What is the difference between our Mine Duty CEMA C (MD30X) and Standard CEMA C idlers?
Standard CEMA C idlers are rated 30,000 hours L10 Life, typically 900 lbs. load, designed for 500RPM, and is a very popular product in the aggregate industry.
30,000 hours is a big number, yet most manufacturers warrant the product for “one year”. And even in their warranty, some only warrant above 3% failure because they expect a 3% failure rate. One manufacturer advertises “2-year warranty” but in fine print offers 24 months or 2000 hours whichever comes first.
Before designing our idler, we decided to understand how idler life is determined by CEMA.
There are 4 overlooked equations in the CEMA Standard 502-2004 when predicting idler life.
- IML, forces due to idler height deviation.
- K4A Factor = Effect of Maintenance
- K4B Factor = Effect of Environment
- K4C Factor = Effect of Temperature
After applying these factors, the 30,000 hours is reduced to 11,250 hours L10. Still a large number when comparing to a 1-year warranty or 2000 hours.
L10 Life represents 90% reliability. However, American Bearing Manufacturers Association gives a factor to increase the reliability to 99%, referred to as L1 Life. This factor equates the bearing life of a CEMA C Idler to 2363 hours.
Now it makes sense on how the Idler manufactures assess their risk in determining a warranty.
A quick bit of history…
In 1996, CEMA changed its conveyor idler standards. This change enabled manufacturers to build idlers with inadequately sized “Sealed for Life” ball bearings when comparing it to the pre-1996 tapered roller bearing. The result of this change was a reduction in bearing and idler life.
We then set out to design our conveyor idler. We decided “Sealed for Life” ball bearings were exceptional alternatives to the tapered roller bearings. We simply disagreed with the manufacturer’s interpretation of the CEMA criteria on the size of the ball bearing they use. So instead of a standard CEMA 20mm bearing and axle assembly, we selected a 30mm assembly with equal life to the pre-1996 tapered roller bearing. We called it the MD30X.
Our MD30X has a L1 life of 21,656 hours. 9X greater than CEMA C.
To maintain this increase in life we had to design in the following features…
- Increased roll thickness, thickest standard on the market
- Select a special formulated di-polyurea grease
- Seven stage seal design.
Our MD30X, designed here in the USA, is proprietary to our company.