Hydrostatic pressure testing of pipelines (water supply engineering): What do we call the maximum internal pressure that a pipe is required to safely withstand without leakage during a hydrostatic pressure test?

Introduction / Context:
During commissioning of a new water main or a repaired pipeline, engineers carry out a hydrostatic pressure test to confirm structural integrity and tightness. The objective is to pressurize the line to a specified value that is higher than routine operating conditions and then verify that there is no leakage or unacceptable pressure drop. Understanding the correct terminology helps avoid confusion between design, working, and test conditions.

Given Data / Assumptions:

• The pipeline is filled, vented, and pressurized with water.
• The specified target pressure is above normal service (working) pressure.
• The acceptance criterion is no visible leakage and pressure decay within allowable limits.

Concept / Approach:
Standards define several pressures: working (routine operating), design (basis for thickness and class), and test pressure (pressure applied during a hydrostatic test to prove tightness and strength). The correct term for “maximum pressure which the pipe can withstand without leakage during the hydrostatic test” is test pressure. This is not necessarily the ultimate strength; it is the verification pressure used during testing, commonly expressed as a factor of the rated pressure class or the maximum allowable operating pressure (often 1.25 to 1.5 times, depending on the code and material).

Step-by-Step Solution:
Identify the context: formal hydrostatic testing (not day-to-day service).Relate the definition to pipeline QA/QC procedures.Match the term used by standards for that pressure: “test pressure.”

Verification / Alternative check:
Commissioning checklists and standard specifications (for example, municipal water specifications) always label the applied proof pressure during hydro-testing as the test pressure, distinct from the working/design values.

Why Other Options Are Wrong:

• Working pressure: the everyday operating level, typically lower.
• Design pressure: basis for design calculations, not necessarily the applied test level.
• Hydrostatic pressure: a generic phrase; not the specific acceptance pressure.
• Proof stress: a material property term, not a pipeline test term.

Common Pitfalls:

• Assuming test pressure equals burst pressure; the test is far below failure.
• Confusing “no leakage” with “no pressure drop”; some standards allow a small pressure decay due to temperature or trapped air as long as leakage is absent.

Final Answer:
Test pressure