Cyclone Pre-filters can filter out 90% or more particulate before it reaches downstream filters, significantly reducing fabric filter wear and protecting other industrial dust collection equipment.

The Unique Dust Challenges In Foundries:

Foundries are hot, dusty places—factories where metal castings and other casting services come to life. Castings are produced by melting metal into a liquid, pouring it into molds, and allowing it to solidify. Sand, characterized as an abrasive, is used in metal casting for molding and core making, and silica is typically a key ingredient in molten metal shaping due to its uniform physical characteristics. Unfortunately, silica poses major health risks to humans if inhaled, and so the airborne dust created from sand molds and casting cleanups must be managed properly. The majority of manufactured goods rely in some way on the castings produced by foundries, and like other areas of manufacturing, the dust they produce must be managed via a dust collection system to keep the working environment safe and compliant.

Why Fabric Filters Struggle With Heavy Loading:

Baghouse and cartridge filter collectors are a core piece of many foundry dust collection systems, and are generally very well suited to filter dust from the air in these operations; situated towards the end of the dust collection system, they take on heavy loads of metal, sand, and silica. Depending on the particle size and loading rate of the dust particulate, these fabric filters can suffer from plugging or overloading, inhibiting the airflow of the dust collection system and allowing dust to escape and settle in work areas.

This is a serious concern for foundry personnel because of the increased risk of health hazards and potential explosions.

How Cyclone Pre-filters work:

Enter the cyclone pre-filter. Widely endorsed as a proactive measure for reducing filter loading and increasing dust collection system efficiency, they can be placed upstream of fabric filters to separate out the majority of particulate before it comes in contact with said filters. Cyclones also serve as spark arrestors, increasing the amount of time a spark has to travel before it reaches the filter, and helping to cool down sparks that touch the walls but are not captured—an added bonus for foundry applications.

Cyclones use centrifugal force to capture and remove dust from the airstream, and can often remove 90% or more particulate before it comes in contact with downstream fabric filters. They’re one of the simplest dust collectors available on the market: dirty air enters the cyclone’s inlet and swirls around the separation chamber, where centrifugal forces then force dust out towards the walls.

Once the mixture of air and dust gets down near the hopper, the air changes direction (called vortex reversal) and leaves through the center of the cyclone separation chamber. The solid particles that were concentrated near the wall fall into the hopper and are then removed from the hopper via the airlock.

Any small dust that makes it through the cyclone is then captured by downstream fabric filters, easing the load on the filters themselves and drastically changing the way that dust is managed in the system. Any sparks from the process and the majority of abrasive dust are removed before they can reach the filters, reducing filter cleaning requirements, fire risk, and the amount of compressed air required for cleaning (pulse jet type). Significant savings can be seen if the compressor loading can be downsized for a facility. Ultimately, less dust escapes into the surrounding work areas—lowering the risk of silica damage to employees, and decreasing the risk of explosions or fires.

Aerodyne’s GPC cyclones are compact models with removal capacities comparable to those of traditional cyclones; they differ from traditional cyclones in that they’re shorter, can be configured horizontally, and have an internal ground plate that acts as an integral vortex breaker. Cyclones can be installed in close proximity to areas where dust is generated, and where a larger, traditional cyclone may not fit, which allows the material to be collected and then directly re-entered into the process. This is critical in foundries, where much of the sand and casting materials are recycled heavily. An optional cleanout door can be configured on the cyclone’s backplate for easy access.

GPC Cyclone Specifications:

• proactive measure for reducing filter loading and increasing dust collection system efficiency by filtering majority of particulate ahead of filters
• serves as a spark arrestor
• designed to be installed vertically or horizontally with little effect on collection efficiencies
• utilizes centrifugal force + a ground plate to maximize collection potential
• handles abrasive materials
• eases filter loading to reduce cleaning cycles and increase filter lifetime
• can be installed in close proximity to areas where dust is generated and then directly re-entered into the surrounding processes
• optional “easy clean door”
• 7 sizes under 8 ft³ per NFPA 654
• Ideal for applications with limited space

Dust collection systems perform best in any industry when each of their components is optimized for its role in the system. When fabric filters like baghouses or cartridge collectors take the brunt of heavy dust loading by themselves, it’s a matter of time before efficiency becomes an issue. Implementing a high-efficiency cyclone pre-filter like the GPC shifts the heavy loading burden upstream, often capturing 90% or more of particulate, helping to intercept sparks, and ultimately stabilize airflow before it reaches the filters.

