The sand maker

Rotor impact mill


Rotor impact mill

The rotor impact mill is a high-performance crusher with a vertical shaft. The rotor impact mill enables you to achieve a high reduction ratio and excellent particle shape. The mill is suitable for crushing all low to moderately abrasive minerals and is therefore used predominantly in the production of sand for the concrete, asphalt and dry mortar industries.

Benefits at a glance:

  • Unique operating principle
  • Superior crushing performance
  • Selective crushing
  • Low maintenance requirements

The rotor impact mill (RPM) for sand production


The rotor impact mill (RPM) for sand production

Since the end of 2022 the Ernst Derfeser GmbH relies on a BHS rotor impact mill of type RPM 1513 for the production of sand at their quarry in Vomp (Tirol). The video shows a short overview of the plant with the BHS crusher.

Superior machine technology

Unit Ready for Operation

The machine and drive train are assembled onto a base frame as a unit that is ready for installation. A large cover that can be raised hydraulically and pivoted by 360° allows unimpeded access.

Reliable Greasing

The BHS rotor impact mill is supplied with a recirculating oil lubrication system with cooling and integrated monitoring. This allows for low-maintenance, reliable operation.

Easy Maintenance and High Availability

All areas of the machine that are in contact with the crushing material are protected by wearing parts that are easy to exchange and made of materials that can be optimized for specific applications.

Vibration Absorption

The rubber spring elements between the base frame and the machine absorb vibrations generated during operation and keep them away from the support structure. Excessive vibrations are registered by an electronic vibration monitor and cause the machine to be shut down.

Production of quality sand

Unique crushing principle

The impeller rotor of the BHS rotor impact mill is the only one of its kind worldwide. The high circumferential speed of the rotor results in an almost permanent gap between the tips of the horseshoe-shaped hammers and the anvil ring. The small gap width and the high energy input due to the circumferential speed result in a very high, targeted crushing ratio.

Particle shape

Rock crushing with the BHS rotor impact mill produces high-quality crushed sand with a cubical grain shape. This is ideally suited for ensuring the workability of dry mortar, for example.

Consistent grading curve of the final product

The unique functional principle of the BHS rotor impact mill guarantees consistent grading curves. The reduction ratio is determined by the speed of rotation and the gap size. The degree of wear on the crushing tools has no negative influence on the quality of the grading curve.

Ultra-fine sand

Thanks to the narrower milling gap and the higher circumferential speed of the rotor, the material in the RPMF rotor impact mill is exposed to more intense stress. The result, in percentage terms, is a higher proportion of fine sand in the grain-size range from 0 to 2 mm.


Rotor impact mill RPM

The feed material is loaded into the top center of the machine. When it impacts the rotor, the material is accelerated towards the outside by means of centrifugal forces; there, the horseshoe-shaped hammers engage it and throw it against the anvil ring, In the milling gap, it is crushed as a result of the impact and shearing forces. The material leaves the rotor through the gap and falls down through two outlet chutes.

Rotor impact mill RPMF – the pulverizer

The pulverizer uses the same crushing principle as the RPM. The difference is that the rock is exposed to more intense stress through a combination of higher circumferential speed and a narrower milling gap. The result, in percentage terms, is a higher proportion of fine sand.


Two versions of the rotor impact mill

BHS rotor impact mills are not only used in the production of sand for the dry mortar industry. They have also proved themselves useful in the production of surfaces for sports facilities, as well as in the milling of fertilizers from limestone, dolomite, gypsum, anhydrite and burnt lime.

Rotor impact mill RPM

The RPM rotor impact mill is used in the building materials industry. The machine has been a proven and reliable tool in the production of sand for many years.

Rotor impact mill RPMF

The RPMF pulverizer produces even finer fractions, and the output material contains a significantly higher percentage of fine sand.

The RPFM is characterized by a higher circumferential speed and a significantly smaller milling gap. This makes the pulverizer ideally suitable for producing sand with particle sizes from 0 to 2 mm.


