Demoore:

Mechanical Engineering is very diverse. First of all are you a graduate of Mech Engr? I sincerely doubt if you can get what you are looking for. But you could see certifications in sub-departments under Mech Engr like:- Refrigeration and air conditioning, Industrial safety & management, Metallurgy & Corrosion, Power plant Engr. and so on and so fort.
So you really have to be more specific and have an idea of what interests you. Like olanajim said, mech Engr is very diverse.

Good luck in your endevaours.

DAVIMOORE PLEASE IS IT POSSIBLE TO GET A CERTIFICATION AND TRAINING IN GENERTOR INSTALLATION AND MAINTANCE IN NIGERIA? ANY INFO LL BE USEFUL TO ME PLS