How to classify a pump

How to classify a pump

Choose all the characteristics your pump have :

1. Positive displacement or kinetic ?
2. Reciprocating or Centrifugal ?
3. Horizontal End-Suction or Vertical In-Line ?
4. Impeller open, semi-close, close  or double suction ?
5. Close-Coupled or Separately-Coupled ?
6. Overhung Impeller or Impeller between bearing ?
7. Axial split or Radio split ?
8. Single stage or Multi-Stage ?

1. Positive displacement or kinetic ?

Positive Displacement Pump:

Operate by forcing a fixed volume of fluid from the inlet pressure section of the pump into the discharge zone of the pump.


Kinetic Pumps:

Add energy directly through a rotating part in the form of velocity, and converts the velocity to pressure.

 2. Reciprocating (positive displacement) or centrifugal (kinetic)?

Reciprocating pump :


Exemple of a reciprocating pump... Metering (chemical) pump


Metering Pump (use for chemical) are always of reciprocating type, as we need really high discharge pressure and small volume of liquid to be pump.


Also, a Metering Pump, unlike a Centrifugal Pump, will produce the same flow at a given speed no matter the discharge pressure. That way, we can control exactly the amount of chemical being added.

Centrifugal Pump :

Centrifugal pump get their name from from the way they impart energy to fluid.
When fluid enter the pump it come into contact with the rotating impeller, and is throw outward by centrifugal force, which implys velocity to the fluid. It then travel to a specialy shape chamber call the volute chamber and exit the pump at the outlet.

Example of centrifugal pump... Horizontal end suction pump

Most pump use for water or glycol are of centrifugal type, as we need medium discharge pressure and large volume of liquid to be pump.

3. Orientation relative to the pump shaft :

Horizontal End suction (90O) or Vertical In-Line ?

Horizontal end suction pump :

This configuration place the suction and discharge piping at 90 deg to one another.
The inlet is directly in front of the suction eye at the center of the impeller.
This is why these kind of pump are called End Suction Pump or Horizontal End Suction Pump.

End-suction pumps are the most cost-effective solution for most every day pumping applications. End-suction pumps are available from dozens of manufacturers, in a wide range of materials of construction, and offered as both off-the-shelf and custom-engineered products.

End-suction pumps can be found in virtually every industrial facility and water treatment plant in the world. In addition, they are commonly used in fire protection and HVAC systems, and as pressure-boosting pumps (booster pumps) in plumbing systems for large buildings such as big-box stores, stadiums, office buildings, and shopping malls.

Vertical in-line pump :

If you were to take an end-suction pump, stand it on end, and fashion a suction elbow to the bottom, you would have created a crude vertical inline pump. In fact, many manufacturers share hydraulic designs between end-suction and vertical inline products.

Vertical inline pumps can be considered for any application for which an end-suction pump is considered acceptable as they offer similar longevity. While typically a little more expensive than end-suction pumps due to slightly higher motor costs, vertical inline’s have the added benefit of requiring very little floor space, which explains their popularity in commercial construction where square footage is at a premium.

4. Which type of impeller ?

Open, Semi-Close, Close Impeller (End-Suction, In-Line) or Double-Suction Impeller (split-case) ?

1 - Open Impeller

Consist of a few vane equaly space around the hub on the rotating pump shaft
These large unrestricted vane allow this type of impeller to pump fluid containing mud, leaves, sand and many big and dirty stuff (like sewage).

2 - Semi-Close Impeller :

If the vane are mounted on a backing plate call a Shroud then the impeller is a semi-close impeller.

3 - Close Impeller

If the vane are sandwhich between two Shroud, then it’s a close impeller.
Close impeller are more effective than open or semi-close impeller, because the fluid have a more define pathway. That means that more of the fluid is pump around the system and less of it is recerculated around again and again. The trade-off is that they can more easely get clog with debris.

4 - Double Suction Impeller

Double suction impeller mean that the fluid enter on both side of the impeller. It’s use on split-case pump which have their impeller between bearing

5. Close-Coupled or Frame Mounted (also called separately coupled) ?

Close-Coupled mean that the shaft of the motor and the pump is the same. There is no coupling between the two.


Separate coupling can be of flexible type (for end-suction horizontal) or rigid type (for vertical in-line)

6. Overhung Impeller (End Suction and In-Line) or Impeller Between Bearing (split-case)?

Overhung impeller mean that the impeller is supperted by two bearing on one side of the pump (motor side). This configuration is use for Horizontal End Suction and Vertical In-Line Pump.

Impeller Between Bearing mean that the impeller is sandwhich between two bearing situated on each side of the impeller. This configuration is use on split-case pump.

7. Axial Split Case ( Horizontal/Vertical) or Radial Split Case ?

Axial split case refers to a pump casing that is split on a horizontal axis.

Radial split case refers to a split case pump casing that is split on a vertical axis.

Split-case pumps are the workhorses of industrial and municipal applications. They are more expensive than end-suction or vertical inline pumps, and not as flexible or adaptable as vertical turbines. However, what they lack in low-cost flexibility they make up for in durability, efficiency, and dependability.

A split-case pump, properly installed, designed, and operated, can provide decades of service.

So what makes split-case pumps the dependable workhorses that they are?
It all comes down to design.

• Between-the-bearings: Split-case pumps are what is referred to as a “between-the-bearings” pump. This means that split-case pumps mount the impeller on a shaft that is supported by bearings on both sides of the impeller.
• Double-suction impeller: Split-case pumps are the only COMMON pump type with a double suction impeller. A double-suction impeller imposes dramatically fewer loads on the bearings than an impeller that only draws in water from one side of the impeller (single-suction).

Split-case pumps are, by-design, a more-balanced machine than most other types of pumps. Coupled with robust bearings and a maintenance-friendly casing design, split-case pumps are the design-of-choice for many municipalities and industrial facilities.

8. Single-Stage or Multi-Stage ?

Single stage pump means that a single impeller is use to build pressure.

Multi-stage pump means that multiples impellers are use to build high pressure. These multiples impellers will work in team to build high pressure as the fluid circulate successively to one another.

For instance, multi-stage impeller are use on reverse osmose system as RO need high discharge pressure to overcome the resistance of the filtering membrane use to filter water.