Enhancing Refinery Safety: SIL Verification & SRS Development for IOCL Barauni

Introduction

Safety is at the core of any refinery operation, and ensuring the integrity of Safety Instrumented Systems (SIS) is a critical aspect of industrial risk management. At iFluids Engineering, we specialize in delivering SIL verification and Safety Requirement Specification (SRS) services that align with international safety standards, helping refineries like IOCL Barauni achieve optimal risk mitigation and operational efficiency.

Overview of IOCL Barauni Refinery

The Barauni Refinery, commissioned in 1964, is one of India’s pioneering refineries, initially designed to process 1 MMTPA of crude from Assam. Over the decades, technological advancements expanded its capacity to 6.0 MMTPA, integrating advanced processing units such as the Hydrogen Generation Unit (HGU-1), Residue Fluidized Catalytic Cracker Unit (RFCCU), and Sulphur Recovery Unit (SRU). In line with its commitment to safety and compliance, Indian Oil Corporation Limited (IOCL) partnered with iFluids Engineering to execute a comprehensive SIL verification and SRS preparation project.

Project Objectives

The project’s objective was to ensure the functional safety and reliability of safety loops within the refinery by conducting a structured SIL verification and developing an SRS document that meets the stringent requirements of IEC 61508 and IEC 61511.

The Scope included:

• Verification of 250 Safety Instrumented Functions (SIFs) identified in the SIL assessment study.
• Providing recommendations for system gaps and improvements.
• Utilizing industry-approved software for SIL verification calculations.
• Developing Safety Requirement Specification (SRS) documentation per global safety standards.
• Delivering reports, knowledge transfer, and implementation.

Methodology & Approach

SIL Verification Process

The SIL verification study was conducted using the Layer of Protection Analysis (LOPA) methodology, ensuring a structured approach to risk reduction by:

• Assessing the Probability of Failure on Demand (PFDavg) to determine SIL compliance.
• Validating the architectural constraints to ensure design integrity.
• Identifying potential system gaps and recommending effective mitigations.
• Ensuring adherence to safety integrity levels through systematic calculations and reviews.

The assessment was performed using exSILentia, a widely recognized software for SIL verification and risk assessment. This ensured accuracy and compliance with IEC 61508 and IEC 61511.

Safety Requirement Specification (SRS) Development

The Safety Requirement Specification SRS document, a crucial part of the Safety Lifecycle, was meticulously developed by IEC 61511–1:2016, Clause 3.2.72. It provided:

• A detailed breakdown of functional safety requirements for each SIF.
• Specification of performance requirements, including response time and safety integrity level.
• Clear verification and validation checkpoints for compliance.

Project Execution & Timeline

The project was structured for completion within six months from the site handover date. Our team conducted:

• Field assessments to verify existing safety loops.
• Detailed calculations and analysis to validate SIF compliance.
• Technical discussions with IOCL stakeholders to align on safety requirements.
• Finalization and submission of reports, ensuring thorough documentation and approval processes.

Key Deliverables

Upon successful execution, the following deliverables were provided to IOCL Barauni Refinery

• Comprehensive SIL Verification Report, including system enhancement recommendations.
• Finalized SRS documentation post-approval and review.

Impact & Benefits

The SIL verification and SRS preparation project brought significant improvements by:

• Enhanced reliability of safety instrumented functions.
• Compliance with international safety regulations, reducing regulatory risks.
• Optimized process safety, leading to lower operational risk levels.
• Improved decision-making for future risk management strategies.

Conclusion

By conducting SIL verification and SRS development, iFluids Engineering supported the enhancement of Barauni Refinery’s safety framework. Our expertise in risk assessment methodologies assisted IOCL in maintaining compliance and improving operational efficiency.