GPT Corrosion Control & Cathodic Protection 3

Question 1

Per 49 CFR Part 192, how often must a technician inspect and test rectifiers on impressed current cathodic protection systems serving gas pipelines?

Accepted Answer

Every 2 months (six times per calendar year)

Answer

Annually

Answer

Every 5 years

Answer

Only after a reported corrosion event

Question 2

Which soil characteristic most increases the external corrosion risk for a buried steel gas pipeline?

Accepted Answer

Low soil resistivity (below 1,000 ohm-cm)

Answer

High soil resistivity (above 10,000 ohm-cm)

Answer

Dry, sandy, well-drained soil

Answer

Neutral soil pH of 7.0

Question 3

A direct current (DC) potential of -1.5 V (CSE) measured on a coated steel gas main could indicate:

Accepted Answer

Overprotection, which can cause hydrogen embrittlement or coating disbondment

Answer

Inadequate cathodic protection requiring an increase in current

Answer

Normal operating range for a well-coated pipeline

Answer

A reference electrode that needs recalibration to a less negative value

Question 4

Which document provides the industry standard guidelines for external corrosion control of underground or submerged metallic piping systems?

Accepted Answer

NACE SP0169 (now AMPP SP0169)

Answer

API 1104

Answer

ASME B31.8

Answer

OSHA 29 CFR 1910.119

Question 5

When a gas technician installs a new steel service line adjacent to an existing copper water service, what corrosion risk must be managed?

Accepted Answer

Galvanic corrosion if the two metals are electrically connected through soil or direct contact

Answer

Microbiological corrosion caused by copper-loving bacteria

Answer

Stress corrosion cracking from pressure differentials

Answer

Thermal corrosion from heat transfer between the pipes

Question 6

What is the function of a decoupler (DC decoupler / gradient control mat) in a cathodic protection system?

Accepted Answer

It blocks DC current while allowing AC fault current to pass safely, protecting CP continuity at electrical isolation points

Answer

It reduces operating gas pressure at the CP test station

Answer

It converts AC cathodic protection current to DC

Answer

It measures stray current magnitude in millivolts

Question 7

According to 49 CFR Part 192, which of the following pipelines installed after July 1971 in a designated high consequence area (HCA) MUST have cathodic protection?

Accepted Answer

All steel pipelines, regardless of operating stress level

Answer

Only plastic pipelines in corrosive soils

Answer

Only pipelines operating above 60% SMYS

Answer

Only pipelines buried deeper than 5 feet