Conveyor Bearings Aren’t Expensive

Andrew Jennings, Statewide Bearings

Conveyor Bearings aren’t expensive – when they work!

It’s when they don’t work that they start to cost.

For example, a standard head drum bearing (75mm spherical roller and housing) can cost anywhere from $500-$750. But what is the ‘Total Cost of Ownership’ (TCO) of this bearing? It is installed, lubricated, maintained and eventually changed out. In a well run plant such a bearing’s TCO might be $5000.

In most plants it is a lot more. So how can the TCO be reduced? Some choose to buy cheaper bearings, however a better approach is to increase the bearing life and reduce the impact of its eventual failure. This can cut your TCO by up to 50%.

Factors effecting bearing life—it is accepted across the bearing industry that around 5% of bearings last their designed life. Therefore, 95% of bearings fail earlier than the design engineer intended (usually 5-10 years). When was the last time a conveyor bearing lasted 10 years?

The big question is ‘why do they fail so quickly?’

Dead from the Start—A

In a dirty dusty environment, such as a quarry, most bearings are contaminated at installation. It is almost impossible to keep 100% of the dirt and dust out whilst trying to set up a spherical roller bearing. The best you can do is to get it installed as quickly as you can using the best available fitters.

Dead from the Start—B

In doing your best to get the bearing installed quickly, shortcuts are often taken. The most common shortcut is failure to set accurate bearing internal clearances. It is a simple fact in our industry that most fitters do not use feeler gauges, so most bearings are not set up correctly.

Seals

Due to the versatile nature of the spherical roller bearing there are only 3 main seal types expected to work in 100’s of applications. It is vital that the right seal is chosen for each application – note the most expensive seal is not necessarily the best.

Lubrication

Who completes the lubrication at your plant? Is it a task given to your most qualified fitter? Or is it left to operators or even neglected altogether? Considering the cost of a bearing failure and the amount we spend on quality lubricants, it is a crime that 35% of all bearing failures are lubrication related.

Take the time to ask BOTH your bearing AND lubrication supplier for their opinion on exactly how much grease each bearing should get and how often.

Then give this vital information to someone who knows what they are doing. As they are greasing the bearing they should be considering areas such as the condition of the seals, heat and noise. Preventative maintenance starts here.

So, assuming we get the best life from our bearings, how do we minimise the impact of their eventual failure?

Condition Monitoring

Whole books have been written on the value of those little black cases hidden in a drawer somewhere, but I will leave this discussion for others more qualified. However, I will say that knowing when a bearing is likely to let us down helps considerably in reducing the impact on production.

Preparation

Knowing the part numbers for bearing housing, seals and the EXACT shaft size prior to failure is vital. A bearing survey is often available free or with little cost from many bearing suppliers. Some plants already have this information but don’t use it.

If you do know what bearings you have on site, STOCK THEM, or have your supplier stock them, especially if you are using something non standard. Hours (and big dollars) can be wasted waiting for an inexpensive bearing to be couriered in, while equipment stands idle.

Speed of Change Out—A

Are your conveyors set up to make change out quicker? Are slings and jacks and other tools available? Do you have platforms and frames to set them up on? All these preparations should be taken WELL before your bearings reach their working life.

Speed of Change Out—B

Have you considered Split Roller bearings? There are basically 2 types on the market. One makes use of your existing housing and has limitations on speed, capacity and sealing. The other is a complete bearing and housing unit that has superior sealing, but can have reduced load carrying capacity.

Both are extremely easy to fit and can be changed out in minutes, not hours, and generally without having to adjust bearing bases or centre heights, and more importantly without having to remove other assembled equipment like shaft mounts, gearboxes or pulleys.

You simply support the belt load, cut the old bearing off and install the split bearing in-situ. A 6-hour down time is generally reduced to 1. This reduces the TCO by up to half and this includes the extra cost of the split bearing.

In summary, if you’re looking to reduce your TCO on conveyor bearings, fit them right, lubricate them, prepare for their eventual failure and consider split bearings for critical conveyors. Its not rocket science, but how many of you are currently doing it and doing it every time?

Andrew Jennings, National Product Manager for Bearing Resolutions and Innovations, a company importing a range speciality bearing product designed to increase bearing life and reduce the cost of down time).

Statewide Bearings—03 9768 2688 or www.statewidebearings.com.au

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