Hammer Mills: 5 Key Styles You Need to Know About

You Need a Hammer Mill for That…

So, you have a material that you would like to make smaller for a given purpose. Sounds simple, right?  Well, in most cases it is. However, there are a number of considerations that must be made to get you to the finish line in the most efficient and  most economical way.

Xingfeng supply professional and honest service.

But First a Little Background

Hammer mills are just one type of machinery among the much larger category of size reduction equipment that also includes:  shredders, jaw crushers, ram fed grinders, roll mills, ball mills, and more. Looking a bit closer, even within hammer mills, there are several styles to choose from. Among those styles, the functionality of a hammer mill remains basically the same:

• -Material is fed into a grinding chamber
• -Contact with moving hammers, and interior mill components reduce the material’s size
• -Material remains in the hammer mill’s grinding chamber until it is able to pass through a screen or grate with certain size openings.

The following is a comparison of five key styles of hammer mills:

Gravity Discharge Industrial Hammer Mills

Industrial hammer mills have the simplest and most recognizable functionality. A rectangular steel chamber houses a shaft to which swinging hammers are attached. As the shaft rotates at high speed, the hammers flail out impact the material. In addition to the hammers, size reduction occurs through particle on particle contact and through contact with the breaker plate inside the grinding chamber. Because of their simplicity, the industrial hammer mill is easily adaptable to different sizes and mill designs. Important to know: Replaceable steel liner plates protect the mill’s interior from wear caused by grinding abrasive materials. Ideal Applications: glass, coal, coke, dry chemicals, metals, resin, porcelain, aggregates, brass, ceramics

Pneumatic Discharge Hammer Mills

The grinding mechanism of this group is quite similar to the gravity discharge hammer mills. However, the pneumatic mills typically use a thinner hammer and the interior wall of the grinding chamber features a ribbed liner plate. This plate has a washboard effect on the material, and works in unison with the hammers and particle on particle impact to reduce the material.
The biggest difference of course is the group’s the use of air assistance to evacuate material from the mill. Whether attached to the main mill shaft, or as a separate optional component in a high production model, the fan pulls the the material through the mill, and conveys it to storage.

Important to know:  Specially designed notched hammers are ideal for tearing and shredding. In addition to assisting the evacuation of  light or low density materials, the pneumatic suction can increase throughput up to 00% over gravity discharge hammer mills.

Ideal Applications:  hogged wood scrap, wood chips, green wood, biomass, paper, carpet, meat and bone meal

Full Circle Screen Hammer Mills       

This next group also features the same grinding mechanism as the first two, and the same thin hammers as the pneumatic hammer mills. The amount of screen coverage is what sets the full circle screen hammer mills apart.

The nearly 300 degree coverage of the rotor translates to a greater surface area for the processed material to evacuate the grinding chamber. As a result, compared to the industrial mills, you get greater throughput per horsepower with full circle screen hammer mills.
Important to know: To achieve the circular, nearly full coverage of the rotor requires that the screen be somewhat pliable and therefore relatively thin. Because of this, the full circle screen mill is best suited for light, easy to grind materials to that do not require initial grinding against a breaker plate. Ideal Applications: corn, grain, spices, grasses, planer shavings, sawdust

Horizontal In-Feed Hammer Mills

The unique quality of the horizontal in-feed mills is that material is fed into the side of the hammer mill, instead of the top. This design makes them ideal for long, linear or otherwise large, geometric materials to be processed with out a pre-grind. This group includes trim scrap grinders and pallet grinders. As with the prior styles, the horizontal mills use heavy duty screens covering the discharge area to determine finished particle size.
Important to know:  the style and design of the hammers aggressively moves the material into the mill. Feed rolls are ideal to properly control the rate that material enters the grinding chamber.
Ideal Applications: trim scrap, truss plant scrap, 2x4s, whole pallets, pallet scrap

Lump Breakers

The lump breaker is quite different from the prior categories in both design and functionality. Instead of swinging hammers attached to a shaft rotating at high speed, the lump breaker has stationary hammers attached to a slower moving shaft. As the shaft rotates, the hammers remain rigid, and pass between combs attached to the wall of the grinding chamber. Lump breakers do not use screens for sizing. Instead, the configuration of spacing between the hammers and combs, along with hammer size and RPM allows some control over the finished particle size. Important to know: The open in-feed, fixed hammers and slow shaft rotation give the lump breaker the ability to accept a certain amount of a head load, making it suitable for large blocky materials, de-agglomerating, de-lumping, and returning materials to a flowable consistency. Ideal Applications: sugar, cement, dry chemicals, agglomerated powders

Broad Categories

For the purpose of this post we broadly examined five of the more common styles of hammer mills. It is important to note that each of these categories could be further broken down to highlight the scope of its variables.

When deciding on the right milling equipment for your operations, it’s essential to understand your options. Two primary types of machinery available are roller mills and hammer mills. Now, RMS also offers the VersaMill, a direct-drive roller mill that allows for even greater control.

