Induction Furnace Coil Maintenance: Proven Insulation Techniques for Longer Life
Understanding the System
An Induction Melting Furnace is primarily a static system — it has no moving parts except for the water circulation pump.
A common misconception is that only moving parts require maintenance. However, this is not true for the induction coil.
The induction coil is the most active and critical component of the furnace and must withstand several demanding operating conditions:
- High temperature from molten metal, which transfers heat to the coil through the ramming mass.
- High current, causing electrical losses that increase the temperature of the copper tube.
- High voltage, which may cause leakage currents to ground or to other live potentials.
- Rapid heat transfer from copper tube to cooling water.
- Mechanical stress due to lining expansion and contraction.
- Vibration generated by the large current flow.
Because of these challenges, regular coil insulation maintenance is essential for reliable operation and long service life.
Procedure for Coil Insulation
1. Preparation
- Disconnect all hose connections and drain the water from the coil.
- Remove the coil supports, spacers, and old insulation materials.
2. Cleaning and Heating
- Place the coil in an oven at 400°C for 2 hours.
This process burns off old insulating paint, oil residues, and internal scaling inside the copper tubes.. - Clean the copper surface thoroughly — sandblasting is preferred.
If not available, use emery paper to clean the surface manually.
3. Alignment Check
Inspect the coil for the following parameters:
- The coil diameter must be uniform at both the top and bottom.
- The coil must be perfectly round (check for ovality).
- All supports must be perpendicular to the coil base.
- The gap between turns must be consistent throughout.
If any irregularities are found, rewind the coil on a sturdy former to correct alignment and maintain proper shape.
4. Water Flow & Pressure Tests
- Conduct a water flow test. Flow should meet the OEM specifications.
If flow is insufficient, descale the coil using descaling chemicals or mild acid. - Conduct a pressure test at 15 bar for 1 hour.
Ensure there is no leakage; if necessary, perform brazing repairs.
Once these tests are successful, the coil is ready for insulation work.
5. Coil Insulation Process
- Use Flexocoat Epoxy, a two-component, flexible, epoxy-based insulating coating.
- Stir the base and hardener separately to homogenize any settled particles.
- Mix them properly before use. For spray applications, add a suitable thinner.
Application Guidelines:
- Apply 4 to 5 coats to achieve a total thickness of 0.5–1.0 mm.
- Each coat must cure completely before applying the next.
- To speed up curing, circulate hot water (60–80°C) inside the coil for 30–40 minutes between coats.
- Ensure every surface is fully coated to prevent electrical sparking or short circuits.
- A film thickness of 0.4 mm provides insulation resistance of at least 5 kV.
- Prepare only the quantity that can be used within the pot life specified.
6. Wrapping and Assembly
- Wrap 0.5 mm thick silicone rubber tape around the coil turns.
- For large furnaces: wrap all turns.
- For smaller furnaces: wrap the top two and bottom two turns.
This helps reduce turn-to-turn leakage current.
- Wrap 10 mil glass fiber tape or glass-mica tape over all coil turns.
- Reinstall coil supports and ensure the coil is perpendicular to the base.
- Insert spacers between turns (every 150 mm) — FRP, mica, or syndanio can be used.
You may also add 3 mm fiberglass tape along with spacers to maintain uniform gaps. - Tighten all support bolts two or three times to complete final assembly.
- Cover all nuts and bolts using a flexible sealant such as Techseal or silicone sealant.
7. Final Protection Coat
Apply a Bisphenol resin coat to protect against moisture.
This is a four-part system consisting of:
- Base
- Catalyst
- Cobalt
- Promoter
Mixing ratio:.
Allow 1–2 hours for complete curing.
Apply 1–2 layers over the coil turns and supports for optimal protection.
Result
- Longer coil life
- Reduced leakage current
- Better thermal stability
- Improved electrical insulation
- Safe and efficient furnace operation
Keep Your Furnace Running at Peak Performance — Contact Us Today
At Electro Power Enterprise, we provide high-quality induction furnace spare parts and expert coil maintenance solutions designed for uninterrupted performance. From reliable spare parts and precision coil repairs to durable insulation materials, our team ensures lasting efficiency and dependability.
Call +91 76003 43075/ Email – info@electropowerenterprise.in to get genuine parts and trusted technical support from India’s leading Induction Furnace Spare Parts Supplier — your long-term partner in furnace reliability and performance.
Also Read: Dissecting the Induction Furnace: A Deeper Look at Induction Furnace Spare Parts
Rajesh Baraiya, Founder of Electro Power Enterprise, is passionate about making induction furnaces run more efficiently and last longer. Backed by three decades of hands-on experience, He provides practical insights into Induction furnace spare parts, enabling industries to achieve higher efficiency and longer furnace life.