Silencer ideas please.

[Graham_Wright]

My soon to be installed generator is in a cramped space leaving no room for a conventional silencer.
I was going to fit a Vetus waterlock which, I was assured, would provide some attenuation but it won't fit.
A cylindrical silencer with side entry and exit would fit.
What do I use as an absorbent fabric bearing in mind this is a wet exhaust?
I can buy perforated tube on ebay.

 

[alahol2]

Vetus do these... Do they not fit?

 

[Graham_Wright]

Yes - ideal.

I wonder how much.

Edit £179!!!!!

 

[PCUK]

This is the basis of a water-lock silencer, Just make one from GRP to fit the space.

(2) How a wet-lift muffler works:

 

[Graham_Wright]

This is the basis of a water-lock silencer, Just make one from GRP to fit the space.

(2) How a wet-lift muffler works:

Thanks.

I don't need a watercock, genny and outlet well above the waterline.
That appears to rely just on the empty space for noise reduction. I thought there may be some sound absorbent material involved. This, of course, would have to be water tolerant.
I can easily make a stainless tube to fit the space and perforated tube is readily available.

 

[ean_p]

This is the basis of a water-lock silencer, Just make one from GRP to fit the space.

(2) How a wet-lift muffler works:

Your links wont work for me....could you re post them please?

 

[ean_p]

Thanks.

I don't need a watercock, genny and outlet well above the waterline.
That appears to rely just on the empty space for noise reduction. I thought there may be some sound absorbent material involved. This, of course, would have to be water tolerant.
I can easily make a stainless tube to fit the space and perforated tube is readily available.

Doesn't the sound attenuation come from the gas expansion when entering a larger volume, ie as in going from tube to silencer box? I may be waffling and need a little attenuation myself!

 

[DownWest]

Quite a while back, I installed a 'Sailor Silent Set' genset. It came with Vetus bits for the intake and exhaust systems. The Intake was a baffled dry system and the exhaust a water lock with a baffled exit. It really was quiet, far more than the Onan it replaced.
But, on the way down to the Canaries, a bolt in the generator worked loose and lunched it. So, as often happens, they had to wait in the islands for a new one to be flown out..
When running, we could happilly chat over the unit. Very quiet.

 

[penfold]

Wet exhausts are silenced by the cooling of the gases, obstructing the direct transmission of noise by forcing the gas through water in the water lock and by the elastic properties of the hose. Absorbent material will fill up with soot and stop being absorbent. If one water lock isn't reducing noise enough add another one.

 

[DownWest]

^^^What he says. Recently, given the tight space available, I made a waterlock out of GRP (use polyester resin, not epoxy) The Vetus ones would not fit.
If you have the time, the materials are very little.

 

[Graham_Wright]

Wet exhausts are silenced by the cooling of the gases, obstructing the direct transmission of noise by forcing the gas through water in the water lock and by the elastic properties of the hose. Absorbent material will fill up with soot and stop being absorbent. If one water lock isn't reducing noise enough add another one.

#4 (Pcuk) shows the reverse direction. I.e. the gas has to expel the water before it itself can escape. Please help my confusion.

 

[PCUK]

Does your genny exhaust have water cooling in with the exhaust gas or is it a dry exhaust. A waterlock silencer isn't there to stop back flow and isn't necessarily used below the water-line. There is no absorbent in any wet exhaust system. It all relies on baffles and in the waterlock silencer the water acts as a moveable baffle. I was thinking along the same lines as DownWest that you could fabricate a silencer on the principal of the waterlock type to suit the space available.

 

[geem]

Does your genny exhaust have water cooling in with the exhaust gas or is it a dry exhaust. A waterlock silencer isn't there to stop back flow and isn't necessarily used below the water-line. There is no absorbent in any wet exhaust system. It all relies on baffles and in the waterlock silencer the water acts as a moveable baffle. I was thinking along the same lines as DownWest that you could fabricate a silencer on the principal of the waterlock type to suit the space available.

