Fire proof insulation

[lymmranger]

Can anyone suggest a suitable insulation material to place close to the exhaust system.

 

To be specific, I am part way through building a soundproof (hopefully!) enclosure around my Generator. The exhaust system has been wrapped with asbestos bandage, but I wish to "stuff" the box, ideally, with a rock wool type material to further deaden the sound.

 

If I use household roof insulation will it stand the heat?

 

I seem to remember hearing that exhaust systems can get to over 1000 degrees....... ?

 

Any suggestions would be most welcome

 

[gbmud]

Can anyone suggest a suitable insulation material to place close to the exhaust system.

 

To be specific, I am part way through building a soundproof (hopefully!) enclosure around my Generator. The exhaust system has been wrapped with asbestos bandage, but I wish to "stuff" the box, ideally, with a rock wool type material to further deaden the sound.

 

If I use household roof insulation will it stand the heat?

 

I seem to remember hearing that exhaust systems can get to over 1000 degrees....... ?

 

Any suggestions would be most welcome

 

 

 

Well, isn;t household roof insulation made from glass fibres? What temperature does glass melt at? Less than 1000 degrees C I suspect - or are you working in English?

 

Chris

 

Added on edit: http://hypertextbook.com/facts/2002/SaiLee.shtml

Edited March 10, 2006 by gbumd

[DHutch]

I just further to that, i google "melting point of rockwool" and found the spec sheet to say:

 

"Fire resistance: The wool is non-combustible in accordance with ISO 1182.

[The] Melting point of fibres is above 1000°C."

 

Also, steel its self has a melting point of about 1370°C

 

 

 

But back to problem in hand, what do you mean by "household roof insulation"

- Rockwool/glass fibre should be ok, as you say, there glass tape round the exhast already.

- But if try solid-foam roof insulation, your going to end yop with a big sticky mess at best!

 

 

Daniel

[lymmranger]

Yes... I do mean the rockwool,

 

- I also reckon that the bandage adds to the safety factor - but I am not sure.........

 

Clearly it would be a potentially expensive mistake, so I do not want to guess...

 

I need facts guys

 

Any one tried this?

[ChrisPy]

Filling the enclosure with any material creates a different problem, because there is no ventilation to take the heat away. As I see it, you will trap the heat and gradually build up a hot box.

[bottle]

Heat insulation and sound insulation are two different things.

 

'Rockwool' is a heat insulator not a material for sound insulation.

 

There well may be a small reduction in sound transmission with the use of 'rockwool' but that is not its design parameter.

 

You require sound insulation that can withstand high temperature environment.

 

As Chris says do not forget about ventilation.

[Supermalc]

http://www.ketogroup.com/3m/thinsulate.htm

 

This is what you need for sound insulation. Sadly it is too expensive for me to have used, so I had to compromise.

 

I wanted a cheap boat with a single diesel, partly because I 'like the sound' of one.

 

However the engine only has a thin plywood cover, and when I first cruised home, I found it impossible to talk. Even shouting in your ear. It was louder than a Quo concert so I had to do something.

 

From talk on other forums, and help from friends, plus my own experience of noisy old vehicles I found a solution.

 

I had a roll of thick fibreglass roof insulation left over. I covered this with baking foil, then on the suggestion of someone else, I protected it with plastic netting.

 

Because I had got a single diesel because I like the sound, and then soundproofed it, some 'clever' people naturally took the p*** however I could now here what others said. It was still noisy, but bearable. As the oil mist lessened the sound deadening to some degree, I covered it with a piece of thick old carpet last year and now simply talking loudly is sufficient.

 

Adequate sound deadening should have no gaps, something that is impossible in an engine compartment, as ventilation is of course essential, but a 50 to 60 percent reduction will make all the difference.

[Supermalc]

I've finally found the photo...

 

[David Schweizer]

The proper material to use is "Quietlife" Sound proofing or another tradename equivalent. which you line the box with. This allows for air to ciculate which as Chris has pointed out is essential for cooling. It can be obtained from any decent Chandlery, although the cheapest I have found it is direct from ASAP Supplies at www.asap-supplies.com

 

The standard stuff comes in various thicknesses and can be used close to the exhaust providing it does not actually touch the pipes. They also do several alternatives which are more heat and/or fire resistant.

 

I have just re-lined my engine box whilst the engine is out for a re-build, I used the standard type and fixed it with spray on adhesive. The engine is not back in yet so I don't know how effective it is, but it must be better than the old fraying carpet underlay type stuff that was in it before.

