Wikipedia defines EXPLOSION and CONFLAGRATION as follows: “An explosion is a rapid expansion in volume associated with an extreme outward release of energy, usually with the generation of high temperatures and release of high-pressure gases… A conflagration is a large fire.” What suddenly increases is temperature, pressure, energy and material volume, thus making explosion and conflagration destructive. Flammable solids (especially dusts or particulate solids), liquids, and gases are most common sources of explosion.
There are three types of explosions, namely CHEMICAL EXPLOSION, MECHANICAL EXPLOSION, and NUCLEAR EXPLOSION.
CHEMICAL EXPLOSION: Chemical explosions occur due to either decomposition or combination reactions, which both give off heat. The rapid increase of gas release forms a shock wave. There are two types of chemical explosives, namely Detonating (High-Order Explosives), and Deflagrating (Low-Order Explosives) as described below:
- Detonating (High-Order Explosives): These explosives cause destructive shock waves due to overpressure, such as dynamite and gun powder.
- Deflagrating (Low-Order Explosives): These explosives lack the excessive pressure shock wave.
MECHANICAL EXPLOSION: A mechanical explosion requires a physical reaction, which is neither chemical nor nuclear. Mechanical explosions occur when high pressure gas expansion in a containing vessel results in exceeding of the overpressure limit or tensile strength of the container, causing bursting in order to release the pressure, and ignition of fire due to stored flammable gas.
NUCLEAR EXPLOSION: A nuclear explosion occurs due to either a fusion (integration of radioactive particles) or fission (disintegration of radioactive particles) reaction, resulting in sudden release of enormous quantity of heat and gas. Heating of the environment, and blast waves are generated.
There are numerous types of explosives, like – Trinitrotoluene (TNT), Detonating cord (detonating fuse), Ignition systems (electric, and fuse-type firing), fuel oil mixtures, Natural Gas, Ammonium nitrates, Low-freezing dynamites, Nitroglycerin, Black powder, Liquid oxygen, Chlorates and Perchlorates, Nitrostarch, Nitramon and Nitramex. Liquified petroleum gas, ammonia, acetylene, hydrogen, propane, butane, ethylene, propylene, ethane, methane and other gaseous and liquid hydrocarbons are good examples of flammable gases that can propagate explosion when exposed to heat. Inert gases are not explosives in themselves, but Argon may become explosive if it reacts with nitrogen.
CAUSES OF EXPLOSIONS AND CONFLAGRATIONS
Major causes of explosions and conflagrations are – combustible dusts, heating, electrical source, flammable gases and liquids, and equipment and machineries. Combustible chemicals, energy storage, like hydrogen fuel cells, petroleum and natural gas storage as commonly seen in chemical plants, mining facilities, oil and gas processing facilities are of high hazard potential when it comes to explosion and deflagrations. Explosions and conflagrations are mainly caused by – overheating of boilers, malfunctioning equipment and machinery, lack of equipment maintenance, electrical hazards, unsafe procedures, well blowouts, use of impure chemicals, exposure to flame, heating or smoking, flammable materials, fatigue due to corrosion, poor training, lack of ante-explosion construction such as bond walls, lack of cooling systems for heat control of heating equipment, and poor labelling and documentation.
EMPLOYEE’S NEGLIGENCE OR IGNORANCE: Employees or operators may contribute to explosions and conflagrations if they fail to:
- Carry out operational risk management.
- Implement emergency response systems.
- Carry out routine facility audits and checks.
- Implement and enforce good place of work safety culture.
- Monitor and imbibe control measures for safety of combustible materials.
- Provide adequate handling, transportation and storage of hazardous substances.
EMPLOYER’S NEGLIGENCE: Employers or owners of oil and gas companies are responsible for explosions and conflagrations, if they fail to ensure that there is:
- Good workplace health, safety, and environment.
- Provision of early warning systems for workers.
- Training of workers on health, safety and environment standards.
- Maintenance management of equipment, and tools within the facility.
POOR MAINTENANCE OF FACILITY: Inadequate maintenance of facility could result when the provisions of statutory organizations, and specialized standards for oil and gas industry. This is particularly important when it comes to adoption, and working with the maintenance checklists, work procedures – Nigeria Upstream Regulatory Commission (NUPRC), National Fire Protection Association (NFPA), American Petroleum Institute (API) standards as applicable in the context of Nigeria.
