For high-pressure process equipment and pressure vessels, which type of nozzle connection is generally preferred for integrity and leak tightness?

Introduction / Context:
Nozzle connections provide attachment points for piping, instruments, and relief devices on pressure vessels. At high pressure, joint integrity, resistance to leakage, and structural robustness are paramount. Choosing the proper connection type is essential to meet code requirements and ensure reliable operation.

Given Data / Assumptions:

• “High pressure” implies conditions where threaded or brazed joints are unsuitable due to stress and leak risk.
• Industry codes (e.g., pressure vessel codes) emphasize welded construction for primary pressure boundaries.

Concept / Approach:
Welded nozzles create a continuous metal-to-metal pressure boundary with full structural continuity. They minimize potential leak paths and handle cyclic loads better than mechanical joints. Screwed and brazed joints are limited by pressure ratings and creep/leakage risk. Flanged joints, while common, introduce gasketed interfaces and multiple potential leak paths—acceptable for many services but not favored for very high pressure unless unavoidable.

Step-by-Step Solution:

Verification / Alternative check:
Review of high-pressure vessel designs shows predominance of integrally reinforced welded nozzles with full-penetration welds, stress-relief where required, and NDE verification to code.

Why Other Options Are Wrong:

• Screwed: limited pressure ratings; thread leakage and galling risks.
• Flanged: gasketed joint introduces leak path; used but not preferred when highest integrity is needed.
• Brazed: not appropriate for high pressure due to metallurgical and strength limitations.

Common Pitfalls:
Assuming flanged joints are always acceptable at high pressure without considering gasket load and bolt stress; overlooking thermal and cyclic loads on nozzle connections.

Final Answer:
Welded