 

I would not have thought that rockwool loft insulation will be very effective as a sound insulator, that is certainly not what it is designed to do. I remember in years past we used to use it to fill the interiors of large loudspeaker enclosures, the theory being that it discouraged the Bass response from passing out through the back of the enclosure. I still have a pair of those speakers at home. One of them is filled with rockwool, and the other one has never been filled. I cannot tell the difference between them which suggests that the rockwool has very little sound insulation properties.

Edited March 11, 2006 by David Schweizer

[John Orentas]

As David suggests sound insulation materials must have a lot of 'mass' about them, they must adsorb energy and not pass it on, the best will have a layer of high hysteresis, high density lead or similar material incorporated. Lower density materials can make some effect in that they can break up sound waves but that is marginal.

 

In my view a heavy rubber / fabric carpet underlay material can work as well as many of the expensive alternatives and the fire hazard argument can be much exaggerated. Other than perhaps the area immediately around the exhaust the temperature surrounding a water cooled engine should never rise above 100 deg. C.

 

Where does the 1,000 deg. figure come from you would need an acetylene burner in there to achieve that figure. Although the engine enclosure should be well ventilated it does not rely on ventilation for cooling, that it done by the cooling water taking taking the heat away to the keel tank or out via the exhaust system.

Edited March 11, 2006 by John Orentas

[David Schweizer]

..... the best will have a layer of high hysteresis, high density lead or similar material incorporated.

 

The Quietlife Sound Proofing has exactly that, a heavy 5kg per sq mtre lead loaded barrier which is bonded between two high density (fireproof) layers. Total panel thicknesses range from 23mm to 58 mm, with 32mm being the most popular application.

Edited March 11, 2006 by David Schweizer

[lymmranger]

OK ...thanks for that

 

I just realised that I had not given the full story.

 

The (diesel) genset is in a sound deadened box, this has been designed to allow a flow of fresh air to dissipate heat build up. Induction air is drawn seperately from outside. The exhaust system is mainly outside the box and consists of two silencers connecting to a skin fitting. The silencers almost fill a cubby hole part of the engine bay, between the soundproof genny box and the bulkhead. as discussed previously they are carefully wrapped in the asbestos(?) exhaust bandage, but for a mad moment I considered filling the gaps with rock wool.

 

Having sobered up, and having read the replies I will not do that!

 

I may try carpet underlay but would still prefer a fire proof material.

 

BTW I will NOT be purchasing the proper stuff its bl**dy expensive!

 

So far I have had amazing results with home made virtually free insulation.

 

I aquired a large (huge) quantity of closed cell foam with adhesive on both sides. It has many apllications, but one of its original purposes, was to stick car mirror glass therefore the strength and longevity of the adhesive is not in question! This has been used to stick foil covered foam panels to aluminium sheets (forming the sides of the enclosure) more foam then a layer of "sticky lead" (yes the flashing stuff) then more foam and finally copper sheet (again aquired - free!). The whole lot measures just under 2inches thick and when finished should be equal to the pucker stuff. I understand that the trick is lots of layers with a sound barrier in the centre (sticky lead and aluminium)

 

(I am not going into air flow here but yes it has been facilitated)

 

Total cost so far is around £20.00, but I was lucky enough to drop on to the raw materials.

 

Results? - well I am not sure yet (no lid yet!). I have more to do yet, including a thorough test (with fire extinguisher standing by!) But it has made a very noticeable difference.

 

I am secretly hoping that when I have finished I will be able to run the genset without potentially offending neighbours........

 

John asked:

 

Where does the 1,000 deg. figure come from you would need an acetylene burner in there to achieve that figure.

 

Err......... no idea just something I got into my head, What temp does an exhaust get to anyone?

Edited March 11, 2006 by lymmranger

[John Orentas]

You haven't mentioned engine cooling, water or air, if air is it force cooled.

[lymmranger]

Well as usual we are sticking to the topic!

 

John since you asked.........

 

Engine is aircooled, this is facilitated by utilising a 240v AC bathroom extractor fan which forces fresh cool air in at the bottom of the enclosure, It is directed at the cooling fins of the engine, heat then does its stuff and rises to a vent in the (yet unfinished) lid. Coincidentally this is positioned to warm the stern deck or vent overboard dependant on season!

 

At the time of design I had lengthy discussions with the engine manufacturer and they were unbelievably helpful. They took alot of time explaining suitability of parts and suggesting suitable modifications and after along time eventually secured an order for some parts.

 

WELL DONE LOMBARDINI ! (sorry John got carried away there)