In pressure vessel design, openings (nozzles, manholes, sight glasses) require reinforcement for strength and rigidity. Which type of compensation is considered the most efficient for such openings?

Introduction / Context:
When a hole is cut in a pressure vessel shell to attach a nozzle, manhole, or sight glass, shell strength is reduced locally. Designers therefore provide 'compensation' or reinforcement to restore the lost metal area so that stresses remain within code limits. Knowing which reinforcement method is most efficient is important for safe and economical fabrication.

Given Data / Assumptions:

• Thin cylindrical or spherical shells under internal pressure.
• Openings require added reinforcement to meet applicable codes (e.g., area replacement concepts).
• Efficiency refers to stress distribution quality and reinforcement effectiveness per unit added metal.

Concept / Approach:
The most efficient reinforcement uses the nozzle neck and adjacent shell as an integral reinforced region (often termed nozzle, hub, or rim type). By thickening the nozzle neck and blending it into the shell, the added metal lies exactly where stresses concentrate, providing superior load transfer compared with external pads or rings.

Step-by-Step Solution:
Identify reinforcement methods: (i) integral nozzle/rim, (ii) pad/ring plate, (iii) flared-out lip, (iv) non-structural attachments.Recognize efficiency metric: restore area and control peak stresses with minimal added weight.Integral nozzle (nozzle or rim) places material in the highest-stress zone and promotes smooth stress flow.Therefore, the nozzle or rim type is the most efficient.

Verification / Alternative check:
Codes allow area-replacement using nozzle wall thickness plus a portion of the shell. Experience and analyses show self-reinforced nozzles deliver better stress contours and fatigue resistance than external pads.

Why Other Options Are Wrong:
Flared out: difficult to fabricate and may not provide optimal stress flow.Fluid in: not a reinforcement method.Ring plate: workable but less efficient than integral reinforcement; can introduce local stress discontinuities.

Common Pitfalls:
Assuming thicker pads are always better; ignoring nozzle–shell junction stress concentration; overlooking fatigue and cyclic loads.

Final Answer:
nozzle or rim