Refrigeration Plant Operator B Practice Test

When a reciprocating pump discharges while its piston moves in only one direction, it is termed a single acting unit. This terminology refers specifically to the operational mechanics of the pump. In a single acting unit, the piston utilizes the force during one stroke to draw in fluid during the backward movement and then forces the fluid out during the forward stroke. This design is contrasted with a double acting unit, where the piston acts upon the fluid on both the forward and backward strokes, effectively doubling the pumping action with each complete cycle. A single acting unit is characterized by its simplicity and the effective design for specific applications where high discharge pressures are not always required. Understanding the distinction between these types of units is essential for effective pump selection and operational efficiency in various refrigeration and fluid dynamics applications.