Safety Integrity level (SIL) Assessment Study for IOCL – Mathura Refinery

Mathura Refinery, the sixth refinery of Indian Oil was commissioned in 1982 with a capacity of 6.0 MMTPA to meet the demand of petroleum products in north western region of the country. Refinery is located along the Delhi-Agra National Highway about 154 KM away from Delhi. The major secondary processing units provided were Fluidized Catalytic Cracking Unit (FCCU), Vis-breaker Unit (VBU) and Bitumen Blowing Unit (BBU). The original technology for these units was sourced from erstwhile USSR, UOP etc.

Diesel Hydro-treating unit (DHDT) & MS Quality Up-gradation Unit (MSQU) was installed with world class technology from Axens and UOP respectively in 2005 for production of Euro-III grade HSD & MS with effect from 1st April 2005 as per Auto Fuel Policy of Govt. of India. Project for FCC Gasoline Desulphurization (FCCGDS) and Selective Hydrogenation Unit (SHU), the Prime-G technology of Axens, France was commissioned in February 2010 and supply of Euro-IV grade MS and HSD started on continuous basis from February 2010.

Mathura Refinery is having its own captive power plant, which was augmented with the commissioning of three Gas Turbines (GT) and Heat Recovery Steam Generator (HRSG) in phases from 1997 to 2005 using Natural Gas (NG) as fuel to take care of environment.

Mathura Refinery is the first in Asia and third in the world to receive the coveted ISO-14001 Certification for Environment Management System in 1996. It is also the first in the world to get OHSMS certification for Safety Management in 1998.

The SIL Assessment study for IOCL- Mathura Refinery covers almost all the units mentioned in the following figure.

The Safety Integrity Level (SIL) Study here is required to assess the discrete level for specifying the safety integrity requirements of the safety instrumented functions (SIF) to be allocated to the safety instrumented systems. Layer of Protection Analysis (LOPA) methodology was followed for this assessment which accounts the protective layers available to prevent and to mitigate hazardous events with inherently safe design concept, to prevent the occurrence / mitigate the consequences from such hazardous event.

The scope of the safety instrumented functions (SIFs) were identified in the P&IDs and the C&E matrices, relevant to project, having the main objectives to:

  • Identify potential risks to the people, environment and equipments due to failure of Safety Related Systems and associated facilities in the plant to operate on demand.
  • Define the basic performance requirements of all Safety Related Instrumented systems to reduce the above risks to “As Low as Reasonably Practicable”.