If you are interested in how ��һ��ݶ�can help your business, contact us.

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Industrial Exhaust Stack Design and Fabrication

��һ��ݶ�designs and fabricates custom steel stacks for a wide variety of applications for customers allover the world. ��һ��ݶ�works with customers ranging from the pulp and paper industry to industrial steel foundries.

We fabricate stacks that range in sizes from 8 inch diameters all the way upto 15 feet diameters. Heights range anywhere from couple feet all the way up to over 200 feet.

The Stack Design Process

When first starting a stack project ��һ��ݶ�works with our customers to determine the stack location. From there we can determine wind loads and seismic forces that will be acting on the stack.

��һ��ݶ�works with our customers to figure out the correct height and diameter of the stack based on each client’s specifications.

Because stacks are so slender they have a tendency to vibrate as the wind hits them at a critical wind speed. To eliminate harmonic resonance and vortex shedding there are many methods that can be used. IVI’s standard is to use helical strikes because they tend to be the most economical.

Your Industrial Exhaust Stack Project Partner

��һ��ݶ�is a complete design build firm which means we can control the design of the stack, the materials that are selected and the level of fabrication. This allows us to provide a superior product to our customers. ��һ��ݶ�will do everything from lifting the stack off the truck, to setting in place, to attaching all ladders and crow’s nests as needed.

Before we leave the site, ��һ��ݶ�will work with the customer to make sure the stack is running smoothly and meeting all customer expectations.

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Transcript

Explaining the Vortex Shedding Phenomenon

When designing stacks one of the things that ��һ��ݶ�takes into account is the vortex shedding phenomenon that occurs naturally due to wind loads. ��һ��ݶ�takes into account the vortex shedding in the design phase. So any possible failures such as base plate or anchorage may not be an issue in the future.

Overcoming Vortex Shedding

There are a couple methods to overcome vortex shedding. One of them may be helical strakes. They’re easy to design. They are most common as well. Another method is liquid tuned dampers. These aren’t very common, but they can also be used for large diameter stacks. And finally another option is a tuned mast damper. These provide the most dampening effect for a larger diameter stack. They can be costly however you can visually see them work as they’re inoperation.

Your Expert Stack Design Team

��һ��ݶ�has the design and engineering expertise to help you implement the best method necessary for your stack design.

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Considerations in designing a new stack

Exhaust stack manufacturers generally fabricate using steel, the most economical option. Several factors are critical in determining the design of a stack.

Volume: The most critical parameter for stack design is the volume of air that is being discharged. The volume will determine the stack diameter required to achieve the desired air exit velocity that is used in the modeling process.

Location: Stacks must be able to resist the prevailing wind and seismic loadings they will experience:

• Coastal regions would present higher wind loadings than inland locations.
• Exposures also influence wind loadings depending upon whether the location is in an urban area, on open terrain or in an area with hills.
• More active seismic areas would result in higher earthquake design forces.

Configuration: Stack diameters are based on a minimum exit velocity for dispersion; however, oftentimes the required height of the stack will result in a stack that requires special design considerations. Taller, slender stacks are more prone to excessive vibrations caused by dynamic wind load effects. To limit vibrations, designs may include aerodynamic methods like helical strakes or shrouds. Designs also may include damping to absorb energy, such as tuned mass dampers or preformed base fabric pads.

shows how helical strakes help to reduce vortex shedding.

Air Temperature: The type of steel (stainless, carbon, COR-TEN®) used in stack fabrication often will be dictated by the temperature of the air being discharged. For example, the strength and elasticity of carbon steel declines as air temperatures exceed a few hundred degrees Fahrenheit. In those cases, stainless steel is preferred as it performs better in temperatures up to and exceeding 1,000 degrees.

Testing: Test ports are often required to facilitate air testing at different elevations of the stack. Test platforms with caged ladders or stairs are then required for access. These platforms are considered a source of additional gravity, wind and seismic load when designing a stack.

Complying with air quality requirements

Stacks are an essential part of maintaining air quality emissions that are regulated for your facility. State Departments of Natural Resources determine throw regulations. Depending upon the amount of emissions, you may need to conduct modeling, which will include:

• A site map
• Proposed locations of the stack(s)
• Estimated stack height
• Discharge velocity

Modeling will assume a volume of air and a discharge elevation, which are provided to stack designers and fabricators. Models are complex and often costly, so a significant amount of pre-planning should take place to ensure modeling is done correctly.

Complying with OSHA’s new fixed access ladders regulations

In 2017, introduced  to increase safety on raised walking surfaces, such as walkways and fixed ladders. ��һ��ݶ�is up to date on recent OSHA regulations and understands the new requirements for fixed ladders.

If you are unfamiliar with the new rule, its primary focus is on having a fall protection system, other than a cage, for fixed ladders with a fall distance of more than 24 feet.  As of November 19, 2018, new fixed ladders, including those being replaced, must include an updated ladder safety system. Within these fixed access ladders regulations, OSHA is giving companies until November 18, 2036, to install a safety system that fits the new compliance, regardless of when the fixed ladders were installed.

��һ��ݶ�industrial exhaust stack manufacturers

At IVI, we design, fabricate and install many sizes of industrial ventilation stacks—our exhaust stack manufacturing has ranged from 2 feet to almost 20 feet in diameter. We build stacks, as well as access platforms, with a variety of structural steel, including carbon, stainless and COR-TEN. ��һ��ݶ�also designs and builds foundations.

Our staff of professional engineers design for wind and seismic loadings and to maintain air quality emissions per the provisions of ASCE 7 (Minimum Design Loads for  Buildings and other Structures) and IBC (International Building Code) The design analysis for stacks is done in accordance with ASTM STS-1, Steel Stacks.

Contact IVI to learn more about our work as industrial exhaust stack manufacturers. 

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