CEMA has changed designations in the latest 6th edition. Which edition are you refering to?

You have a letter followed by a number. The letter is the bearing size or rating and the second is the roll diameter in inches. CEMA further is based on tapered roller bearings at 500 rpm.

Your 30 mm bore diameter must also have further designation according to ISO. There are many bearings with 30 mm bore. The 30 mm is the last digit in a bearing series multiplied by 5 eg.:

6206

6306

6406

A close estimate to your D6 or E6 would be D6 which is close to 6306. ■

In addition to Larry's comments CEMA 5th edition states that the L10 bearing life must reach a minimum of 60,000 hours at 500 RPM on both D series and E series.

In reviewing the load rating tables in CEMA 5th an E series idler idler must be capable of carrying approx. 50% greater load than a D series idler. Therefore the bearings will need to be larger. Manufacturers must supply a bearing that meets these table values and the L10 life.

Regards

Gary Blenkhorn ■

Hello Rajeev,

In finalising your design you must also consider the minimum shaft diameter to satisfy the bearing manufacturer's maximum cage misalignment requirements. Typically the shaft angular deflection at the journals must not exceed 8 minutes of arc (typically) when calculated under full design load.

CEMA does not consider this factor.

It becomes increasingly critical on long lightly loaded rolls - such as flat returns - bearing life using stanadrd formula is compliant but roll will fail due to excessive misalignment of the races as a result of large angular deflection.

Regards,

Adi Frittella

AFRIPP PROJECTS CC ■