Lokesh Ojha,
Separate order types may make sense for example, if these plants are completely different business sectors (e.g. Automotive and Medical), or there may be valid financial reasons to have it this way..
If the plants are the same business sector (e.g. Chemical plants), then my first question would be: why do you feel you need specific order types per plant?
By having the same order types you maintain an element of consistency throughout your organisations. Training can be standardised and people move easily between locations, etc, etc.
PeteA