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Centrifugal pump noise : formula, step by step calculation guide

How to calculate the noise level emitted by a centrifugal pump ? How to reduce a pump noise level ?

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1. Introduction
2. Noise of a centrifugal pump : step by step calculation
3. Noise reduction for pumps
4. Manufacturers

1. Introduction

Why are centrifugal pumps noisy ?

The impeller of centrifugal pumps is rotating at very high velocity, in consequence, the different parts of the impeller are hitting the fluid and create vortex, turbulent flow, at a specific frequency which is then transmitted as a vibration through the shaft, pump casing and pipes to the surrounding of the pump. The air is then continuing to transfer the vibration, leading to a noisy environment.

2. Noise of a centrifugal pump : step by step calculation

How to estimate what will be the noise emitted by a pump ?

2.1 STEP 1 : Define the type of pump

Different types of centrifugal pumps lead to different noise levels. One should 1st define if the pump studied or designed is of the following types :

  • Side channel pump
  • Single stage volute or ring section pumps with multi impellers
  • Multi-stage ring section pump

2.2 STEP 2 : Calculate the absorbed power

The absorbed power of a pump can be calculated thanks to the procedure given in this MyEngineerinTools page : Pump Power

2.3 STEP 3 : Calculate the noise emitted

The noise emitted by the pump is a function of the type of the pump and the absorbed power [Sihi] :

Type of pump Absorbed power Noise emitted
Side channel pump 2 kW < P < 40 kW LwA = 67+12.5*log(P/P0)
Single stage volute or ring section pumps with multi impellers 10 kW < P < 2000 kW LwA = 66+13.5*log(P/P0)
Multi-stage ring section pump 10 kW < P < 2000 kW LwA = 78+8.5*log(P/P0)

With :
LwA = A weighed sound pressure level (dB(A))
P = Absorbed power (kW)
P0 = 1 kW

3. Noise control : reduction for pumps

How to make a pump less noisy ?

3.1 Noise reduction by design

It is necessary to calculate the pump head and power requirements as accurately as possible, indeed, an oversized pump will lead to more noise. In addition, different features can contribute to reducing the noise generated by a pump :

  • Prefer design leading to low flow velocity in pipes
  • Use low noise fittings, have the pump mounted on a base plate with dampers, use vibration reducing pipework
  • Avoid sudden changes in cross section of the piping
  • Use long radius bends
  • Use low noise motors and gear boxes

Special case of cavitation

A pump that cavitates leads to a very specific noise. It is then possible to reduce strongly the sound emitted by the pump by ensuring the pressure at the inlet of the pump is higher than its NSPHr and therefore do not cavitate.

3.2 Noise reduction by insulation

It is also possible to foresee an insulation, like an enclosure of the pump within sound absorbing panels. A specific attention to the design of the sound proof enclosure must be given in order to ensure a good maintainability of the pump.

4. Manufacturers

The reader can refer to the following manufacturers for new pumps :

  • GrosClaude pumps (for all kind of pumps)
  • Sihi pumps (for side channel pumps)

Note that MyEngineeringTools has no link with those companies.

Source

[Sihi] Basic Principles for the Design of Centrifugal Pumps Installations, Sihi, 2003



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