From the graph shown in the illustration, determine the size of the regulating ring required for the proper operation of the fuel oil centrifuge if the fuel oil specific gravity is 0.9 kg/dm3 at 68°F, and the separating temperature is 158°F. Illustration MO-0113

Correct Answer: Option C — 110 mm

Centrifuge gravity disc sizing relies on specific gravity and operating temperature curves provided by manufacturers. Entering the nomograph at 0.9 sg and 158°F intersection determines the exact regulating ring diameter required to position the water-oil interface correctly, preventing contamination of the purified fuel oil.