Grounding static electricity, electrical hazards

In most chemical areas, grounded persons can wear any type of clothing safely. For the unusually sensitive environments hsted above, antistatic or conductive clothing shoiild be worn, and persons must be grounded. Removal of outer garments in a flammable location can cause hazardous discharges and should be avoided (NFPA 77, Static electricity, para. 2-2, 1993). 

Auxilliary and support equipment, required to sustain the operation and not easily adapted to use in the explosive environment, was located in an equipment module (Figure 4) attached to the end of the shop and sufficiently isolated to preclude any hazard to operations conducted therein. The gasoline driven electric generator supporting total electric power requirement, a heat pump, air compressor and hydraulic pump are all located within this equipment module. A sectionized rod with self-contained hammer is provided and stored in the equipment module. This rod is driven into the ground at each work location and connected to the shop frame to insure electrical grounding and prevention of any buildup of static electricity that could produce a spark within the shop. 

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. 

One of the main hazards of air-entrainment sublimation is the risk of fire many substances that are considered to be quite safe in their normal state can produce explosive mixtures with air. All electrical equipment should be flameproof, and all parts of the plant should be earthed (grounded) efficiently to avoid the build-up of static electricity. Vacuum operation after nitrogen purging can provide a much safer processing enviromnent. 

Static electricity is generated by the friction and separation of two dissimilar nonconducting materials. A positive charge accumulates on one material and a negative charge on the other. Eventually, the potential difference between the two materials or between one of them and a nearby ground can allow sudden discharge in the form of a spark. Static electricity is an insidious hazard whch often appears when not expected. Two examples will illustrate this point ... 

These two quite different operations share the specied hazards that are presented by small, dry particles. These hazards, which relate to surface activity, include static electricity accumulation and the possibility of dust explosions. These can occur in any type of apparatus. No product, therefore, should be dried, ground, or milled without thorough knowledge of its safety-related properties. All of the following must be considered in a hazard evaluation ... 

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