The short answer is no. Radiographic Testing (RT) and pressure testing (Hydrostatic or Pneumatic) serve two (2) fundamentally different purposes in piping integrity. While it might seem like “over-testing,” they are not interchangeable in ASME B31.3 (Process Piping) or ASME B31.1 (Power Piping).
Here is the breakdown of why 100% RT does not exempt you from a pressure test:
- Workmanship vs. Structural Integrity Radiography (RT): This is a volumetric examination used to find internal flaws like porosity, slag inclusions, or cracks. It tells you if the weld was performed correctly according to workmanship standards. Pressure Testing: This is a mechanical strength test. It verifies the structural integrity of the entire system, including the pipe material itself, gaskets, bolts, and valves—not just the welds. It also ensures the system can handle the internal stresses of operation without yielding or bursting.
- What RT Can’t See
RT is excellent for welds, but it cannot detect:
- Whether a flange bolt is loose.
- If a gasket is seated incorrectly.
- Material laminations in the pipe wall away from the weld.
- Whether the wrong grade of pipe or fitting was accidentally installed.
Code Requirements (ASME B31.3)
Under most international codes, a leak test is mandatory. Even with 100% RT, you are still required to perform a hydrostatic or pneumatic test.
There are very rare exceptions where a “Closure Weld” (the final tie-in weld) cannot be pressure tested. In these specific cases, codes allow for a “Substitution of Test” where 100% RT plus 100% Ultrasonic Testing (UT) or Dye Penetrant (PT) is used, but this usually requires a formal engineering justification and owner approval.
Source Aid: Google Gemeni