Many industries, such as oil & gas, petrochemicals, and more, operate in hazardous environments due to the presence of explosive, flammable liquids, gases, and fumes. Proper ventilation is mandatory in these environments as part of the process safety protocol, preventing the accumulation of combustible substances, ensuring safety, and adhering to good engineering practices. These areas are categorized into classes and divisions based on their level of hazard. For instance, less hazardous areas may be classified as Class 1 Division 2, where flammable liquids, vapors, or gases are handled, processed, or used, but are contained within closed systems or containers. Class 1 Division 1 areas are more hazardous. Both categories require continuous operation, adequate airflow, proper exhaust, and mechanical ventilation. Equipment such as flow switches and meters, used to confirm the presence of ventilation, must be explosion-proof. This post discusses the significance of using explosion-proof flow meters and switches to ensure adequate ventilation in hazardous areas.
Understanding Ventilation Requirements and Standards for Safety and Compliance
Proper ventilation is essential in industrial applications to ensure safety and compliance with specific codes and standards, including NEC, ASHRAE, NFPA, and EPA regulations. Factors such as exhaust and duct locations, the existing ventilation setup, vapor density of materials, and the classification of the operational environment, including Class 1 Division 1, must be carefully evaluated. Below are some important considerations.
- Article 500 of the National Electrical Code (NEC): NEC 500.5 acknowledges the impact of ventilation in the area classification process. Adequate ventilation, as defined in Section 1-3 of NFPA 497, is “a ventilation rate that affords either 6 air changes per hour, or 1 cubic foot per minute (cfm) per square foot of floor area, or other similar criteria that prevent the accumulation of significant quantities of vapor-air concentrations from exceeding 25 percent of the lower flammable limit.”
- NFPA 497 Guidelines for Open Structures: Outside and partially open installations are generally assumed to possess adequate ventilation; however, the following classifications must be considered to ensure this assumption is correct.
- Section 3-3.2 of NFPA 497 states that outside installations and those within open or partially open structures may be assumed to have adequate ventilation and may not be classified into any class. However, after review, these areas may also get classified into one or the other category.
- Section 1-2.3 of NFPA 497 emphasizes the importance of an occupancy document as a guideline for making sound engineering judgments. For instance, some outside installations may be categorized as unclassified, while others result in classified areas after a more thorough review.
Hence, one should exercise caution when changing the classification of a space and the type of electrical equipment based on the level of ventilation provided. Ventilation is required in almost all areas, and various sections of the NFPA emphasize its importance. For example, ventilation is mandated in elevator rooms to maintain required temperatures, and in all rooms and occupied spaces in buildings to ensure acceptable air quality.
- ASHRAE Standards for Occupied Spaces: ASHRAE standards provide ventilation requirements for spaces with human occupancy and requirements to be met in terms of ventilation air quantities required for an occupant’s health, safety and well-being.
- NFPA Exhaust System Requirements: The Standard for Exhaust Systems for Air Conveying of Vapors, Gases, Mists and Noncombustible Particulate Solids by NFPA provides general guidelines for the design and construction of exhaust systems. These systems have certain limitations on the level of flammability or the lower flammable limit allowed unless they meet the NFPA Standard on Explosion Prevention Systems.
Role of Explosion-Proof Flow Switches and Meters in Hazardous Environments
Explosion-proof flow meters and switches are specifically designed to handle the toxicity in hazardous environments, dust, flammable materials, and more, ensuring reliable operations and safety. Below are some key points regarding the role of explosion-proof flow switches and meters in large duct flow measurement across various industries.
- Oil & gas: These flow meters may be required during storage and transportation of oil products as well their loading and unloading as they may catch fire.
- Oil storage: They are required in oil & gas storage facilities, which may pose leakage risks.
- Petrochemicals: They are useful during oil extraction, processing, and transportation as also the storage of natural gas and oil.
- Chemicals: Chemical production involves dealing with abrasive, flammable, and explosive gases, solvents, acids, bases, and more, wherein explosion-free flow switches become essential for safety.
- Timber and wood processing: Wood processing generates a large amount of dust which may be explosive. The same applies to other industry segments that generate dust or fine particles which may be flammable, such as grain processing. Here, mass flow sensing insertion probes are useful for vent air and other non-condensing gases in air ducts and process gas pipes.
- Coal mines: As there may be explosive and flammable gases such as methane and other toxic chemical compounds in coal mines, explosion-proof flow meters are paramount.
- Pharmaceuticals: The processes using flammable organic solvents and explosive chemicals.
- Battery rooms and storage systems: Batteries are filled with hazardous chemicals such as lead-acid, nickel-cadmium, and so on, and must be stored as per regulations to prevent explosion. These include fire-rated enclosures and adequate ventilation to prevent hydrogen gas from reaching 4% of the lower explosive level. This is because hydrogen is released during the charging and discharging process of batteries, and is explosive. Here, explosion-proof flow switches can monitor the airflow in the ventilation systems installed.
- Closed buildings: Certain areas in closed buildings such as rest rooms, kitchen, and more need proper ventilation as per regulation. Any combustible materials must be enclosed in piping systems with proper valves, flanges, and intrinsically safe barriers to isolate flow sensors. Here, flow meters help determine of the building infrastructure complies with ASHRAE standards for indoor air quality and other industrial and regulatory requirements.
- HVAC systems: Flow meters monitor and control air flow and variable air volume in large ducts and ventilation systems. This ensures the required indoor air quality, and supply and circulation of fresh air.
How Explosion-Proof Flow Meters by Bionetics Are Useful in Hazardous Environments?
Many applications require compliance with ventilation systems and may be classified as hazardous based on their classification. Bionetics Corp. offers explosion-proof flow meters and switches for large duct flow measurement in such areas across various industry segments.
The Rheotherm instruments by Bionetics Corp. are designed for use in hazardous environments and comply with various industry standards and regulations. We offer Rheotherm sensing probes for duct gases that are easily installed and require minimal maintenance. These probes measure air and most non-condensing gases, including corrosive and explosive ones. Our flow meters have Factory Mutual (FM) approved integrated designs for use in both liquids and gases. For hazardous environments, the sensors come with an explosion-proof NEMA 4X enclosure. Additionally, they are available with a remote electronics configuration, allowing the electronics to be located up to 200 feet from the sensor and connected through an ISB for isolation of electrical components. These are suitable for pipes with 1” and beyond are FM-Approved for:
- Class I, Div. 1, Groups B, C, D;
- Class I, Zone 1, IIB+H2 (US);
- Class II, Div. 1, Groups E, F, G;
- Class III, Div. 1
The Bionetics Corporation is one of the leading manufacturers of measuring instruments and provides associated data monitoring and diagnostic services. If you require any further information about our explosion proof flow switches and meters and their use in ventilation systems in hazardous areas, contact our team today.
