Comparison between Dynamic pump and Positive displacement pump

💧 Comparison Between Dynamic Pumps and Positive Displacement Pumps :

In fluid handling systems, pumps are essential for moving liquids from one place to another. The two most common categories are Dynamic Pumps and Positive Displacement Pumps. While both serve the same purpose—transporting fluids—their operating principles, applications, and performance characteristics differ significantly. Understanding these differences helps engineers, plant operators, and maintenance professionals select the right pump for their process.

🔹 What is a Dynamic Pump?

- Operating Principle: Dynamic pumps impart energy to the fluid continuously through a rotating impeller or rotor. The fluid gains velocity and pressure as it flows through the pump.  

- Types: Centrifugal pumps, axial flow pumps, and mixed flow pumps.  

- Flow Characteristics: Continuous, smooth flow; performance depends on system resistance and pump speed.  

- Applications:  

  - Water supply systems  

  - HVAC circulation  

  - Irrigation and drainage  

  - Chemical and process industries  

-:Dynamic pumps are best suited for large flow rates at relatively low pressures.

🔹 What is a Positive Displacement Pumps

- Operating Principle: Positive displacement pumps trap a fixed volume of fluid and physically displace it from the suction side to the discharge side.  

- Types: Gear pumps, screw pumps, piston pumps, diaphragm pumps, lobe pumps.  

- Flow Characteristics: Delivers a constant flow regardless of discharge pressure (until relief valve opens).  

- Applications:  

  - Hydraulic systems  

  - Oil and gas industry  

  - Food and beverage processing  

  - Dosing and metering applications  

-  Positive displacement pumps are ideal for high‑pressure, low‑flow applications and for handling viscous fluids

🔹 Advantages of Each Pump Type

Dynamic Pumps  

- Simple design and lower cost.  

- Suitable for large volumes of water or thin liquids.  

- Easy to maintain and widely available.  

Positive Displacement Pumps  

- Accurate flow control for dosing and metering.  

- Handles viscous, abrasive, or shear‑sensitive fluids.  

- Maintains constant flow regardless of pressure changes. 

🔹 Choosing the Right Pump

- Use Dynamic Pumps when you need large flow rates at low pressures, such as in municipal water supply or cooling systems.  

- Use Positive Displacement Pumps when you need precise flow control, high pressure, or to handle viscous fluids, such as in chemical dosing or hydraulic systems.  

Dynamic Pump	Positive Displacement Pump
High flow rate pump	Low Flow rate pump
Low Pressure pump	High Pressure pump
Steady flow	Pulsating flow
Relief valve not needed	Relief valve needed
Less noise	More noise
High speed	Low speed
High efficiency for low head	Low efficiency for low head
Mostly utilize for fluid transfer	Mostly utilize for fluid power
Course strainer(filter)	Fine Flow filter
Flow control valve used	Flow control valve cant be used
NRV needed at discharge and sometime at suction	NRV needed at discharge side only
Uniform torque	Torque not uniform
Installation easy	Installation difficult
Flowrate varies with change in pressure	Flowrate constant with change in pressure
Low initial cost	High initial cost
Low maintenance cost	High maintenance cost

 Key Takeaways -

- Dynamic pumps = velocity energy → flow.  

- Positive displacement pumps = volume displacement → flow.  

- Dynamic pumps excel in high‑flow, low‑pressure applications.  

- Positive displacement pumps excel in low‑flow, high‑pressure applications.  

- Selecting the right pump depends on fluid type, viscosity, required pressure, and application needs