Drum Mixers

Chapter 1: What is a Drum Mixer?

Drum mixers are specialized devices designed to blend free-flowing materials by rotating them forward and backward. They utilize welded chutes or flights to fluidize the mixture, making them suitable for handling materials of varying consistencies, such as granular substances and powders with different densities and particle sizes. One of the most prevalent examples of drum mixers is the concrete mixer, also referred to as a tilting mixer, which is used to mix concrete in a single batch.

In a drum mixer, the mixing process begins by loading the ingredients into the mixer’s barrel. As the barrel rotates around its central axis, the contents inside are moved up, down, forward, and backward. Drum mixers are known by various names including dimensional mixer, rotating horizontal mixer, rotary drum blender, and rotary drum mixer. They are characterized by their compact design and minimal footprint, operating quietly and safely to ensure straightforward use. These mixers are particularly prevalent in the food and pharmaceutical industries for the gentle blending of powders and granules.

Chapter 2: How Drum Mixers Work?

How a drum mixer works depends on the type of drum mixer, which include mixers that rotate 55-gallon drums, direct drive mixers, cement mixers, and rotary mixers that are complex mixing devices that are constantly mixing and discharging mixtures. Of the different types, 55-gallon drum mixers and direct drive mixers are the least complicated and have the fewest components.

How 55-Gallon Drum Tumbler Works

A 55-gallon drum tumbler is designed for blending or mixing the contents of a drum, operating similarly to rolling a drum across the floor. There are two main types of drum tumblers: end-to-end tumblers and drum rollers. The end-to-end tumbler lifts and rotates the drum end over end, effectively shaking its contents as one would shake a bottle. Conversely, the drum roller places the drum on a series of rollers and rotates it to achieve mixing.

How a Direct Drive Mixer Works

A direct drive mixer is a larger variant of a hand mixer designed to fit on top of a 55-gallon drum. This portable mixer can be mounted on a drum in various ways, including through the drum's bunghole. It is intended for mixing small batches of materials with light to medium viscosity. Typically, these mixers feature a 36-inch long mixing shaft connected to the motor coupler, with different types of impellers secured by a set screw.

Direct drive mixers come with a variety of clamp types, such as plate, cup, clamp, and angle, which facilitate positioning and secure the mixer to the drum. These mounting options are designed to accommodate user needs and enable high shearing with lower torque. Unlike geared mixers, direct drive mixers have a fixed motor speed, usually around 2000 rpm.

These portable mixers or agitators are ideal for high-speed mixing when intense shearing is required for small batch processing. The impellers are engineered to generate high-velocity eddies, which are effective for dispersing and dissolving materials into a solution.

How a Cement Mixer Works

Unlike a direct mixer and tumbler mixer that are more blenders than mixers, cement mixers have the structure of a mixer. Inside the drum of the mixer are fins that are designed to mix the contents of the mixer. At the top of the drum is a large opening into which the ingredients are poured for mixing. Once all ingredients are loaded, the mixer is turned on and rotates continuously until the contents are thoroughly mixed.

How a Rotary Drum Mixer Works

Among the different types of drum mixers, rotary drum mixers are relatively sophisticated. Ingredients are introduced into the mixer through a top inlet, relying on gravity for initial placement. The drum rotates at a slow speed, utilizing gravity to facilitate the gentle blending of ingredients. Internal flights or chutes within the drum work to fold, cut, and turn the materials, enhancing the mixing efficiency. Once the mixing process is finished, the blended mixture is released either by gravity through a discharge gate or with the assistance of a discharge auger.

Chapter 3: What are the different types of drum mixers?

Drum mixers come in a wide array of types, reflecting their widespread use, user-friendliness, durability, and efficiency. This range includes both compact, portable drum mixers and extensive, long horizontal rotary drum mixers. Each type is tailored to address specific needs across various applications.

The drum mixer category encompasses various methods for handling the contents of 55-gallon drums to ensure proper mixing. This category is defined by the type of container used, with the goal of blending ingredients that may have settled or separated during transit.

Among the drum mixer categories, two prominent types are drum concrete mixers and direct drive drum mixers. Concrete drum mixers are further classified into tilting, non-tilting, and reversing drum mixers. Additionally, rotary drum mixers, which are capable of continuously mixing large quantities in a long horizontal drum, are often less recognized but serve an important role in large-scale mixing operations.

Barrel Drum Mixers

Barrel drum mixers are designed to blend loose and granular materials within a rotating transport barrel. These mixers use a drum, typically measured in gallons, that rotates to achieve uniform mixing of powders. The design includes a hoop that secures the drum while it spins, effectively mixing the contents through rotation alone, without the need for impellers or blades.

