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Hazardous Area Classification (HAC) - ATEX

The emission of flammable substances can give rise to a considered explosive atmosphere region so that safety measures must be followed according to  Hazardous Area Classification (HAC) established by regulatory standards.

 

ATEX: “ATmosphere EXplosible”

*IEC 60079-10-1 standard defines a hazardous area as an area where an explosive gas atmosphere is expected to be present in quantities requiring special precautions for the construction, installation, and use of equipment. In the region where it is considered that there is a high probability of an explosive gas atmosphere to be formed, equipment having a low probability of ignition must be used, which are naturally more expensive.

BC performs comprehensive studies for HAC by using advanced Computational Fluid Dynamics (CFD) capabilities:

  • Precise dispersion assessment

  • Economic and competitive solution

The methodology is capable of providing a detailed review of the probable extent of potential hazardous zones:

  • Producing more refined zone areas (i.e., fewer and/or smaller)

  • Reducing the need for protected electrical equipment.

Direct benefits of the methodology are the following:

 

  • Visually show the outputs of a HAC compliant result.

  • Help justify smaller hazardous area zones where electrically protected equipment is required.

  • Reduce the initial capital cost of electrical equipment (as fewer “protected” items may be required).

  • Reduce the overall life cycle cost as there is less equipment subject to a strict maintenance and inspection regime.

  • Be regarded as a suitable tool for use by an expert witness in a legal context.

*IEC: International Electrotechnical Commission

Safety Instrumented Systems (SIS) - Functional Safety Standards Compliance

A clear methodology for linking the Quantitative Risk Assessment (QRA) results with functional safety principles was developed by Dr. Dunjó. The methodology was published in reference [1], and it is mainly focused on estimating the Risk Reduction Factor (RRF) that a selected Layer Of Protection (LOP) requires for ensuring a new tolerable risk level of the affected area.

[1] J. Dunjó, M. Amorós, N. Prophet, G. Gorski. “Advanced QRA Methodology: Quantifying Risk Reduction Measures to Minimize Economic Investment”. 14th Global Congress on Process Safety, Orlando, FL. April 2018

A Safety Instrumented System (SIS) consists of at least three subsystems: sensor, logic solver, and final element. All subsystems must simultaneously act to detect the deviation, and bring the process into a safe state by implementing a Safety Instrumented Function (SIF) ensuring the necessary level of functional safety based on the process characteristics during the "Safety LifeCycle" (SLC).

The SLC is an engineering process that contains all the steps needed to achieve high levels of reliability during conception, design, operation, and maintenance of instrumentation systems.

The three (3) SLC phases are the following:

1. PS Analysis / PS Assessment, which identifies and quantifies the process risk level, and compares it with applicable tolerability criteria to verify whether risk reduction is required or not; i.e., see RRF Assessment. This phase also includes the information for defining the safety functional and integrity requirements; i.e., Safety Requirement Specification (SRS).

2. Design & Implementation, which requires the following tasks:

  • Completion of the SIS conceptual design and architecture

  • Review of the periodic test philosophy

  • Verification of the SIS based on RRF requirements.

3. Operation & Maintenance, which ensures proper operating procedures and maintenance activities, and implements modifications during the system life-cycle; i.e., Management Of Change (MOC).

BC approach ensures all SLC phases are successfully executed. This is performed by conducting a rigorous and robust Functional Safety Assessment (FSA) examination of the adequacy of the functional safety achieved by the SIS within the particular environment; i.e., following guidance for FSA requirements established in Chapter 8 of IEC 61508-1.

Emergency Relief Systems (ERS) Design and Analysis

OSHA PSM Rule (29 CFR 1910.119) requires companies to compile information involving the design and design basis of Pressure Relief and Flare System (PRFS).

The goal of ERS is to provide a venting path from equipment to prevent excessive pressure accumulation for all credible upset scenarios. They are intended to avoid hazardous Loss Of Containment (LOC) scenarios, and this is the reason why BC considers ERS as the last line of defense of prevention measures.

OSHA PSM: Occupational Safety and Health Administration Process Safety Management

BC applies criteria established in ASME (American Society of Mechanical Engineers) and API (American Petroleum Institute) standards with the aim to ensure:

  • Relief devices provide adequate capacity.

  • Inlet pressure drop and built-up backpressure are within recommended limits.

  • Physical installation meets the requirements; e.g., eliminate restrictions on the inlet line and absence of pockets in the discharge line.

  1. Overpressure scenarios and relief requirements are quantified in accordance with API 521.

  2. Relief devices are sized and installed per ASME and API 520.

Furthermore, BC considers essential to comply and go beyond RAGAGEP (Recognized and Generally Accepted Good Engineering Practices) guidance and criteria.

Accordingly, BC ensures additional numerical analyses such as:

  • System engineering stability analysis beyond the 3% rule, which is based on the force balance on the disk.

  • Evaluation of the relief system piping (e.g., vibration risk and noise, reaction forces and structural support, temperature excursions).

  • Ventilation / Dispersion Assessment for those devices that require further analyses:

  • Toxic/Flammable dispersion analysis.

  • Analysis of safe discharge locations.

  • Thermal radiation analysis.

  • Noise analysis.

Based on BC experience on designing and analyzing PRFS, BC is a reliable collaborator for performing Third Party Reviews of PRFS evaluations.

 

Accurate Calculations, Robust Results, and Elegant Cost-Effective Solutions