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How To Do V-Belt Maintenance for Electric Motors


One of the most important tasks for any manufacturing plant is to ensure that all V-belts on electric motors are properly installed, maintained and stored. Improperly maintained V-belts wear out faster and make motors work harder to produce the same power output, which wastes energy. This can be significant when you factor in the number of electric motors your facility runs continuously. Keeping the many V-belts in your plant working as efficiently as possible can also prolong belt life and improve machine uptime and plant productivity.

Different Types of V-Belts

V-belts are common drive belts that transmit power from motors to driven devices. These flexible belts are typically made of elastic materials such as rubber and are available in different styles and types depending on the application.

Standard V-belts are used in the majority of belt drives. They have a trapezoidal cross-section that fits tightly onto a sheave to increase friction and power transfer capability. V-belt drives can run at a peak power efficiency of 95% or more when first installed. The efficiency rating depends on pulley size, pulley wear, V-belt alignment, transmitted torque and if belts are under- or over-sized for specific load requirements. If the belt is not periodically re-tensioned, power efficiency can deteriorate over time due to slippage.

Banded V-belts
are typically one or more single V-belts that are fused together and have a reinforced backing. These belts, also known as multi-groove or combination V-belts, are used in applications where speed fluctuation, vibration or misalignment could cause a single v-belt to flip or slide off the pulley. These belts are categorized by their cross-section, making them easier to identify when replacements are needed.

Cogged V-belts are either banded or standard; they are distinguished by grooves which run the width of the belt. The grooves reduce heat by allowing the band to flex in contact with the pulley.

Timing belts, which have teeth, can run at about 98% efficiency and can maintain that efficiency over a wide range of loads. Also known as gear belts or synchronous belts, timing belts require less maintenance and re-tensioning than standard V-belts and cogged belts and can operate in wet and oily environments. Timing belts are used to transmit power to equipment that requires precise position control, such as 3D printers and robotic arms.

Auditing and Diagnosing

The primary goal for a regular belt maintenance program is to make sure all belts are installed properly and are running every motor at peak efficiency. The other goal is to do everything possible to extend the life of your V-belts. To get started, you'll need to conduct an audit of every motor in the facility, their location and purpose. Then look at each for some basic problems. First, make sure all of the right belts are installed. It may sound simple, but if it was ever common practice at your plant to replace belts with anything available, this is an immediate fix you can easily identify. When conducting your initial assessment, make sure every motor has the right belt installed for that application. Also check to make sure pulleys are in alignment and all belts are properly tensioned.

Common operating problems for belt-driven equipment include improper tension and alignment. The worn sheaves that result from these problems will reduce system efficiency, while adding to maintenance costs. When installed properly, V-belt drives can run at a peak efficiency of 95% or higher, but efficiency can deteriorate by as much as 5% due to slippage if the belt is not periodically checked.

Testing V-Belt Tension

If a belt is not tensioned properly, or is too loose or too tight, it can lead to inefficient power transmission, belt wear, belt failure and sometimes even premature motor failure. A V-belt that is over-tensioned can reduce the bearing life of the motor and is one of the leading causes of V-belt failure. To combat tensioning problems, your maintenance shop should stock an arsenal of tools including a V-belt tension checker to measure V-belt deflection and tension and a belt frequency meter to find the natural vibration frequency of a belt strand so you can closely monitor belt tension. The device also calculates the corresponding belt tension.

Replacing V-Belts

Safety should be the top priority when installing, maintaining or replacing V-belts on electric motor drives. There is always the potential for injuries from sharp objects, extreme temperatures, high-speed abrasions, pinch points, confined spaces, unexpected movement and blunt-force injuries from excessive force or uncontrolled release of belt tension. Other hazards include unbalanced loads, airborne objects, inadequately secured pulleys and loose bushings and screws. You can avoid some of these hazards in well-organized, well-lit work area with little clutter. Before doing any inspection or maintenance on belt drives, turn equipment off and lock out the power source.

Before replacing V-belts, first confirm that the replacements are the correct size and the belt is the right match for the application. Belts to be installed on the same motor should beĀ from the same manufacturer. Belts from different manufacturers may vary, with different stretch characteristics and coefficients of friction. Overloading will cause rapid wear and reduced belt life.

Timing Belts Can Save Energy
There are formulas that can help you determine how much money you can save with the switch.
Efficient Plant Magazine suggests this formula. It may seem complicated to start but an example will follow: (motor horsepower) x (operating hours per year) x (load factor) x (100/v-belt efficiency - 100/synchronous belt efficiency) x (electrical cost per KWh) x 0.746
Let's use an example of a 100-hp fan that runs for 7,000 hours a year at an average load of 80%. The average efficiency of a v-belt is estimated at 94% and the synchronous belt is estimated at 98%. Finally, assume an electrical cost per KWh of 10.5 cents, or .105. Check your electric bill or use data from the U.S. Energy Information Administration to find an applicable amount. The 0.746 converts horsepower to kilowatts.
Plugging in these figures, the formula looks like this:

100 x 7,000 x .8 x (100/94 - 100/98) x .105 x .746

100 x 7,000 x .8 x .0434 x .105 x .746 = $1,903 saved in one year.

Those are the savings just for this one fan. Apply this formula across your facility to estimate overall energy cost savings from the switch.

V-belts are an important part of any plant maintenance program. By covering the basics of proper tensioning, belt and sheave maintenance, and proper monitoring, maintenance technicians can get far more efficiency and service life out of the many V-belts and motors throughout the plant.

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The information contained in this article is intended for general information purposes only and is based on information available as of the initial date of publication. No representation is made that the information or references are complete or remain current. This article is not a substitute for review of current applicable government regulations, industry standards, or other standards specific to your business and/or activities and should not be construed as legal advice or opinion. Readers with specific questions should refer to the applicable standards or consult with an attorney.