1. Bolt Heater / Expanding Cartridge Heater for Turbines
Hongtai Bolt Heaters are specialized, high-power thermal tools used specifically for the assembly and disassembly of large hollow bolts on steam turbines, pressure vessels, and heavy machinery. During maintenance shutdowns, these heaters are inserted into the hollow stud to rapidly expand the bolt thermally, allowing the nut to be tightened or loosened without damaging the threads.
Our Turbine bolt heating elements feature a high watt density design to deliver intense heat quickly. We offer both rigid and Flexible cartridge heater designs (using a segmented ceramic core) to allow insertion into bolts where overhead clearance is limited.
2. Key Technical Features
-
Extreme Watt Density: Designed to run at 30-50 W/cm² for short bursts to expand steel rapidly.
-
Flexible Design: Segmented ceramic construction allows the long heater to bend slightly, enabling installation in cramped power plant environments.
-
Expanding Diameter: (Optional) Some models are designed to expand when heated to maximize contact with the bolt wall.
-
Handle & Plug: Comes with an insulated handle for safe removal while hot and heavy-duty industrial plugs.
-
Custom Lengths: Manufactured to match the specific bolt depth, from 300mm up to 3000mm.
3. Technical Specifications
| Parameter | Standard Specification |
| Diameter | 11mm to 50mm (Custom to fit bolt bore) |
| Length | 300mm – 3000mm |
| Voltage | 110V, 220V, DC |
| Watt Density | High (Up to 50 W/cm²) |
| Sheath Material | High-Temp Stainless Steel / Incoloy |
| Core | High-Grade Ceramic |
| Termination | Insulated Handle + Heavy Duty Plug |
| Duty Cycle | Intermittent (Maintenance Use Only) |
4. How It Works (Thermal Expansion)
-
Insertion: The Bolt heater is inserted into the hollow center of the stud.
-
Activation: High power is applied for 5-15 minutes.
-
Expansion: The heat transfers to the bolt, causing it to elongate (stretch) due to thermal expansion.
-
Action: The nut is tightened (for assembly) or loosened (for disassembly) while the bolt is stretched.
-
Cooling: Once the heater is removed and the bolt cools, it contracts, creating the massive clamping force required for turbine casings.
5. Safety & Handling
These heaters are designed for intermittent use only.
-
Fit is Critical: The heater diameter must be close to the bolt hole diameter (clearance <1mm) to prevent heater failure.
-
Don’t Run in Air: Never power on a bolt heater in free air; it will melt instantly due to the extreme watt density. It must be inside the metal bolt to dissipate heat.
6. FAQ
Q: What information is needed for a quote?
A: We need: 1. The diameter of the hole in the bolt; 2. The depth of the hole; 3. The voltage available on-site; 4. The desired heated length.
Q: Can you make flexible heaters for restricted headroom?
A: Yes. Our flexible cartridge heater design uses articulated ceramic beads, allowing the long heater to be fed into the bolt hole even if there is a pipe or wall directly above the turbine casing.
Q: Do you supply the control box?
A: We can supply the heater with a matching plug. We also offer portable temperature control panels for managing multiple bolt heaters simultaneously during shutdowns.
Need urgent turbine maintenance tools?
Contact Our Engineering Team for rapid manufacturing of custom bolt heaters. We understand the cost of power plant downtime.
