AWWA Pipeline Integrity and Testing 5

Question 1

What is the purpose of a 'step pressure test' used to evaluate unlined metallic water mains?

Accepted Answer

To apply successively higher pressures in steps, monitoring leakage rate changes to locate and characterize defects

Answer

Step pressure testing increases pressure in increments and measures leakage at each step, helping engineers identify defect severity and differentiate joint leakage from pipe body cracks.

Question 2

Which method is used to locate a buried pipeline's exact position before excavation to reduce the risk of accidental damage?

Accepted Answer

Electronic line location or electromagnetic pipe locating

Answer

Electronic pipe locating uses an electromagnetic signal applied to the pipe or tracer wire to precisely map horizontal and vertical position of buried mains before any digging.

Question 3

Ultrasonics testing (UT) of pipe walls measures what property to assess pipe condition?

Accepted Answer

Remaining wall thickness by timing ultrasonic pulse echo return

Answer

Ultrasonic testing sends a high-frequency sound pulse into the pipe wall and measures the time for the echo to return, calculating remaining wall thickness from that travel time.

Question 4

What is the significance of a 'negative pressure transient' (vacuum condition) in a water main for pipeline integrity?

Accepted Answer

It can cause pipe collapse in thin-walled pipes and draw contaminants inward through leaks

Answer

Negative transients reduce internal pressure below atmospheric, risking collapse of flexible pipe and creating a pathway for contaminated groundwater to enter through existing leaks.

Question 5

A utility suspects internal tuberculation in a cast iron main is reducing hydraulic capacity. Which test directly quantifies this loss?

Accepted Answer

A flow test measuring headloss and calculating the effective C-factor (Hazen-Williams)

Answer

Measuring flow rate and pressure drop across the main allows calculation of the Hazen-Williams C-factor; a lower-than-expected C-factor confirms hydraulic capacity loss due to tuberculation.

(AWWA) American Water Works Association Practice Test

(AWWA) American Water Works Association Practice Test

AWWA Pipeline Integrity and Testing 5