Piping Piping Inspection and Testing 3

Question 1

What is 'high-frequency guided wave ultrasonic testing (GWUT)' used for in piping inspection?

Accepted Answer

Screening long sections of pipe for corrosion from a single test point, even under insulation or through road crossings

Answer

Measuring precise wall thickness at a single point

Answer

Testing pipe welds for internal defects

Answer

Checking pipe alignment and straightness

Question 2

What is the purpose of 'baseline thickness measurements' taken when a new piping system is commissioned?

Accepted Answer

To establish reference values for future corrosion rate calculations and remaining life assessments

Answer

To verify the pipe was manufactured to the correct schedule

Answer

To satisfy hydrostatic test documentation requirements

Answer

To confirm proper installation of pipe supports

Question 3

What is 'erosion corrosion' in piping, and where does it most commonly occur?

Accepted Answer

Accelerated metal loss caused by the combined effect of corrosive fluid and mechanical erosion from flow, most common at bends, tees, and reducers

Answer

Chemical corrosion in alkaline environments, most common in straight pipe sections

Answer

Corrosion caused by electrical grounding current, most common near electrical equipment

Answer

High-temperature oxidation, most common near furnaces

Question 4

According to API 570, how is the 'long-term corrosion rate' different from the 'short-term corrosion rate'?

Accepted Answer

Long-term uses all inspection data back to baseline; short-term uses only the last two inspection readings

Answer

Long-term rate is for buried pipe; short-term rate is for above-ground pipe

Answer

Long-term applies to external corrosion; short-term to internal corrosion

Answer

There is no distinction — only one corrosion rate is calculated

Question 5

What is the 'minimum required thickness' (t_min) in piping inspection?

Accepted Answer

The calculated minimum acceptable wall thickness based on design pressure, material strength, and applicable code formula

Answer

The thinnest pipe wall commercially available for a given size and schedule

Answer

The minimum thickness before which the pipe must be recoated

Answer

The manufacturer's tolerance minus 12.5% for pipe wall under-thickness

Question 6

What type of inspection is required to identify 'high-temperature hydrogen attack' (HTHA) damage in piping?

Accepted Answer

Specialized metallurgical examination and advanced UT techniques such as phased array UT or velocity ratio measurement

Answer

Standard ultrasonic thickness measurement at ambient temperature

Answer

Visual inspection of external pipe surface

Answer

Magnetic particle testing of pipe welds