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

Have a look at this link as well:
https://www.ecfr.gov/current/title-29/s ... n-1910.119
And remember 29CFR1910.119 to start with and understand in full.