Heat Trace Flashcards
Four main types of electrical heat trace
- Series fixed resistance
- Parallel fixed resistance
- Self regulating variable resistance
- Skin effect
What are two main types of series fixed resistance cables
- Mi cable (Mineral insulated)
2. Polymer insulated series cable
What are the two main types of self regulating cables?
Self regulating polymer cable
Power Limiting cable
What are the two ways an on/off thermostat can be used to control heat tracing?
- Connected in series with the cable
2. In the control circuit of the electromechanical heating contactor
What types of switching are used for electronic control of heat tracing?
Solid state switching
What are the two application 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 starting voltage compare with normal operating voltage for soft start control?
a) Lower
b) Higher
c) The Same
Lower
Why does a flange or a valve require more heat tracing than a pipe?
Flanges and valves have higher heat loses
How are Mi cables typically secured on a pipe?
With metallic banding
How are heat trace cables with non metallic covering typically secured to a pipe?
Fiber tape
What is the proper way of preparing a self regulating cable for termination?
a) Slice the metallic braid and fold it back
b) Cut the braid off without damaging the inner cable
c) Spread an opening in the braid to pull the inner cable out
d) A self regulating cable does not have a metallic braid
c) Spread an opening in the braid to pull the inner cable out
What are the three main reasons to use electric heat tracing?
- To prevent freezing of liquids in pipe or containers
- Melt snow and ice
- To maintain a specific fluid temperature in a pipe or vessel
