Question 1260 Deck General

The correct answer is D) All of the above. Pressure/vacuum valves are designed to provide for the flow of small volumes of tank atmospheres caused by thermal variations in a cargo tank (A). They should be kept in good working order by regular inspection and cleaning (B) to ensure they operate properly. Additionally, pressure/vacuum valves should operate in advance of the pressure/vacuum breakers (C) to prevent excessive pressurization or vacuum in the cargo tank. The other options are incorrect because they only describe one or two of the key features and requirements for pressure/vacuum valves, while the correct answer encompasses all three.