Understanding Hammer Mills: Operation, Types, and Industrial Applications

Hammer mills are whole purpose machines that are designed to crush, grind, and mill material. As the name suggests, the purpose is served by grinding material by small hammer blows. The history of hammer mills is quite old, as the first invention was made in 488 AD. Hammer mills are used for material processing in the food, construction, chemical, and cosmetic industries. This post gives insights about working, types, and industrial applications of hammer mills.

Working of a Hammer Mill

The operation of a hammer mill is simple. It has a cylindrical steel drum inside which hammers are mounted on a horizontal or vertical shaft. These hammers freely rotate around their axis. The material is fed in the drum, which when rotating causes the hammers to blow on the fed material. The ground material is shredded and made to pass through the screens of desired sizes, which are placed inside the drum. There are screenless hammer mills, which use air to separate large and small-sized particles.

These hammer mills serve as primary, secondary, or tertiary material crushers. The size and power capacity of hammer mills vary according to the application. The industrial hammer mills use the electric motors of power over 2000 to 5000 horsepower.

Types of Hammer Mills

Hammer mills are categorized based on industrial functions. The function-based types of hammer mills are detailed as follows.

• Gravity Discharge Industrial Hammer Mills: In these hammer mills, the swinging hammers are mounted on a shaft. The particle size reduction takes place by hammering application, as well as by particle on particle force. The discharge in these mills is subjected to gravity and is from the bottom, therefore are called bottom discharge or gravity discharge hammer mills. These mills are used for crushing glass, dry chemicals, ceramics, etc.
• Pneumatic Discharge Hammer Mills: The hammering function of pneumatic hammer mills is similar to gravity discharge mills despite the fact that chamber walls and hammers are thin. However, this type has a plate dashboard that contributes to size reduction. In this type, the discharge is assisted by the air evacuation process to enhance overall output. These hammers are used for lighter material such as paper, biomass, greenwood, etc.
• Full Circle Screen Hammer Mills: These industrial hammers feature a 300-degree rotating screen that improves particle evacuation. It is suitable for lightweight components, which do not require initial grinding. These mills are used for hammering spices, grasses, etc.
• Horizontal In-feed Hammer Mills: These hammer mills are designed to insert the material from the side, not from the top. These mills are aggressive in function, therefore, are used for heavy particle grinding. Trim scrap grinders and pallet grinders are featured in these hammer mills to perform hardcore industrial grinding.
• Lump Breakers: Lump breaker is by design and functionally very different from other hammer mills. In this type, there are no swinging hammers but it features a small fixed hammer structure on the shaft. The purpose of this hammer mill is not to reduce the particle size but to smoothen the powder or paste. The hammer structure on the shaft is called comb. The particles are made to pass through the comb to achieve the desired particle size. These hammer mills are used for sugar, dry chemicals, cement, etc.

The applications of Hammer Mills

Farm grain machines, sawmills, plastic grain milling, shredding paper, automobile shredding machine, are some of the excellent examples of hammer mills. Although the specific hammer mills applications in different industries are as follows:

1. Powder Production: In the pharmaceutical and chemical industries, various types of hammer mills are used for powder making. All required ingredients are crushed in hammer mills, and an intermediate grade of powder is obtained. Nearly precise grain size can be obtained in using the hammer mills. The one constraint that these mills have is no sticky material can be hammered because it may stick to the perforated screen.
2. Legume, grains, and food product grinding: In the food processing industries, the hammer mills are used to grind various types of legumes. They are mainly used to grind soya, nutshells, groundnuts, and different types of beans. The hammer mills with low hammer blows are used to remove hard nutshells.
3. Material Size Reduction: In pharmaceutical industries, the hammer mills are used for micronization. The medicinal grains are required to fit inside the capsule packaging in precise quantity. Therefore, the grains are micronized using the hammer mills before packaging.
4. Speeding up the dissolution process: In chemical, food and pharmaceutical industries, the hammer mills are used for formulation and quick dissolution. During the dissolution, the small-sized particles dissolve faster. Therefore, hammer mills are used for fast formulation.
5. Mixing solid dry and fibrous material: Hammer mills are also used for mixing two solid powders. They are used to produce a consistent mixture of two fibrous solid ingredients.
6. Enhances Activeness of an ingredient: Many ingredients bring active reactions when added to certain formulations they are slightly crushed using hammer mills to enhance their activeness.
7. Easy scrapping and recycling processes: In industries like automobile and mechanical, the hammer mills are used for scrapping purposes. The irreparable overused automobile parts are scrapped by hammering and the crushed metal is sent for melting. The molten material is used for new production and recycling.

The quality of a reduced product depends on the quality of the hammer mill, so it is important that you choose good quality hammer mills from recognized suppliers. Many times, used hammer mills are also equally good as new ones. JM Industrial is a prominent supplier of Used and Surplus Size Reduction Equipment and related products.  These used hammer mills are sourced from brands like Dresser Industries, Bliss Industries, and so on. They are available in different configurations and price ranges to meet your application requirements.