IEEE 622-1987 pdf free.IEEE Recommended Practice for the Design and Installation of Electric Heat Tracing Systems for Nuclear Power Generating Stations.
IEEE 622 A device that regulates the state of a system by comparing a signal from a sensor located in the system witha predetermined value and adjusting its output to the predetermined value.Controllers, as used in electric heat tracingsystems，regulate temperatures on the system and can be referred to as temperature controllers or thermostats.Controllers can be mechanical (bulb, bimetallic) or electrical (thermocouple, RTD, thermistor).
critical freeze protection: The use of electric heat tracing systems to prevent the temperature of fluids from droppingto or below the freezing point of the fluid in important or critical outdoor (usually) piping systems at nucleargenerating stations. An example of a critical freeze protection system is the heating for the nuclear service watersystem.
critical process control: The use of electric heat tracing systems to increase or maintain (or both) the temperature offluids (or processes) in important or critical mechanical piping systems including pipes，pumps， valves，tanks,instrumentation, etc.An example of an important or critical mechanical piping system would be the safety injectionsystem.
electric heat tracing system: A system of components and devices consisting of electric heaters, controllers, sensors,dedicated power systems components，such as transformers，panelboards,cables，and system alarm devices (asrequired) that, when taken together as a system, are used toincrease or maintain the temperature of fluids in mechanicalpipes, valves. pumps, tanks, instrumentation, etc.
electrical insulation, insulation (cable): A part that is relied upon to insulate the conductor from other conductors orconducting parts or from ground.Electrical insulation as related to electric heat tracing systems includes that part of aheater that electrically insulates the currentcarrying conductor(s) from the sheath material.
freeze protection: The use of electric heat tracing systems to prevent the temperature of fluids from dropping to orbelow the freezing point of the fluid. Freeze protection is usually associated with piping,pumps，valves，tanks,instrumentation, etc, such as water lines, that are located outdoors or in unheated building.
heater, electric heater, heating element: A length of resistance material connected between terminals and used togenerate heat electrically.Heaters, as used in this application, can take the form of cables with various sheathmaterials， blankets, and pads.
heat sink: A part that absorbs heat. Heat sinks, as related to electric heat tracing systems, are those masses of materialsthat are directly connected to mechanical piping,valves, tanks, etc, that can absorb the heat generated by heaters, thusreducing the effect of the heater. Typical heat sinks can be pipe hangers, valve operators, etc.
process control: The use of electric heat tracing systems to increase or maintain, or both, the temperature of fluids (orprocesses) in mechanical piping systems including pipes，pumps，valves，tanks，instrumentation, etc,in powergenerating stations.
redundant, redundancy: The introduction of auxiliary elements and components to a system to perform the samefunction as other elements in the system for the purpose of improving reliability.Redundant electric heat tracingsystems consist of two heaters and two controllers, each with its own sensor, supplied from two power systems and twoalarms，each system independent of the other but all applied to the same mechanical piping，valves，tanks， etc.Redundant electric heat tracing systems are referred to as primary and backup in this recommended practice.
sensor, sensing element: The first system element that responds quantitatively to the measurand and performs theinitial measurement operation. Sensors, as used in electric heat tracing systems, respond to the temperature of thesystem and may be directly connected to controllers, alarms, or both. Sensors can be mechanical (bulb, bimetallic) orelectrical (thermocouple, RTD, thermistor).
thermal insulation: A material having a relatively high resistance to heat flow and used primarily to retard the flowof heat.IEEE 622 pdf download.