Bolt Electric Heating Rods
Bolt electric heating rods are specialized tools for the hot assembly and disassembly of large bolts in steam turbines, high-pressure vessels, flanges, etc. The core logic is to insert them into the central hole of the bolt and heat by electricity, using the principle of thermal expansion to loosen or tighten the bolt. The surface power density is strictly controlled at 8-11W/cm², and the working temperature can reach 400°C. They must be used with a DC adjustable control cabinet.
I. Core Selection Parameters
1. Size Matching — Must Fit the Bolt Center Hole Perfectly
Diameter: The diameter deviation of the insertion part must be controlled between -0.20mm and -0.50mm, and the total clearance with the bolt center hole should be maintained at 0.8-1.3mm. Excessive clearance will cause a sharp drop in heat conduction efficiency, while too small clearance will make insertion and removal difficult or even cause jamming.
Length: The heating section must cover the smooth shank of the bolt (avoiding threads and nuts), and the cold end at the bottom should be 25-30mm long; when the insertion length ≤1m, the straightness of the centerline should be ≤0.3mm, and when 1-2m, ≤0.4mm.
Structural Form: Divided into hard tube, flexible tube, and semi-flexible types. For working conditions with limited space or requiring bending during insertion, choose flexible tube/flexible cable heaters.
2. Electrical and Performance Indicators
Voltage: Rated 220V±20V, supports DC 100V or low voltage 50V, overvoltage use is strictly prohibited.
Power: Common single unit 1.5-6kW, customized according to bolt size, allowable deviation ±5%.
Insulation: Cold insulation resistance ≥50MΩ (DC500V), withstand voltage 1500-2000V/1min without breakdown, hot leakage current ≤0.5mA/kW.
Life: Intermittent heating (10-20min each time) cumulative ≥50h, high-end products continuous service life ≥5000 hours.
3. Material Requirements
Heating wire: 0Cr27A17Mo2 high-resistance heating alloy wire, working temperature 400°C.
Sheath: 1Cr18Ni9Ti heat-resistant stainless steel tube (310S stainless steel for high-end products), formed by one-way cold drawing and tube reduction, no cracks on the surface.
Insulation filling: High-purity magnesium oxide powder, must be dried before use.
II. Manufacturer Resources in Yangzhou and Surrounding Areas
Based on your location in Yangzhou, the following enterprises can be directly contacted:
Manufacturer Location Core Advantages Application Scenarios
Baoying County Hengtai Electrical Equipment Factory Yangzhou Baoying Bolt heating rods with aviation plugs, unit price about 80 yuan/piece, customizable Conventional steam turbine bolt hot assembly and disassembly
Yangzhou Huaneng Electric Heating Technology Yangzhou Baoying Mainly produces bolt heating rods, crawler heaters, thermocouples, integrated R&D, processing, sales, and maintenance Power station maintenance support
Zhenjiang Yunlong Electrical Equipment Zhenjiang Joint venture, ISO9000 certified, focuses on explosion-proof and air duct composite bolt heating systems, ExdⅡCT4 grade, built-in dual thermocouple redundant temperature measurement Petrochemical/explosion-proof occasions with multiple bolts synchronous constant temperature
Yangzhong Dongsheng Electric Power Equipment Yangzhong Product line covers air heaters, plate heat exchangers, etc., convenient for centralized procurement Power station auxiliary equipment support, high cost-performance
Yangzhong Changhe Electrical Equipment Factory Yangzhong 28 years of focus, segmented mica insulation structure, supports M24-M120 full series threaded interfaces, 0.5-level precision temperature control module, has supported Huaneng Yuhuan Power Plant 1000MW units Large power station maintenance
III. Pitfall Avoidance Reminders
No plugging or unplugging with power on: Power must be disconnected during loading and unloading, and the phase/neutral wires of the plug and cabinet socket must not be connected incorrectly.
No local overheating: The heating position is the smooth shank section of the screw, directly heating the thread and nut parts is strictly prohibited, and inserting a torch directly into the hole for static heating is strictly prohibited.
Must be equipped with a control cabinet: A DC adjustable control cabinet (output 0-220V adjustable) is required. When multiple units are connected in parallel, pay attention to three-phase load balance.
Don't just look at unit price: The life difference between an ordinary rod at 80 yuan/piece and high-end products can be more than a hundred times. Power plant maintenance schedules are tight, and the comprehensive cost of repeated replacement is far higher than choosing the right one at once.
Complete parameters required for ordering: Bolt outer diameter, total length, nut length, center hole diameter, matching control cabinet model, none can be omitted.