The absence of impellers or blades in barrel drum mixers prevents product degradation caused by frictional heat and eliminates dead zones where ingredients might accumulate. These mixers are powered by either pneumatic or electric motors, available in various sizes to suit different mixing needs. The control system of a barrel drum mixer ensures effective blending of the ingredients, resulting in a high-quality mix.

The wide use of barrel drum mixers is due to the need for low batch mixers that can be used for mixing, blending, homogenizing, dyeing of powders, and mixing of granules. They are ideal for small industries or when frequent product changes are necessary. The barrel of a barrel drum mixer can be welded to the hoop or be any barrel that has been strapped to the hoop mechanism, which is referred to as a roll on and roll off ramp.

55-Gallon Drum Mixer

55-gallon drum mixers are primarily designed to remix and blend the contents of drums that have separated during storage or transportation. While they can also be used to mix ingredients added to a drum, their main function is to reblend products that have settled or separated over time.

These mixers come in various configurations, including closed head mixers, open head mixers, and direct drive mixers. They typically feature a long shaft with impellers or blades attached either at the bottom or along its length, along with a motor that drives the shaft. Some models use ribbon-like impellers to enhance mixing efficiency.

The key difference between closed head and open head mixers lies in their design and how they are inserted into the drum. Closed head mixers are designed with small impellers that can pass through the bunghole of the drum. The term "closed head" refers to the drum's sealed structure, which has a bunghole for access and is sealed at both ends. The closed head mixer is inserted through this bunghole and is powered by an electric motor connected to the shaft.

Open head mixers, on the other hand, have a motor and shaft assembly that attaches to a lid fitting the drum's top. These mixers can accommodate a variety of impeller types and sizes. After removing the drum's lid, the open head mixer’s lid is placed on the drum and sealed. This type allows for additional ingredients to be added during the mixing process. Once sealed, the electric motor is activated to begin blending.

55-Gallon Drum Rollers or Drum Rotator

One distinct type of 55-gallon drum mixer is the drum roller, which mimics the effect of rolling a drum across the floor to mix its contents. Drum rollers are designed to blend and mix materials within sealed plastic and steel 55-gallon drums, reducing worker exposure to the contents and simplifying cleanup.

The operation of a 55-gallon drum roller involves rotating the drum on its side, allowing the ingredients inside to be agitated and mixed effectively. This method facilitates the use of separate drums for each batch, and the roller's portability enables it to be moved to different drum locations as needed. Since the drums remain sealed during the process, there is no need for a direct drive drum mixer that would require cleaning afterward.

Similar to a dolly, a 55-gallon drum roller lifts and tilts the drum to place it horizontally on the roller's wheels. This setup is ideal for blending various substances, including liquids, slurries, powders, granular materials, and coatings. Some drum roller models can also be used for ball milling, rotating the drum at speeds of around 44 rpm. Additionally, certain drum roller designs feature adjustable rollers, allowing for the use of smaller drums alongside standard 55-gallon drums.

Tilting Drum Mixer

A tilting drum mixer discharges its contents by tilting downward once mixing is complete, which allows for quick unloading, especially useful for large-scale projects. The efficiency of this mixer largely depends on the drum's shape, the angle at which it tilts, and the size and positioning of the blades inside the drum. Tilting drum mixers are commonly employed for mixing concrete, particularly when dealing with large aggregate materials.

The blades of a tilting drum mixer lift and tumble the ingredients on themselves. Horizontal tilting drum mixers have an open end for inserting the ingredients and a discharge end. Single drum tilting drum mixers have the ingredients charged and discharged through the same opening. The difference between the types is the tilting mechanism.

No-Tilting Drum Mixer

A non-tilting drum mixer, often referred to as a reversing drum mixer, features a drum that continuously rotates while ingredients are introduced through a charge chute. After mixing, the blended material is expelled through a discharge chute located at the opposite end of the drum. The drum contains impellers or mixing blades that are affixed to its sides, similar to those in a tilting drum mixer. As the drum turns, the ingredients are repeatedly lifted and dropped in a continuous cycle, ensuring thorough mixing.

When the ingredients are adequately mixed, the drum’s rotation reverses, directing the mixture towards the discharge chute. Non-tilting drum mixers use fixed blades to lift and drop the materials during mixing. These mixers typically feature a single drum that rotates along a horizontal axis and generally have a capacity of 1 cubic yard (CY) or 0.76 cubic meters.

Continuous Drum Mixer

A continuous drum mixer operates by gravity feeding ingredients into the drum from one end while discharging the mixed material from the other end in a seamless flow. This type of mixer is equipped with a conveying system to ensure a steady supply of materials. Notable features of a continuous drum mixer include a stationary inlet and outlet, and a rotating drum with mixing flights that blend the ingredients with each drum rotation. The drum typically rotates at speeds ranging from 8 to 10 revolutions per minute (rpm).

