Many industries in which combustible dusts or gases are handled risk the devastating effects of an explosion. The amount of heat liberated during an explosion creates extremely high pressures which can result in damaged process equipment, loss of production and serious injury to personnel. Leading insurance firms estimate the average direct costs of an explosion in the hundreds of thousands of dollars, with many unprotected explosions leveling plants, or even closing businesses.
Explosion isolation systems prevent the propagation of flame from one part of the process to another through the use of fast-acting explosion isolation valves and/or chemical barriers operated via high speed control systems. Mechanical explosion isolation involves the use of uniquely designed mechanical devices which provide an actual physical barrier or diversion. Chemical explosion isolation is achieved through a rapid discharge of a chemical explosion suppressant to prevent the flame from continuing through to other areas of your process system.
The risk of an industrial explosion occurs in many stages of production, transportation and storage of combustible dusts and gases. Apart from preventative measures to reduce the explosion risk, appropriate constructive explosion measures will protect against the effects of explosions.
Valve closure is achieved when the GCA is activated by the system controller, causing release of gasses into the actuator. Closure is accomplished in 5 milliseconds per inch of valve diameter or less.
Explosion protection, such as explosion venting or explosion suppression, have been widely practiced for many years, explosion isolation has only recently been recognized in the United States. The 1997 edition of National Fire Protection Association’s (NFPA 69) Standard provides guidance on the subject.
The EIPV, used in conjunction with other Fike explosion protection system components, is designed to provide an economical way to prevent deflagration propagation through interconnecting pipes or conveying lines to additional process equipment or operating locations.
The enactment of the Clean Air Act has placed an increasing focus on the need to recover and/or destroy vapor emissions. This requirement has led to the development of closed vapor collection or destruction systems where volatile gases or vapors are collected and transported to some type of processing equipment, i.e. thermal oxidizer, flare, boiler, condenser, etc. These vapor collection systems help safeguard the environment, but can also create a dangerous potential for fire and explosion.
In the production of powdered food or pharmaceutical products, one process step involves drying the product. This is commonly done by a fluid bed or spray dryer. Inherent to this process is the requirement to suspend the powder in air. The suspended powder may create a dangerous potential for an explosion and in cases where a flammable solvent or gas is present with the powder (hybrid mixture) this explosion potential is magnified.
Dust collection involves the removal, or collection, of solid particles from a flowing air stream, for the purpose of eliminating nuisance dust, the safety and health considerations of employees, product quality improvements, and the collection of powdered products.
To bring VOC emissions and air toxins into compliance with the Clean Air Act Amendments of 1990 many facilities are utilizing thermal oxidation systems. A thermal oxidizer is a refractory-lined vessel equipped with a burner, which thermally decomposes volatile organics in a gas stream. These systems include direct-fired oxidizers, recuperative and regenerative thermal oxidizers, and catalytic oxidizers.
Bucket elevators are among the most common conveyors used for making vertical lifts of bulk materials. The materials being conveyed can vary over a wide range of sizes, from powders to pellets. Most of these bulk materials inherently produce dusty conditions within the bucket elevators, creating explosion hazards.
Most manufacturing processes require the removal or collection of dust particles, whether that is eliminating nuisance dust or collecting powdered products. After removal or collection of dust particles, the solid particles typically must be separated from the flowing air stream. One method of separating the solid particles involves using a cycling and dust filter (see figure on page 3). Heavier dust particles are first separated from the air stream into the cyclone through centrifugal forces, then the smallest particles are separated from the air into the dust filter
This process includes a hopper for manually feeding product into a powder handling plant (see figure on page 2). Filling of product hoppers can cause dust particles to become agitated and suspended in air. This dust laden atmosphere can then support a deflagration if an ignition is introduced. A dust collector is installed onto the hopper to pull vacuum, which in effect limits the amount of dust that will become airborne both inside and outside the hopper when feeding the product.
At an elevator facility, a truck unloading system is used to move grain from the truck into storage silos. While conveying grain throughout the system, fine dust will become airborne creating a risk for dust explosion in practically every process section: (see Figure on page 3 from left to the right) truck unloading hopper, bucket elevator, silo and dust aspiration/filter system.
PTFE contained in the grades listed below comply with 21 CFR 177.1550 and may be safely used in articles or components of articles intended to contact food. It is the customer’s responsibility to test finished articles to ensure compliance with the extractives limitations of applicable regulations (see FDA regulations for any limitations or conditions of use).