Q22. A hydrotest of a plant pipe spool shows a pressure drop of 5% after 1 hour (design pressure test). The QA engineer discovers all gauges/calibrations are in order. What next? Accept because 5% drop is acceptable. Immediately condemn the spool. Investigate for undetectable micro-leaks, trapped air, and retest. Reduce test time to 30 minutes to save schedule.

A hydrotest is performed to verify the integrity and leak-tightness of a pipe spool or system. Any significant pressure drop that cannot be attributed to temperature changes or gauge error is a strong indication of a problem.

A 5% pressure drop is substantial and generally not acceptable for a successful hydrotest, even if micro-leaks are not immediately visible. It suggests a potential integrity issue.

• 1. Accept because 5% drop is acceptable: This is incorrect. A 5% drop is usually not acceptable without investigation, as it indicates a leak or other issue.
• 2. Immediately condemn the spool: While serious, immediate condemnation might be premature. There are often troubleshooting steps to take first, such as checking for trapped air or very small leaks.
• 3. Investigate for undetectable micro-leaks, trapped air, and retest: This is the standard and most appropriate procedure. A pressure drop, even with calibrated gauges, can be caused by factors like trapped air (which compresses and expands differently than water) or very small leaks that are hard to spot initially. A thorough investigation is necessary before retesting.
• 4. Reduce test time to 30 minutes to save schedule: This is a dangerous and unacceptable practice. It compromises safety and quality by shortening the test duration to potentially hide a defect, which goes against the purpose of the hydrotest.

The most responsible and technically sound approach is to investigate the cause of the pressure drop thoroughly before making a final decision or retesting.

The correct answer is 3.
$\text{3}$