This section of IEC 60519 is applicable to indirect resistance heating equipment and direct resistance heating equipment specified in items a) and b) below, respectively, operating in voltage bands 1 and 2.
The objective of this standard is to standardize safety requirements for both indirect and direct resistance heating equipment described below.
a) Indirect Resistance Heating Equipment
These particular requirements apply to equipment for indirect resistance heating, which is energized with d.c. voltage or with single-phase or multiphase a.c. voltage of frequency up to 60 Hz.
Heat generation is achieved through current flow in solid metallic heating conductors; solid non-metallic heating conductors; radiant tubes and immersion heaters.
Examples of general use indirect resistance heating equipment include discontinuous furnaces such as batch-type furnaces, muffle furnaces, pot-type furnaces (crucible furnaces), pit-type furnaces, bell-type furnaces, bogie-hearth furnaces, fluidized-bed furnaces, immersion heater metal baths; continuous furnaces with continuous or discontinuous charge conveyors, such as roller-hearth furnaces, pusher furnaces, walking-beam furnaces, rotary-retort furnaces, rotary-hearth furnaces, tunnel furnaces (kilns), continuous muffle furnaces.
Generally used indirect resistance heating equipment also includes equipment for heating solids, liquids or gases; equipment for melting and holding; individual heating-element assemblies (movable or fixed heaters).
Equipment likely to experience specific hazards includes nitrite bath furnaces; indirect resistance heating equipment where an explosive atmosphere is likely to occur inside the furnace during heat treatment: furnaces for carburizing in gas atmospheres consisting of the mixture of hydrogen and methane or propane and carbon monoxide; indirect resistance heating equipment with protective gas and/or reaction gas atmosphere: furnaces for gas carburizing, gas nitriding, carbo-nitriding (protective gas, for example, argon); equipment with infrared heating elements.
These requirements do not apply to trace heating systems dealt with in IEC 60519-10.
b) Direct Resistance Heating Equipment
These particular requirements also apply to equipment for direct resistance heating by means of current introduced by electrodes passing through the charge or a fluid to be heated. Such equipment includes, for example, salt-bath electrode furnaces; glass-melting furnaces; furnaces for graphitizing; furnaces for silicon carbide production.
These requirements do not apply to equipment for direct resistance heating where, due to the technology used, IEC 60519-3, IEC 60519-4, IEC 60519-8, and IEC 60519-21 are applicable. Moreover, they do not apply to electrode-steam-boiler instantaneous water heaters and electrode pressure vessels.
