PetroStreet

Please guide me towards OSHA Process Safety Management Standards /Guidelines.
Where to start from to have a good understanding of the requirements to be applied at a major petrochemical plant?

Since you belong to a major petrochemical unit, and if your focused area is process safety then you need to take a start from OSHA PSM 1910.119.
14 elements which has been contained in PSM should be covered in detail.
You can use the following link to start:
https://www.osha.gov/sites/default/file ... ha3132.pdf