How many actual experience years ( Do you think ) enough For a site engineer to become a Project Manager ?

Its more on knowledge not by experience.

about15 years to be project manager

Just counting years not an scale to become a Project Manager. Decision making, Problem solving, Interpersonal relationship, Communication are some of the skills are required to become a Project Manager

Site Engineer shoud have minium of8 year experience to become a Project Manager, It amy differ from person to person based on their ability.

We need2-3 years of unique experience to be manger ,, and at the same time need15 years of repeated experience to be manger ,, ;) choose what you want ,, finally it refers to the person itself

5 years is more than enough

this depends on realized workload

for site engineer first he should be promoted to Senior Engineer for2 years then Assistant Manager for1 years then deputy manager for2 years than only he shoulb be promoted to Project manager so atleast5-7 years.

Project management is an art as well a skill . To become a successful project manager , it is important to have great time management and people skills . It is difficult to lose resources in a project and the project manager cannot simply replace resources or simply fill in resources .

The site manager has an easier task of employing and replacing staff .The project manager on the other hand is pushed by time and success and has to deal with the stress of  people management as well as ensuring that risk mitigation is working . The site manager will need to understand project management before being regarded as a project manager .