Effluent Handling System Detailed Analysis Case Study


The Challenge

An international energy company required an effluent handling system detailed analysis. ioMosaic was to update and evaluate their flare system model in the event of power failure with a subsequent loss of cooling global overpressure event.

The main challenge encountered during this project was to properly define the flare baseline model. In order to do that, ioMosaic modeled the simultaneous relief of 50 Emergency Relief Systems (ERS) discharging to the main flare header line through multiple sub-headers with widely different relief conditions such as pressures, temperatures, and mixture compositions.

Our Approach

The project was conducted using Process Safety Office® SuperChemsTM. Detailed pressure relief valve reports and supporting documentation were managed with Process Safety Enterprise®. Three main different cases were developed:

  • Base Case: flare model considering that all existing High Integrity Pressure Protection Systems (HIPPS) fail
  • Best Case: flare model considering that all existing HIPPS operate as intended
  • Worst Case: flare model considering a partial failure on demand of some existing HIPPS

For each case, the flare system performance was studied from three different points of view:

  • Hydraulic analysis, 
  • Consequence modeling, and 
  • Vibration risk.

IEC 61511 Source: International Electrochemical Commission, “Functional Safety - Safety Instrumented Systems for the Process Industry Sector, Parts 1-3,” IEC 61511, Geneva, Switzerland (2018).

The Results

The hydraulic analysis activity consisted of calculating the overall flare system performance during the identified global overpressure event. For each individual system, the following data was produced:

  • Required, maximum and actual flow rates,
  • Inlet pressure, inlet temperature, backpressure and Mach number, and
  • Protected equipment accumulation level.

Additionally, during this activity, the minimum required Safety Integrity Level (SIL) of all HIPPS was calculated using the following internally developed overpressure tolerability risk criterion, which is based on ASME Section VIII pressure vessel code for a healthy ASME vessel.




ioMosaic’s Maximize the Use of Your Existing Flare Structures white paper details the construction of this overpressure tolerability risk criterion, which is based on correlating the consequences of the overpressure in terms of vessel integrity, and the frequency at which the overpressure severity can be tolerated.

The consequence modeling activity consisted of estimating the hazard impact distances using various consequence models due to the potential of a flammable and/or toxic dispersion in the event of a flame-out scenario, as well as the thermal radiation and noise contours at different specified thresholds consistent with worldwide recognized criteria.

Finally, an Acoustic Induced Vibration (AIV) assessment was conducted using the Carucci & Mueller methodology in order to identify the potential for risk vibration on all piping segments defined within the flare system model. 

The final project deliverable was a report that summarized the study scope, technical criteria, results, conclusions and study recommendations, and helped the client gain a better understanding of their effluent handling system performance to ensure safer operation.

Learn More

Our mission is to help you protect your people, your plant, your stakeholder value and our planet. To learn more about how we can help you manage risk, call us at 1.844.ioMosaic.