REMco'S COMMON VSI QUESTIONS

 

 

At REMco, we have been in the crusher business for over 40 years and here are some answers to common questions about VSI crushers that we receive regularly from a wide variety of interested parties.

 

If you have additional questions that you would like answered, contact REMco.

 

What is a VSI crusher?
A VSI crusher is a vertical shaft impactor. It is a mineral crushing machine that uses velocity and impact to reduce the size of minerals fed to it to a smaller size.

 

Is there more than one type of VSI?
Yes, there are three basic types. Autogenous, semi-autogenous and standard hard parts. Autogenous VSI units use a rock lined rotor and a rock lined chamber; semi-autogenous use a rock lined rotor and a crushing chamber with anvils; a standard VSI uses a rotating impeller with iron wear shoes and a chamber with anvils. Within these three basic machines, REMco offers over 30 standard configurations to meet specific product requirements.

 

Compared to cone crushers, are VSIs more expensive to operate?
When properly applied and operated, VSI crushers can produce crushed materials at the same or less wear cost per net ton of product as a cone crusher. REMco VSI Crushers can produce materials smaller than 1/2" (13 mm) at lesser costs than cone crushers.

 

Can VSI crushers make the same products as a cone crusher?
Yes! VSI crushers can produce the same products as a cone crusher. Closed circuit operation is preferred when the VSI is operated in a 3rd or 4th stage application. One of the major benefits of a VSI when compared to a cone crusher is the shape of the finished particle which is typically more cubical and uniform when compared to a cone crusher product. REMco VSI discharge grading are finer than cone crusher gradings when operating in closed circuit.

 

Is the product grading affected by wear of the rotor parts?
No. The REMco rock-on-rock VSI's product grading is affected by power demand for the feed load, feed grading and rotor speed. The grading remains constant regardless of wear parts condition. For REMco ST/AR machines with anvils, wear of the crushing parts will coarsen the discharge grading.

 

How often will the REMco VSI need to be serviced?
It is recommended that a visual inspection be made on a regular daily basis. Actual service intervals will be determined by the nature of the application, abrasiveness of the rock, and expertise of the operator.

 

Is the REMco VSI noisy in operation?
The REMco VSI is not a noisy crusher. Sound levels during normal operation range from 75dB to 85dB at a point 1 meter from the machine. The rock lining within the chamber is a very effective sound insulator. Often, the electric motor and surrounding machinery are noisier. Noise levels will vary with installation.

 

Does the REMco VSI vibrate when in normal operation?
If the REMco VSI rotor is in proper balance, vibration is nil or often non-existent. However, some vibration during the crushing process is normal. Coarser feeds result in more noticeable vibration. Finer feeds tend to result in smoother crusher operation. Pulsing of the vibration level is normal as the rotor builds and sheds different size rock pieces.

 

Is the REMco VSI dusty in operation?
The REMco VSI is fitted with an air re-circulation system designed to reduce the air pressure build-up within the machine. Under normal operating conditions, this recycles the air which enters with the feed material, lowering the emission of dust below the machine. If the feed material is very dry or extremely fine crushing is desired, and any objectionable dusting appears, it is suggested that a water fogging nozzle be added in the feeding area.

 

Can the REMco VSI be installed on an existing or rigid support structure?
Yes, REMco VSI crushers may be installed on a wide variety of support systems. The vibration isolators protect not only the crusher but also anything on which it is mounted from most vibrational loads. Many are installed on old existing crusher footings of fabricated construction or concrete. REMco offers a low cost installation kit or adapter plate, if required.

 

What is the feed size that REMco VSIs can accept?
The larger models of REMco units (5080 and 9150 series) can accept feed sizes up to 4" / 100 mm. The medium size units (2040 and 4060 series) can accept feed sizes to 3" / 75 mm and the smaller machines below 2040 series are limited to 2" / 50 mm or smaller.

 

Can a REMco VSI be used to improve product shape?
All REMco VSIs provide excellent shaping of all materials crushed. In some applications, by operating the machine at a low speed, a dry scrubbing action can be achieved to remove soft, undesirable particles and also to shape sharp angular material produced by compression crushers.

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Anvil Type Crushing Chamber Questions

What is it?
An anvil type crushing chamber consists of 15 to 20 chrome iron blocks positioned around the circumference of the machine against which the rotor throws the rock to be crushed.

 

What does it do?
These anvils are positioned at an angle to maximize the perpendicular impact of the rock exiting from the rotor.  When the rock strikes the anvil surface, particle breakage occurs.

 

Will the anvils wear?
Yes, the anvils will wear.  The wear rate as measured in hours, days, weeks or tons produced will depend on a number of factors.  These are:

A. The tonnage being fed to the crusher.  The greater the tonnage, the faster the wear.
B. The largest particle size being fed to the crusher.  The coarser the feed, the faster the wear.
C. The rotor speed.  The faster the rotor rpm producing a higher particle velocity will result in faster wear of the anvils.
D. The percent total abrasives content of the rock.  (SiO2 Silica; AL203 Alumina; and Fe Iron).
E. The water in the feed. The higher the content of water (H2O), the greater the wear rate.

