Types of Centrifugal Pumps:
Centrifugal pumps are available in different types. Depends on the industry or nature of process different types of centrifugal pumps are used. Centrifugal pump can be classified as:
1. Types of Centrifugal Pumps w.r.t Impeller position:
a. Horizontal: In this type of pump, the pump impeller is horizontal. Horizontally mounted pump/motor set will occupy almost three times of floor space as compared to same capacity vertical impeller pump.
b. Vertical: In this type of pump, the pump impeller is vertical. Vertical impeller allows the pump impeller to be immersed in the liquid to be pumped. Therefore, no need for priming at the start of the pump.
2. Types of Centrifugal Pumps w.r.t Number of stages:
a. Single stage: In a single stage pump, the head develops through a single impeller. This type of pump can develop a differential pressure 150 psid across the suction and discharge of the pump.
b. Multi-stage: If two or more single stage pumps connect in series or all the impellers combine in a single casing, than this will called multistage pump.
3. Types of Centrifugal Pumps w.r.t Impeller type:
a. Single suction: In single-suction impeller, liquid enters the center of the impeller eye from only one direction.
b. Double suction: In a double-suction impeller, liquid enters the center of the impeller from both sides simultaneously.
c. Shrouding design:
- Open: The open impeller consists only of blades attached to a central hub. The open impeller has structural weaknesses. If the vanes are long they need to strengthen through ribs or a partial shroud.
- Semi Shrouded: The semi-open impeller is built with a circular plate (the web) or integral sidewall attached to one side of the impeller. This integral sidewall or shroud increases the strength of the impeller. Semi shrouded impeller has greater efficiency as compared to open impeller.
- Fully Shrouded: The fully shrouded or enclosed impeller has circular plates attached to both sides of the impeller. This type of impeller has the highest efficiency due to no slippage between shrouds and vanes.
4. Types of Centrifugal Pumps w.r.t direction of flow through impeller:
a. Radial flow impeller:
In radial flow pump, liquid enter at the center of the impeller axially and flows radially to the periphery. The liquid gains kinetic energy through the action of centrifugal force. This centrifugal force causing the liquid to accelerate radially through the impeller. as the liquid passes through the volute, the kinetic energy converted into pressure energy.
Use: when higher discharge pressures are required with relatively low flow rate than radial flow impeller pumps are used.
b. Axial flow impeller/Propeller:
In this type of pump, the impeller pushes the liquid parallel to the pump shaft or the liquid passes axially through the impeller. Axial flow pumps are also known as propeller pumps because operate same as the propeller of a boat.
Use: Axial flow impeller use for high flow rates when sufficient head is required to overcome friction losses.
c. Mixed flow impeller:
In this type of pump, the liquid enters axially in a pump and leaves with both axially and radially. In mixed flow impeller, head partly developed by centrifugal force and partially developed by the lift of the vanes on the liquid.
Use: The mixed flow impeller is a compromise where some pressure rise, together with a reasonably high flow rate is required.
5. Types of Centrifugal Pumps w.r.t casing split:
a. Axial split: In this type of pump, the joint between two casing halves parallel to the shaft. Axial split casing allows inspection of pump internal parts without disturbing the bearings and seals.
b. Radial split: In this type of casing, the casing divides in a plane perpendicular/ vertical to the axis of the pump. Radially-split casing volute which carries the high-pressure liquid made from one casting. So radial split casing inherently stronger than the axial split casing.
c. Double casing or Barrel: The double casing or barrel casing has evolved out of the requirement for the convenience and expediency of an axial split casing together with the strength of the radial split casing.
6. Types of Centrifugal Pumps w.r.t energy conversion:
a. Volute: The volute is a chamber with increasing the diameter around the impeller or cross-sectional area increase steady towards the discharge. Due to this gradually increasing cross-sectional area, the kinetic energy of liquid converts into pressure energy. Volute generally used in radial flow impellers.
b. Double volute: The double volute casing incorporates a wall which divides the original single volute into two 180 degree volutes.
c. Diffuser Vanes: A diffuser is a set of stationary vanes that surround the impeller. The purpose of the diffuser is to increase the efficiency of the centrifugal pump by allowing a more gradual expansion and less turbulent area for the liquid to reduce in velocity. Diffuser vanes fitted to the discharge from a centrifugal pump impeller to reduce the turbulence generated in the flow as the liquid emerges from the impeller.