Transcript

五一茶馆儿Engineers Share the Keys to Proper Industrial Ventilation Hood Design

Hood design is very important and actually crucial for the functionality of a collection system. Improper hood design can cause a lot of issues and probably the most common one is the placement of the hood in relation to where the contaminant is being generated. A lot of times the hoods are too far away from the contaminant generation point to be effective.

Industrial Ventilation Hood Design: What Sets 五一茶馆儿Apart?

五一茶馆儿takes the design of hoods very seriously. One of the things that sets us apart the most I believe is just our experience. And two things that we do to ensure that hoods are going to function properly when they’re installed are to first look at them through Computational Fluid Dynamic Modeling to see where air is going within the hoods. And the other thing that we do is we have built a test lab for trying out some of these hoods to ensure that they’re properly collecting the contaminant that we’re trying to capture.

The Science and Art of Hood Design

Hoods are kind of a unique balance of science and art. We use a lot of equations from industry publications on sizing and determining volumetric flow rate for our hoods. But there’s also an art to ensuring that these hoods fit within the applications and the needs of our customers.

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Transcript

Reasons For Engineering Studies

There’s a couple reasons why customers should contact us to do these evaluations and what the benefit from those are. After time goes on they realize or they notice that some areas of then plant just seem more dusty or there’s more smoke than there used to be. That could be that there was a process change. Or secondly, they call us in and we look at the ventilation and we might get into the system doing the evaluation and come to find out that a blast gate or an orifice plate was changed. And the volume that they think that they have at current equipment really isn’t true.

The Engineering Study Process

Each branch has to be balanced at the beginning of the system startup and that plays a role at the volume and the static pressure. So as soon as you touch one piece of this entire network, it directly affects every branch. When you’re changing the volume going to a certain piece of equipment, you could see a lot of dropout in your ductwork. And over time, that material drops out and fills up in your ductwork. You’re adding a lot of weight to a suspended piece of ducting that may or may not have had a hanger properly designed to support that weight.

Engineering Studies Ensure Optimal Operation

For us to get in there and see exactly what’s going on with the system and make sure that everything’s clean and clear, each branch has good volume, the fan is operating at a good point in the curve. It all kind of ties together just to make sure that it’s operating the way it should be.

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Why Conduct an Industrial Ventilation Analysis

In an industrial ventilation analysis, we conduct an air quality survey by taking air readings of the ventilation system, as well as evaluate the dust collector, fans and all system components. From there, we develop a baseline rating of the entire system鈥攁 useful tool in determining what may need to be done, or not done, with your dust collection system. If you鈥檙e unsure whether an engineering study is right for you, here are the primary reasons to request an analysis.

Reason #1: Adding equipment

When adding equipment, you may need to expand the ventilation system. The best way forward is to start by evaluating the current system and its capacity. With that knowledge, you鈥檒l then know whether your current system can handle more volume and how that may affect the collection volume from other equipment.

Also, adding equipment doesn鈥檛 automatically mean you need to add to your ventilation system. A ventilation analysis may show that you already have excess capacity. We may also be able to redesign the system to keep you from rerouting ductwork or buying a new dust collector.

Reason #2: Changing a manufacturing process

A manufacturing process change may mean greater particulate volume being directed to an area not equipped to handle the excess. If gone unchecked, particulate can build up in the ductwork, adding weight that can cause the duct to fail. And if the duct isn鈥檛 built to carry extra weight, facility damage and employee injuries may occur.

Reason #3: Becoming more energy efficient

Many companies are looking to be more environmentally conscious by using less energy. Even though an older dust collection system continues to do the job well, it may be costing more to run. Older fans, for example, can be a culprit. An engineering survey would show whether you could save energy and money with newer, more efficient equipment, depending upon your system design and layout.

Reason #4: Becoming silica standard-compliant

The silica standard is a high bar. If silica is part of your manufacturing process and you are having difficulty meeting the standard, there are a couple of things you should do. First, hire an industrial hygienist who will analyze your facility for silica risk. For example, the hygienist will take samples for every employee in every area of your plant for every shift. Once you have that information, we can then conduct an engineering study to review your entire system and determine how best to capture the silica.

What to Expect When Your Industrial Ventilation Analysis is Complete

Once we take the air quality survey readings and inspect your system, we develop a comprehensive written report of our findings. You鈥檒l receive data on your equipment and ventilation system with indication of whether it鈥檚 collecting particulate effectively and where improvements, if any, are needed. We then:

• Request a follow-up meeting to discuss areas that need improvement
• Develop a conceptual design
• Develop a proposal that includes our costs based on our design
• Once agreed upon, implement the solutions

Getting an engineering study done is much like going to the doctor鈥攊t helps ensure everything is operating the way it should. If you believe an industrial ventilation analysis would benefit your company, contact us to schedule a survey.

