How does the sieve affect the hammer mill

In industrial hammer mills there is a sieve system in which several sieves are housed. The sieve influences the performance of the hammer mill in several ways.

The distance from the sieve to the hammers is 2 - 4 mm. This distance determines the fineness of the grind produced.

The diameter of the perforations in the sieve influences the quality of the grind. The diameter of the perforation determines the maximum size of the grains that can pass through the screen. The effectiveness of the screening is partly determined by the number of holes in the screen in relation to the size of the holes. If the distance between the perforations is too great, there is a risk that the material will stick or stick between the holes and that clumping will occur.

The sieve system is responsible for a large part of the total energy consumption of the hammer mill. This can vary from 15 - 40%, depending on the material to be processed. The finer the sieve, the higher the energy consumption. It takes more energy to grind with a sieve with small perforations than with a sieve with larger openings. The shape of the perforations also affects energy consumption. Round perforations lead to less friction than lamella-shaped holes and thus ensure lower energy consumption.

A screen damaged by wear can increase the power consumption of the hammer mill by 25%. In addition, a worn sieve can influence the product properties of the grind. These two reasons are an important reason to replace the sieve regularly. The procedure and frequency for replacing the screen can be included in the maintenance plan. Preferably, changing the screen is a quick and easy process. For this reason, industrial hammer mills are often equipped with a semi- or fully automatic system for changing the screens.

How can the grinding process run more efficiently

A constant supply flow of product affects the efficiency of the grinding process. If there is an accumulation of material in the grinding chamber or if the grinding chamber is not evenly loaded, the grinding process will not proceed in an optimal manner and the energy consumption will increase. By blowing air into the supply of the ground material, a more homogeneous and open structure is created. This makes the grinding process more efficient and the capacity can be increased by up to 40%. The supply of air also has a cooling effect and ensures that the material does not heat up too much. This is beneficial for products that become sticky as a result of the higher temperature and are therefore harder to grind. If a mixture of ground materials has to be produced, there are two possibilities. One option is to first grind the two materials separately and then mix them. The other option is to mix the unground materials first and then grind the mixture as a whole. Research shows that the second grinding method is the most effective.

Counteracting unwanted objects, noise nuisance and explosion risk

Installing a magnet reduces the risk of damage to the screen and removes unwanted metal objects.

The grinding of materials in a hammer mill results in a certain noise level. This is partly inherent to the process. One of the causes is high engine speed. It can be driven at 3000 rpm. It is possible to make a hammer mill with 1500 revolutions / min. This generates less noise than at 3000 rpm. To achieve the same impact on the product with this lower speed, hammers are equipped with a rotor diameter twice as large. The larger rotor results in a larger grinding chamber. The capacity of the hammer mill will increase. Due to the larger grinding surface and sieve surface, grinding will be 20-25% more efficient.

Sometimes ground products are highly flammable or explosive. This is especially true for finely ground products and when dust is released. If there is a real explosion risk, it is possible to provide the hammer mill with explosion protection. Safety valves are then installed. These valves open or close automatically if the pressure in the grinding chamber becomes too high.