Stoneware (vitrified clay) sewers: Identify the correct statements about uses, manufacture, firing, and glazing treatments applied during production.
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AUsed for carrying domestic sewage and house drainage connections
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BManufactured from selected clays and shales for vitrified strength
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CAfter forming, units are dried and then fired through staged temperatures (about 150°C, 700°C, and up to around 1200°C)
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DOften provided with a waterproof glazed surface by salt glazing (vaporised sodium chloride) during firing
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EAll the above
Answer
Correct Answer: All the above
Explanation
Introduction / Context:Stoneware (vitrified clay) pipes are widely used for small-diameter gravity sewers because of their chemical resistance, smooth glazed interior, and longevity when properly installed and bedded.
Given Data / Assumptions:
- Small to medium house connections and laterals in sanitary sewers.
- Pipe manufacturing includes forming, drying, firing, and glazing steps.
- Glazing improves hydraulic smoothness and reduces infiltration/exfiltration risks.
Concept / Approach:
Selected clays/shales are formed into pipe shapes, dried to remove free moisture, and fired to achieve vitrification. Salt glazing (introducing sodium chloride into the kiln atmosphere) creates a hard, glossy, impervious finish. These properties make stoneware well-suited to house drainage where corrosion resistance to domestic sewage is essential.
Step-by-Step Solution:
Form the pipe (extrusion or molding) to required size with socket/spigot ends.Dry at low temperatures (~150°C) to remove moisture and avoid cracking.Fire through intermediate (~700°C) to high temperatures (approaching ~1200°C) for vitrification.Apply salt glazing to achieve a durable, impermeable surface as required.Verification / Alternative check:
Quality control includes dimensional checks, ring crush tests, absorption limits, and hydrostatic leak tests to verify vitrification and glazing integrity.
Why Other Options Are Wrong:
Options (a) through (d) are accurate descriptors; therefore the comprehensive correct choice is “All the above”.
Common Pitfalls:
Improper bedding and backfilling causing cracking; using inappropriate jointing materials; ignoring differential settlement at house connections.
Final Answer:
All the above