Question: Why do heater plates for fusion require surface temperature checks with a probe when they already have a temperature gauge?
Answer: The dial thermometer on the heater indicates internal temperature which can be different from the actual surface temperature. The dial thermometer can be used as a reference once the surface temperature has been verified with a surface probe (pyrometer).
If the surface temperature is within the proper range, you can then utilize the temperature thermometer on the heater plate, as a reference check prior to inserting the heater plate for each fusion joint. If the reference thermometer temperature drops, the surface temperature should be re-checked. The generator may have run out of gas or a heating element/thermoswitch inside the heater plate may have been damaged (this requires heater repair).
In addition, remember to shield the heater from cold weather and wind by keeping it stored in the insulated sling or stand; when not being used to make a fusion joint.
Tip: Always follow company procedures and/or PE pipe manufacturer’s heating temperature requirements. It is very important that before each fusion joint is made, that the heater surfaces be wiped with a clean, non-synthetic cloth.