The technical constraints and financial consequences resulting from the need to retro-fit an effective Explosion Protection System into an existing process plant were well illustrated by a Dairy Industry project recently evaluated by IEP Technologies.Read more
Safe Handling of Powders and Bulk Solids
Precautions must be taken in connection with processes, such as grinding, atomizing, conveying, collecting, drying, screening, grading, blending, weighing and packing, in these industries.
Handling and processing of dry materials / dusts present unique fire, explosion, and toxicity hazards.
Materials that are practically inert in consolidated form can become quite hazardous when converted to powders and granules.
- Safe Handling of Powders and Bulk Solids
- Combustible dust explosions
- Combustible dust explosion protection
- Explosion Protection Standards
Safe powder handling
Powder handling equipment manufacturers should be well aware of regulations governing machine safety and should have taken actions to ensure the safety of their products.
Powder handling equipment operators should be involved in the process and should be correctly trained. This not only involves operators, but maintenance technicians, cleaning staff, and anyone who comes into contact with the powder handling equipment.
Safe powder handling equipment must be designed for two things:
- to remove all of what is identified as 13 possible sources of ignition (primarily by making sure the equipment is grounded) and,
- by ensuring that the equipment is as easy to clean as possible.
Combustible dust explosions
Combustible dusts are fine particles that present an explosion hazard when suspended in air under certain conditions.
Combustible dust explosions can cause tragic loss of life, injuries, and destruction of industrial buildings, and occur within milliseconds.
In many incidents, workers and managers are unaware of the potential for dust explosions or fail to recognize the serious nature of dust explosion hazards.
Five elements to initiate a dust explosion
Five elements are necessary for a combustible dust explosion to occur: fuel (combustible dust), ignition source (heat), oxygen, dispersion and confinement of the dust cloud.
Different approaches to protecting against the ravages of the explosion are regularly used to limit this damage.
Good housekeeping is an essential first step toward mitigating dust explosion hazards.
Other safety measures include:
- The use of proper dust collection systems and filters,
- The use of vacuum cleaners specifically approved (ATEX) for dust collection,
- Implementation of a hazardous dust control program that includes dust inspection, testing, and housekeeping,
- Regular inspection of both open and hidden areas for dust residue,
- Ensuring that employees are trained on the hazards of combustible dust.
The use of proper electrical equipment in hazardous locations is crucial to eliminating common ignition sources. Other ways of controlling ignition sources include:
- Ensuring the use of appropriate electrical equipment and wiring methods,
- Keeping heated systems and surfaces away from combustible dust,
- Controlling the use of open flames and static electricity,
- Having an ignition control program, such as grounding and bonding, and other methods, for dissipating any electrostatic charge that could be generated when transporting and handling dust.
Combustible dust explosion protection
The complexity of the processes that can lead to a dust explosion means that it is extremely difficult to assess the actual risks in dealing with combustible dust/air mixes. This makes combustible dust explosion protection very important. These are generally considered to mean avoiding or limiting the build-up of a hazardous explosive atmosphere.
Dust explosion testing
Results of dust explosion testing can be used to determine the appropriate solutions to protect potential dust explosion hazard areas within facilities.
Dust explosion mitigation
Dust explosion mitigation systems can be categorized into two main types of technologies, being:
Passive safeguards: passive safeguards react to an event
Active safeguards: detect and react prior to or during an event
Through the use of passive, active, or a combination of both safeguards, a custom explosion protection solution can be designed to mitigate or prevent dust explosion hazards specific to particular process needs.
Explosion Protection Standards
Companies that manufacture explosion-proof equipment and systems for the global market must conform to applicable explosion protection standards.
ATEX (ATmosphere EXplosibles – French for Explosive Atmospheres) is the formal name given to the two European Directives for controlling explosive atmospheres.
There are two European Directives in place for the control of explosive atmospheres:
Directive 1999/92/EC (also known as 'ATEX 153' or the 'ATEX Workplace Directive')
Directive 2014/34/EU (also known as 'ATEX 114' or 'the ATEX Equipment Directive')
ATEX is the European certification given to equipment tested and approved to be intrinsically safe in potentially explosive atmospheres.
Equipment and protective systems intended for use in potentially explosive atmospheres (ATEX) cover a range of products, including those used in chemical plants, food manufacturing plants, flour mills, pharmaceutical production and other areas where a potentially explosive atmosphere may be present.
ATEX is not harmonized with NFPA combustible dust standards and not considered by OSHA an acceptable certification for electrical equipment used in hazardous locations.
NFPA 652 - Standard on the Fundamentals of Combustible Dust
The National Fire Protection Association (NFPA) 652, Standard on the Fundamentals of Combustible Dusts, provides requirements for the management of combustible dust fire and explosion hazards and directs the user to appropriate NFPA industry or commodity-specific standards. The standard also ensures that crucial requirements are addressed consistently across industries, processes, and dust types.
IECEx is a global standard to ensure explosion-proof equipment and systems are safe for use in countries that participate in the IECEx system. To be validated against the IECEx Certified Equipment Scheme, manufacturers need to obtain the Certificate of Conformity (CoC), validation of the technical report (ExTR) and the quality assurance report (QAR).
Because combustible dust issues are complex and incidents can be devastating, it’s important to use experienced, independent, and professional engineers to help design and install powder handling systems.
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