When replacing connecting bolts for steam turbine cylinders, flanges, or large equipment on site, difficulties are often encountered in inserting the heating rod or the heating section not being fully in place. Selecting a bolt electric heating rod with a diameter and length matching the actual size of the bolt center hole is the prerequisite for ensuring uniform heating and safe operation.
Before inserting the heating rod into the bolt center hole, oil stains and burrs inside the hole should be cleaned. For center holes with good straightness, a rigid straight rod can be used; maintain coaxiality during insertion to avoid damage to the tube wall caused by forced pushing. After confirming that the heating section is fully inside the bolt, connect the DC adjustable control cabinet.
Set the voltage and heating time according to process requirements. During heating, observe the current indication on the control cabinet. When the temperature of all three-phase windings drops to the set fan stop temperature, the fan automatically shuts off and the fan indicator light goes out. This process is commonly used for preheating before bolt tightening or removal.
After heating is completed, disconnect the power first, then remove the heating rod, and subsequently perform bolt tightening or removal. If the ambient temperature is low or the bolt specification is large, the holding time can be appropriately extended, but it should not exceed the allowable working temperature range of the heating rod.
