Guide to V-Belt Replacement

The V-belt appears to be a relatively benign and simple device. They’re basically a glorious rubber band, right? Do you need to replace it? Just measure the top width and circumference, find another belt with the same size, and place it in the drive. There’s just one problem: this approach is the biggest mistake you can get.

Like their synchronous belts, the V-belts have undergone tremendous technological development since John Gates invented them in 1917. New synthetic rubber compounds, cladding materials, structural methods, advances in tensile rope, and cross-sectional profiles have resulted in an often confusing series of V-strips that have a high degree of application characteristics and offer vastly different levels of performance.

Size Isn’t Everything

Despite their physical similarity, each of these belts was designed for a unique purpose. Using the wrong belt can cause equipment damage or cause serious safety problems. What is a suitable working belt? It depends on the application.

Following are some environmental and application design criteria that will influence belt selection:

• Ambient temperature

• Oil resistance

• Ozone resistance

• Static conductivity

• Power capacity

• Pulsation or shock loading

• Small sheave diameters

• Backside idlers

• Misalignment tolerance

• Serpentine or quarter turn layout

• Minimal take-up

• Clutching

• High speeds

• Energy efficiency

• Dust and abrasives

As you can see, there are many factors to consider before choosing the right V-belt for the job.

Generally speaking, V-belts fall into these classifications:

• Ambient temperature

• Heavy-duty

• Industrial machinery

• Continuous operation

• Heavy loads and often harsh conditions

• Light-duty

• Fractional horsepower applications

• Intermittent usage

• Automotive

Don’t Forget Sheaves

The pulley is an essential V-belt transmission component. As mentioned earlier, the degree to which the V-belt fits the pulleys determines how much power the belt drive can transmit and how efficient it runs. The correct fit is the function of the belt and the metal pulley. A well-designed belt and a well-machined, matching wheel provide the best combination.

Many users change the V-belt repeatedly without checking the wheel for wear. Wear, break or damage to pulleys can reduce the life of the belt. Pulley damage can be due to improper installation, such as over-tightening of bushing bolts or prying the belt into the pulley. Another cause of pulley damage is debris falling into the gear, which can be prevented by installing a gear shield.

Signs of pulley wear include groove side walls that are concave and/or polished groove side walls that are angular. Use a pulley meter to detect excessive wear in the pulley grooves and replace the pulley immediately after wear.

Upgrade V-Belts and Drives for Higher Performance and Savings

Advances in V-belt technology offer users the opportunity to upgrade older drives and gain performance improvements while saving time and money. For example, the industry-standard V-belt can fail prematurely due to thermal cracking, stretching, or excessive wear under extreme operating conditions, such as heat inside the belt shield. Frequent re-tensioning and belt replacement results in downtime, inefficiency and lost productivity.

However, with today’s new technology, you can upgrade to a grooved V-belt made of vinyl rubber material that can withstand extreme temperatures from -57°C (70°F) to +121°C (250°F), an increase of 88% over the industry standard V-belt temperature range. These newer belts can resist hardening to avoid cracking, provide better flexibility, and run more smoothly in pulleys to reduce vibration and extend the life of other driving components, such as shafts and bearings.

As another example, replacing the old classic V-belt drive with a newer narrow-notch V-belt using vinyl elastomer and aramide fiber tensile rope can produce up to three times the load capacity while reducing the weight and size of the drive, relieving pressure on shafts, bearings, and other components.

Consider your options when it comes to V-belt drives with multiple grooved wheels. If the wheels are not worn out, you can either use fewer, higher-performance belts (leaving open grooves) or fill all the grooves with higher-performance belts to increase the load capacity of the drive and extend belt life. If the wheels have worn out and need to be replaced, you can upgrade to a more compact (but equally powerful) drive to save weight and space, or keep the same drive configuration while improving drive capacity.