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Why balancing your system is important

Well-designed industrial dust collection systems will achieve ideal airflow and improve the process performance. See our 鈥�Industrial dust collection design strategies for optimal industrial airflow鈥� blog for more information.

However, plugged filters or even changing weather patterns can affect the airflow in your dust collection system. In a facility with a ventilation system having to 25 pickup points on a single-fan system, each of those points may need adjustment to provide adequate airflow.

Your system鈥檚 air velocity needs to match the range required for the particulates you are capturing:

• Too high of air velocity may decrease filter life; erode the ductwork; coat duct walls with dust in the case of moist or sticky particulates; and waste energy.
• Too low of air velocity may cause dust to drop and build up in the ductwork.

Dampers ensure the fan is pulling the air volume needed, so that adjusting the dampers creates resistance. By creating this resistance, it鈥檚 easier to pull air from the different branches of the system.

Benefits of running your ventilation system on a VFD

Fans that run at a fixed speed are controlled with dampers. But, by running your ventilation system using a variable frequency drive (VFD), you can change fan speeds at the push of a button. There are three reasons VFDs should be considered:

• Energy conservation: Because you are using the correct amount of horsepower needed to run the system, you鈥檒l conserve energy and lower operating costs.
• Flexibility: VFDs give you easy flexibility to adjust fan speeds.
• Reduces maintenance: VFDs increase equipment life because they lessen the wear on motors.

Some people correlate VFDs to the cleanliness of a baghouse. They monitor differential pressure across the baghouse and adjust the fan speed to maintain the correct volume even when the filter media gradually deteriorates and creates more resistance.

Installing VFDs is more expensive than manual dampers, but you will save on operating costs and maintenance in the long run.

五一茶馆儿analysis

滨痴滨鈥檚 airflow analysis method, 五一茶馆儿Flo, identifies areas for improvement within an industrial ventilation system. Once we identify these areas, we can adjust dampers to provide proper airflow, or we will discuss with you the benefits of installing a VFD. Learn more about our Airflow Analysis and contact us for more information.

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The importance of optimal industrial airflow

Proper airflow is an important element of any dust collection system. Benefits include:

• Extended dust collection filter life
• Increased energy savings
• Reduced maintenance and replacement costs
• Better overall fume and dust collection

Risks of poor airflow

The consequences of improper airflow and system maintenance include:

• Too much airflow can pull valuable product out of the process and into the waste stream.
• Too high transport velocity can increase wear on ductwork.
• Too little airflow can allow dust to escape the process and increase the dust hazards in the facility.
• Poor duct routing or low transport velocities can cause dust and particulates to settle in ductwork.

Proper industrial airflow requires a balanced approach. Optimization keeps a facility, people and equipment working at peak performance.

Techniques to maintain proper industrial airflow

Manually adjust the industrial fan鈥檚 outlet damper, inlet damper or variable frequency drive:

If the fan鈥檚 outlet damper, inlet damper or variable frequency drive (VFD) is adjusted properly, airflow can be controlled.  If done improperly, this adjustment can create a shorter filter life, product quality issues and increased operating costs.

Best practice: Monitor differential pressure readings regularly. Once an initial air reading is complete and it is known how the system should operate – a differential pressure benchmark can be set and the operators will be able to easily see when the system is not operating within acceptable limits.

Manually adjust the industrial fan鈥檚 inlet damper or blast gates at collection points:

Making sure airflow is balanced is a critical maintenance step.

Best practice: Keep an eye on airflow. Settling dust could indicate slow airflow. Wear spots could indicate high airflow.

For more details on maintaining airflow for an industrial dust collection system, reference the . Reference 滨痴滨鈥檚 blog: 鈥�Design strategies for optimal industrial airflow鈥� to learn more about optimizing airflow with the correct dust collection type and design.

滨痴滨鈥檚 Flo Air Analysis

五一茶馆儿can do a complete airflow analysis on any air ventilation system. Our proven airflow analysis method, called 五一茶馆儿Flo, uses state-of-the-art modeling technology to visualize the flow of air within a system to identify opportunities for improvement. Learn more about our Airflow Analysis and contact 五一茶馆儿today.

