When the cover chamber pressure of the 90AF-8 refueling control valve matches the inlet pressure, what will the valve do?

When the cover chamber pressure of the 90AF-8 refueling control valve matches the inlet pressure, the valve will close tightly. This situation indicates that the pressure is balanced; thus, there is no differential pressure to keep the valve open. A refueling control valve needs a pressure difference to maintain an open state, and when the pressures equalize, the valve responds by closing. This closure is essential for safety and operational control during refueling operations to prevent leaks and ensure that the flow of fuel is halted properly in case of a system operation change.

The other options relate to behaviors of valves under different pressure conditions. For instance, pulsation might occur due to fluctuating pressures but is not a stable state caused by balanced pressures. Opening fully would typically require a greater inlet pressure than the cover chamber pressure for the valve to function effectively. Modulating would involve adjusting to maintain flow under varying conditions, which again hinges on differential pressure rather than equal pressures. Therefore, in the context of the original question, the closure of the valve serves a fundamental role in maintaining safe and controlled operations.