The flow rate of a reciprocating pump is independent of the discharge head; instead, it depends on the pump cylinder dimensions, piston stroke, and reciprocating frequency. While the theoretical flow rate remains constant, the actual flow rate decreases slightly as the discharge head rises due to leakage. The discharge head is independent of the flow rate and pump dimensions, being determined instead by factors such as the pump's mechanical strength and the power of the prime mover.
The flow rate of a reciprocating pump cannot be regulated using a valve on the discharge line, as manipulating the discharge valve causes drastic pressure fluctuations that could damage the equipment. Appropriate methods for flow regulation include using a bypass line to recirculate a portion of the discharged fluid, or adjusting the piston's reciprocating frequency or stroke length.
Significant pulsation in flow rate and pressure is a primary drawback of reciprocating pumps. Traditional mitigation measures include installing air chambers on the discharge line (and sometimes the suction line) or utilizing double-acting or multi-cylinder pump designs. Newer configurations, such as constant-flow pumps, employ modified power-end drive mechanisms (e.g., cam drives) to significantly reduce flow and pressure pulsations, thereby improving operating conditions for pump valves and extending the service life of wear parts. Pulse-free hydraulic reciprocating pump technology aims to minimize pressure fluctuations during the stroke reversal phase to near-zero levels, enhancing operational stability and component reliability.
Key factors to consider when selecting a reciprocating pump include: maximum flow rate; the pressure differential (or head) required by the system; fluid properties (physical, chemical, and other characteristics); piping layout (lifting height, distance, routing, pipe specifications, etc.); and operating conditions (temperature, pressure, continuity of operation, etc.).
Volumetric efficiency is a critical parameter for reciprocating pumps, and it can be improved by minimizing clearance volume. For instance, patented technology known as a "piston pump clearance detection device" can automatically detect and adjust the clearance in piston pumps, thereby enhancing volumetric efficiency.
