Conductive floors

The combination of conductive flooring 7/ia conductive footwear is the preferred method of grounding. Untreated concrete flooring with conductive footwear is usually adequate, but its conductivity should be measured (Fowler and Klein, Static Phenomena and Test Methods for Static Gontrolled Floors, EOS/ESD Symposium Proceedings, pp. 27-38, 1992). Where this method is impractical, personnel grounding devices are available. 

Laboratories working frequently with flammables, such as in extraction processes, may set aside a separate room for such work for maximum safety. Ideally, this room should have explosion-proof electrical equipment and special ventilation. Rigid work rules should be enforced, such as requiring workers to leave matches and lighters on a shelf outside before entering. Installation of conductive flooring should be considered, and steel tools should be prohibited at times when work is in progress. 

Estimate the capacitance of a person standing on a conductive floor. Assume that the person s shoe soles separate the person from the floor that is, the shoe sole is the dielectric of the capacitor. Given... 

For facilities susceptible to the contamination of nitroglycerin liquids and vapors, basic construction materials of wood framing, reinforced concrete, fiberglass reinforced plastic, and sandwich panels were chosen for development of architectural details incorporating lead conductive floor lining, equipment doors, personnel escape chutes and doors, ceiling and wall interfaces, interior finishes, joint sealing, door and wall louvers, wall vents, wall penetrations, and fixed windows. 

For facilities susceptible to nitrocellulose, single base and multibase dusts, the same details could be used with the addition of alternate basic construction types. Six types of construction were chosen which included wood frame, concrete masonry units, reinforced concrete, modified preengineered buildings, fiberglass reinforced plastic and sandwich panels. These were chosen for development of architectural details similar to those mentioned above for nitroglycerin facilities except troweled-on conductive floor lining was to be used instead of lead. 

The following statement appears consistently on the details and will determine the choice of all materials including the basic building construction system chosen, special floor coatings, conductive flooring, interior finishes and construction sealants. 

Figure 1 indicates a typical nitroglycerin facility "inside out" wood frame construction at a concrete floor slab. Note that the exterior cant strip, the lead conductive floor cant and the wood cap are all sloped to discourage product build-up and facilitate cleaning. This assembly also indicates spray-on foam insulation as an optional construction item. At Radford AAP this is a safety approved insulation system. The insulation at Radford AAP received a chlorinated rubber paint coating for weathering. 

Figure 2 is a detail of the sloped wood cap used in Figure 1. Note that the joints are taped (at the top of the cant) and caulked (between the lead flooring and wood cant) to keep manufacturing components and product out of joints. The tape material is 3 inch wide, 2 ply, 100 percent cotton, grade B fabric with a warp and fill of approximately 78 x 78 x 72 pounds breaking strength. It should be adhesive-applied using a water insoluble nitrile rubber/ resin solution. These are commonly referred to as "Airplane Fabric" and "Pliobond 20" adhesive. The Fiberfrax Paper is used below lead flooring as an insulation barrier with a low thermal conductivity to resist heat required for installation of lead conductive floor. Note also that nonsparking nails are required. These are usually aluminum or brass.

Figure 4 utilizes similar sloped cant strips, taped joints, sloped conductive floor cant and wood cap above lead flooring. 

A typical interior trench or floor gutter is shown in Figure 14. Note the rounded bottom shape and the canted or rounded bends of the lead conductive flooring. Also, note the requirement for rounding bearing surfaces of the cover, which prevents damage to the lead floor surfacing. 

Figure 14. Lead conductive floor. Floor gutter/floor interface.

Sn, Sb)02/Mica Sn(0,F)2/Mica electrically conductive conductive flooring, antistatic packaging materials, light colored primed plastic surfaces which can be electrostatically painted in further coating process, light colored conducting surfaces in clean room conditions for dust reduction [5.235]... 

Grade E Mg powd and BkPdr dust when exposed in layers. Dust of solid proplnts can also be ignited from the spark that can accumulate on a person, and conductive floors Sc shoes must be used when the dust is present. In addn, dust-air mixts of Amm Picrate, Tetryl, Tetrytol dust of solid proplnts are sensitive to static elec discharges. Many flammable liquids Sc air mixts ( ether, ethyl alcohol, ethyl acetate, acetone gasoline) can also be ignited by static discharge from a person (Refs 1 3)... 

Equipment connected to standard grounds and conductive floors used in propellant handling laboratories. 

Conductive floors provide effective control of static electricity Available in the form of screeds, self-levelling floors and floor coatings Water resistant... 

Floor selection criteria should include chemical resistance, stain resistance, scuff and marring resistance, ability to radius cove, durability, esthetics, and ease of maintenance and repair. Table 3 lists several floor compositions and selection criteria. Special areas may require static dissipative or conductive flooring in order to minimize explosion potential with flammable material. 

Electrical sparks are not only generated in the electrical installation, but also by discharge of static electricity. These sparks can ignite just as well. Expert grounding of all relevant parts of the installation is an important part of this chapter. This is true not only for the gas containing parts of the facility but also for e.g. radiators, water and gas pipes and other metallic parts. Also conductive floors can be very useful. 

Applications of electrically conductive concrete include conductive floors and cathodic protection of reinforced bridge decks. 

Conduct floor cleaning at least three times weekly. 

Conductive Soles and Non-sparking Shoes People who work in hospital operating rooms where there is a danger of fire or explosion from flammable gases may wear conductive shoes. The shoes contact a conductive floor to prevent static charge buildup. 

USA, stipulates that the resistance of a conductive floor shall be less than 1 megohm as measured between two points 3 ft (1 m) apart the resistance of the floor shall be over 25 000 ohm between a ground connection and any point on the surface of the floor or between two points 3 ft (1 m) apart on the surface of the floor,... 

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