Pipe Silencer Design

[borobam182]

Good afternoon,

I have an issues which I'm having trouble with and was hoping to get some advice if anyone can help......

My company would like to design its own pipe silencer rather than buy one from a acoustic company.....

The concept is a 6" pipe contained within a 12" pipe and 12" end caps, the 6" pipe would pass through the 12" end caps and connect into the system via 6" flanges.

In order to perform as a silencer, the 6" pipe will have 5mm diameter holes drilled into the wall on a 8mm triangular pitch to allow for noise reduction in the cavity between then 6" and 12" pipes.

I don't feel confident that the 6" pipe will be okay with these 5mm holes drilled in at this close spacing. But, I'm not sure how to justify my concern either way. Just saying, I don't like it isn't washing, as I'm just being asked to prove why it wont work. Frustrating.

I've had a review of B31.1 and it offers guidance on branch openings and spacing limitations based on reinforcement zones not overlapping, minimum distance between welds etc, but, I'm not welding on branches, I'm not welding anything, its just lots of small holes in a 6" pipe.

The temperature is 365 C, but the pressure is only 0.05 barg.

Does anyone have any experience of designs like this and how they justified the hole spacing?

I thought the code might have offered a minimum spacing of 3D of the drilled hole or 1 thickness of the 6" pipe - and it might do, but I just cant find it!

Any help would be appreciated.

Thanks

 

[SandCounter]

I'm not sure of you application, but in my experience made-to-order silencers themselves are probably cheaper to purchase than the cost of the engineering man-hours you've already spent wrestling with the design yourself.

I used to count sand. Now I don't count at all.

 

[bimr]

From your post, the fabrication of a chamber type silencer is the purpose of your project.

Don't think there will be a minimum spacing specified by the piping code for this application since this application is not a piping system, but an equipment item.

There should not be any pressure drop across the holes as the holes are located inside the vessel. The design will have to account for vibration, erosion, and maybe metal corrosion.

Changing the number, size, and orientation of the holes will change the performance characteristics of the silencer. The pipe schedule used for the silencer will also have an effect on the performance characteristics.

Why don't you just buy a silencer and reverse engineer the design. If you buy a silencer, you will also be purchasing the performance data. Otherwise, you will have to develop the performance data on your own. Developing the performance data will cost more than fabricating a silencer.

Do you plan on making different sizes of the silencer?

 

[borobam182]

Hi guys,

Thank you for your comments.

They are both kind of backing up my feeling that it would be best to just buy in the equipment instead of designing our own.

We wouldn't be making them in different sizes.

The only involvement I've had is someone coming to me and asking, 'is this okay?' I just cant justify yes or no.

I was thinking of doing an FE study to verify its integrity, but even then, I wouldn't be sure which load cases to set - its just a bit of an oddball for me!

Thanks

 

[itsmoked]

The way I see it is that you are effectively replacing the 6" with the 12" which is a bigger structure capable of replacing the lesser 6" structure contained within. I would expect you could saw the six inch in half and nothing would change. Bring on the holes!

Keith Cress
kcress -

http://www.flaminsystems.com

 

[LittleInch]

What you're designing is a mesh. The real issue will be collapse under self weight. The length of the unsupported spam will determine how much material you can remove.

Calculating that will be difficult without FEA or trial and error.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[KevinNZ]

To check the strength of the diffuser pipe, look that long section through the holes. The reduction in area is equal to the reduction in strength for pressure containment. But also add some extra allowance to allow for stress intensification.

 

[borobam182]

Thank you for the advice all!