Noise Reduction Calculation 1

[hadams417]

I have done some rather extensive work regarding IEC 60534-8-3, Control Valve Aerodynamic Noise Prediction Method.

Now that I am able to predict rather accurate noise levels I need to take it a step further. I need to make educated predictions as to noise reduction solutions. I am aware that there exists a number of solutions to this problem. I am wondering if anyone has experience in either of what I am looking at as two categories.

1. Internal noise reduction solutions - ie, diffusers, inline-silencers, orifice plates...etc. The ones that I have access to specifify "up to x dB(A) noise reduction," however I am looking for a slightly more detailed approach to determining the amount of noies reduction I can expect from any of these particular solutions. **Perhaps some calculations based on diffuser design, number and size of holes, etc....


2. External noise reduction solutions - This basically includes any and all types of insulation, most specifically acoustical pipe insulation. I dont know if there might exist some sort of pre-determined method for predicting noise reduction based on insulation material properties and thickness or if, again, it was basically left up to what the manufacturer specifies.

I appreciate any help you may be able to provide on this matter.

 

[LSThill]

Team Members:

http://www.llnl.gov/es_and_h/hsm/doc_18.06/doc18-06.html

with Additional Technical ES&H Manual:

http://www.llnl.gov/es_and_h/crosswalk/crosswalkpsort.html

 

[fwcatr]

hadams417

There are many options when dealing with what to do internally regarding noise being generated from control valves. Each vendor of a control valve should have different levels of noise attenuation trim, depending on flow rates through the valve. Like you mentioned, there are also inline techniques that can be quite effective too.

I would not use an orifice plate though, the orifice does put a sufficient back pressure on the control valve to reduce the noise radiating off the control valve's downstream piping, but downstream of the orifice will now be the dominant noise source, and depending on how close the orifice is to the control valve, the noise being generated downstream of the orifice will impact the noise measurements downstream of the control valve.

I have heard of control valve vendors saying that they can deduct 10 dB for 4 inches of insulation, but to effectively quantify that, experimental validation would have to be looked into.

If you are looking into a solution for a current or proposed pipe line, you could call the vendor of the control valve and discuss control valve trim options, inline silencers, and attenuation due to insulation.

I hope this helps.

Regards,
Fred