Process Safety and SIL

Any process that handles hazardous substances has the potential for a loss of containment event that could lead to a significant incident. Asset owners need to ensure that the process equipment is designed, maintained, and operated to minimize the likelihood of this. 

Process Safety is a framework for ensuring that the process design envelope is protected and has resilience against system failures and degradation. Process safety consequently focuses on preventing or mitigating loss of containment scenarios that could lead to fires, explosions, and accidental chemical releases at process facilities. 

An important part of Process Safety is Functional Safety (also called SIL). The core of functional safety is about defining requirements for instrumented safety systems and so-called safety instrumented functions, which normally include an input device, logic solver, and a final element.

ORS is a leading provider of Process Safety and SIL. We are helping businesses and facilities with a wide range of services, including all lifecycles of functional safety management, HAZOPs, dynamic process simulations, process safety time assessments and overpressure protection assessments.

process safety and SIL

Process Safety and SIL Realted Studies


HAZOP is a structured, multi-discipline assessment of a process system to ensure that the risk for loss of containment is minimized and that the design meets process safety-related standards.

Dynamic Process Simulation

Dynamic simulation of a process plant behaviour to better understand the effects of failures and the ability of the design to safely address these failures.

Process Safety Time Assessment

Ensuring that Safety Instrumented Systems can react within a suitable period following a process disturbance and avoid the design envelope from being exceeded. Steady-state and dynamic methodologies are used to meet IEC 61511 and ISO 10418 requirements.

Flare, Venting, Relief, & Blowdown System Performance

Safe disposal of fluids in an emergency situation is an essential part of any process plant design. Hence flare systems are considered safety-critical. We use Flare System Analyzer and other industry-standard tools to ensure back-pressures, velocities, momentum, flare tip radiation, and low-temperature material design constraints are all met.

Overpressure Protection assessment

Different combinations of instrumented and mechanical overpressure protection systems exist in all process plant designs. Vessel and piping design reviews, relief valve sizing and selection to the requirements of API 520/521/526, and reliability assessments of instrumented systems under IEC61511 are all necessary to ensure the system is suitably protected.

Functional Safety Management Plan

The Functional Safety Plan describes the project plan, organization and principles to ensure functional Safety throughout the entire period of the project development and asset operation. A functional safety plan must state a set of measures to ensure that the target Safety Integrity Level (SIL) is achieved.

SIL Allocation/LOPA

SIL allocation, e.g. with Layers of Protection Analysis (LOPA) is a methodology for defining performance requirements for safety instrumented functions. In addition, the assessment can be used to evaluate whether adequate protection layers are in place to reduce risks to acceptable levels.

SIL Compliance verification

A SIL Compliance verification is applied to confirm that Safety Instrumented Functions (SIFs) meet the performance requirements, as detailed in the functional safety process. Such requirements include reliability requirements, architectural requirements as well as a demonstration of avoidance and control of systematic errors.

Functional Safety Assessment (FSA)

FSA is a third-party evaluation of the functional safety activities in a project, to confirm that standards (such as IEC 61508 and 61511) as well as Company requirements are correctly applied. FSAs are typically performed in steps depending on the phase and maturity of the project. The FSA prevents systematic failures and helps to ensure that functional safety is achieved in facilities.

Safety Manual

A Safety Manual is documentation provided by equipment or system suppliers justifying use in SIL-related functions. The intention with the Safety Manual is to provide input documentation for the overall SIL Compliance verification, and to demonstrate that the supplier organization, management systems and manufacturing process ensure sufficient reliability and minimizes systematic errors.

SIS Performance Monitoring

Safety Instrumented Systems (SIS) performance monitoring involves follow-up and benchmarking of SIS component failure frequency against design documentation and acceptance criteria. Among others, this can be used to adjust test intervals, improve test and maintenance regime or input to modification projects.

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