Heads for process vessels: the usual apex (included) angle selected for conical bottom heads is most commonly which of the following?

Introduction / Context:
Conical heads are widely used at the bottoms of reactors, crystallizers, and storage vessels to aid drainage and solids removal. The “apex angle” (included cone angle) affects headroom, holdup, and the ability to avoid solids buildup. Industry practice gravitates to certain standard angles for fabrication convenience and process performance.

Given Data / Assumptions:

• Typical chemical-process vessels handling liquids or slurries.
• Trade-off between steep cones (better drain) and shallow cones (less height).
• Common plate fabrication and forming constraints apply.

Concept / Approach:
An apex angle near 60° is common because it offers good drainage while keeping vessel height manageable. Steeper cones (smaller angles) may be used for heavy slurries or self-draining requirements, but 60° remains a widely adopted “default” in many industries and standards unless special needs dictate otherwise.

Step-by-Step Reasoning:

Verification / Alternative check:
Vendor catalogs and mechanical design guides often list 60° cones as standard offerings, with other angles available on request.

Why Other Options Are Wrong:

• 30° or 45° may be used for special cases but are not the most common default.
• 75° and 90° become too shallow, increasing holdup and risking poor drainage.

Common Pitfalls:
Ignoring solids-handling: even at 60°, internals and outlets must avoid dead zones; neglecting headroom and nozzle clearances when selecting the cone angle.

Final Answer:
60°