbox can be replaced.  In other cases, an integral right-angle gear drive motor is recommended.  Increasing the gear reducer efficiency may provide an opportunity to downsize the replacement motor. Additional energy savings are obtained when an old standard efficiency motor is replaced with aPremium Efficiency model. .  

Baseline Example:

Baseline Description: Worm Gear
Baseline Energy Use: 3385 kWh per year per hp

Comments:

Worm gears may have an efficiency of 55% to 75% at high gear ratios. Helical/bevel gears are about 95% efficient. For very high gear ratio applications, two-stage gearboxes can be provided that use two sets of gears and achieve a high gear ratio while still maintaining an efficiency of about 90% (95% x 95%).
Improving gear efficiency from 75% to 90% results in a 16.7% reduction in baseline energy use. Assume a 3 hp driven equipment load---with a 75% gear efficiency, the load imposed on the drive motor is 4 hp. A 5 hp drive motor would typically be installed and operate at its 80% load point. Given a 90% combined gear efficiency, the load on the motor decreases to 3.33 hp. The 5 hp motor is now only 66.6% loaded. Assuming an energy efficient motor and 5000 hours per year of conveyor operation, the baseline energy use is 16,924 kWh/year with an energy savings of 2798 kWh given installation of the more efficiency combination gear. Energy savings are 16.5% of the baseline use (note 16.7% as the drive motor efficiency is slightly decreased at the reduced load point).

Manufacturer's Energy Savings Claims: Currently no data available.
Best Estimate of Energy Savings:

"Typical" Savings: 17%
Energy Savings Reliability: 4 - Extensive Assessment

Comments:

Energy Use of Emerging Technology:
2,809.6 kWh per hp per year What's this?

Energy Use of an Emerging Technology is based upon the following algorithm.

Baseline Energy Use - (Baseline Energy Use * Best Estimate of Energy Savings (either Typical savings OR the high range of savings.))

Technical Potential:
Units: hp
Currently no data available.
First Cost: Currently no data available.

Cost Effectiveness:

Simple payback, new construction (years): N/A

Simple payback, retrofit (years): N/A

What's this?

Cost Effectiveness is calculated using baseline energy use, best estimate of typical energy savings, and first cost. It does not account for factors such as impacts on O&M costs (which could be significant if product life is greatly extended) or savings of non-electric fuels such as natural gas. Actual overall cost effectiveness could be significantly different based on these other factors.

Reference and Citations:

Jennifer Werger, 01/01/2009. Food Processing Machinery: Improving Energy Efficiency
FoodProcessing.com

John Lytle, 01/01/2011. Switching Gears to Save Energy Costs
Material Handling & Logistics News

Tejindar Singh, 11/01/1994. Motor and Drive Application Notes: The Mechanical System
Pacific Gas & Electric Company

Sadrul Ula, 01/01/1992. Energy Efficient Drivepower: An Overview
Office of Conservation and Renewable Energy

Bernd Stoeber, 07/01/2000. Gear Efficiency -- Key to Lower Drive Cost
Motion System Design

Hermann Siebert, 05/01/2011. Worm Gears -- Higher Energy Efficiency and Less Strain on Resources
Gear Technology

John Malinowski, 05/01/2009. Maximizing Energy Savings by Replacing Motors and Reducers
Plant Services

Rank & Scores

Combination Gears for High Gear Ratio Applications

There is no TAG available for this technology.
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