Yoyik develops and manufactures specialized AC/DC Bolt Heaters for steam turbine units. These industrial heating elements provide controlled thermal expansion to facilitate the tightening or removal of large turbine bolts during plant maintenance.
Technical Parameters
| Parameter | Range / Specification |
|---|---|
| Casing Type | Hard (rigid) / Flexible (soft) |
| Diameter (φ) | 9 mm – 42 mm |
| Total Length (L1) | 200 mm – 1800 mm |
| Heating Part Length (N) | Customized per bolt depth |
| Cold Part Length (M) | Engineered transition zone |
| Rated Voltage | 220V, 110V, 50V (AC / DC) |
| Power Rating | 0.3 kW – 18 kW |
| Sheath Material | 1Cr18Ni9Ti stainless steel |
| Heating Wire Material | 0Cr27AlMo (high‑temperature alloy) |
| Insulation Filler | Crystalline magnesium oxide (MgO) |
| Lead Wire Type | High‑temperature insulated, flexible |
Product Structure & Components
Construction: Heating element compressed with magnesium oxide powder for high dielectric strength and efficient heat transfer.
Installation & Usage Flow
- Pre‑check: Inspect heater for damage, measure insulation resistance (>50 MΩ). Clean bolt bore from debris/moisture.
- Insert heater: Gently insert into bolt central hole. Ensure heating section aligns with bolt threaded zone.
- Electrical connection: Connect leads to matched AC/DC supply. Use proper grounding and temperature controller if required.
- Heating operation: Set power / target temperature. Monitor heating curve to avoid overshoot.
- Power off & stabilize: After required expansion, switch off heater. Allow 1–2 minutes for temperature equalization.
- Remove & store: Extract heater carefully, clean surface, store in dry non‑corrosive environment.
Important: Never energize the bolt heater outside the bolt bore. Always follow turbine maintenance heat schedule.
Safety Warnings & Precautions
- Electrical isolation: Disconnect power before inserting or removing heater. Ensure proper grounding and use RCD protection.
- High temperature hazard: Sheath reaches high temperature during operation. Do not touch without protective equipment; allow cooling before handling.
- No dry energizing: Operating heater in free air causes immediate overheating and failure.
- Insulation check: Perform insulation resistance test before each use. Do not use if reading <1 MΩ (indicates moisture or damage).
- Mechanical integrity: Avoid hitting, bending cold end or scratching sheath. Replace deformed heaters.
- Environment & storage: Keep in ventilated, dry warehouse. Protect from moisture, corrosive vapors.
Common Faults & Troubleshooting
| Fault / Symptom | Possible Cause | Remedy |
|---|---|---|
| No heating | Power failure, broken wire, loose lead connection | Check supply voltage, test continuity. Replace element if open circuit. |
| Slow heating / low temperature | Undervoltage, internal short or worn heater | Measure voltage and current; compare with rated values. Replace if resistance deviates >10%. |
| Low insulation resistance (<5 MΩ) | Moisture ingress, cracked MgO insulation | Dry heater at 150–200°C for 2–4h. If still low, replace heater. |
| Local overheating / sheath discoloration | Heating part partially exposed, excessive power density | Ensure full insertion in bolt bore; use recommended power. Replace damaged heater. |
| Mechanical damage or bending | Impact or incorrect insertion/extraction | Do not use deformed heater. Order replacement with correct dimensions. |
Packaging & Storage
Store in original packaging in a well‑ventilated warehouse at -20°C to +40°C, relative humidity below 80%. Avoid stacking heavy items.
YOYIK Bolt Heater series — Designed for steam turbine, gas turbine, and heavy rotary machinery. AC/DC flexibility supports standard workshop power or portable generators.
