Lancashire boiler — typical shell diameter range Choose the correct nominal range for the cylindrical shell diameter of a Lancashire boiler used in industry.

Introduction / Context:
Recognizing practical geometry ranges helps identify a boiler type on site and ensures correct proportions in sketches and design problems. Lancashire boilers are large shell, internally fired units with two furnace flues.

Given Data / Assumptions:

• Conventional Lancashire designs typically used for low-to-medium pressures.
• Shell with twin internal furnaces and multiple gas passes.

Concept / Approach:
Empirical design ranges from classic practice place the shell diameter of Lancashire boilers roughly in the neighborhood of 1.8 to 2.7 m, with shell lengths commonly about 7 to 9 m. Options closer to this span are more realistic for standard capacities and draught arrangements.

Step-by-Step Solution:

Verification / Alternative check:
Historic data tables and engineering handbooks list shell diameters in this ballpark for typical Lancashire installations.

Why Other Options Are Wrong:

• 1–2 m or 1.25–2.25 m: undersized for two internal furnaces plus adequate water volume.
• 1.5–2.5 m: lower bound too small for many standard units.
• 2.5–4.0 m: upper bound unusually large for classic Lancashire design.

Common Pitfalls:
Confusing Lancashire with Cornish proportions; forgetting allowance for water space, stays, and tube clearance.

Final Answer: