Measurement of Aerodynamic Noise from Valves 1

[BHMech]

Does anyone have a procedure for the measurement of aerodynamic noise from valves. In particular, steam power processes. I'm looking for a field measurement test rather than a lab test.

Thanks.

 

[MachineryWatch]

Are you actually trying to determine the radiated noise levels from these valves, or are you trying to determine if there is leakage? There are ultrasound based devices that are available and are often used to check for leaks of steam valves and steam trap function.

Skip Hartman

http://www.machinerywatch.com

 

[BHMech]

No, leakage is not the issue. I need to measure noise in dB(A).

 

[hacksaw]

Most valve manufacturers have standardized test, but to perform such a test on a single valve and to isolate it from the pipe noise and the noise from all other adjacent sources is a real problem.

There are quite a few noise survey codes on the market to compile the data.

Good luck and don't forget the ear plugs...

 

[BHMech]

Thanks Hacksaw,
Can you give me any leads, references ?

 

[khan101]

BHMech,
Noise tests can be performed to ISA S75.07 or the essentially equivalent international standard, IEC-534-8-1. Hydrodynamic noise can be measured using IEC-534-8-2. It is often impractical to test at actual service condition. Methods for predicting the noise at actual service condition must be used in those cases. One of the most important parameters affecting noise is the ratio of upstream to downstream pressure, p1/p2. I hope this helps.

 

[BHMech]

Thanks Khan101,

I have this code, together with IEC-534-8-3 for predicting noise. Unfortunately IEC-534-8-2 is a lab test rather than a field test. I could adapt this but I prefer a procedure that is suited to the field.

 

[khan101]

BHMech,
It is not practical to measure the aerodynamic noise out in the field because out in the field too many factors are involved. If you persist then you can measure it with a microphone and a decible meter. Please read the following paper which might help you with your concern.

http://users.rowan.edu/~savelski/researchpapers/ControlValves.pdf

 

[GregLocock]

You may be able to use acoustic intesnity in this case, for a field measurement. It does not work well with reverberant sound fields, but if you were to build a temporary acoustic barrier around the valve it may work.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[BHMech]

Thanks Khan101 and GregLocock.
These will bring me some way foraward.

Bryan Hall

 

[fwcatr]

What are you going to do with the information? Are you trying to see if the valve supplier conformed to the specified sound pressure levels? The supplier of the valve should be able to predict the sound pressure level one meter downstream, one meter away from the valve while flowing steam and supply that information to you.

For field measurements, I agree with Greg Locock on the sound intensity method. If you are able to remove the downstream insulation, and the plant operator can run through some varying pressure conditions and valve travels (which are big ifs), you would be able to get some good information using sound intensity. Doing a noise survey of the area while certain valves are running, using sound intensity, would provide valuable information too. If you are able to get to the downstream pipewall, and use an accelerometer that can withstand the heat, you could take some pipewall vibration velocity response measurements and calculate the radiated sound pressure levels.

 

[BHMech]

I am working for the valve manufacturer and I wish to validate our noise prediction calculations. We already have predictions based on IEC 534-8-1, and based on test values gained from similar equipment in semi-anechoic chambers but these are based on air flow and were tested at lower velocities. I am attempting to trully validate the prediction method by measuring exactly what the customer gets.

I have several plant managers that are very willing to help. And they have no problem in setting a steady system for a couple of minutes while we take readings.

I dont think I can find an accelerometer that will withstand this sort of heat but I would be interested in the procedure for measuring viration and calculating noise in this way? I may be able to provide some sort of rigid insulator to fit between the pipe and an accelerometer.

Thanks for your efforts guys, any references for my futher reading would be appreciated.

Bryan Hall

 

[fwcatr]

Bryan,

Here is a link that will get you to some technical monographs. Technical monograph 33 should help you with determining radiated sound pressure levels from pipe wall vibration velocity. I have had great success with utilizing that method.

http://www.fisherregulators.com/technicalmonographs/various/

I know that PCB makes accelerometers that can withstand 900 deg F, but keeping them on a pipe with a magnet or adhesive at elevated temps is the problem. Depending on the pipe wall temp, you might be able to attach the accel with a magnet for a brief moment while you acquire some data.

Do you have access to a sound intensity probe?

Regards,
Fred Catron

 

[BHMech]

Fred,
This is excellent information. We have access to a variety of equipment through contacts at a local university.

I shall keep you posted.

 

[fwcatr]

I am glad I could help. I am interested to see how the testing goes.

In the past, I have attached a magnet with accelerometer to a pipe flowing steam, with the accelerometer being rated to 250 deg F, and have gotten reasonable results. I brought along a temperature gun to measure temps on the pipewall and my equipment in case I needed to let my equipment cool off some.

Most of the time that type of testing was to look at comparisons of pipe wall velocities at various locations on the pipe line to see if responses were higher near piping sections, like tees, or downstream of the control valves.

Regards,
Fred