By Jason Industrial
The cost of energy in manufacturing has a major effect on overall cost of a product. In fact, energy cost is currently one of the main drivers in reshoring, the growing movement of bringing manufacturing operations back to the United States from offshore locations. By introducing energy efficient belt drives, you can implement a simple, cost-effective solution to achieve energy savings. Proper installation and maintenance combined with the latest drive belt technology can improve efficiency through reduced energy consumption and enhance drive performance.
Regular Maintenance – Synchronous and V-Belt Drives
Proper Tensioning – One third of electric motors employed in industrial and commercial applications use belt drives. The majority of these drives use wrapped (fabric covered) V-belts, relying on the friction between the belt and sheave groove to transmit power. Relatively inexpensive, wrapped V-belts are designed to allow for limited slippage; intended to slip only in potentially problematic situations, this slippage prevents damage to expensive driven equipment by acting as a safety fuse. The belt can slip or break rather than damaging the more expensive driven unit.
But without frequent periodic maintenance, these belt drives tend to slip excessively during normal operation and result in reduced efficiency and increased operating costs. A correctly installed wrapped V-belt drive can attain 95-98% efficiency soon after installation, rapidly declining to approximately 93% efficiency during the course of normal operation. Without continued periodic tensioning maintenance, efficiency will decrease even further and components will wear more quickly. Belt drive tensioning maintenance is often neglected due to higher maintenance priorities, meaning belt drives receive attention
only when a belt finally breaks. This situation can be avoided by periodically monitoring the tension and adjusting if necessary, increasing the lifespan of belts and reducing the frequency of service interruptions.
Proven Energy Saving Solutions
The U.S. Department of Energy recommends replacing V-belts with proven belt drive solutions, including cogged raw edge V-belts and synchronous belts, as best practice for increasing belt drive energy efficiency. Upgrading from a wrapped V-belt to a raw-edge cogged belt yields an average 2% increase in efficiency, a good return for a very low-cost investment. For new drives, using synchronous belts can provide an average 5% efficiency increase compared to V-belts. While increases of 2–5% may seem insignificant, when considering the energy cost savings over multiple drives and longer running times, the savings soon become substantial. The following overview of the available belt options, as well as the pros and cons of each solution, is a useful guide for evaluating and selecting the best belt for the task.
Figure 1. Good: Standard wrapped V-belt – typical efficiency = up to 93%
The wrapped V-belt is typically the standard belt utilized in many applications. The excellent mechanical
characteristics and high transmission efficiency make this type of belt a popular choice.
The wrapped V-belt will protect the drive from shock loads where torque spikes are present, by allowing some slippage and act as a safety fuse reducing risk of damage to valuable components.
- Any application where some slippage is desirable will be better suited to using a wrapped V-belt.
- A wrapped V-belt offers more protection against contamination as the cover offers protection to the rubber body of the belt.
Among available belt drive options, wrapped V-belts are the least efficient.
- This type of V-belt requires frequent tensioning to maintain its initial efficiency. If not properly maintained on a regular basis, it will lose up to 20% efficiency.
- There is a sharp reduction in efficiency after installation due to slippage, as the V-belt stretches during operation.
- There is a large variation in efficiency between V-belts, on multi-belt drives, tension variation between multiple belts can result in a belt that is not working as hard as the others, therefore impacting overall drive efficiency.
Figure 2. Better: cogged raw edge V-belt – typical efficiency = up to 95%
Cogged raw edge v-belt
“Raw Edge” construction differs from wrapped v-belt in that it does not have external fabric on the sides of the belt. This puts rubber in direct contact with the pulley grooves greatly reducing slippage. The cogged raw edge V-belt also has notches cut in the underside for cooler operation and greater flexibility, making it ideally suited for smaller diameter pulleys. More efficient than a wrapped V-belt, it is the best choice where a synchronous drive is not cost-effective but greater efficiency is desired.
- The cogged or notched construction reduces bending resistance in the belt, so it is able to bend around smaller diameter pulleys than a wrapped V-belt. Smaller pulleys require less material to produce, meaning they are generally cheaper than larger versions.
- The raw edge sidewall construction (meaning no fabric cover) has a greater coefficient of friction than a wrapped V-belt, making it more slip-resistant and allowing it to transmit more power.
- A cogged V-belt runs cooler than a wrapped V-belt, and, as a result, will last longer. The US DoE estimates that this belt type is 2% more efficient than standard V-belts.
- This belt runs on the same pulleys as a standard V-belt, so upgrading is a simple process of changing the belt without incurring the cost of new components.
- Unlike a synchronous belt, a cogged V-belt provides better vibration damping where excessive vibration is a concern.
- Initial cost of raw edge v-belt is higher although return on investment is rapid.
Figure 3. Best: synchronous belt – typical efficiency = up to 98%
Also known as “timing belt”, synchronous belt teeth engage with corresponding pulley teeth. This belt eliminates slippage and provides the highest efficiency. However, it is not a direct replacement for existing v-belt drives as it requires a new drive design that will require all new belts and pulleys.
- The teeth in a synchronous drive create positive engagement with the sprockets for zero belt slippage and maximum efficiency.
- A synchronous belt is the best choice for new drive applications, as the initial cost is offset against the increased efficiency and reduced downtime for maintenance that it offers.
- This belt maintains its efficiency over its lifespan, unlike a standard V-belt, which loses efficiency over time.
- This type of drive runs cooler and with less tension than V-belts, which extends the life of both bearings and belts.
- Capable of operating in wet and oily conditions that would hinder a V-belt, a synchronous belt requires only minimal maintenance and re-tensioning.
- Conversion of a v-belt drive to synchronous belt will require both new belts and pulleys, making it a higher initial cost than simply replacing v-belts on a v-belt drive.
- Synchronous belt generates more noise than V-belt.
- A synchronous drive is less suited for applications where some slippage is desirable.
- Alignment and tension is critical as synchronous belt is not as tolerant as a V-belt to misalignment.