The steam turbine bolt electric heater should meet the following requirements: 1. The raw materials used for the electric heater should meet the following requirements: ① The composition of the insulating material magnesium oxide should comply with HG3-1294-80 "Magnesium Oxide"; ② Magnesium oxide must be dried before use; ③ The heating material used for the electric heater is 0Cr27A17Mo2 high resistance electric heating alloy wire, with an operating temperature of 400°C, technical requirements according to GB1234 "High Resistance Electric Heating Alloy"; ④ The protective tube material for the electric heater is 1Cr18Ni9Ti heat-resistant stainless steel tube. Technical requirements according to YB804 "Stainless and Acid-Resistant Seamless Steel Tube". Use of other materials shall be agreed upon between the manufacturer and the user; ⑤ The protective tube for the electric heater should be deburred internally, then cleaned with gasoline or kerosene, dried before use. 2. The finished electric heater should meet the following requirements: ① The rated working voltage of the electric heater is 220±20V. DC 100V, low voltage 50V; ② For insertion length within 1m, the straightness of the center line is not greater than φ0.3mm; for insertion length between 1-2m, the straightness of the center line is not greater than φ0.4mm; ③ The diameter deviation of the insertion part is -0.20mm/-0.50mm; ④ The length deviation of the insertion part is ±5mm, the heating length deviation is ±5mm, and the cold end length at the bottom is 25-30mm; ⑤ The electric heater should heat evenly during use, and local overheating is not allowed. (2) When performing life tests on the electric heater, each heating time is 10-20min. Under intermittent heating conditions, with the total gap between the bolt center hole and the outer diameter of the electric heater being 0.8-1.3mm, the cumulative life is not less than 50h. (3) The connection between the alloy resistance wire and the lead wire should be firm and reliable, without looseness. The shell must be properly grounded. (4) After cold drawing of the steel tube of the electric heater, inspect its surface with dye penetrant testing or a magnifying glass of 5x or more; there should be no cracks or other defects. The tube should be formed in one direction during drawing. (5) The seal at the cold end of the electric heater must be tight to prevent moisture ingress and insulation damage.
Note: The above information and technical parameters are compiled and released by Yangzhou Dali Electric Co., Ltd.
