Static Electricity 2000 Edition
–49 2000 Edition FIGURE C.1(g)
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NFPA 77 Static Electricity
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- D.1.2 Antistatic Additives.
- D.1.4 Bulking Brush Discharge.
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–49 2000 Edition FIGURE C.1(g) Typical grounding system for small volume solvent handling at dispensing station. FIGURE C.1(h) Typical grounding system for small equipment. Building static grounding system “bus” Grounding tab for portable grounding attachment Grounding clamp for filling drum Pipe grounding clamp and cable Grounding tab for portable grounding attachment Building grounding “bus” with jumper to table ¹⁄₄-in. stainless steel grounding cable around lighting piston or tilting pivot for grounding upper part of unit; allow slack for maximum travel (lug to framework) Open pail with grounding cable and clamp attached Angle clip grounding tab bolted to table 77– 50 STATIC ELECTRICITY 2000 Edition FIGURE C.1(i) Typical grounding system for small volume for portable tank and drum transfer area. FIGURE C.1(j) Typical grounding system for drum rack. #1/0 –1/C stranded wire building ground “bus” Standard wall-mounted grounding tab Open pail grounding arrangement Grounding clamp Portable grounding reel with 20 ft of ⁵⁄₃₂-in. diameter stainless steel cable ratchet latching Note: IMPORTANT Identical grounding arrangement required for each pair of drums Fasten ground cable to rack with ³⁄₈-in. one- hole conduit clamps on 2 ft, 0 in. centers Building ground “bus” Clamp to drum “lip” Top beam clamp on upper drum Grounding tab for connecting clamps when transfering solvents APPENDIX D 77 –51 2000 Edition FIGURE C.1(k) Typical grounding system for tank car or tank truck loading/unloading station. Appendix D Glossary of Terms This appendix is not a part of the recommendations of this NFPA document but is included for informational purposes only. D.1 General. This glossary contains terms and definitions that are not included in Chapter 3. The terms are presented here to assist the user. D.1.1 Air Ionizer. A device for producing ions in air. Ions from an air ionizer can be attracted to stationary charges on nonconductive items (or items insulated from ground) to eliminate the charge imbalance. Other air ionizers are used to inject ions of a single polarity into an enclosure. D.1.2 Antistatic Additives. Additives used to change the elec- trostatic properties of solid and liquid materials. Extrinsic and intrinsic antistatic additives can be distinguished according to the method of addition. Based on the permanence of their effect, antistatic treatments can be short- or long-term. D.1.3 Brush Discharge. A higher energy form of corona dis- charge characterized by low-frequency bursts or by streamers. Brush discharges can form between charged nonconductive surfaces and grounded conductors acting as electrodes. For positive electrodes, pre-onset or breakdown streamers are observed and the maximum effective energy is a few milli- joules. For negative electrodes, the maximum effective energy is a few tenths of a millijoule. Brush discharges can ignite flam- mable gas and hybrid mixtures but not dust in air. D.1.4 Bulking Brush Discharge. A partial surface discharge created during bulking of powder in containers, appearing as a luminous, branched channel flashing radially from the wall toward the center of the container. Its maximum effective energy is 10 mJ to 25 mJ. It can ignite flammable gas, hybrid mixtures, and some fine dusts in air. D.1.5 Charge. A collection or imbalance of electrons or of positive or negative ions that can accumulate on both conduc- tors and insulators and that has both magnitude and polarity. Movement of charge constitutes an electric current. Excess or deficiency of electrons is expressed in coulombs. An electron carries a charge of –1.6 × 10 −19 coulombs. Download 1.59 Mb. Do'stlaringiz bilan baham: |
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