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Types of industrial exhaust fans

Axial fans

Axial fans, sometimes called 鈥渋n-line鈥� fans transfer large amounts of air with a lower rate of resistance by drawing air straight through the fan. Axial fans are generally not used for industrial ventilation systems with air cleaning devices because they do not generate a lot of static pressure.

Types of axial fans

• Propeller fans: Most commonly used fan for general ventilation such as dilution ventilation or cooling.
• Tubeaxial fans or duct fans: Also a propeller fan made to fit in ductwork with cylindrical housing, usually without any type of straightening vanes and transfer air against moderate static pressure (up to 4鈥漺g). They are best used for clean-air applications, such as exhaust ducts going through the roof.
• Vaneaxial fans: Share similar characteristics to a propeller fan. In contrast to tubeaxial fans, vaneaxial fans have a hub and airfoil blades mounted in cylindrical housings usually with straightening vanes on the discharge side of the impeller. Vaneaxial fans also handle larger static pressure (up to 10鈥漺g). Like tubeaxial fans, vaneaxial fans are best used for clean-air applications.

Centrifugal fans

Centrifugal fans are said to look like 鈥渟quirrel cages.鈥� They transfer small amounts of air with a higher rate of resistance by drawing air through the center of the fan. The air is then released through the exhaust at a 90-degree angle. The fan blade determines the three centrifugal fan types.

Types of centrifugal fan blades

• Forward inclined blades: The blades curve toward the rotation direction and are quiet during operation. Due to the short curved blades, these fans are not recommended for dust or particulate.
• Radial blades: The blades are straight from the hub. They are shaped to resist material buildup, allowing them to be used for a variety of exhaust systems handling clean or dirty air.
• Backward inclined blades: The blades curve opposite the rotation direction, are quiet during operation, and have the highest mechanical efficiency of all fan blades. Because they are prone to buildup, fans with these blades are best for light dust or clean-air environments.

Fan selection considerations

Referencing the original equipment manufacturer is best when selecting the right fan for an industrial dust collection system. However, here are general guidelines to consider:

• Capacity, such as flow rate and pressure requirements
• Airstream, including materials handled through the fan
• Physical limitations
• Drive arrangements/power source
• Noise
• Safety and accessories
• Flow control

These considerations are explained in greater detail in 鈥�Industrial Ventilation Fan Selection 鈥� Part 2.鈥�

滨痴滨鈥檚 engineering and design team provides start-to-finish, air quality control solutions keeping costs affordable and efficiency high. Contact IVI today for assistance in selecting a fan for an industrial dust collection system or for any industrial ventilation need.

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However, as recommended in the , 鈥渢he exact performance and limitations of a particular fan should be obtained from the original equipment manufacturer.鈥�

Considerations for selecting a fan

Selecting a fan for an industrial dust collection system requires more than selecting the fan type. Other characteristics such as the airstream, operating temperature, drive arrangements and mounting, as well as those listed below, should also be considered.

Capacity

• Flow rate: The flow rate is based on system requirements. The flow rate should be specified as ACFM or SCFM. The air temperature, fan elevation, moisture content and other air density factors need to be provided to the fan manufacturer.
• Pressure requirements: The Fan Static Pressure (SP) or Fan Total Pressure (TP) based on the system pressure requirements. A system pressure drop calculation should be completed to determine the SP and TP values.

Airstream

• Material handled: If there is particulate or moisture in the air stream, the right fan wheel or blade needs to be carefully selected and depends on what is being conveyed.  Build up or corrosion of fan wheels can lead to safety concerns, decreased performance and bearing failure due to imbalance.
• Explosive or flammable material: Always refer to the standards of the and other governmental regulations when dealing with explosive or flammable materials. If there is a risk of explosion or flammability, non-sparking wheel material and special bearings and controls should be considered.
• Corrosive applications: A protective coating or special material, such as stainless steel, fiberglass or plastic may be required if used for corrosive applications.
• Elevated airstream temperature: An awareness of the maximum airstream temperature is required because the temperature affects the strength of fan materials.

Physical limitations

• Inlet size and location
• Outlet size and location
• Fan arrangement/ orientation
• Weight of the fan
• Ease of maintaining the fan
• The physical space available

Drive arrangements

• Power source: All industrial fans require a power source. If electric motors are utilized, a variable frequency drive (VFD) can be used to control fan speed.
• Direct drive: Direct drive ensures a consistent fan speed while offering a more compact assembly.
• Belt drive: The drive ratio allows for adjusting the speed of the fan. The system capacity or pressure requirements may require changes if there are modifications to the process, the hood design, the location of equipment or the air cleaning equipment. With belt driven fans, the motor can be located in a variety of locations/arrangements.

