Dear Mr. Mahmud,

when reference is made to DIN 22112-2: 2010, clause 3.9 then the term "tightness" is used to describe that

- from the outside no water as drops or splashes may enter the bearing under operational conditions

- from the inside no water as condensate water may enter the bearing under operational conditions.

Additionally the tightness of the connection mantle - bearing housing is required in clause 3.2 .

DIN 22112-3: 1996 clause 4.8 defines the testing to tightness against dust and water, concerning water this is essentially a test run under water, followed by a repose time in the fresh air and then opening & control of the idler.

Regards

R. ■