SIL Assessment as per OISD 152 and IEC 61508 for IOCL Panipat Refinery and Panipat Naphtha Cracker

The IOCL Panipat Refinery is located in the state of Haryana’s ancient district of Panipat and commenced operations in July 1998. The Panipat Complex is the third-biggest petrochemical and refinery hub in South East Asia and the largest in India. PX/PTA Aromatics and Naphtha Cracker Olefinic Complex make up the Refinery. IOCL Panipat has awarded iFluids Engineering to carryout “SIL Assessment as per OISD 152 and IEC 61508 for IOCL Panipat Refinery and Panipat Naphtha Cracker”

Following facilities are to be covered as part of SIL assessment

Panipat Refinery

  1. Atmospheric Vacuum Unit AVU-1 & AVU-2
  2. Once through Hydrocracker Unit (OHCU)
  3. Hydrocracker Unit (HCU)
  4. Hydrogen Generation Unit HGU-06, HGU-76, HGU-77
  5. Residue Fluidised Catalytic Cracking, RFCCU
  6. Propylene Separation Unit, PSU
  7. Continuous Catalytic Reforming Unit, CCRU
  8. Diesel Hydrodesulphurisation Unit, DHDS
  9. Vis breaking Unit, VBU
  10.  Bitumen Blowing Unit, BBU
  12.  Sulphur recovery unit (U-22, U-44, U-25, U-55, U-56)
  13.  Amine recovery unit (U-21, U-51)
  14.  Refinery sour water stripper (U-17 & U- 53)
  15.  Hydro processing sour water (U-18, U-20, U-54)
  16.  Delayed Coker Unit, DCU
  17.  Diesel Hydro treating Unit, DHDT
  18.  Tail gas recovery unit (U-57, U-26)
  19.  Para xylene Block (PX)
  20.  Purified Terepthalic Acid Block (PTA)
  21.  Isomerisation Unit (ISOM)
  22.  FCC Gasoline Desulphurisation Unit (PrimeG)
  23.  Reformate Splitter Unit, RSU
  24.  Hydrocarbon storage facilities (All class of products/ intermediate/ crude oil tanks)
  25.  Effluent Treatment plants (3 nos)
  26.  Fire Station/ Fire pump house
  27.  All auxiliary facilities such as TPS, DM Plant, Water block, Cooling towers, Laboratory
  28.  Storage vessels of LPG (HS& MB), Propylene (HS&MB), Hydrogen, Nitrogen.

Panipat Naphtha Cracker

  1. Naphtha Cracker unit (NCU) + Amine treatment unit (ATU) + PSA & Hydrogen Compression system
  2. C4 Hydrogenation unit (C4HU)
  3. Pyrolysis gasoline hydrogenation unit (PGHU)
  4. Benzene Extraction Unit (BEU)
  5. Butadiene Extraction Unit (BDEU)
  6. High density polyethylene unit (HDPE)
  7. Poly propylene unit (PP line 1 & 2)
  9. BUTENE-1 Unit
  10.  Mono ethylene glycol unit (MEG)
  11.  Captive power plant (CPP)
  12.  DMRO Plant
  13.  Offsite/Product Transfer


All Safety Integrity Function (SIF) loops from Cause and Effect diagram (C&E) and HAZOP report were identified, in addition to that initiating causes and their initiating likelihood were identified. Consequence level and severity with respect to people, environment and assets were determined. Independent protection layers (IPLs) that can mitigate the initiating causes were listed out. The Probability of Failure on Demand (PFD) and in turn analyze as per SIL requirement was calculated. In this case recommendations were not provided for additional Safety Instrumented System (SIS)