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amitnagpal
Active Contributor

Join Date: Feb 2007
Location: Chandigarh, India
Posts: 20

Fire Tube Boilers

05/04/2007 2:45 AM

Somewhere i have read that:

Fracture of the protective magnetite layer due to cyclic stresses. Magnetite forms on the furnace

tubes and acts as a protective layer but it is brittle and subject to spalling under cyclic stresses.

Its fracture exposes unprotected surfaces to further corrosion.

But i dint get it. Please explain it in simple and clear way.

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aurizon
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#1

Re: Fire Tube Boilers

05/05/2007 7:49 AM

Many metals oxidize. If the oxide is larger in volume or discontinuous it tends to break away and expose fresh metal. An oxide that forms a hard continuous layer can protect the metal from further oxidation.

Once formed and at a steady state it can endure. Going from hot to cold and back can cause differential stresses that breaks bits off (spalling).

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