Professional production of steam turbine bolt heating rod
(1) The steam turbine bolt electric heater shall meet the following requirements:
1. The raw materials used for the electric heater shall meet the following requirements:
① The composition of the insulating material magnesium oxide shall comply with the provisions of HG3-1294-80 "Magnesium Oxide";
② Magnesium oxide must be dried before use;
③ The heating material used in the electric heater is 0Cr27A17Mo2 high-resistance electric heating alloy wire, with an operating temperature of 400°C, and technical requirements according to GB1234 "High-Resistance Electric Heating Alloy";
④ The protective tube material of the electric heater is 1Cr18Ni9Ti heat-resistant stainless steel tube. Its technical requirements shall comply with YB804 "Stainless and Acid-Resistant Seamless Steel Tubes". Use of other materials shall be agreed upon between the manufacturer and the user;
⑤ The inside of the protective tube for the electric heater shall be deburred, then cleaned with gasoline or kerosene, and dried before use.
2. The finished electric heater shall 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 centerline shall not exceed Ø0.3mm; for insertion length between 1-2m, the straightness of the centerline shall not exceed Ø0.4mm;
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 shall heat evenly during use, and local overheating is not allowed.
(2) When conducting 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 shall be no less than 50h.
(3) The connection between the alloy resistance wire and the lead wire shall be firm and reliable, without looseness. The shell must be properly grounded.
(4) After cold drawing of the steel tube of the electric heater, the surface shall be inspected by dye penetrant testing or with a magnifying glass of 5x or more, and there shall be no defects such as cracks. The tube shall be formed in one direction during drawing.
(5) The cold end seal of the electric heater shall be tightly sealed to prevent moisture from entering and damaging the insulation.
(6) After the electric heater is manufactured, after one and a half months, its insulation resistance shall be measured at room temperature with a 500V megohmmeter (can be performed at the manufacturer or user site) and shall not be less than 50MΩ.
