Control Valve Noise Prediction 1

[militarysam]

One of my customers is insisting I provide noise calculations done by hand to IEC 60534-8-3. The main problem I get is that the noise levels I get from the by hand method are 20-30 dB higher than the computer model. I noticed on a Weir data sheet that they show both Predicted Noise @1m and System Noise @1m both of which are very different. Does anybody know how I can get my results to match the computer calculated values? or why the Weir data sheet would show two different noise levels and what the difference is between them?

Any answers would be helpful

Thanks

 

[stanier]

Why not ask Weir to justify their model? As part of QA have they validated their software?

Most common mistake in sizing valves is using gauge pressure instead of absolute pressures in the sizing. I am not suggesting you have done or not done this in your calculations but raise it for others to learn. I made this mistake as a junior engineer many years ago and was suitably chastised by my supervisor.

"Sharing knowledge is the way to immortality"
His Holiness the Dalai Lama.

http://waterhammer.hopout.com.au/

 

[gerhardl]

A comment on the side:

One well-renowned European producer I know always refused to give out noise calculations, argumenting that the total installations could give as much, or more, additional noise.

Measurement by actual conditions at site, beeing the only accurate method of noise-level predictions in their opinion.

(I can well see that both law and practical issues gives the necessity of some pre-indication of noise level)

The limitatations I found by googling gives a self-explanation for the reluctance to pre-calculate noise level, or giving out any guarantee for this.

Most people (including other engineers and myself) are perhaps not aware of the actual limitatations cited.

You could almost directly say that by most installed valves you will not get anything but a rough indication on where you theoretically should be! ;-)

Please allow me!:

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IEC 60534-8-3: Industrial-process control valves – Part 8-3: Noise considerations – Control valve aerodynamic noise prediction method

Publication Date: Nov 1, 2010
SDO: IEC: International Electrotechnical Commission
DOD Adopted ANSI Approved Approved

This part of IEC 60534 establishes a theoretical method to predict the external sound-pressure level generated in a control valve and within adjacent pipe expanders by the flow of compressible fluids.

This method considers only single-phase dry gases and vapours and is based on the perfect gas laws.

This standard addresses only the noise generated by aerodynamic processes in valves and in the connected piping. It does not consider any noise generated by reflections from external surfaces or internally by pipe fittings, mechanical vibrations, unstable flow patterns and other unpredictable behaviour.

It is assumed that the downstream piping is straight for a length of at least 2 m from the point where the noise measurement is made.

This method is valid only for steel and steel alloy pipes (see Equations (21) and (23) in 5.5).

The method is applicable to the following single-stage valves: globe (straight pattern and angle pattern), butterfly, rotary plug (eccentric, spherical), ball, and valves with cage trims. Specifically excluded are the full bore ball valves where the product FpC exceeds 50 % of the rated flow coefficient.

For limitations on special low noise trims not covered by this standard, see Clause 8. When the Mach number in the valve outlet exceeds 0,3 for standard trim or 0,2 for low noise trim, the procedure in Clause 7 is used


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