Why McLanahan Hammermill Crushers
Through years of experience and refinement, McLanahan engineers have designed two distinct families of Hammermill Crushers. These crushers are capable of processing a wide range of materials. If you are looking for reliable performance and a solid return on your investment, McLanahan’s Universal lines of Hammermill Crushers are the perfect answer for you. With numerous models to choose from, and a wide selection of hammers and grate combinations, McLanahan can provide a specially formulated mill to fit your specifications, along with customer support to ensure it runs efficiently for the life of the machine.
How Hammermill Crushers Work
All Universal Hammermills work on three principal reduction methods: impact, shear and attrition. As material enters the mill from a vertical chute, it comes in contact with the leading edge of the hammers, each of which is firmly secured to the spinning rotor. The hammer is pinned to the rotor body and allowed to swing, and lay back to some degree. The centrifugal force keeps the hammers extended, and the inertia force unleashed on the material shatters the rock on impact. The particles rebound off the impact plates or breaker blocks back into the hammer circle. In an instant, the material is carried into the grate or cage assembly, where shear forces reduce the larger particles and carry them across the grate surface, grinding the particles into a controlled gradation. Openings in the grates and cage assemblies allow particles to escape the mill once they are reduced to the appropriate size.
Hammermills can be used to achieve a number of goals beyond simple material reduction. In many limestone formations, seams or stratus contains soft deleterious material like chert, shale or mudstone. This material can adversely affect the value of the finished product. A hammermill can be set to pulverize the soft stone and shear the edges of the harder stone in a single pass through the mill. Screening after the mill allows for separation of the pulverized deleterious material, while the more cubical stone continues through the system.
The Standard and Non-Clog Industrial Hammermills are designed to reduce the material to a nominal 3" to 5" (75mm to 25mm) output. These are primary stage crushers, commonly followed with Centerfeed Mills or other types of secondary stage crushers. The HammerMaster is also a secondary stage crusher in that the maximum feed size is 6" (150mm). The hammers used in the HammerMaster line of mills all weigh 60 lbs (27kgs), which creates a sufficient force to fracture a 6” stone and remain extended from the rotor. The Centerfeed Industrial Hammermills incorporate various hammers of size and weight. Larger models of Centerfeed Hammermills may allow up to 8” (200mm) maximum feed size.
Models of McLanahan Hammermill Crushers
The Universal HammerMaster has been refined over many years, beginning with the Universal Pulverizer nearly a century ago. The HammerMaster is a high-speed mill noted for its ability to generate high-quality aggregates, cubical in shape, with superior soundness. Available in three sizes, the HammerMaster is known for making excellent asphalt chip material, concrete stone, and general base material and road rock. This mill is also capable of making agricultural lime for pH control in farm fields.
The Universal LimeMaster was developed over the same time period as the HammerMaster and incorporates many of the same components. However, the LimeMaster is solely focused on generating pulverized lime. Most limestone quarries and mines produce an abundance of fines. In some cases, with careful screening they can create a marketable aglime or chemical lime without further investment. As these markets expand, the LimeMaster can be added to the operation and greatly increase the production of this valuable product, also known as calcium carbonate.
Universal Industrial Hammermills are available in three distinct styles designed around specific types of operations. We offer the Standard Hammermill, the Non-Clog Hammermill and the Centerfeed Hammermill. All the Industrial Hammermills share a common emphasis on severe-duty construction and the ability to conform to a broad range of application issues. The Standard and Non-Clog Hammermills are considered primary crushers, with some models capable of accepting a maximum feed size of 72" (1,830mm). The Centerfeed Hammermill is a secondary crusher designed to accept feed from a primary with controlled top size ranging from 3" to 5" (75mm to 125mm). Industrial Hammermills are not limited to limestone or gypsum — they are known worldwide for processing bauxite, nickel ore, phosphate ore, coal, pet coke, clay, shale, and of course, limestone.
Popular Applications for Hammermill Crushers
Hammermill Crushers are known to generate material finer than 4mm (3/16”), which in some applications may be undesirable. However, if there is a market for finer material, or if it is acceptable within the desired product size, Hammermills can achieve reduction ratios that may otherwise require multiple crushers.
These crushers can be used in mining and aggregate material reduction, beneficiation of finished products, primary reduction of bauxite and similar ores, and fine grinding of lime (calcium carbonate).
Benefits of McLanahan Hammermill Crushers
- Welded steel base
- Abrasion-resistant steel liners
- Cast manganese breaker plates
- Rotor assembly with step-out holes
- Robust construction of housing and rotor
- Double row, self-aligning spherical roller bearings
- Tapered shafts drilled to permit hydraulic bearing removal
- Numerous types and model sizes
- Pre-engineered models for aggregate
- Custom configured mills for industrial use
- Selection of hammers for all models
- Grates and cage assemblies to fit application
Frequently Asked Questions
What kind of reduction ratio can I expect with a Hammermill Crusher?
Reduction ratio is often measured by dividing the F80 by the P80. The F80 is the particle size where 80% of the feed material is smaller than that size. The P80 represents a particle size where 80% of the product is smaller. Reduction ratios will vary with each application within each family of Hammermills and by the amount of applied energy.
