CONTROL VALVE NOISE 1

[roker]

Hi,
We got a quotation for a 24" butterfly conrol valve (to be installed on a 28" line splitter overhead) with a predicted/calculated noise level of 105 dBA.
Can this noise level also cause mechanical damage beside health incidence?
How can we lower this noise level?
Is there any correlation between the calculated noise level to measured noise level after installation and operation of the control valve?

regards,
roker

 

[khan101]

roker,
there are 3 basic types of noise sources in valves:
1) mechanical vibration
2) cavitation
3) aerodynamic noise

Noise is bad for your health and valve's health. What method was used for predicted/calculated noise level? Please refer to ISA S75.17 for a fairly accurate prediction method.

OSHA limit for noise level is 90 dB. Even if you ignore OSHA then anything above 110 dB is dangerous for equipment and personnel safety.

There are ways to reduce noise, like:
1" thick pipe insulation will reduce noise 5 to 10 dB
If you double the pipe thickness it will reduce around 5-6dB
Silencer downstream will cut it by 10dB
Silencer up and down stream will give you 20 dB reduction
Multiport resistance plate down stream will cut it 15-20 dB
Special low noise valve for 15 - 30 dB

of course you can apply a combination of the above methods, which is sometimes more cost effective.

 

[sshep]

Is this vapor only service? The aerodynamic noise possible from the vapor flow possible in a 28" line with a sizable pressure drop could be very noisy, but probably not destructive to the valve.

If this noise is from vibration or cavitation, then the noise is a byproduct of potentially destructive forces.

Regardless of the source of the 105dBA noise, in the USA engineering controls are required if practical. Khan101 gives several likely options to address noise sources.

Best of luck, sshep

 

[hacksaw]

mechanical damage? yes especially with a butterfly.

Health risks? Yes.

SPL calculations work fine as lone as you include the line noise but they do have limitations; such calcs are not an exact science given the number of variables.

Reduce the noise? It all depends on how the noise is generated. Lagging is not always the best cure.

Good luck,

 

[jsummerfield]

Is there a velocity problem with the pipe size or the sizing data? A line splitter does not seem like a high pressure drop application.

For a globe valve in the six-inch or smaller category I would assume mechanical damage around 115 dB. Check with the manufacturer. Howver, 105 dB seems potentially damaging for a 24-inch butterfly.

John

 

[121202]

You've got the wrong type of valve. Suggest that you look at valves with multistage trims.

 

[sshep]

I would like to remind that noise is not always a good indicator of the forces involved relative to possible mechanical damage. We have on at least one occasion had an unexpected noise crop up (compressor interstage cooler) which was loud enough to cause worry about possible damage from the energy involved. A company specializing in these types of analysis was brought in. They hooked up a bundle of sensors worthy of Ghost Busters and after readings and calculations were able to determine that the energy levels were not of concern.

Aerodynamic noise is caused by the turbulent energy of pressure drop that cannot go into increasing the bulk fluid velocity- which is why pressure drops resulting in sonic velocity are very noisy (the energy must go somewhere). The volume of flow possible in a 24" line increases the noise proportionally. Presumably the vendor sizing the valve understands the application and would not deliberately design something that would fail mechanically even though the application involves a generally undesirable (and in some cases unavoidable) amount of source noise.

just my thoughts, sshep

 

[CARF]

thread698-95817

Good luck,
CARF

http://www.carf-engineering.com

 

[brainstorming]

We did use Acoustic insulation to reduce such noise level but the reason that the velocity was high (small size selected) but since the services were intermittent this insulation was used.

Butterfly valve is sensitive to vibration and might get damaged with time if much vibrations present in the valve disk.

Regards

 

[hacksaw]

sshep,

with valves, especially butterflf designs, high noise invariably coincides with reduced valve reliability and life time.

noisy HEX are another problem all together

 

[sshep]

Hey Hacksaw,

Thanks for your observations and for teaching me something. As a mechanical engineer you are probably much better informed about the nature of damage and repairs.

As a chemical engineer my experience has been that there are usually very few economic alternatives to butterfly valves in large vapor lines. We (chem e's) can essentually only deliver up the correct process conditions and require that the vendor either deliver something that works or notify us if he can't.

I believe our butterfly valve mechanical problems (in clean vapor service anyway) are primarily due to movement wear in the shaft, linkages, and actuators rather than damage to the disk or other wetted components such as might occure with cavitation or critical frequency vibration at lower noise levels. Since you obviously have more applicable experience with mechanical problems, I would be interested to learn what types of damage you are observing in your butterfly valves.

Thanks and best wishes, sshep