Since mechanists are not skilled labour and still they get away without being fired shows that the organization is one, which has a union.
Since Ganesh has no complaints with the work that Dinesh does and since Dinesh is known for his temper and alcoholism Dinesh seems to be facing some kind of problem in family or factory. He is not someone who evades work by nature or is ineffective but only reacts badly to situations a few times. He is facing some kind of pressure and when it becomes too much he takes his anger out on someone in the work place.
The fact that he has been with the organization for 5 years seem to suggest that he feels fairly experienced and does not want the supervisor to tell him to do things other than what he was already doing.
"Critical Incidents Method" can be used effectively here. The work of a mechanist is quite routine and does not need constant appraisal. It would be better if the appraisal system were such that it only takes into account special events.
Since this kind of behaviour exists elsewhere in the job it suggests that there is some sort of pressure in the job. This could also be caused due to the monotonous nature of the work. A training program designed to release stress can prove beneficial here.
Yoga is something that comes to mind immediately.
The problem of the supervisor telling Dinesh to pick up the trash and he abusing him shows that there is a need to train the supervisors as well. Although Ganesh is doing an excellent job of talking to each employee separately and pushing the change he and other supervisors are facing difficulty in tackling a few workers. A training program teaching them how to deal with such exceptional cases may yield benefit to the company as all this adds to the frustration of the Supervisors as well. The company must see to it that the supervisors don't lose their heart to work.