Noising from Genset

[honglien]

Hi everybody!
I have a small question and wish you would help me.
I am finding some information about standards or recommendations of Diesel Generator (Vol. How to mitigate the noise when the Genset operates.
that's great if you could give me a link for these.
Thank you in advance!

 

[alehman]

Allowable noise levels are usually dictated by local laws. It is usually specified in terms of dbA as measured at your property line or the impacted neighbor's property line. Many times, allowable levels vary by time of day. Ranges I've seen are from no limit down to 55dbA.

 

[honglien]

Thank you,Alehman.
You're right to say noise levels always dictated by local laws. Refer to technical specifications of Genset, on the catalogues of some manufacturer, the noise level is limited, 75dB in 7m.
By the way, Could You tell me how to design a "Noise Absorption Chamber" to limit noising from Operating Genset?. I'm looking to hearing from You.

 

[itsmoked]

It often is not just "building something". Quiet generators are designed from the ground up.

Baffles are needed, special mufflers, the sound paths must be identified and dealt with.

Enclosing a generator then requires maintaining its cooling properly too.

There are companies that sell sound blocking and sound absorbing materials.

http://www.surfacingsolution.com/AcousticalMaterials.htm

http://www.firwin.com/pages/what/firwin_newsletter_Feb07.html

http://www.acoustiblok.com/marine.html#cooliris

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[alehman]

This company has built sound attenuation systems for us. They can design a system based upon a specified genset, installation configuration and sound level requirements. I'm sure there are others.

http://www.cmcousa.com/intro.html

 

[waross]

There are three main sources of noise from a gen-set.
Exhaust, fan, and direct noise radiation from the engine block.
The larger manufacturers offer enclosures that contain much of the sound.
In the field, I have had good luck with constructing a concrete block generator room with a flat roof. I install a partition about two feet from the end of the room. This void space is constructed about 1.5 ft. to 2 ft. higher than the roof and opens back over the roof. The hot air from the radiator discharges into this void and exits over the roof. The exhaust is also piped into this space and back over the roof.
The walls in the generator roof and sometimes the void are covered or partially covered with sound absorbing material.
The material most readily available in the third world is the board used to fabricate air conditioniong ducts. It is one inch of rigid fibreglass insulation with a backing on one side. It is available in sheets, typically 4 ft. by 8 ft. It is apllied to the walls and held in place with a wire screen with about a 2" x 2" mesh. We have found that any amount helps. Typically we will install a sheet on each side of the generator and then add more sheets later if more sound attenuation is needed.
respectfully

 

[itsmoked]

Hey Bill what about the fan engine noise end? Seems that big fan and the engine block are going to radiate noise out the other end.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[MikeHalloran]

I think the radiator will attenuate some of the fan's noise signature in that direction.

Marine gensets don't have a radiator or fan, and can be equipped with enclosures that are effective enough that you can't tell which one is running without looking at the instruments. They have ventilation openings for the generator and the alternator, usually configured as a labyrinth lined with acoustical damping material.

The same technique (soft- faced labyrinth) would be effective in a building, too.





Mike Halloran
Pembroke Pines, FL, USA

 

[alehman]

Attenuators are readily available and can achieve quite remarkable results if enough space is available. Frequently it is necessary to provide attenuators on both the air intake and radiator discharge. I've seen genset enclosures for large units with radiators that are as effective as Mike described.

One of the problems for gensets with skid-mounted radiators is providing the required level of attenuation without creating excess back-pressure on the radiator fan. Radiator fans typically can only tolerate 0.5" of water column to maintain rated engine capacity. This may result in very large attenuators to minimize air flow restriction.

 

[rbulsara]

The source of noise from geenerators cab be grouped in 4 categories.:

1. Air exhaust (radiator): Rquires silencers in air stream for sound attenuation. Radiator itself is noise generator not an silencer.

2. Air intake louvers: Also requires silencers in air stream.

3. Exhaust stack (flue gas): Requires sound attenuaitong mufflers.

4. Sound eminatiing from enginer block/alternaotr etc.: This requires sound absorbing enclousre walls.

If the unit is packaged by manufactueres, they do the needful accoustic design to meet a given performace.

If the unit is in a building, you will need services of professional accoutic consultants.

 

[waross]

Hi Keith;
The noise in a concrete block generator room seems to ricochet and re-inforce itself. It seems to radiate sideways, both from the engine and the fan. One sheet of sound absorbing fiberglass on each side of the engine does a remarkable job of reducing noise levels. The radiator does seem to attenuate the noise somewhat. It is somewhat noisy up on the roof in front of the discharge but noise levels at the residence are much reduced. We have discussed installing a sheet of fiber glass material in the void space in front of the radiator discharge but so far we have been able to achieve acceptable sound levels without sending someone into the void. Access is possible but difficult.
This is cut and try rather than pre-planned engineering, but when the customer wants it quiet, you don't work to a dB figure, you make progresive improvements until there is a balance between the customers noise tolerance and his budget. Also, there are not a lot of resources available in parts of Central America. Find what material is avalable and then "Exercize Ingenuity".
I have also had very good luck with the factory packaged noise attenuating enclosures that have been mentioned here.
Respectfully

 

[itsmoked]

Thanks Bill.

You guys seen a WhisperGen? I ask because you pretty much won't be hearing one! I walked with 5 feet of a trailer mounted 200kW one running, and only realized it was running because the meters were active. It was putting out 140kW!! The only sound was about like a one foot dia room fan on medium speed. It was providing power to a movie set. It was amazing.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[rbulsara]

How about some 2000kW gens...like that..

 

[rbulsara]

The last post was in response to Keith's previous post.

 

[itsmoked]

Hi rbulsara.

I bet it could be done.. Not on a trailer though.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[rbulsara]

Keith:

Almost looks a trailer, just bigger, when assmebled in field it is 67'L x 12'W x 14'H. We also desinged a few sound attenuated buildings housing several of them. The latest one will have (5)2500kW gens.

 

[ruggedscot]

You want quiet generators ? Try Ballard fuel cells, those are quiet!

Rugged