 

When should an anvil chamber be used?
The use of anvils is common and very successful for the crushing of low to medium abrasion material.  It is generally accepted that when the material being crushed contains less than 15% total abrasives, anvils will provide superior crushing at an acceptable wear parts cost per ton.  The lower the abrasives content, the longer the wear life.

Anvils are also useful for minimizing oversize produced by the crusher and minimizing recycle loads.  Anvils will produce a sharper less cubical material than rock-on-rock chambers but the product shape will be more cubed in comparison to the product of compression crushers such as jaws, gyratories and cones.

 

An anvil rock chamber in a VSI crusher, depending on rock type being crushed, may produce less microfines in the product in comparison with a rock-on-rock type chamber. This applies to material smaller than 200 mesh, .075 microns.

 

When should an anvil chamber not be used?
An anvil chamber should not be used if the material to be crushed is known to contain more than 15% abrasives as noted above.  Extremely wet feeds should not be applied to an anvil crushing chamber. With sound, hard stone, when reduction ratios exceed 4:1 of feed to final product, the use of anvils should be carefully evaluated for cost and product rate.

 

When feeding fine feeds, smaller than 1/2” (12 mm), to produce sand, extreme care must be used to size the crusher properly to the required feed and production rate. Underfeeding an anvil type VSI can result in poor wear patterns and higher crushing costs.

 

What is the typical cost considerations between an anvil chamber and a rock-on-rock chamber?

 

  A REMco crusher with an anvil chamber as a tertiary feeding minus 3” will typically produce minus 3/4” (20mm) for 25 to 40 cents per ton wear cost.
  Depending on the nature of the rock being crushed, an anvil chamber will have to be changed between once a week to once a year.
  An anvil chamber will require more frequent inspections and have a higher labor cost for service.
  The crusher discharge grading of an anvil crushing chamber will vary during the life of the anvils. Crushing efficiency will be reduced as the amount of wear increases producing a coarser product.
  A REMco crusher with a rock-on-rock chamber as a tertiary feeding minus 3” will typically produce minus 3/4” (20mm) for 5 to 10 cents per ton wear cost.
  Depending on the nature of the rock being crushed, a rock-on-rock chamber insert may have to be changed between once a year to once every five years.
  A rock-on-rock chamber will require infrequent inspections and will have little or no cost for service.
  The crusher discharge grading of a rock-on-rock crushing chamber will remain constant as long as feed rate and rotor speed is maintained. Crushing efficiency remains constant.

 

Can REMco crushers with anvil chambers be converted to use rock-on-rock chambers?
Yes, all REMco crushers designated as ST/AR models can be readily converted in the field from anvil chamber to the rock-on-rock chamber designation, ST. What is required is the removal of the anvils and the anvil support ring, the chamber cleaned of rock build up and the installation of a rock chamber insert which is bolted into position. Rotor speed or type of rotor may have to be altered depending on the required crushing task.

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Rock-on-Rock Crushing Chamber Questions

What is it?
A rock-on-rock crushing chamber, sometimes referred to as an autogenous chamber, is a circular ring of pockets, that fill with rock, positioned in the crusher around the full interior circumference of the machine at a position directly opposite the rotor.  It is lined and packed with the feed material which is being fed to the machine and through the rotor.  REMco rock-on-rock chambers are designed as an insert and can be readily changed or replaced in the field.

 

What does it do?
A rock-on-rock crushing chamber eliminates the use of wear iron to receive the impact from high velocity rock exiting the rotor.  This provides a tightly-packed rock lined bed of material on which the crushing can take place.  By using a rock lined chamber, the crushing cost is significantly reduced due to the elimination of wear iron. 

 

Will the crushing chamber wear?
A rock-on-rock crushing chamber normally does not experience any significant wear when the crusher is fed the proper material at a continuous rate.  The feed rate should be such that it causes the consumption of at least 60% of the crusher’s drive power.  With the crusher properly fed and with regular inspections, a rock-on-rock chamber can last the life of the crusher with no service or replacements required.

 

If a rock-on-rock crushing chamber is fed very dry material, a low feed rate or only coarse stones, the rock lining of the chamber may be scoured out or not build up properly.  This will cause damage and erosion of the rock-on-rock chamber gussets.  Conversely, feeding very wet or sticky material can also cause wear of the rock-on-rock chamber insert.

 

When should a rock-on-rock chamber be used?
Rock-on-rock crushing chambers are most effective when handling abrasive materials. They can also be used for the production of sand and other fine products.  Rock-on-rock chambers are available for REMco crushers in a variety of configurations to meet specific application requirements.

 

How are RockMax and SandMax crushing chambers different?
All REMco crushers are field convertible to meet any of three basic model requirements, SandMax, RockMax and ST/AR.  RockMax and SandMax rock-on-rock chambers differ in that the RockMax chambers are more open and provide a reduced density for the coarse material typically fed to RockMax crushers.  SandMax rock-on-rock chambers are more closed and achieve a denser particle cloud within the crusher. This allows for a greater concentration of the crushing energy, producing a finer discharge.

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