Power Station Cooling Water Pump

Introduction

This is a 3D model of an Axial Flow Cooling Water Pump.

3D Model Annotations

Axial Flow Cooling Water Pump

This 3D model represents a large axial flow cooling water pump often used in the power generation industry. Axial flow pumps are used for low pressure, high flow, applications. Almost no radial force is imparted onto the pumped liquid, but the pump is still classified as centrifugal because some small part of the pumped liquid’s movement is radial.

Discharge Elbow

Liquid is discharged from the pump through this connection.

Suction Bell Mouth

Liquid is drawn into the pump through this connection.

Impeller

Axial flow impellers are similar to the propellers used on marine vessels (ships, boats etc.). This type of impeller is ideal for high flow, low pressure applications. The rotational speed of the impeller is relatively low, typically less than 150 rpm. Operational pressure heads are typically between 5 to 25m. In addition to axial flow impellers, closed and semi-closed centrifugal impellers may also be used for cooling pumps of this size.

Thrust Bearing

The type of bearing used depends upon where the bearing is installed. A thrust bearing at the top of the shaft must cater for axial loads (due to the pump’s weight and direction of pump thrust) and radial loads (alignment). The thrust bearing for this model is located within this casing.

Shaft

The shaft transfers the rotary motion created by the electric motor to the impeller. Shorter shafts can be manufactured from a single piece, whilst longer shafts are manufactured from several pieces and assembled using couplings. The shaft is held in alignment using bushing sleeves or bearings.

Guide Bearing

Radial loads exerted by the pump during operation are transferred to bushings or bearings. Sacrificial bushings are favoured because they have a very simple construction and are relatively cheap. Each bushing consists of a cylindrically shaped sacrificial material (thane, rubber, bronze etc.) that is installed between the shaft and guide bearing supports. Small grooves cut into the bushings serve as cooling and lubrication channels.

Water Column

The water column is a long cylindrical welded piece. The outside of the water column often has a lifting eye installed to allow for removal during maintenance periods.

Diffuser

As liquid is discharged from the impeller, it flows over the diffuser. The shape of the diffuser causes the liquid’s velocity to decrease and its pressure to increase (Bernoulli’s principle); a volute casing performs a similar function, but it is not always practical due to its size.

Electric Motor

An electric motor is used to rotate the impeller. Three phase variable frequency drive motors are typical for this type of application.

Guide Bearing Support

The guide bearing is held in position using supports connected to the water column.

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