Question 36 TK02 - Tank Vessel Assistant - Liquefied Gas

The Correct Answer is D **Why option D is correct:** Insulating flanges (or isolation joints) are critical components used, particularly in pipeline systems, to electrically separate sections of pipe. They are essential for controlling stray electrical currents, preventing galvanic corrosion, and ensuring the effectiveness of Cathodic Protection (CP) systems by confining the CP current to the protected segment. Because their function is purely electrical separation, if the insulating material becomes contaminated (e.g., by moisture, dirt, or scale) or damaged, the joint can short-out, rendering it useless. Therefore, regular inspection, cleaning, and testing (measuring resistance) are necessary to ensure the integrity of the insulation and the continued effectiveness of the isolation joint. **Why the other options are incorrect:** **A) After the insulating flange is installed, hot-work may be performed on deck.** This statement is incorrect and dangerously misleading. Insulating flanges are used for electrical isolation in pipelines, not as a blanket safety measure for hot work (welding, cutting). Hot work requires strict safety protocols, including gas testing, permits, fire watches, and often specific isolation procedures (like purging lines or using water curtains). The presence of an insulating flange does not inherently make hot work safe or permissible in an area; proper hot-work procedures must always be followed independently of the flange's function. **B) The measured resistance value after installation should be less than 1,000 ohms.** This statement is incorrect. Insulating flanges are designed to *isolate* electrical current, meaning they must present a high resistance to current flow. A properly functioning insulating flange should exhibit a very *high* resistance value—typically measured in megaohms (millions of ohms)—to ensure effective electrical separation. A resistance value of less than 1,000 ohms indicates a near-short or complete failure of the insulation. **C) Switching off a cathodic protection system may be substituted for using an insulating flange.** This statement is incorrect. Insulating flanges are used to create permanent electrical separation between different parts of a system (e.g., between a protected pipeline and an unprotected structure, or between pipelines made of dissimilar metals, or to block telluric currents). While switching off the Cathodic Protection (CP) system stops the impressed current, it does not address the underlying need for permanent electrical separation, nor does it prevent galvanic corrosion caused by dissimilar metals or stray currents that the flange is designed to block. The flange is a structural component for isolation, whereas the CP system is an active corrosion mitigation system. They serve different, though related, purposes.