Emergency Relief System Design

Reducing costs and increasing accuracy in the design or revalidation of relief systems.

Effective Emergency Relief System (ERS) design helps companies meet risk-management goals, compliance requirements, and sound business practices. ioMosaic provides a total ERS solution with our comprehensive ERS design services, from reactivity testing for design basis determination to calculations for Z-axis deflection from dynamic loads.

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How We Can Help You

Our team has decades of experience performing PRFS analysis and design.

Our risk-based approach helps mitigate near-unventable scenarios to a tolerable level of risk.

Better evaluate hazards in your facility with an accurate process simulation.

Delivering properly designed pressure relief systems that save both money and time.

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Featured Resources

RAGAGEP Considerations for Overtemperature Protection in Relief Systems

How to Calculate ETTF or ETTY in Fire Exposure Scenarios

Reasonable estimates of the expected time to failure (ettf) or expected time to yield (etty) are required and necessary for effective risk management as well as effective emergency and fire protection and response. Read this paper for a demonstration of calculating ettf or etty in fire exposure scenarios with Process Safety Office® SuperChems™.

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Calculate Flammability Limits Using Process Safety Office® SuperChems™

This paper presents a general method for the estimation of flammability envelopes for chemical mixtures containing gases, liquids, and/or solids based on chemical equilibrium. The impact of mixture initial temperature, the presence of diluents and elevated system pressures are implicitly accounted for. The performance of this method is tested against much of the experimental data reported in the literature for systems containing a wide range of chemicals from CHNO compounds to compounds containing sulfur, phosphorus, silicon and halogens.

This method presents a very useful and accurate approach for assessing the flammability envelopes of mixtures where no experimental data is available, and to guide experimental flammability testing work, using Process Safety Office® SuperChems™ software.

Flammability Limits

Figure 1 summarizes thermochemical estimates of flame temperature for a mixture of methane and oxygen at 1 bar and 25 C. We observe from Figure 1 that both the lower and upper flammability limits occur at a temperature of around 1500 K. We also observe from Figure 1 that the lower flammability limit (LFL) and the upper flammability limit (UFL) do not change significantly over a 500 degrees window. The calculated LFL varies from 3% at 1000 K to 4.8% at 1500 K. The calculated UFL varies from 60% at 1000 K to 68% at 1500 K.

At the reported literature flammability limits (LFL of 5% and UFL of 60%), the methane-oxygen system has a threshold theoretical flame temperature of 1500 K. At this temperature, the combustion reaction is able to generate enough heat to produce a self-sustaining (propagating) reaction.

Many other systems of interest have a similar behavior. Table 1 summarizes estimates of calculated theoretical flame temperatures at both LFL and UFL limits for a variety of chemicals. Most calculated flame temperatures are between the range of 1000 and 1500 K. For most organic chemicals, the flammability limits in air can be approximately related the the stoichiometric limits in mole or volume percent:

Calculate-Flammability-Limits-Diagram-1

The stoichiometric limit can be obtained by finding the composition in air that yields the highest theoretical or adiabatic flame temperature. For the combustion of methane in air, the above equations yield:

Calculate-Flammability-Limits-Diagram-2


Our Team

Georges A. Melhem, Ph.D., FAIChE

President & CEO The founder of ioMosaic and internationally renowned expert in the areas of pressure relief and flare systems design, chemical reaction systems, process safety and risk analysis. Read more...

Neil Prophet

Senior Vice President and Partner He brings over 20 years of experience in pressure relief and flare systems design project management and engineering expertise for chemical, pharmaceutical and petrochemical companies. Read more...

John Barker, Ph.D.

Director The head of our international offices in the U.K. and the Kingdom of Bahrain and an expert in risk management for oil, gas and transportation. Read more...

Marcel Amorós Martí

Director and Partner His expertise consists of a diverse range of industries from chemical and petrochemical to oil and gas and utilities. Read more...

Charles Lea, P.E.

Director, Minneapolis Office Lead He directs a number of large technical projects across multiple offices and is also responsible for all project management in our Minneapolis office. Read more...

Matthew LeVere, P.E.

Senior Safety and Risk Management Consultant Experienced in PRFS design and analysis for clients in the petrochemical, chemical, and pharmaceutical industries. Read more...

Neal Dahlheimer, CPPM

Senior Safety and Risk Management Consultant Technical lead on PRFS projects for chemical, petrochemical and oil facilities as well as QA/QC reviews and training on advanced techniques for complex systems. Read more...

James Close

Senior Consultant Mr. Close is focused on pressure relief and flare system design and analysis for large chemical and petrochemical companies in Europe and the United States. Read more...

Christian Sarno

Senior Safety and Risk Management Consultant Focuses on quantitative risk assessment (QRA), facility siting, pressure relief and flare system (PRFS) design and analysis for chemical and utility companies. Read more...

Featured Videos

 

Emergency Relief System Design Workflow

This PSE module performs efficient tracking of process safety related data and analysis. A customized workflow allows for a specific operating unit or the entire facility to be studied and evaluated for compliance.

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Featured Case Studies

Validate Relief System Performance and Flare System Capacity for Increased Unit Charge Rate

A major petroleum company recently increased production capacity and required an analysis of its existing relief systems to validate performance and design. As a result of increasing production capacity and debottlenecking studies, several refinery units were found to be operating at charge rates higher than the design basis for the relief systems documentation.

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A refinery approached ioMosaic for the purposes of ensuring that pressure relief capacity was adequate for the loss of liquid seal scenario in a high-pressure separator (2,000 psig). They were also concerned about the pressure waves that would occur in the high-pressure separator’s outlet lines on rapid closing of the isolation valves and sought our expertise.
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A large oil refinery with a very complex flare network had become so complex that the tools the refinery was using to evaluate the flows through the flare network could not adequately model the system. Management no longer had confidence that their model results reflected the actual network performance and therefore, could not be sure the system would perform properly in the event of a global relief scenario at the facility.
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A multinational energy company wanted to complete an evaluation of a pressure relief valve system in order to comply with the PSM standard OSHA 29 CFR 1910.119 which requires that employers compile information pertaining to the equipment in the process, including relief system design and design basis. 
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Featured Services

Pressure Relief and Flare System Design

Our risk-based approach helps mitigate near-unventable scenarios to a tolerable level of risk and develop economical designs for more credible events. Read more...

Relief Header and Flare Analysis Systems

Delivering properly designed pressure relief systems for refineries and chemical plants that save both money and time. Read more...

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