On-site maintenance personnel often need to distinguish sheathed electric heating tubes from ordinary immersion heating tubes. Sheathed electric heating tubes place the heating element inside a metal sheath, transferring heat through heat transfer oil or a medium with good heat transfer performance, without direct contact with air. Ordinary immersion heating tubes directly contact the liquid being heated, with a higher surface load, and in heat transfer oil, localized overheating can easily cause oil carbonization. When selecting the FBY-45 model, the contact area between the sheath and the oil must be calculated to ensure the heat load per unit area does not exceed the allowable value for the oil.
The internal control system of this model automatically adjusts the output power based on the temperature sensor signal at the outlet, keeping the outlet medium temperature uniform. When the heating element overheats, an independent overheat protection device immediately cuts off the heating power, preventing coking, deterioration, or carbonization of the material due to overheating, reducing the possibility of burning out the heating element, and helping to extend service life. Daily inspections should confirm that the sensor signal is normal and the protection circuit has not been artificially short-circuited.
During on-site maintenance, the working voltage must be measured, with an allowable error not exceeding 1.1 times the rated value. The casing should be effectively grounded; if abnormal grounding resistance is found, the machine must be shut down for investigation. The FBY-45 model is suitable for heat transfer oil or oils and media with good heat transfer performance for internal heating, and is not recommended for media prone to scaling or with poor flowability. Compared with conventional heating tubes, the insulation resistance of the sheathed structure recovers more slowly after moisture exposure, so the junction box should be kept dry after shutdown.
When the heating tube shows decreased insulation or sheath deformation, it should be replaced as a whole, and local repair is not recommended. Spare parts selection requires checking the sheath material, diameter, unfolded length, and voltage and power. The FBY-45 model can be interchanged with some old models in installation dimensions, but the oil contact area must be reconfirmed for matching to avoid localized high oil temperatures caused by insufficient heat exchange area.