The GPC’s compact footprint and flexibility of installation make it particularly suited for space constrained foundry applications. Improving dust collection system performance doesn’t always translate to replacing the collector itself, but improving the system around the collector by evaluating upstream separation.

Dust collection is often one step in a series of steps used to treat an airstream or process stream. Often times the airstream will require heating or cooling, gas scrubbing, and/or dilution of gas stream, etc. All of these processes usually require additional equipment to work in tandem with the basic dust collector. Adding additional equipment is not only expensive, but it consumes floor space and often purchasing new equipment will get overlooked simply due to lack of space to accommodate it. 

Standard dust collectors often have operational issues with abrasive, sticky, and fibrous dusts. Standard pre-filters for these applications can have high maintenance costs, however without a pre-filter the particulate will often foul or erode the process equipment. Sticky dust will plug filters and foul heat exchangers. Abrasive dust will prematurely wear heat exchangers and dust collectors. Fibrous dust will foul in tight areas. Wet scrubber applications can experience higher water usage when the particulate amount increases.

There are 5 applications that utilize standard dust collectors:

1. Temperature Adjustment of an Airstream

The SplitStream cyclone uses a secondary airstream to convey the dust from the walls of the cyclone down into the hopper for dust collection. The secondary airstream can be used to heat or cool the primary airstream before it is vented outside or fed to other process equipment. The two airstreams will combine in the cyclone and they will leave together at a uniform temperature.

2. Abrasive Dust

Abrasive dust will shorten process equipment’s life span by eroding away the walls of the equipment. Due to the design of a standard cyclone, the lifespan is shortened quicker. A standard cyclone is designed so that the dust is conveyed to the outside of the cyclone, where it hits the walls and fall into the hopper. Abrasive dust will also wear out filter bags, the inlet distributor, tube sheets, and the baghouse walls.

3. Sticky and Hygroscopic Dust

Sticky and hygroscopic dust can also cause issues with standard dust collectors and cyclones. Sticky dust will accumulate in any dead zones in standard cyclone. This causes a gradual reduction in the internal volume of the cyclone, and changes the geometry of the cyclone, which could cause a change in the removal efficiency of the unit.

4. Fibrous Dust

Fibrous dust causes many issues for standard dust collectors. The fibrous dust floats in the airstream and often will be re-entrained back in to the air exiting the cyclone. In baghouses and cartridge collectors, fibrous dust when cleaned off the filters, will float in the dirty air plenum. This increases the concentration of the dust in the unit. The dust will not settle into the hopper to be removed from the system. Overtime this will cause the dirty air plenum to plug up, thereby plugging up the dust collector.

5. Oxygen Reduction

Many dusts are explosive and with growing scrutiny of new and existing operations by inspectors and insurance companies, existing processes are being found that require explosion protection. One way of protecting from explosions is to prevent an explosion from ever occurring by lowering the oxygen level of the system below the Lower Explosive Level (LEL). This is done by adding an inert gas such as nitrogen to decrease the concentration of oxygen.

Aerodyne’s SplitStream cyclone offers a strong advantage over standard dust collectors. Coupled with its unique design and its ability to be configured multiple ways, it is the ideal dust collection solution. Whether it is using it as a pre-filter for an existing system or replacing a faulty dust collector in a plant, the SplitStream will reduce maintenance, increase efficiencies, and improve the overall process.

To learn more about the right dust collection solutions for your application, please contact our experts at 440-543-7400 or visit our website: www.dustcollectorhq.com.

To improve efficiency and safety, there is no substitute for an on-site inspection by an experienced expert. Click here to connect with a member of our engineering team for questions, information, or quote requests.