A Two-Piece Design Fusible Plug is a critical safety device used in steam boilers to prevent accidents caused by overheating of the boiler shell or crown plate due to low water levels. It consists of a gunmetal or brass body with a fusible alloy (generally tin, lead, or bismuth-based) inserted into the core. This alloy is designed to melt at a predetermined temperature (usually between 425°C – 450°C) when water level falls below the safe limit, thereby allowing steam or water to escape and warning operators of unsafe conditions.
The two-piece construction ensures better ease of maintenance and replacement of the fusible metal without changing the complete body. It provides reliable performance, durability, and long service life under continuous boiler operations.
Technical Highlights
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Design Type: Two-Piece Construction – body and fusible plug core designed separately for ease of maintenance.
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Material: High-quality gunmetal, brass, or bronze body with fusible alloy insert.
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Application: Installed at the crown plate or firebox top of the boiler.
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Operating Principle:
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Fusible alloy melts when the boiler crown plate is exposed to direct flame due to insufficient water level.
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This creates an opening, releasing steam and water into the furnace.
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Immediate audible and visible warning is given, ensuring boiler shutdown to prevent explosion.
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Melting Point Range: 425°C – 450°C (adjustable as per boiler design).
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Threading Standard: BSP / NPT threads for easy installation.
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Safety Compliance: Conforms to IBR 1950 (Indian Boiler Regulations) and other international boiler safety codes.
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Service Life: Long-lasting design, replaceable fusible element.
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Maintenance Advantage: Only the fusible core needs replacement, reducing downtime and cost.
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Sizes Available: ½” to 2” NB (as per boiler rating and design).