Many people have questions about the difference between a roller mill vs. a hammer mill. Here, we dig deeper into the most commonly asked questions, including what is a hammer mill, what is a roller mill, what are their common benefits and applications, and what machine owners can expect in regard to maintenance for each type of equipment.

What’s the Difference Between a Roller Mill vs. Hammer Mill?

A hammer mill acts like the name implies, milling grain with a smashing motion. If you took a kernel of corn and smashed it, you would have multiple pieces with variation in size.

A roller mill acts more like a cutting knife. As one roller spins against another, it creates a shearing effect. Roller mill particle size generally sees lower variance than hammer mills, which results in a more consistent grind.

Hammer mills also use different screen sizes to adjust the particle size for either a coarser or finer grain. Often, they have to shut down their entire mill to change a screen.

On the other hand, roller mills can alter the grind simply by changing the roll position. If you want to achieve a finer grind, you can move the rolls in. If you’re looking for a coarser grind, you do the opposite and back the rolls out.

The VersaMill can also control the speed of each roller. Differential roll speeds allow for greater sheer, and an even finer grind than with a traditional roller mill.

If you are looking for more details, kindly visit maize hammer mill.

Is a Roller Mill Better Than an Industrial Hammer Mill?

Target particle size is a leading factor in determining if a roller mill vs. hammer mill is better for your application. If the material has high moisture, then a roller mill is also generally better. With a hammer mill, you run the risk of the temperature of the product rising as it runs through the machine, which can lead to plugging and increased fire risk.

If a coarse grind is desired, a roller mill can generate coarser particle sizes at a much higher consistency. The pulverizing motion of a hammer mill often leads to more waste in the form of “fines” than grinding with a roller mill.

What Are Some Common Industrial Roller Mill Uses and Benefits?

Simply put, roller mills are used for particle size reduction, taking raw material and reducing it into a usable size for a given application. They are used to execute consistent, high-quality particle reduction in non-fibrous materials such as grains, fertilizers, coffee beans, and other biomasses.

One key benefit of a roller mill is its ability to produce a consistent grind profile. Due to its grinding process, the distribution of particles sizes is far more predictable than a hammer mill. Another main benefit of a roller mill vs. hammer mill is that it uses substantially less energy. The roller milling process does not produce excess heat and other energy-consuming effects like hammer milling does.

Energy efficiency is becoming a top priority for many mill owners, and roller mills are typically around 25 to 30% more energy efficient than their hammer mill counterparts. The VersaMill is even more efficient than a traditional roller mill because it does not use belts. It’s a higher end machine than your typical roller mill, but the energy savings pay dividends down the line.

Which Industries and Applications Typically Use Roller Mills?

Many industries rely on roller mills for their operations. Many are upgrading directly from hammer mills to the VersaMill:

Agriculture

This industry relies heavily on roller mills for feed applications where it previously relied on grain hammer mills. Integrators and toll mills that feed cows, chickens, and pigs are implementing roller mills because the machines are an efficient way to achieve the appropriate feed particle sizes for different animals. A feed hammer mill generally cannot compete with the benefits of a roller mill.

Breweries & Distilleries

These industries depend on a consistent crush profile for the different grains they use to create their products. Because of their reputation for a consistent crush, roller mills are becoming the mill equipment of choice for breweries and distilleries in the United States and overseas.

Fertilizers

Many companies and farms on the West Coast are looking to reduce the amount of unabsorbed materials in their products to create a more even application. They need a consistent, fine grind to increase the absorption rate into the water because they’re looking to spray the liquid through a fertilizing unit. A better grind not only allows for better coverage, it also prevents blocking in the application units.

Coffee

Some businesses in the coffee industry have been employing roller mills to grind up coffee beans for larger companies. For those businesses, the coffee grounds must be a consistent grind, and the roller mill is an optimal way for them to do that.

Biomass

This is a newer industry integrating roller mills. One example is biochar. This is used as a fertilizer and as a filter to clean out contaminants in water sources and other applications. Biochar comes from wood that’s been burned in a vacuum chamber. Often, this wood has to be sized at a consistent output before it can be utilized.

What’s the Maintenance Like for a Roller Mill vs. a Hammer Mill?

Both roller mills and hammer mills use tooling to reduce the particle size. Like most tools, the hammers used in a hammer mill will wear out and will need to be replaced.

Roller mills use corrugated rollers to reduce the particle size. Those will also eventually become dull over time. How often the rollers will need to be replaced depends on the target particle size, how often the machines are running, and the cleanliness of the grain or product.

Foreign materials such as rocks, cobs, sand, and metal material will reduce the life expectancy of the rollers, in addition to adversely affecting the hammer and screens of the hammer mill. Fortunately, when the rolls become dull, they can be easily taken out and replaced with sharp ones.

Are you interested in learning more about Maize Milling Machine for Sale? Contact us today to secure an expert consultation!