Sound doesn't like to go around 90 degree bends in square ducts. It loves circular ducts, but square once cause reflection of the sound back in the way it came. We used to use labyrinth silencers on some equipment where space was tight. This would be a number of 90 degree bends. You can form these from baffles that make the sound run around a maze. Hard to explain but just Google labarynth silencer

 

[DownWest]

Sound doesn't like to go around 90 degree bends in square ducts. It loves circular ducts, but square once cause reflection of the sound back in the way it came. We used to use labyrinth silencers on some equipment where space was tight. This would be a number of 90 degree bends. You can form these from baffles that make the sound run around a maze. Hard to explain but just Google labarynth silencer

Depends on how much space, since the exhaust is wet, the water lock is probably the easiest and smallest solution.

Again, I was tasked to install a 4-pot Lister 35kw aircooled genset, with the proviso that they didn't want to hear it, as it was under the extended pool patio.

Since it had to be solidly mounted, the big block of concrete it sat on was in a cork lined pit. The room was lined with 10cm of cork and the air cooling intake had multiple soft baffles. The exhaust was a trench with your labyrinth baffles. The result even surprised me. Just a background murmor, instead of the usual roar. But, it need some space and cost a bit. But the cost was secondary to the noise.

 

[geem]

Depends on how much space, since the exhaust is wet, the water lock is probably the easiest and smallest solution.

Again, I was tasked to install a 4-pot Lister 35kw aircooled genset, with the proviso that they didn't want to hear it, as it was under the extended pool patio.

Since it had to be solidly mounted, the big block of concrete it sat on was in a cork lined pit. The room was lined with 10cm of cork and the air cooling intake had multiple soft baffles. The exhaust was a trench with your labyrinth baffles. The result even surprised me. Just a background murmor, instead of the usual roar. But, it need some space and cost a bit. But the cost was secondary to the noise.

My water lock on the generator provides little in the way of sound attenuation. By contrast the water lock on the main engine is effective at reducing noise. Even with a Vetus silencer the generator exhaust is noisy. One day I will get around to building a decent labarynth silencer for the generator.

 

[penfold]

^^^What he says. Recently, given the tight space available, I made a waterlock out of GRP (use polyester resin, not epoxy) The Vetus ones would not fit.
If you have the time, the materials are very little.

For the non-DIY inclined Halyard Marine have a range of waterlocks which are a different shape to Vetus' products, worth a look.

 

[jwfrary]

Centek, similar to the halyard ones but with a few other options. ASAP are the dealer but don't stock or list all the options

 

[PCUK]

Sound doesn't like to go around 90 degree bends in square ducts. It loves circular ducts, but square once cause reflection of the sound back in the way it came. We used to use labyrinth silencers on some equipment where space was tight. This would be a number of 90 degree bends. You can form these from baffles that make the sound run around a maze. Hard to explain but just Google labarynth silencer

I'm not sure what your point is. I've not mentioned square section anything. In fact it never occurred to me that someone might want to make a square silencer with square tubes as it would be more difficult than fabricating rounded parts.
The later references to Halyard and Centek have already been dismissed as not the right shape or size, hence the DIY custom made suggestion.

 

[geem]

I'm not sure what your point is. I've not mentioned square section anything. In fact it never occurred to me that someone might want to make a square silencer with square tubes as it would be more difficult than fabricating rounded parts.
The later references to Halyard and Centek have already been dismissed as not the right shape or size, hence the DIY custom made suggestion.

I was suggesting that a custom made silencer with square sections to encourage end reflection was the way to go. You just need a grp box with internal staggered baffles. Not hard to make

 

[penfold]

I'm not sure what your point is. I've not mentioned square section anything. In fact it never occurred to me that someone might want to make a square silencer with square tubes as it would be more difficult than fabricating rounded parts.
The later references to Halyard and Centek have already been dismissed as not the right shape or size, hence the DIY custom made suggestion.

The OP makes a general statement that there's no room for a conventional silencer. We've no idea what brands of waterlock he has looked at other than Vetus. None of us are likely to be of much help without a sketch and dimensions of the available space or some photographs.