For a large high-pressure pipeline, which stress consideration chiefly determines the minimum wall thickness during design?

Introduction / Context:
Pressure piping is sized primarily to resist circumferential (hoop) stress from internal pressure. Correctly identifying the governing stress ensures that required wall thicknesses meet code and safety margins for burst and leak integrity under operating and test conditions.

Given Data / Assumptions:

• Long straight run of large-diameter pipe at high internal pressure.
• Design per standard pressure piping codes with joint efficiency and corrosion allowance considered separately.
• No unusual external loads beyond typical supports.

Concept / Approach:
For thin-walled cylinders, internal pressure produces hoop stress σh = p * D / (2 * t) and longitudinal stress σL = p * D / (4 * t). Since σh is twice σL, hoop stress generally governs minimum wall thickness. Codes incorporate allowable stress, weld efficiency, and allowances, but the primary driver remains hoop stress.

Step-by-Step Solution:
Write hoop stress relation: σh = p * D / (2 * t).Rearrange for thickness: t = p * D / (2 * σ_allow * E) with code factors.Confirm longitudinal stress is lower, thus non-controlling for straight runs.

Verification / Alternative check:
Code formulas (e.g., Barlow’s equation basis) for pressure design thickness emphasize hoop stress; longitudinal loads are addressed by closures or special cases.

Why Other Options Are Wrong:
(a) End loads affect local regions and closures, not typical run thickness. (b) Bends and dynamics require reinforcement/support checks, not baseline run thickness. (d) Thermal stresses are important for flexibility but do not set pressure minimum thickness. (e) Torsion is not normally governing for straight pressure runs.

Common Pitfalls:
Ignoring joint efficiency, corrosion/erosion allowances, or test pressure multipliers; misapplying thick-wall formulas when t/D is small.

Final Answer:
Circumferential (hoop) wall tension due to internal pressure