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 – what most don’t realize is that they often only make the problem worse. When arguments are made to do something about the problem, the discussion often centers on one simple phrase: “belts are cheap.” They’re easily replaced with ease. 

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. 

Why Belt Drives Fail 

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. 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. 

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 misalignments 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. 

Replacing Belts Doesn’t Work 

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 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.

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.

The Alternative 

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 

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