noise absorption of a tailpipe within a pressure relief system

[kingsss]

In order to evaluate the necessity of noise reduction measurements in a PSV/tailpipe system, I am looking for information to estimate the potential noise absorption of the tailpipe.

So far, I only found a rule of thumb: - 3dB/50D_pipelength, without any reference or description. However, I would like to have somewhat more detailed info, e.g. function of tailpipe dimensions/shape/material and potential noise reduction by this tail pipe.

Who can help?

Regards, Kingsss

 

[Latexman]

kingsss,

In your case, why is noise level of a PSV discharge important? I think folks would want to hear it so they can steer clear of the area.

Good luck,
Latexman

 

[sailoday28]

I hope this helps.

Penn Separator Corp.
21 Pickering St., P.O. Box 340
Brookville, PA 15825-0340
Phone: (814) 849-7328
Toll Free: (888) 736-6737
Fax: (814) 849-4510
Activity: Manufacturer, Service

Keywords:
Boiler Blow-Down Systems, Inline & Flash Separators, Tanks & Pressure Vessels, Silencers For Steam, Air & Other Gases, Mist Eliminators, Blow-Off Tanks & Heat Recovery Systems

 

[hacksaw]

noise treament of psv is actually quite common in the powerhouse, but there is no such "firm rule" of db reduction.

you have to detail the noise calculation from your point and distributed sources. true there will be some pressure loss along with some reduction in noise but you have to calculate it.

You can expect to use larger than normal discharge piping and silencers.

good luck,

 

[distracted]

I think most of the noise reduction along a pipe will be from noise breakout. i.e. energy radiating through the pipe.
If you are still interested in some help with this. Post a reply and I will assist you offline. I have experience designing noise control equipment for these types of applications.

 

[CHD01]

I'm not certain if you are interested in hte noise generated at the discharge vent to atmosphere or the noise WITHIN a piping system. For a vent discharge to atmosphere I provide the following:

Formulas for noise level calculations are available from any major relief valve vendor such as Farris, Consolidated or Crosby. Crosby's, for exaample, may be found in hteir Engineering Handbook in Chapter 7, page 7-10. I'm providing it for you below:

L100 = L + LOG10 (0.29354*W*k*T/M)

where:

LOG10 means to take the LOG to the base 10
L100 = sound level at 100 feet from the point of discharge
in decibels.

L = noise int3ensity measured as the sound pressure level at 100 feet from the discharge (from figure 7 in hte handbook) If you don't have the handbook, calculate the pressure ratio = absolute relieving pressure/absolute back pressure. If the pressure ratio calculated is 3 or greater , L as about equal to 55. If the ratio is from 1.5 to 3, L varies in a linear way from 30 (at 1.5) to 55 (at 3). If below 1.5, it is beyoind the chart limits, but assume it varies from 0 (for ratio = 0) to 30 ( at ratio = 1.5).

W = maximum relieving capacity in pph
k = ratio of specific heats
T = absolute temperature in Degrees Rankine
M = molecular weight

Also, when the noise level is required at a distance of other than 100 feet, use the following equation:

Lp = L100 - 20 LOG10 (r/100)

where:

Lp = sound level at a disctance, r, from the point of discharge in decibels
r = disctance from the point of discharge in feet

NOise from the discharge of a vent will of course occur only if the discharge flow is sonic; which means that the pressure at the vent tip is greater than atmospheric pressure. If not sonic tip pressure is equal to atmospheric or containment vesel pressure.



The more you learn, the less you are certain of.

 

[aikmeam]

Kingss. Not sure if you're referring to noise as audible noise, or acoustic induce vibration (AIV). 3dBa/50D pipelength are applied for AIV mitigation.

Noise reduction is usually through trim designs or/and insulation.