Noise

• Noise: All fans produce a 鈥渘oise.鈥�
• Sound power & sound pressure: Noise level is measured in units called decibels (db). The noise level will vary depending on the speed, interconnected ductwork and point of operation. The sound pressure is a measurement affected by the fan鈥檚 location and other environmental factors.

Contributors to noise:

• The type of fan, flow rate, pressure and fan efficiency contribute to the noise generated by a fan.
• The quietest fans are usually those with a backward impeller design.
• The fans noise level can be increased on any type of fan if the airflow at the fan outlet or inlet is non-uniform.
• Silencers or noise enclosures can be added to fans to reduce noise.

For more information about noise, reference the 鈥�.鈥�

Safety and accessories

• Guarding: In order to comply with governmental safety requirements, guarding must be included. Danger points to be considered include inlet, outlet, shaft, drive, belts and cleanout doors.
• Accessories: Accessories such as drains, cleanout doors, split housings, inlet boxes and shaft seals can provide assistance in the installation and maintenance of industrial dust collection systems.

Flow control

• Fan accessories: Dampers, variable pitch blades and speed control (VFDs) are three primary fan accessories and assist in managing an industrial dust collection systems flow rate.
• Flow rates: Properly controlled flow rates provide several benefits, including reduced energy demands.

These guidelines are defined in greater detail in the 鈥淚ndustrial Ventilation: A Manual of Recommended Practice for Design.鈥� Additionally, extended information on flow rates and reducing energy demands will be detailed in the blog 鈥淩educe Your Energy Demands with the Right Fan.鈥�

Learn more about 滨痴滨鈥檚 industry solutions. Contact us today for more information or to start planning your industrial dust collection system.

Resources:

“7.3.1.” Industrial Ventilation: A Manual of Recommended Practice for Design. 26th ed. Cincinnati, OH: ACGIH Signature Publications, 2007. 7-6 – 7-13. Print.

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The rate at which the dust is carried through the system is known as the conveying velocity. And the correct velocity helps with system safety and maintenance, as well as energy use. Too low a velocity and the danger is that dust will start to collect within the duct system; too high, and the threat is wasted energy and faster erosion of the ductwork. Sticky or moist dust could also smear the duct wall if the velocity is too high.

Dust Control Systems: Velocity Matters

So, it is important to maintain the conveying air velocity in every part of the duct within a reasonable range.  The determination of that range is dependent upon the kind of dust that is being transported. For example, an extremely fine, lightweight material that will not clump together, such as cotton dust, may need a velocity of 3,000 fpm. However, if you are handling something like lead dust, or other metalworking dust, you may need to accelerate the system to between 4,500 fpm and 5,000 fpm.

A good rule to follow: the heavier the dust, the higher the velocity. And the higher the velocity, the higher the potential operating costs. So, it really is good to understand the demands that will be placed on your system. For guidance on the appropriate velocity for your application, refer to the recognized industry resource: The Industrial Ventilation Manual from .

Too Slow: Dust Collection Can Be Dangerous

As mentioned, the collection of dust within the ductwork is really something that you want to avoid. This can happen when the dust is moving too slowly through the ductwork and starts to settle inside the pipes. As it collects, this dust can lead to a number of potential problems:

• It could fuel a combustible dust explosion
• Ductwork and hangars can fail due to the additional load or corrosion
• The system may not perform as well as expected as the ducts narrow due to the dust build-up

Too Fast: Abrasive Dust Wears on Ductwork

Dust moving too quickly through the system is also clearly a problem. Dust can be abrasive. This causes wear and tear on the ductwork, which will have to be replaced at some point at an additional cost. Transporting the dust faster may also require a bigger fan than you really need. These fans cost more and also have higher operating costs.

So, you don鈥檛 want that dust moving too fast or too slow. You are aiming for just right when you are designing your system.  The things you can do at the design stage to help control conveying velocities include:

• Sizing the ductwork to allow for adequate volume and velocity for the dust it will be carrying
• Calculating the static pressure level required to determine the size and power of your dust collection unit

Just the Right Speed Dust Collection Systems

So there you have it. Moving dust through your collection system too fast or too slow comes with undesirable costs and problems, from dust collecting within the ductwork to parts wearing out faster than necessary. When designing your system, make sure you have an accurate understanding of how fast you will need the dust to be transported through the system. And then design your system around that conveying velocity. It will save you money in the long run.

五一茶馆儿has years of experience conveying all sorts of dusts. Whether you are designing a new system or troubleshooting an old one, 五一茶馆儿has the solution for your dust conveyance needs.

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