STANDARDS FOR CONTROL OF EXPLOSION AND CONFLAGRATION
NFPA 68 Standard on Explosion Protection by Deflagration Venting – This standard is for the design, location, installation, maintenance, and use of devices and systems that vent the combustion gases and pressures resulting from a deflagration within an enclosure so that structural and mechanical damage is minimized.
NFPA 69 Standard on Explosion Prevention Systems – This provides requirements for installing systems for the prevention and control of explosions in enclosures that contain flammable concentrations of flammable gases, vapors, mists, dusts, or hybrid mixtures.
NFPA 660 Standard for Combustible Dusts (this new standard is combining NFPA 61, NFPA 484, NFPA 652, NFPA 654, NFPA 655, and NFPA 664). Application standards for the oil and gas industry specific standards on explosions in the NFPA 660 are NFPA 484, NFPA 652 and NFPA 654.
- NFPA 484, Standard for Combustible Metals – stipulates the provisions for production, processing, finishing, handling, recycling, storage, and use of all metals and alloys that are in a form that is capable of combustion or explosion, as well as to operations where metal or metal alloys are subjected to processing or finishing operations that produce combustible powder or dust.
- NFPA 652, Standard on the Fundamentals of Combustible Dust – provides the basic principles of and requirements for identifying and managing the fire and explosion hazards of combustible dusts and explosives.
- NFPA 654, Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids – presents safety measures to prevent and mitigate fires and dust explosions in facilities that handle combustible particulate solids, which includes combustible dusts, fibers, flocks, flakes, chips, and chunks.
NFPA 54, National Fuel Gas Code – provides minimum safety requirements for the design and installation of fuel gas piping systems in homes and other buildings.
NFPA 55, Compressed Gases and Cryogenic Fluids Code – facilitates protection from physiological, over-pressurization, explosive, and flammability hazards associated with compressed gases and cryogenic fluids.
NFPA 56, Standard for Fire and Explosion Prevention During Cleaning and Purging of Flammable Gas Piping Systems – provides comprehensive requirements to help develop safe operating procedures.
NFPA 290, Standard for Fire Testing of Passive Protection Materials for Use on LP-Gas Containers – provides a test method to determine the fire resistance of passive fire protection (PFP) materials applied to the exterior of LP-Gas containers. It is intended to identify insulation systems that retard or prevent the release of the container’s contents in a fire environment.
SPECIFICATION OF EXPLOSION PROOF MATERIALS
The application explosion protection solutions based on ATEX directives are two EU directives describing the minimum safety requirements for workplaces and equipment used in explosive atmospheres.
DIRECTIVE 99/92/EC OR ATEX 137
- Responsibilities of employers with regard to worker safety.
Employers are required to carry out an assessment of explosion risks and take the necessary measures to eliminate or reduce these risks.
- Assess explosion risks on their site.
- Classify hazardous zones and provide signage.
- Keep an explosion protection document.
- Take preventive technical and organizational measures.
- Comply with the criteria for selecting electrical equipment.
DIRECTIVE 2014/34/EU (RECAST OF 94/9/EC) OR ATEX 95
- Responsibilities of manufacturers of equipment intended for use in ATEX zones.
The responsibilities of manufacturers include:
- Requirements relating to equipment and protective systems intended for use in explosive atmospheres (such as gas detectors).
- Requirements relating to safety devices and controlling devices intended for use outside potentially explosive atmospheres but required for the proper functioning of equipment and protective systems (for example, controllers).
- The classification of equipment groups into categories.
- Essential health and safety requirements relating to the design and manufacture of equipment or systems.
In conclusion, there is need for adoption of ante-explosion and fire-resistant construction, passive thermal prevention system in design, construction, installation, and maintenance of oil and gas facilities. There is need for explosion resistant and resilient materials and equipment based on NFPA, API, ATEX and other relevant standards.
William Nwaogu, Technical Advisor
SAFETY CONSULTANTS & SOLUTION PROVIDERS LIMITED
