Reciprocating pump — classification by displacement A reciprocating pump is also called a ________ displacement pump. Choose the correct term used in fluid machinery.

Introduction:Pumps are broadly divided into positive displacement (PD) and rotodynamic categories. Recognizing which class a reciprocating pump belongs to is essential for understanding its flow characteristics, control methods, and protections.

Given Data / Assumptions:

• Piston/ plunger mechanism with suction and delivery valves.
• Finite swept volume per stroke; relatively low speed.

Concept / Approach:Positive displacement machines transfer a nearly fixed volume of fluid each cycle irrespective of discharge pressure (within mechanical limits). Reciprocating pumps trap fluid in a chamber and displace it by piston motion, making them quintessential PD pumps. Consequently they require relief valves to prevent overpressure and often benefit from air vessels to smooth pulsating flow.Step-by-Step Solution:

Verification / Alternative check:Manufacturer curves for PD pumps show near-vertical head–flow characteristics: flow rate changes little with discharge pressure compared to centrifugal pumps.

Why Other Options Are Wrong:

• Negative/non-displacement/centrifugal: do not describe reciprocating mechanisms.
• Variable-inertia: not a standard category.

Common Pitfalls:Operating PD pumps with closed discharge without relief valves; confusing their control logic with that of centrifugal pumps.

Final Answer: