What distinguishes a piston from a plunger in pump operation?

The distinction between a piston and a plunger in pump operation primarily lies in their functional design and movement. A piston operates within a cylinder and is typically surrounded by piston rings that help create a seal, allowing it to push fluid with precision as it moves back and forth. This sealing mechanism is essential for maintaining pressure and preventing fluid leakage during operation.

In contrast, a plunger is typically a solid rod that moves through a stationary casing but does not require the same sealing mechanisms as a piston because it relies on the friction between the plunger and the casing to push the fluid. This design means that while both have similar applications in fluid movement, their operating principles and the way they interact with their surrounding components differ significantly.

The notion that a piston must always be larger than a plunger or that they operate on different fluid types does not necessarily hold true, making those characteristics less relevant for distinguishing the two. Instead, their movement relative to surrounding components and the design of their respective sealing systems are what truly set them apart.