In the steam turbine bolt electric heater standard approved by the Ministry of Machinery and Electronics Industry in 1988, clear provisions were made for the raw materials used in electric heaters: the insulating material magnesium oxide shall comply with HG3-1294-80 "Magnesium Oxide" and must be dried before use; the heating material adopts 0Cr27A17Mo2 high-resistance electric heating alloy wire, with a working temperature of 400°C; the protective sleeve material is 1Cr18Ni9Ti heat-resistant stainless steel tube. These basic parameters are the starting point for evaluating whether the BRJ-12 bolt electric heating rod is suitable for specific working conditions.
Selection Logic for Core Materials of Heating Rods
When checking BRJ-12 bolt electric heating rods, procurement personnel should first pay attention to the heating wire and sleeve materials. The 0Cr27A17Mo2 high-resistance electric heating alloy wire has stable resistance characteristics at a working temperature of 400°C, making it suitable for the continuous power-on conditions required for bolt heating. The 1Cr18Ni9Ti heat-resistant stainless steel tube, as a protective sleeve, has oxidation resistance and corrosion resistance at high temperatures. The drying treatment of magnesium oxide insulating material directly affects insulation resistance; magnesium oxide that has not been fully dried may experience reduced insulation due to moisture after being energized. Therefore, requiring suppliers to provide material compliance certificates is more practically meaningful than simply comparing prices.
Lead-out Methods and Temperature Control Selection for Bolts Above M36
For bolts of M36 and above, BRJ-12 bolt electric heating rods can use double-end lead-out or models with K-type thermocouples. The double-end lead-out structure helps achieve more uniform power distribution on long heating rods and reduces the operational difficulty of single-end wiring when installation space is limited. Models with K-type thermocouples support closed-loop temperature regulation, controlling the bolt heating temperature within the set range and avoiding overheating that affects bolt material performance. In procurement decisions, if the heating process has high requirements for temperature consistency, priority should be given to models with thermocouples, and it should be confirmed that the temperature control instrument matches the thermocouple graduation.
Procurement Checklist and Common Oversights
Before placing an order, it is recommended to check the following items: whether the heating rod diameter matches the clearance of the bolt center hole; whether the rated voltage is consistent with the on-site power supply conditions; whether the lead wire length meets the wiring space; and whether a matching temperature control cabinet is needed. Common oversights include ignoring the tolerance fit between the actual bolt hole size and the heating rod outer diameter, and failing to specify the thermocouple lead wire length, which causes wiring difficulties on site. For bulk procurement, suppliers can be asked to provide cold-state resistance sampling data for the same batch of heating rods as a reference for consistency.