- HammerMaster Crushers are limited by horsepower and feed size, so depending on the grate selection and desired product size in closed circuit, reduction ratios will range between 6:1 to as much as 20:1.
- LimeMaster Crushers are also limited by horsepower and feed size, so whether you are looking to make a coarse 3/8” chemical lime or a typical 3/16” aglime, reduction ratios will range between 16:1 to as much as 60:1.
- Industrial Hammermills, like the Standard, Non-Clog, and Centerfeed, are designed with components that enable them to focus on the reduction and output most desired in every application. This means, given a broad scope in applied energy, the reduction ratios may span a very broad spectrum.
What materials are commonly processed for reduction in a Hammermill Crusher?
Hammermill Crushers commonly process limestone, marble, shale, gypsum, phosphate, bauxite, aluminum dross, uranium, cryolite, clinkers, quicklime, petroleum coke and coal.
In what industries would you find Hammermill Crushers at work?
Hammermills are common in the following applications:
- Energy plants conditioning the lime and coal for fuel
- Cement plants milling limestone, shale, and clay
- Chemical plants producing various carbonate powder
- Aluminum smelting plants processing ROM bauxite and dross
- Drywall manufacturers begin by cooking and milling gypsum
- Quicklime manufacturers cook and pulverize calcium carbonate
- Petroleum coke as an oil refinement byproduct milled to size
- Coal mines reducing ROM to stoker coal or finer for shipment
What type of tests should be considered before deciding on a Hammermill Crusher?
Testing for abrasive characteristics in the material is a logical first step when considering the cost to replace hammers and liners. In some instances, when you are replacing a similar type Hammermill also fitted with manganese wear metal, this is less of a factor. However, in new installations, chemical analysis of the material is strongly recommended. This also applies when expanding the mine into formations where material characteristics may be changing.
Some questions to consider include:
- What is the geological description or mineralogy of the material?
- What is the specific gravity of the hardest or most abrasive element to be processed? This is often the host stone surrounding the objective ore. If there is significant difference, we need the percentage of each.
- In case of limestone, we need a chemical analysis depicting the amount of each of the following compounds as a percent by weight: SiO2, Al2O3, Fe2O3 and MgCO3.
What are the key options that should be considered when purchasing a Hammermill Crusher?
Drive and power components are important not only for budgetary reasons, but also due to line power restrictions from the utility company. Hammermill Crushers often require a 1:1 ratio comparing horsepower to tph throughput. That ratio can grow to 3:1 for many applications, and even 5:1 when fine-grinding is required.
Direct drive via a flexible coupling is often the choice, when and if a motor of the same rpm can be locally sourced and serviced. However, this limits the ability to change rpm in case of changes in material formation or product specifications.
V-belt drive arrangements are very common for smaller mills, offer the ability to alter the speed with a sheave change and may be set up with one or two electric motors.
Dual motor drives allow for smaller standard frame motors, which may be more available at lower, competitive prices. You may also save on operating costs if one of the motors is wired with a solid state reduced voltage starter. Peak amperage draw is kept at a minimum when starting the crusher with the reduced voltage starter. The second motor is engaged via across-the-line starter only after the crusher is fully up to speed. Utility companies often charge a premium for peak amperage draw.
HammerMasters and LimeMasters are also available with replaceable tip hammers in lieu of the standard bullhead hammers. They are also offered with an optional feed chute to accommodate the conveyor feed.
Industrial Centerfeed Hammermills are also available with a trap mechanism located under the rotor at the central discharge point. This trap blocks the flow of material, forcing all the material to extrude through the grate openings. This trap also provides a relief for any tramp iron that may enter the chamber. A mechanical arm extends through the base frame to provide easy access when time to empty the trap, which is secured with a pivot pin and hinge.
Hydraulic access into the crusher is also available for the larger Industrial Hammermills. Not only can McLanahan offer hydraulic adjustment, the same hydraulic power unit can be used to open and close the access hatch for inspection and maintenance.
When a Hammermill is selected and recommended for a specific application, the crushing chamber with grates, impact plates and the hammers will be taken into account in the valuation of the Hammermill.
What determines the capacity of a Hammermill Crusher?
In most cases, the capacity of a Hammermill Crusher is based on the desired reduction ratio, the toughness of the material and the energy applied to accomplish the reduction. The diameter and width of the rotor assembly accommodates the top size of the feed and the surface area necessary to grind and extrude the ouput. The amount of energy applied will then result with a design capacity, which will always fluctuate with changes in the toughness or friability of the material. Essentially, for the Industrial Hammermills it is best to rely on the Bond Theory to determine necessary horsepower.
- Bond Theory – This Comminution Theory, developed by Fred C. Bond, establishes a process for determining a work index (Wi) associated with a given material classification. The work index is the comminution parameter that expresses the resistance of the material to crushing and grinding.
In the case of the HammerMaster and LimeMaster crushers, McLanahan has designed the crusher with rotor dimensions, shaft and bearings to handle a variety of applications at a specific horsepower rating. Since the power element is fixed, capacities can be pre-determined based on limestone and various reduction ratios.