What type of system does not require a fuel de-aerator for air reduction?

A one-pipe system does not require a fuel de-aerator for air reduction due to its design, which allows for fuel and return flow to be handled through a single pipe. In such systems, the flow of oil naturally helps to purge any air that may enter. A one-pipe system typically relies on gravity and the weight of the fuel to keep the line filled, thereby minimizing the risk of air pockets forming.

In contrast, two-pipe systems and open systems are more complex in their requirements for handling air. A two-pipe system, for instance, incorporates both a supply and return line, and while it can still function effectively, it may require greater considerations for air reduction. Open systems allow for potential exposure to the atmosphere, leading to more significant air ingress, thereby necessitating the use of de-aeration equipment. Closed systems, while more controlled, still might have scenarios that require air relief or reduction methods due to varying pressures and temperatures affecting the fuel.

Thus, the absence of a need for a fuel de-aerator in a one-pipe system is attributed to its inherent design advantages in managing the presence of air efficiently.