Heating tube and heating rod
Large bolt electric heater for steam turbine maintenance, oil tank heater, explosion-proof oil tank electric heater
(I) 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 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 for the electric heater is 0Cr27A17Mo2 high-resistance electric heating alloy wire, with a working 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 are according to YB804 "Stainless and Acid-Resistant Seamless Steel Tube" provisions. Use of other materials shall be agreed upon between the manufacturer and the user;
⑤ The protective tube for the electric heater shall be deburred internally, then cleaned with gasoline or kerosene, 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. (II) 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 not be less than 50h. (III) The connection between the alloy resistance wire and the lead wire shall be firm and reliable, without looseness. The shell must be well grounded.
(IV) Electric heater steel tube after cold drawing, shall be inspected by dye penetrant testing or with a magnifying glass of 5x or more for surface defects such as cracks. The drawing shall be unidirectional.
(V) The cold end seal of the electric heater shall be tightly sealed to prevent moisture from entering, which could damage insulation.
(VI) After the electric heater is manufactured, after one and a half months, at room temperature, measure its insulation resistance with a 500V megohmmeter (can be done at the manufacturer or user site) and it shall not be less than 50MΩ. III. Test Methods and Acceptance Rules After assembly, each electric heater shall have its insulation resistance measured at room temperature with a 500V megohmmeter, which shall not be less than 50MΩ. It shall also withstand a 1500V dielectric strength test for 1 minute without breakdown or flashover. Then, in air, under rated working voltage, it shall be energized and heated for 2-3 minutes without overheating, and the insulation resistance shall not be less than 0.5MΩ, and the leakage current shall not exceed 0.5mA per kilowatt. Its power shall also be checked to see if it meets the order requirements (deviation ±5%). After the test, check whether all parts of the electric heater are intact.
