Heat Trace Flashcards
What are the three main reasons to use electric heat tracing?
prevent freezing of liquids in pipes or contains, melt snow and ice, to maintain specific fluid temperatures
What are the four main types of electric heat trace system?
series fixed resistance, parallel fixed resistance, self-regulating variable resistance, skin effect
What are the two main types of series resistance cables?
MI, polymer
What are the two main types of self-regulating cables?
power limiting, self-regulating polymer
What are the two ways an on-off thermostat can be used to control heat tracing?
connected in series with the cable, in the control circuit of an electromechanical heating contactor
What type of switching is used for electronic control of heat tracing?
solid state switching
What are two applications of electronic control that a simple thermostat control cannot do properly?
soft start a heat trace circuit, control the average current for fine temperature control
How does the starting voltage compare with the normal operating temperature voltage for soft start control?
lower
Why does a flange or a valve require more heat tracing than a pipe?
flanges and valves have higher heat losses
How are MI cables typically secured on a pipe?
with metallic banding
How are heat trace cables with a non-metallic covering typically secured on a pipe?
fibre tape
What is the proper way of preparing a self-regulating cable for termination?
spread an opening in the braid to pull the inner cable out
