Fire-Tube Boilers — Practical Pressure Limit Fire-tube boilers are generally limited to a maximum safe working pressure closest to which of the following values?

Introduction / Context:
Fire-tube boilers have relatively large water volumes and shells that constrain allowable pressure compared with modern water-tube designs. Knowing typical pressure limits helps in preliminary selection and safety compliance.

Given Data / Assumptions:

• Conventional shell-type fire-tube units.
• Normal materials and code stress limits.
• No exotic high-strength shells assumed.

Concept / Approach:
Common practice places the working pressure limit of fire-tube boilers around 1.7 MN/m2 (approximately 17 bar). Water-tube boilers can safely operate at much higher pressures because their smaller-diameter tubes and drum arrangements better resist hoop stresses and allow superior circulation control.

Step-by-Step Solution:
Convert understanding: 1.7 MN/m2 ≈ 17 bar.Compare alternatives: 0.17 MN/m2 (≈1.7 bar) is too low; 17 MN/m2 or 170 MN/m2 are unrealistically high for fire-tube shells.Select 1.7 MN/m2 as the practical limit.

Verification / Alternative check:
Historical code data and manufacturer catalogues list fire-tube boilers typically up to about 16–18 bar.

Why Other Options Are Wrong:
0.17 MN/m2: insufficient for most industrial service.17 MN/m2 and 170 MN/m2: beyond safe shell stresses for fire-tube construction.

Common Pitfalls:
Confusing absolute with gauge pressure; here the magnitude order guides the choice.

Final Answer:
1.7 MN/m2