Spark testing methods

In enamels for chemical plant such as autoclaves it is not only the degree of acid resistance which is important but also the freedom of the finish from minute flaws detectable by high frequency spark testing or chemical methods. The chemical methods depend upon a colour change when the reagent such as ammonium thiocyanate reacts with the iron exposed at the bottom of the pinhole or flaw in the finish. Alternatively, an electric cell can be formed via the exposed iron in the flaw and detected chemically. 

An alternative method is to use high-voltage spark testing (500 V to 30 kV) either in the DC or the AC mode. There are several methods for carrying out these tests, shown here. 

Steel Structure Paint Council white metal blast surface preparation Proposed test method for pinhole detection by high-voltage spark testing by DC... 

When using the spark test apparatus, the safety factor of 1.5 (if required) shall be obtained by one of the following methods ... 

ISO 5660-1 [92] defines the cone calorimeter, which is probably the most widely used ol the rate of heat release test methods see Fig, 17. A horizontal 100 mm square specimen is exposed to a radiant heat flux of 10 to 100 kW m with a spark ignition. system. The effluent is drawn through a duct fitted with sensors for determining temperature, gas flow rate, and oxygen concentration. These data enable the rate of heat release to be determined using the oxygen consumption method. For most plastics, rubbers, and natural materials, the amount of heat produced per unit mass of oxygen consumed is approximately the... 

Lowest temperature at which a flammable gas or vaporized liquid will ignite in the absence of a spark or flame, as determined by test method ASTM D 2155 not to be confused with flash point or fire point, which is typically lower. Auto-ignition temperature is a critical factor in heat transfer oils and transformer oils, and in solvents used in high temperature applications. The auto-ignition temperature should be viewed in relation to the entire phenomenon of combustion. 

Spark-testing n. Method of detecting holidays (flaws) on metallic substrates by means of spark-test tool. 

Spark Test. A method for the detection of pin-holes in a vitreous enamel surface by the discharge of an electric spark. Sparrow-pecked. See stippled. 

ASTM D2699, Standard Test Method for Research Octane Number of Spark-Ignition Engine Fuel, ASTM International. 

D6729 Test Method for Determination of Individual Components in Spark Ignition Engine Fuels by 100 Meter Capillary High Resolution Gas Chromatography... 

The lowest temperature at which a material will ignite and sustain combustion in the absence of a spark or flame. The properties of liquid can be tested by standardized methods (ASTM E659-78 (2005) Standard Test Method for Autoignition Temperature of Liquid Chemicals). The ignition temperature is the temperature in degrees Centigrade at which the substance shows spontaneous combustion when touching hot bodies. 

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