Historically, we find it is often hard to justify improvements to belt driven equipment.
Squealing, slipping belts are often ignored until they completely fail, causing significant production or safety loss. A variety of products to ‘hide’ the problem are available, but most don’t realize these often make the issue worse. A slip or slippage in a belt drive happens when the belt doesn’t transmit power effectively, leading to energy loss, heat buildup, and accelerated wear. When arguments are made to address the issue, the discussion often centers on one simple phrase: “belts are cheap.” They’re easily replaced with ease, but that replacement rarely solves the root problem.
If your belt drives are squealing and slipping, it may be time to consider that you’re treating the symptom, not the root cause of belt drive failure. Let’s look at why belt drives fail, and why just replacing them doesn’t work. Most belt drive issues come down to improper belt tension or misalignment that disrupts power transmission. When a belt isn’t tensioned correctly, the system experiences heat, friction, and wasted energy. These small inefficiencies eventually shorten belt life and increase overall operating downtime.
Why Belt Drives Fail (Misalignment, Tension Issues & Wear)
Put simply, belt drives fail because they weren’t tensioned properly – the belt is either too loose or too tight. Too loose, and the pulley slips. This improper tension, whether too loose or over-tensioned, creates abnormal stress on the belt and pulleys. Excess tension reduces bearing life, accelerates premature wear, and can even damage sheave grooves. Slippage leads to heat and friction, which will, inevitably, damage those belts. It’ll speed up the process of degradation significantly.
When engineers design belt drive systems, they often focus on how much stress the system can handle without breaking. This is called the static stress strength interference model. However, this model doesn’t take into account how the system behaves over time as it’s used, like how the stress changes when the belt moves or how the materials wear out as they’re used by their operators in a manufacturing setting. These dynamics also shift based on center distances, belt cross sections, and how the belt tracks across the side of the belt during operations. Even small changes in variables can contribute to slippage, vibration, and early failure.
Studies have cropped up to test drive new models that consider these dynamic factors. They used equations that describe how the system moves and how the stress changes over time, along with how the materials degrade. With these new models, we can better predict when the system might fail and how available it will be for use over time.
Additionally, misalignment within the pulleys can lead to premature belt failures. Parallel, angular, and combination misalignment will all lead to the inevitable slip. This is why setting and following proper alignment standards is critical to maintaining all aspects of reliable manufacturing. Proper alignment should be verified using a straight edge or laser tool, ensuring both pulleys remain square under load. Angular or parallel misalignment also produces shock loads that the belt cannot absorb efficiently, contributing to faster failure and lost horsepower.
Why Replacing Belts Doesn’t Solve the Problem
Replacing belt drives solves the immediate problem of ‘the belt drive failed.’ However, after dozens and dozens of belt drives fail, that cost begins to add up. A ‘cheap fix’ isn’t so cheap, and ultimately, it acts as a band aid that doesn’t really fix the problem.
Understanding the timeline of failure and degradation for these belt drives is critical to the way we approach their maintenance. Treating the root issue instead of the symptom is the way to ensure that the symptom doesn’t keep cropping up – it’s what ultimately leads to reliable manufacturing.
So, how do we justify applying Reliable Manufacturing techniques to belt-driven equipment?
It’s not really that hard.
- We all know there are many causes of belt problems out there, including tension, pulley/sheave, wear, overload, contamination, overheating, etc. Nearly all of these end up causing slip.
- We know that properly adjusted V belts slip between 2-5%. Anything more than 5% means energy is being wasted.
- Using a strobe light (or tachometer) to measure the RPM of the driver, and the RPP of the driver allows us to calculate the actual slip occurring.
- The slip is simply the difference between the theoretical RPM of the driven and the actual RPM expressed as a percentage.
Installing a new belt without correcting underlying issues often guarantees another early failure. Incorrect belt installation, contamination, worn pulleys, or lack of lubrication all contribute to repeated breakdowns. These oversights make it seem like belts are unreliable, when the real problem is the absence of consistent preventive maintenance.
Breaking Down the Math Of Belt Drive Reliability
- If I have a 100 horsepower motor and 10% slip, we’re losing 10 horsepower.
- Typically, the manufacturing industry pays between $0.1347/kwhr (MA) and $0.0416/kwr (LA). Depending on where you are in the country and what you pay for power, the cost is between +-$1408/hp/year and $469/hp per year.
- That 10% slip on a single 100 hp motor is costing you at least $5,000 per year and probably more.
Many facilities also rely on older v-belts, timing belts, or synchronous belts without considering whether their application or load has changed over time. Each belt type has unique tension and alignment requirements, and even subtle changes in torque or speed can lead to belt slippage and premature belt failures.
The Alternative: Inspecting Pulleys, Alignment & Load
The alternative is to, through operator rounds and routine inspection, check the drives and pulleys themselves for misalignment, wear, overload, and other factors that might be the real source of the problem. A vibration analysis might relay the source of an alignment.
Then, it’s time to ensure that the teams on the floor are aware of what the problem is and how to keep an eye out for it going forward when enacting maintenance and inspection. Instead of teaching them how to simply replace the belt, show them to first see why it failed in the first place.
The Reliable Solution: Preventative Maintenance for Belt Drive Systems
How many belt drives do you have? Do any of them squeal? We have clients who have documented hundreds of thousands of dollars in energy, to say nothing of the cost of buying new belts and the labor needed to replace them.
Reach out to Reliability Solutions to learn more about our training, which can help impart the importance of precision alignment, or our on-site maintenance visits. For more details on calculating slip and how to prevent it, or to set up a training, assessment, or walkthrough, contact Reliability Solutions
By combining proper tensioning, proper alignment, and routine inspections, facilities can reduce failures, extend belt lifespan, and eliminate unnecessary downtime. With structured operator training and proactive maintenance, belt driven systems can operate at peak reliability for years.
