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    Case study · Retrofit

    Revamping of Aluminium holding furnace

    An aluminium holding furnace where every crucible failure took the SS310 heating elements down with it, for 15 days at a time. We rebuilt it with a Fibrothal heating system and Kanthal AF elements at line voltage, and a crucible problem now costs about 2 days.

    Furnace:
    Aluminium holding furnace
    The furnace's new Fibrothal heating system, wire elements set into the hot face around the crucible pit

    Results

    What the project delivered.

    To recover from a crucible failure
    15 → 2 days
    Charge capacity
    300 kg/h
    Connected power
    36 kW
    Recommended crucible change interval
    6 months

    With the old SS310 heating elements, a crucible failure took the heating system down with it, and getting the furnace back took 15 days. Now, when the crucible gives trouble, the furnace is back in about 2 days.

    The heating elements were designed for line voltage, taking out the power transformer and its losses, and the conventional heating system was replaced with an energy-efficient Fibrothal heating system with Kanthal AF elements, under thyristor control.

    Overview

    The project.

    Case study · Retrofit

    What we did

    The furnace holds molten aluminium in a ceramic crucible, heated by SS310 elements. The crucible failed often, and each failure took the heating elements with it: 15 days before the furnace could run again.

    We retrofitted the furnace with a Fibrothal heating system with Kanthal AF wire elements, designed to run at line voltage so the power transformer could go, and a thyristor panel to control it.

    Planning around the crucible

    A crucible is a consumable. We recommend changing it every 6 months, on a schedule, rather than waiting for it to fail. If it does give trouble, the furnace is now back in about 2 days.

    • CustomerAutomotive components manufacturer
    • EquipmentAluminium holding furnace (crucible type)
    • Charge capacity300 kg/h
    • Connected power36 kW
    • CrucibleCeramic
    • Old heating elementsSS310
    • Heating systemFibrothal with Kanthal AF elements, designed for line voltage
    • ControlThyristor panel
    • Crucible changeRecommended every 6 months

    Scope of work

    How it was done.

    1. 01

      The furnace as found

      SS310 heating elements lining the crucible pit, fed through a power transformer. When the crucible failed, it took these elements with it.

      The old SS310 heating elements lining the crucible pit
      Before
      The old heating element assembly, taken out of the furnace
      Removed
    2. 02

      Stripped to the shell

      The old lining and elements were removed and the furnace shell prepared for the new heating system.

      The crucible pit stripped of its old lining
      Stripped
      The furnace shell cleaned and prepared for relining
      Shell
    3. 03

      Fibrothal heating system

      Fibrothal modules, with Kanthal AF wire elements set into the hot face, line the pit. The elements were designed for line voltage, so no transformer is needed.

      The furnace's new Fibrothal heating system, wire elements set into the hot face around the crucible pit
      Fibrothal
      Fibrothal elements seen from the top of the pit, with back-up insulation around them
      Elements
    4. 04

      Insulation and terminals

      Back-up insulation was built up around the hot face, and the element terminals brought out to boxes on the shell.

      Back-up insulation rings around the top of the new heating system
      Insulation
      Element terminal boxes on the outside of the furnace shell
      Terminals
    5. 05

      Crucible in place

      The crucible was lowered into the new heating system and seated.

      The crucible lowered into the furnace by crane
      Crucible
      The crucible being seated inside the heating system
      Fitting
    6. 06

      Thyristor control

      A thyristor panel with temperature controllers runs the heating, with the elements wired straight to line voltage.

      Thyristor control panel with temperature controllers and meters
      Control
      Inside the thyristor panel: breakers, busbars and the thyristor power controller
      Panel
    7. 07

      Back in production

      The furnace running on the shop floor after the revamp.

      Video

    Outcome

    What the new heating system brings.

    2 days instead of 15

    A crucible problem no longer means two weeks without the furnace.

    No transformer losses

    Line-voltage elements remove the transformer's copper, hysteresis and eddy-current losses, about 2.5–3%.

    Less to maintain

    No transformer oil filtration, dielectric or acidity tests, or capacitor-bank checks.

    A lining that keeps its shape

    Fibrothal shrinks under 1% (against more than 2.4% for ceramic fibre modules) and doesn't recrystallise or sag.

    Thyristor control

    Solid-state power control with temperature controllers on the panel.

    A planned crucible change

    Changing the crucible every 6 months keeps it from failing in service.

    How does Fibrothal compare with brick and ceramic fibre?

    Weight, life, curing time, downtime and more, side by side, plus why ROB elements outperform strip elements.

    Why FibrothalWhy ROB elements
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