Air compressor & generator box

[steran50]

HI ALL:),
I have just Bought Myself one of these Air Compressors UNIMAC CP150 150L 15HP COMMERCIAL PETROL AIR COMPRESSOR | eBay (http://www.ebay.com.au/itm/UNIMAC-CP150-150L-15HP-COMMERCIAL-PETROL-AIR-COMPRESSOR-/130472250358) to run My Sandblast Cabinet when its Finished. We are also getting another Generator soon that will be Diesel - the Power goes off in Mallacoota to often not to have a Generator. I will be putting both of these on a Concrete Slab in the Backyard. I will make a Plywood Box to Cover them. I want to keep their Noise down as much as possible - more so the Air Compressor.

My Boss suggested Acoustop Foam, but its Pricey. I was looking at the the Engine Sound Insulation in the Whitworths Boating Catalogue and it seems much more affordable https://www.whitworths.com.au/main_departments.asp?cat=126&cat1descr=Engine/Steering&cat2=340&cat2descr=Sound Insulation . Has anyone made a Box to insulate the Noise from an Air Compressor and Generator ?.
Just a Note - neither the Air Compressor or Generator will be Run everyday, they will only be used when needed.

[Groggy]

Insulate the box by all means but don't forget to isolate the compressor from the concrete using rubber of some kind. Otherwise the vibration and noise is transmitted into the slab.

[Stustoys]

Do you have neighbors close by or are you just worried about the noise to your house?
Its going to have to be a well ventalated box. I make it around 20kW of waste heat.

Stuart

[BobL]

Trying to retain the combustion engine exhaust noise inside the box will kill your engine. I would treat the exhaust separate from the mechanical and compressor noise.

About the only way to handle the exhaust noise would be a custom made muffler.

To stop the mechanical noise escaping will need a lot more than a ply wood box. Remember it is the mass of material you can place between the sound and the outside that matters. Some acoustic absorber inside the box will also help but primarily for low frequencies it will be bulk matter that makes a difference. You will need at least 25 and given the HP involved in you case preferably 50 mm of dense timber. I am going to use 35 mm chipboard for just my 2.5 - 3 HP electrical compressor housing. Remember, compressors also need cooling and if a opening and fan are added this will allow a considerable amount of sound to escape so a baffled air path will be needed.

I considered a large concrete planter box used for indoor plants tipped upside down but the price and getting it to the place where I need it put me off. If would also still need baffling.

If I had space I would put it underground on a platform.

[Dave J]

Just thinking out loud,
What about a 3 sided brick wall with a insulated roof of your choice?

Dave

[pipeclay]

Couldnt you use old panels from an insulated coolroom?

[steran50]

HI ALL:),
Yes GROGGY it was My intention to use some Rubber or similar between the Compressor and the Slab. I did some Research and found out that some People are using Ice Hockey Pucks under the Air Compressor, I would thought that they would be to dense. I just found out too, that You have to be careful if You Bolt an Air Compressor down as it can cause Cracks in the Air Receiver.

We are pretty lucky with our Neighbours as the Houses either side (left & right) of us are Holiday Houses. The House over our back fence has a barrier of small Trees, Shrubs between us and them. Across the Road from us is a small Lawn Bowling Club. I don't want too much Noise in the House. I will be Ventilating the Box Out of interest STUART how did You Calculate the Waist Heat ?.

BOBL - I realise that I can't keep the Exhaust inside the Box (I work on Engines all the time). I can make a Muffler if the need arises. My Dad and I made a Muffler for a 5hp Mitsubushi Engine Years ago. We stuffed House Bats between the Baffle Tube and the outer casing, We could not believe the difference it made. From Reseach I that I done People are only using 1/2" Plywood for the Box Walls. The Silent Piston Air Compressors that You can Buy only use a Sheet Metal Housing and some sort of Noise Insulation. I have a 3hp Electric Air Compressor now and the noise from it is not a problem. Underground is not a bad idea, but You must have a way of Pumping out any Water that gets in.

DAVEJ - A three sided Brick Wall is not a bad idea. I do have some Bricks, but not sure if enough.

PIPECLAY - Coolroom Panels are a good Idea too and they Should help with the Temperature.

I've done some Research and have picked up some good Ideas. For example to change the Intake Resonance I am looking at using different Air Intake Filters with Pipes on them and Plumbing them into a Manifold with Rubber Hoses and then having an Intake Snorkel outside. I know from Working on Mercruisers at Work that their Mechanical Noise is dramatically reduced when their boxes are closed. I am not really going to know how Loud the Air Compressor is until I get it, which should be this Week. The Air Compressor is My biggest concern. Thanks Fellas.

[Stustoys]

Hi,
Calculate my be a flash word for what I did lol.
15hp = 11.19kW
Being nice the motor would be running about 30% efficient. So its making twice as much heat as power 22.38kW. Though I doubt its running at 15hp all the time you need to add the heat from the compressor, which I didn't, it would be quiet bit of your 15hp but even if its 50% that only adds another 6kW so I called it a wash.
A little rough at best but its a ball park.

I'd start with one longish brick/concrete wall between your house and the compressor and the roof. I think this will reflect most of the noise to your neighbours behind you. (Do you like them? ;) ) You can then see what you need to do to fix that if its going to be a problem.

A curved wall may help. outwards if you like your neighbour, inwards to focus it on his house if you don't. Surely there is a sound buff in here somewhere.

Is your block on a slope?

Stuart

p.s. a quick google says the lost to heat of the air compressor is in the 80-85% range

[steran50]

HI ALL:),
Just to let You know that I did get the Air Compressor that Week when I expected it. I Ran it that Weekend, it Works well. It is Noisy, but not as Loud as I thought it would be. I don't know when I will get around to Making the Slab and Box for it. I am just to Busy at the moment doing everything else.