Continuous drum mixers utilize a low-speed, high-efficiency tumbling action that minimizes residence time to a few minutes, resulting in well-homogenized blends. A metering system regulates the flow of ingredients to maintain the desired material depth. Although the standard residence time is generally a few minutes, adjustments may be necessary for mixtures requiring special additives. The ability of continuous drum mixers to simultaneously feed and discharge makes them particularly suitable for large-scale production processes.

Flotti Mortar Drum Mixers

A Flotti mortar drum mixer is specifically designed for preparing ready-mix dry mortar used in applications such as bricklaying, plastering, cementing, tile adhesives, and anhydrite floor screed. This type of mixer is an economical choice for small-scale operations and serves as an alternative to more complex drum mixers. Flotti mortar drum mixers are intended for handling smaller quantities of bagged materials and are powered by a 220V motor, allowing them to be connected to a standard domestic electrical outlet.

Similar to larger continuous drum mixers, a Flotti mortar drum mixer provides continuous mixing of ingredients, ensuring that the mixture is immediately ready for use. Its compact and portable design allows it to be easily moved across different floors of a construction site, making it convenient for varied applications.

Two Dimensional Rotary Drum Mixer

Two-dimensional rotary drum mixers utilize a combination of two distinct movements: drum swinging and drum rotation. In these mixers, the drum is mounted on a swinging frame supported by wheels. Catch wheels manage the drum's axial positioning, while drive wheels facilitate the rotation of the drum. The swinging motion is driven by a crank rocker mechanism, which moves the swinging frame. To ensure smooth operation and safety, a bearing assembly is essential to support the swinging action of the frame.

The design of a two-dimensional rotary drum mixer features a rotating cylinder mounted on a swinging rack supported by four wheels. Two wheels control the axial rotation of the cylinder, while the other two wheels drive the rotation system. The dual motions—swinging and rotating—occur simultaneously, enabling efficient mixing as the cylinder moves back and forth while spinning. This method ensures thorough mixing of materials through both rotation and swinging action.

Two-dimensional rotary drum mixers find applications across various industries, including pharmaceuticals, food production, dyeing, animal feed manufacturing, chemical fertilizers, and pesticides. The combined motion of these mixers provides a gentle yet effective blending process, suitable for high-volume production without compromising ingredient integrity.

Three Dimensional Rotary Drum Mixer

Three-dimensional rotary drum mixers introduce an additional motion to the two-dimensional mixing process by incorporating a pulsating action. Alongside the fundamental swinging and rolling movements, these mixers also feature a pulsing motion, akin to the action of shaking and twisting a bottle. This results in ingredients moving in multiple directions simultaneously—traveling from the center to the ends of the cylinder, and from the bottom to the top.

These mixers accommodate a range of drum sizes, allowing for batches from 1.3 gallons to 79 gallons (5 liters to 300 liters). The design includes a straightforward mounting system that facilitates quick and easy drum changes, enhancing the overall efficiency of the mixing process and saving valuable time.

Horizontal Rotary Drum Mixer

Horizontal rotary drum mixers are well-suited for batch processing of delicate, easily damaged, and temperature-sensitive materials. Unlike mixers with impellers or blades, these drums operate without such components, ensuring a gentle mixing action that avoids crushing, smearing, or heating the materials. This design prevents heat generation that could potentially be transferred to the mixed content.

In a horizontal rotary drum mixer, the primary part is a drum made of carbon steel or stainless steel, which is supported by rollers mounted on trunnions for smooth rotation. The interior of the drum features flights or chutes and a feed inlet positioned at the top. An electric motor located beneath the drum provides the necessary power to rotate it. Ingredients are introduced through an auger, a specialized tool, or by gravity via the inlet.

The drum rotates at a speed of about 15 rpm, allowing the material to be gently lifted by the flights or chutes and then to fall back due to gravity. The flights help in mixing by folding, cutting, and turning the ingredients, enhancing efficiency without applying force or creating friction. When moisture needs to be added, it is done using a spray nozzle directed at the drum’s inner surface. Mixing typically lasts from two to eight minutes after all ingredients are added, and upon completion, the mixture is expelled through a gravity gate or another auger.

While the fundamental components of a horizontal rotary drum mixer are consistent across various models, there are customizations to suit specific requirements. One design variation includes an inlet at one end and a discharge at the other, with chutes designed to avoid any angles or pockets that might hinder material discharge.

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Chapter 4: What are the advantages of a rotary drum mixer?

Rotary drum mixers are efficient devices that use minimal power for mixing. They offer a cost-effective solution for blending powders, granular materials, and substances that need a slow, gentle mixing process.

Efficiency

The simple design of rotary drum mixers makes them ideal for the blending process. Their rotating motion that continuously moves ingredients upwards and downwards evenly distributes the ingredients into a homogeneous mixture. The constant motion provides full contact and exchange between a material’s particles for fast and uniform mixing.

