Centrifugal Pump Parts and Their Basic Functions

⚙️ Centrifugal Pump Parts and Their Basic Functions

Centrifugal pumps are among the most widely used pumps in industries such as water supply, chemical processing, oil & gas, HVAC, and power generation. Understanding the major parts of a centrifugal pump and their functions is essential for engineers, maintenance teams, and students of mechanical engineering.  

This Blog explains the key components of a centrifugal pump, their roles, and why they are critical for pump performance and reliability.

🔹 Major Parts of a Centrifugal Pump

1. Impeller

- A vaned disk mounted on the shaft.  

- Function: Increases the pressure of the liquid by imparting centrifugal acceleration.  

- The impeller is the main rotating part that drives fluid movement.

2. Impeller Nut

- Locks the impeller in its proper axial position.  

- Prevents axial movement due to hydraulic thrust.  

3. Seal

- Prevents leakage of pumped liquid into the atmosphere.  

- Types: Packing rings or mechanical seals.  

- Ensures safe and efficient operation.

4. Casing

- Acts as a pressure containment vessel.  

- Directs liquid flow in and out of the pump.  

- Types:  

  - Volute casing – builds higher head.  

  - Circular casing – used for low head, high capacity.  

- Diffusers in circular casings convert velocity energy into pressure energy (common in multistage pumps).

5. Wear Rings

- Provide a renewable leakage joint between impeller and casing.  

- Protects against wear and reduces leakage losses.  

- Can be press‑fit, shrink‑fit, or secured with set screws.

6. Shaft

- Transmits torque during start‑up and operation.  

- Supports the impeller and other rotating parts.  

7. Shaft Sleeve

- Protects the shaft from erosion, corrosion, and abrasion wear.  

- Enhances stiffness of the rotating element.  

- Commonly used at stuffing boxes or leakage joints.

8. Coupling

- Connects the pump shaft to the driver shaft (motor or turbine).  

- Transmits input power into the pump.  

- Types:  

  - Rigid coupling – used when no misalignment is possible.  

  - Flexible coupling – accommodates misalignment; can be elastomeric or non‑elastomeric.

9. Bearings

- Support the weight of the shaft assembly.  

- Carry hydraulic loads acting on the shaft.  

- Keep the pump shaft aligned with the driver shaft.  

10. Stuffing Box / Seal Chamber

- Chamber between shaft and casing where sealing media are installed.  

- Stuffing box – used with packing.  

- Seal chamber – used with mechanical seals.  

- Prevents leakage at the point where the shaft exits the casing.

11. Back Plate

- Made of pressed steel.  

- Forms the fluid chamber along with the casing.  

- Provides structural support for fluid transfer.

12. Bearing Housing

- Encloses and protects the bearings.  

- Ensures proper alignment.  

- Includes lubrication and cooling arrangements for bearings.

13. Gland

- Part of the seal chamber or stuffing box.  

- Provides proper fit for packing or mechanical seal on the shaft sleeve.  

- Ensures effective sealing and prevents leakage.

🔹 Why Understanding Pump Parts Matters

- Maintenance Efficiency: Knowing each part helps in troubleshooting and preventive maintenance.  

- Reliability: Proper care of impellers, seals, and bearings extends pump life.  

- Energy Efficiency: Well‑maintained pumps consume less power.  

- Safety: Correct sealing prevents hazardous leaks in chemical and industrial applications.  

🔹 Key Takeaways

- Centrifugal pumps consist of impeller, casing, shaft, bearings, seals, wear rings, and couplings.  

- Each part plays a vital role in fluid movement, sealing, alignment, and reliability.  

- Proper understanding of pump components ensures efficient operation, reduced downtime, and longer equipment life.