Which of the following methods is NOT used to heat oil in storage tanks, according to safety guidelines?

The method that is not used to heat oil in storage tanks according to safety guidelines is heating elements powered by gas. This approach poses significant safety risks, as it can lead to combustion hazards and the potential for explosions if there is an oil leak or vapor accumulation.

In contrast, the other methods mentioned—using a heat exchange system, utilizing steam, and employing low pressure hot water—are considered safer and more effective for maintaining the appropriate temperature of the oil without introducing the combustion risks associated with gas-powered heating elements. Heat exchange systems and steam provide efficient heat transfer without direct flame contact, while low pressure hot water systems maintain safe operating temperatures with reduced risk. Thus, the choice of heating method is critical in ensuring compliance with safety regulations and preventing accidents in oil storage facilities.