Energy Savings

The slow rotation of a rotary drum mixer requires minimal energy, operating at just 5 rpm to 15 rpm. The electric motors used consume very little power and operate nearly silently. The slow and controlled process also produces minimal dust, which helps reduce environmental pollution and issues with airborne dust.

Flexibility

Rotary drum mixers come in various types that can blend a wide range of ingredients. Some models allow for quick changes between different materials with minimal effort. This adaptability is a key reason many industries rely on them. They are effective for mixing a broad spectrum of granular and powdered ingredients, including those needing additives or moisture.

Simple Operation

The operation of a rotary drum mixer is straightforward and uncomplicated, requiring no complex controls or monitoring. Its simple structure includes a drum of various sizes, support rollers, an electric motor, and inlets and outlets. Operators can initiate mixing with minimal training.

Footprint

While industrial rotary drum mixers may occupy a large space, their overall footprint is generally quite compact. Their simple design contributes to their small size, saving both electricity and space.

Quality of Mixtures

Rotary drum mixers ensure thorough mixing by evenly distributing ingredients. This leads to improved uniformity and solubility of dry materials, making the final mixture more consistent and effective.

Durability

Among the different mixing solutions available, rotary drum mixers stand out for their durability and longevity. Constructed from premium stainless steel and carbon steel, these mixers are designed to handle a variety of mixing tasks efficiently over an extended period.

The minimal number of moving parts in a rotary drum mixer reduces the risk of wear and tear, contributing to its longevity. Additionally, the corrosion-resistant metals used in the construction of these mixers make them suitable for use in challenging and aggressive environments.

Mixing Times

Rotary drum mixers have short mixing times due to the absence of friction, rising temperatures, and hot spots. This ensures efficient and quick mixing.

Gentleness

The flights or chutes in a rotary drum mixer gently lift and transfer the product throughout the mixer. Powders and granules of varying densities and particle sizes mix quickly and gently.

Maintenance

Aside from the highly durable materials used to construct rotary drum mixers, the lack of stress and wear removes the need for regular maintenance. Without drive parts or bearings being exposed to ingredients and low power requirement, rotary drum mixers are maintenance free, even after running continuously for long periods of time.

Easy Cleaning

The straight forward design and easy access makes rotary drum mixers very easy to clean, which is especially necessary in food production and the pharmaceutical industry.

Chapter 5: What is the industrial use of drum mixers?

Drum mixers are extensively utilized in both the pharmaceutical and food industries due to their ability to handle ingredients with care. In the pharmaceutical sector, rapid mixing can harm sensitive ingredients, while in the food industry, fast blending might compromise the flavor of certain components.

Food Industry

In the food industry, drum mixers play a crucial role in specialized processes such as vitamin-enriching rice, mixing soup components, and blending various teas. These applications require a gentle mixing approach, often involving the use of a spray. For example, gourmet teas flavored with mango and dried peach blend effectively in a drum mixer. Additionally, drum mixers are commonly employed in the production of powdered nutritional drinks.

Animal Feed

Drum mixers are widely used in the animal feed industry to mix ingredients for large-scale storage. Given the high volume and precision required in feed production, drum mixers are engineered to blend grains and powders efficiently, ensuring consistent quality for bulk storage systems.

Pharmaceuticals

In the pharmaceutical field, drum mixers are ideal for blending delicate powders to produce medicinal products. The absence of moving parts such as impellers and blades allows for a gentle mixing process, minimizing friction that could damage sensitive chemicals. This design feature ensures that ingredients can be mixed and then transferred into barrels or drums without compromising their quality.

Concrete Manufacturing

Drum mixers are integral to concrete production, providing a reliable method for efficiently mixing concrete materials. They ensure a consistent texture, which is critical for high-quality concrete. Due to their durability and ability to endure the rigors of construction environments, drum mixers are a staple in the industry. Their mobility, ease of use, and various sizes make them suitable for diverse construction projects.

Conclusion

• Drum mixers are mixers that are used for mixing free flowing materials by rotating them forward and reverse with welded chutes or flights that fluidize the mixture.
• The process of a drum mixer involves loading the barrel of the mixer with the ingredients to be mixed. The loaded barrel revolves around its central shaft as the ingredients in the barrel make three-dimensional motions
• How a drum mixer works depends on the type of drum mixer, which include mixers that rotate 55-gallon drums, direct drive mixers, cement mixers, and horizontal rotary drum mixers that are complex mixing devices that are constantly mixing and releasing mixtures
• There are an endless number of types of drum mixers due to their popularity, ease of use, durability, and efficiency. The assortment of drum mixers includes small portable drum mixers and large long horizontal rotary drum mixers.
• Rotary drum mixers are highly efficient mixing devices that require a small amount of power to complete the mixing process. They are an economical method for completing the blending of powders, granular materials, and materials that require a slow gentle mixing process.

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