- 2068 Baisakh (old course) · 4+4 marks
Pipe material factors; CI vs steel
Short answer
Factors include pressure, corrosion, friction, cost, weight, jointing ease, availability, and life. CI: strong in compression, brittle, long life, corrosion-resistant, heavy, socket joints. Steel: strong in tension, ductile, needs coating against rust, lighter, welded joints, cheaper in large diameters.
Describe the factors that should be considered while selecting pipe materials for water supply schemes. Give comparative merits and demerits of cast iron and steel pipes.
Factors for selecting pipe materials
| Factor | Consideration |
|---|---|
| Pressure | Working and surge pressure decide strength and class |
| Corrosion | Soil and water quality; need for lining or coating |
| Friction | Smooth interior gives a smaller pipe size |
| Cost | Material, transport, laying and repair; life-cycle cost |
| Weight and handling | Affects labour and transport in hills |
| Jointing | Ease and reliability of the joint |
| Availability | Local supply of pipes and fittings |
| Life and maintenance | Durability, ease of repair and tapping |
Cast iron versus steel pipes
| Point | Cast iron | Steel |
|---|---|---|
| Strength | Strong in compression, weak in tension and impact; brittle | Strong in tension, ductile; high pressure and shock |
| Corrosion | Resists corrosion better; life 100+ years | Rusts quickly if unprotected; needs paint, coal-tar or cement lining; life 25–50 years |
| Weight | Heavy | Lighter for the same pressure (thin wall) |
| Diameter available | Up to about 1000 mm | Large diameters (above 2 m possible) |
| Joints | Socket-spigot, flanged; easy | Welded, riveted, flanged; welding needs skill but gives a continuous line |
| Cost | Costly | Cheaper in large diameters |
| Repair | Easy to cut and drill; breaks by hammer | Easily cut and welded; flexible against ground movement |
| Uses | Distribution mains | Transmission mains under high head, river crossings, exposed lines |
✓ Answer checked by Claude Opus 5.5 (high effort)
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