Piping Piping Inspection and Testing

Question 1

What is the most common NDE method used for measuring remaining wall thickness of in-service piping?

Accepted Answer

Ultrasonic Testing (UT) with thickness gauge

Answer

Ultrasonic thickness measurement (UTM) using a UT gauge is the standard method for measuring remaining pipe wall thickness from the outside without requiring process shutdown.

Question 2

What is 'injection point corrosion' in process piping?

Accepted Answer

Localized and often severe corrosion at or near a point where chemicals are injected into a pipe

Answer

Injection points are high-risk areas for localized corrosion because injected chemicals may not be fully mixed with the process stream, creating concentrated corrosive conditions near the injection nozzle.

Question 3

What is 'pitting corrosion' and why is it particularly dangerous in piping?

Accepted Answer

Localized attack creating small deep holes that can penetrate the pipe wall without significant weight loss or obvious external signs

Answer

Pitting creates highly localized deep penetrations that can cause through-wall leaks while the average wall thickness appears acceptable, making it difficult to detect with routine thickness surveys.

Question 4

What is the purpose of an acoustic emission (AE) test on piping?

Accepted Answer

To detect and locate active crack growth, leaks, or structural defects by listening for stress wave emissions during pressurization

Answer

Acoustic emission testing listens for high-frequency stress waves generated by active defects (crack growth, leaks) during loading, allowing detection and location of damage without full surface access.

Question 5

What is the 'remaining life' calculation used in piping inspection programs?

Accepted Answer

Estimated time until the pipe wall reaches minimum required thickness based on measured corrosion rate

Answer

Remaining life = (actual thickness - minimum required thickness) divided by the corrosion rate, providing an estimate of how much service life remains before mandatory retirement.

Piping Practice Test

Piping Practice Test

Piping Piping Inspection and Testing