Design of large ductwork

[Bruno A.]

Hello guys!

I need to design a large ductwork for an electrostatic precipitator, and would like to know which software and code that you use for this.

I'm thinking of using SAP2000. I will use elements area for plate and frame elements for reinforcements. It is the best method?

Thank you.
Bruno A.
Structural Engineer

 

[Lomarandil]

I don't know what the best practice is, but I've used the same method you propose (with RISA) successfully once in the past.

As with anytime you're mixing plate and linear elements (but especially with the thin walled members I suspect you have), you'll need to be careful about the behavior where the two meet.

 

[Bruno A.]

Lomarandil, Thank you!

The Deflection and stress in the plate I will check with de Roark's Formula (Large Displacement Method) using the Dead Load, pressure load, wind load and the insulation load.

The stiffeners I will check with the SAP2000 (AISC ASD). But, I dont know how I will check the buckling in the plates.

 

[BUGGAR]

Sheet Metal Air Conditioning Contractors National Association (SMACCNA) has guidelines/rules for sheet metal ducts for hvac systems which might offer some guidelines.

Right now, I'm using Risa but it's for aluminum plates with low d/t ratios (to avoid buckling).

 

[SlideRuleEra]

...design a large ductwork for an electrostatic precipitator, and would like to know which ... code that you use for this.

Assuming the ductwork is approximately this size:

To my knowledge, there is not a code. Instead, design in general conformance with the AISC specification and ASCE 7.
The internal operating design pressure loads are established, in part, by the induced draft, forced draft, and any booster fan specifications. Coordinate the design with the mechanical engineers' requirements for proper gas flow.

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[SAIL3]

what are the dimensions of the duct, span, design press, temp, dust loads, snow loads , wind loads,etc....all pertinent engineering parameters...

 

[dvd]

I second the SMACNA recommendation - Rectangular Industrial Duct Construction Standards dictates material gage and stiffener choices. I have used the manual for several ducting projects whether the standard covers your particular construction depends - make a technical inquiry with SMACNA. Using SMACNA standards lends some authority to the design choices that RISA will not.

Rectangular Industrial Duct Construction Standards Foreward
Rectangular Industrial Duct Construction Standards Table of Contents

 

[thaidavid40]

Be sure to include the reasonable accumulation of dust load inside the ducts. This can become a significant portion of the supported live load.
Dave

Thaidavid

 

[Bendog01]

ASCE has a publication that I have used for designing industrial ductwork. "The Structural Design of Air and Gas Ducts for Power Stations and Industrial Boiler Applications". It covers material selection, design loads, service conditions, load combinations, plate design and stiffener locations,everything you need to know.

 

[LannyBudd]

I would not recommend SMACCNA. Large flue gas ductwork is not in the scope of that document. ASCE has a publication "The Structural Design of Air and Gas Ducts For Power Stations and Industrial Boiler Applications," this is what you should be using. I have done a lot of large flue gas ductwork design and you should be using AISC 360. Make sure those mechanical engineers give you operation and excursion pressures and temperatures.

 

[ajh1]

This string brings back old memories. Back in the mid 1970's I was designing such ductwork for power plants. Sizes ranged from 6' in diameter to rectangular cross sections such as shown in the earlier picture of 25' x 50'. (Not a small duct) As I recall our designs tended to be something like 1/4" plate steel with W8 stiffeners around the perimeter of the cross-section on about 1' centers. Dust loads tended to be in the 250 - 300 psf. I don't recall specific codes that may have been used but it was mostly just statics. I still have some of the old Roark formulas (that didn't show up in later editions) for circular ducts with dust loads in the lower portion.

 

[BUGGAR]

ahj1, reminds me of concrete gang forms. Maybe that could be a source of info for the OP.

 

[dhengr]

Bruno A.:
You also have to be carefo that you don’t get any quacks in your duck work, so don’t just wing it.