Safety static charge

Packed full of useful information, this volume helps you solve field engineering problems with its hundreds of common sense techniques, shortcuts, and calculations. The safety chapter covers lowers explosive limit and flash, flammability, as well as static charge. 

It is difficult to obtain accurate particle size analyses of primary expls because (1) consideration and acceptance of necessary safety precautions make the usually tedious job of particle size analysis even more tedious, and (2) many primary expls used in production contain particles which are non-spherical in shape and are in the subsieve size range. Dry screening Lead Azide, for instance, is hazardous and must be done remotely. Furthermore, static charges... 

In areas where dry powder is handled, the buildup of static electricity presents a safety hazard. A static charge could possibly ignite or detonate propellant in the dry state. For this reason, materials used in these areas are conductive and properly grounded. Flooring and footwear must also be conductive as outlined in the Department of Defense Safety Manual. Conductivity tests are made periodically to insure that there is proper protection against static charge buildup. 

Local atmospheric conditions such as thunderstorms and static charge build up are important considerations for electrical safety in your system. Static charges can build up due to windblown dust, snow, water, pollen and many other causes. 

Sensing techniques that are applicable to the measurement of solids concentration can be classified into four groups electrical, attenuation, resonance, and tomographic. The electrical methods utilize the dielectric and electrostatic properties of solids. Typical electrical sensors are capacitive and electrodynamic sensors the capacitive sensors measure the dielectric property of the solids, whereas the electrodynamic sensors detect the static charges that develop because of collisions between particles, impacts between particles and pipe wall, and friction between particles and gas stream. Attenuation methods are used with optical, acoustic, and radiometric sensors. Both optical and acoustic sensors are applicable to relatively low concentrations of solids. Radiometric sensors, in which y-rays or X-rays are used, are expensive and may raise safety concerns. They can, however, offer accurate and absolute measurement of particle velocity and thus can be used as calibration tools for other low-cost sensors such as the capacitive sensor. Resonance and tomographic methods, which are still in developmental stages, will be briefly introduced in Section 6.5. 

Street shoes may not be appropriate in the laboratory, where both chemical and mechanical hazards may exist. Substantial shoes should be worn in areas where hazardous chemicals are in use or mechanical work is being done. Clogs, perforated shoes, sandals, and cloth shoes do not provide protection against spilled chemicals. In many cases, safety shoes are advisable. Shoe covers may be required for work with especially hazardous materials. Shoes with conductive soles are useful to prevent buildup of static charge, and insulated soles can protect against electrical shock. 

Bonding— The interconnection of two objects such as a tank or cylinder with clamps and wire as a safety practice to equalize the electrical potential between the objects and help prevent static sparks that could ignite flammable materials, dispensing/receiving a flammable liquid that requires dissipating the static charge by bonding between containers. 

For BSD safety, a path to ground must be provided for static charges that would otherwise discharge on a device or board assembly. Provisions are made for grounding the worker, preferably via a wrist strap or a heel strap, provided conductive flooring is used. 

For safety reasons, some fireworks manufacturers store their products in metal sheds separated by sand banks. Also, people who work with fireworks are advised to wear cotton clothing because cotton is less likely than other fabrics to develop a static charge, which can cause a spark and accidentally ignite fireworks. 

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