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Study of Intrinsic Safety Basics and Testing Machines. Study of the Effects of Discharge Duration, Electrode Materials and Surface Conditions on the Minimum Igniting Current.

NTIS: PB/297-437 :89 pages
This report presents the results of an investigation of the discharge duration power and current relation required for ignition. The current and power amplitude-discharge time curve flattened out over 3 msec. It is concluded that discharges having at least 3 msec of power maximum are required for reliable testing of the ignition limit for resistive circuits. Ivestigation of the effect of molten cathode on the discharge duration and igniting ability of the discharge showed that the surface tension of the liquid metal causes a very fast separation and consequently a much shorter discharge duration that the solid electrode would have. The minimum discharge voltage effect overrides the effects of the temperature of electrode, material, or atmosphere. Investigation of the effect of different surface layers on the discharge duration showed that the oxides and sulfates were of significantly longer duration than the "clean" metal itself in most cases. The lowest ignition current was obtained with cdso4 coatings. Ignition was obtained with 0.7 A at 30 V, which is below the corresponding minimum igniting current obtained from the curve for circuits containing cd, zn, or mg.
Publication Date
Document Type
CP; Final Contract Report;
Fiscal Year
NTIS Accession No.
NTIS Price
Identifying No.
OFR 68-79
NIOSH Division
Source Name
NTIS: PB/297-437
Performing Organization
University of Denver
Page last reviewed: September 2, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division