Where are refractories never used in construction? Select the application in which refractory materials are not a construction choice.

Introduction / Context:
Refractory materials are ceramic products designed to withstand high temperatures, thermal cycling, and corrosive atmospheres. They form the linings of furnaces, kilns, ovens, and thermal test devices. This question asks you to identify an application where refractories are not used as construction materials.

Given Data / Assumptions:

• Seger/Orton cones are pyrometric devices made from ceramic compositions (i.e., refractories).
• Ovens and retorts operate at elevated temperatures and therefore require refractory linings.
• Pressure vessels are designed primarily for mechanical strength and pressure containment, typically using metals or composites; refractories may line hot zones but do not serve as pressure-bearing construction.

Concept / Approach:
Distinguish between thermal linings versus structural, pressure-retaining shells. Refractories are excellent for thermal and chemical resistance but have low tensile strength and poor shock resistance in tension; hence, they are unsuitable as primary pressure-retaining structures. Metals with well-characterised stress-strain behaviour and fracture toughness are used for pressure vessels, sometimes with an internal refractory or insulation layer for thermal management.

Step-by-Step Solution:
Identify refractories’ roles: thermal containment and chemical resistance.Recognise that pressure vessels require ductile, high-strength materials.Therefore, refractories are never used as the construction of a pressure vessel shell.

Verification / Alternative check:
Design codes for pressure vessels (e.g., boiler and pressure vessel standards) specify metallic or composite shells; any refractory present serves only as lining or insulation.

Why Other Options Are Wrong/Right:
Seger/Orton cones and ovens/retorts are legitimate refractory applications (cones are ceramic; ovens/retorts require refractory linings).

Common Pitfalls:
Confusing “used in construction” of the pressure shell with “used as an internal lining” — the shell is never refractory.

Final Answer:
Pressure vessels