update:
Because the mixture of dust and oil has accumulated at the junction of the pulley and the shaft, so I did not realize that they are separate parts !!
it is relatively easy to split them:
1.first clean any dust and rust that builds up over time like mine. so it should be clean to prevent jamming.
2. hold pully and press shaft out. mine was stuck so hard. so i used a steel bar to move it. then pushed out using M8 bolt .
be careful in this step to not make Run-out on pully. never use hammer
lip seal sizes: 15 * 24 * 6
and this seal is like new!!