RE: Valves regulation query

From: <SARE>
Date: Sat May 04 2002 - 01:42:00 EDT

the noise limit has to be part of the equipment spec to comply with OSHA reqt. Baiscally the nosie level is set at 85 dBA measeured 1 m, as Steve has previuosly mention, from source for continuous service. specifying only the dBa value without reference to octave frequencies may still result in exceesively nosiy control valve.for example, 84 dBa at 500 hz will merit the same consideration as 94 dBA at 125 hz.

One way of offseting the problem assoiictaed with noise (say over 10dBA) is to use a noise reducing trims. The background noise pointed by Steve is very important. The way i'll measure it is to hook up a noise meter to a spectrum
(in this way i'll get both the dBA and Hz), check out the noise contours
(part of the lstk deliverables), do a simple math, make the comparison and
decide whether you need a noise control (passive, active or procedural) or not.

-----Original Message-----
From: Steve McKenzie [mailto:Mechproj@xtra.co.nz] Sent: 03 May, 2002 1:11 PM
To: PipingDesign@yahoogroups.com
Subject: RE: [PipingDesign] Valves regulation query

Hi Ivan,

I doubt if you will find a standard for valve noise limits because installations vary so much. Some users specify a maximum noise level of 85dBA measured at 1 metre from the valve in any direction. The reason for this is that higher levels usually result in hearing protection equipment being required. However this limit is meaningless in itself mainly because of two reasons:

1. Enclosure. The 85dBA is a free field emission and would be measured out in the open with no background noise, or in an anechoic (no echo) chamber. If the valve was located in,say, a small concrete chamber, the noise level would be much higher, possible 30 - 40 dBA more because of echoes from the walls. The Valtek control valve manual states that for a valve installed near a hard wall, add 3dBA. By a floor and a wall add 6dBA. At a corner near the floor (or ceiling), add 9dBA. Often, the valve supplier is not informed of the location of the valve and the properties of its surroundings.
2. Background noise. This is the noise generated by other sources. It contributes to the noise at the point of measurement. For example if we have two 85dBA sound pressure sources at the same point, the combined sound pressure will be 88 dBA (I think). There is also breakout noise to be considered. For your case, this may be taken as the noise emitted from the pipe that the valve is connected to.

The maximum sound pressure level that personnel should be subjected to
(without hearing protection) is normally given as 90dBA at for 8 hours daily
exposure to 115dBA for 15 minutes exposure. Where there are site boundary noise limits (often 40 - 45dBA) , there is a whole extra dimension added. Many "local plan" noise limits are impossible to achieve because the background noise levels, with the plant shut down, exceed the stated limit.

  As you can see from the above, the noise emission requirement for a single valve depends on its local environment and boundary conditions. Many firms use an acoustic consultant. Acoustic principles are fairly basic, but an extremely thorough understanding is required for their successful application. Take care. Remediation can be very expensive.

Cheers

Steve McKenzie

-----Original Message-----
From: Ivan Fernandez [mailto:ifernandez@tecna.com.bo] Sent: Friday, May 03, 2002 7:28 AM
To: PipingDesign@yahoogroups.com
Subject: [PipingDesign] Valves regulation query

Avelino BarreiroHey Guys,

My Control & Automatization coleague, has an interesting query that some of you guys might answer:

Which is the top limit noise level in decibels for a Pressure regulator valve in a process plant.

I must add to ask if there is a Code or Standard for this matter?.

Thanks

Iván Fernández C.

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Received on Sat May 04 01:42:00 2002