Advantages of the Rotor

Interchangeable crushing tools

The anvil ring elements are hooked into the upper milling housing (RPM) or are screwed into it (RPMF). The horseshoe-shaped impact hammers are mounted to the rotor and are held on the rotor pegs by centrifugal force. Both the anvil ring and the impact hammers are easily replaced.

Adjustable gap

A set of replaceable spacers is used to configure the ring gap. The ongoing wear and tear of the impact hammers causes the gap width to change; this can be easily corrected by replacing spacers in different sizes (shown in red in the illustration).

Optimized service life

The rotor direction can be reversed, allowing both sides of the impact hammers to be fully utilized.


Spacers for increasing degrees of wear

Options & accessories

Reinforced cover lining

In order to increase the service life, a cover with reinforced lining can be selected as an option.

Electro-hydraulic cover opening

For even faster opening of the machine cover for maintenance and inspection, an optional electro-hydraulic actuation mechanism is available.

Installation in electrical terminal box

If required, all electrical wiring can be bundled in a terminal box for easy installation.

Intensive cooling

In the event of high ambient temperatures or if the input material is hot, a supplementary lubrication unit featuring a larger storage volume and stronger cooling power can be provided.

Air cannon

In order to reduce material deposits in the outlet area, the crusher can be optionally equipped with air cannons.

Control unit

As an alternative to integrate the machine into the plant control a BHS PLC control (including touchscreen) and a frequency converter can be supplied if required. This allows an autonomous operation and monitoring of the machine’s function.


We can also provide the steel construction, storage bunker and metering equipment, feed and discharge equipment, and dust capture systems – all adapted to your specific applications.

Technical specifications

Performance data
TypeRotor diameter
x height
of hammers
Circumferential speed (max.)Drive power (max.)Throughput rate 1) (max.)Input size 2) (max.)

RPM 1113

1.150 x 135mm70 m/s132 kW35 t/h56 mm
RPM 15131.150 x 135mm12 70 m/s200 kW70 t/h56 mm
RPM 22152.200 x 150 mm18 70 m/s315 kW100 t/h56 mm
RPMF 11161.150 x 160mm90m/s200 kW25 t/h32 mm
RPMF 15161.150 x 160mm12 90m/s315 kW55 t/h32 mm

1) The throughput rate depends on the circumferential speed of the rotor and the grading curve of the input material.
2) The input size depends on the type of rock, the circumferential speed of the rotor, and the percentage of maximum particle size in the grading curve (screened through square mesh).

Dimensions and weights
TypeABCDEWeight 3)

RPM 1113

3.080 mm1.500 mm2.110 mm406 mm940 mm6.800 kg
RPM 15134.500 mm1.900 mm2.125 mm610 mm970 mm9.100 kg
RPM 22155.589 mm2.808 mm2.142 mm610 mm1.211 mm18.320 kg
RPMF 11164.600 mm2.000 mm2.790 mm406 mm1.300 mm8.000 kg
RPMF 15164.900 mm2.120 mm2.850 mm610 mm1.540 mm12.500 kg

3) Weights refer to the standard design without motor and accessories.

All specifications apply to the standard design. Technical specifications for customized models may differ from the data provided here. All technical specifications are subject to change due to continuous development. Subject to change without notice.


Tests give certainty

Which crusher is the right one for your application? Don’t leave anything to chance. Leave it to our team of process consultants. Working together with you, our specialists will test the material and develop a tailor-made solution for you.
“Rotor impact mill (RPM & RPMF)” brochure
“Mixing & crushing” overview brochure
Display all

Technical articles in the media

September 2020
GP GesteinsPerspektiven 06/2020

INTERMAT India 2024

09/26/2024 - 09/28/2024 | Mumbai (India)
Booth B50

SIM 2024

10/2/2024 - 10/4/2024 | Dijon (France)

bauma CHINA 2024

11/26/2024 - 11/29/2024 | Shanghai (China)

bauma CONEXPO INDIA 2024

12/11/2024 - 12/14/2024 | Gurgaon/New Delhi (India)

Satisfied customers worldwide

Find a sales representative

Find your personal contact person on site. We are there for you worldwide.

Find a sales representative

Find your personal contact person on site. We are there for you worldwide.