REMco's common VSI questions

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.

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.

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.

IMPORTANT INFORMATION

REMco crushing machines are industrial, heavy-duty products which operate in a severe, demanding environment. As such, REMco VSI crushers are dependent on proper installation, operation and maintenance to perform trouble-free. In addition, the crusher is dependent on the expertise of crushing plant personnel to provide continued daily operation with the fewest repairs.

Installation and operation maintenance personnel should be aware that poor or incorrect installation, operation and maintenance procedures could be detrimental to the crusher. Over many installations, REMco has become aware of some of these conditions and they are listed here in an effort to inform the purchaser in order to avoid unnecessary failures and the accompanying repair costs and lost operation time.

Installations

1.	Install and maintain all safety protection devices for personnel and for the crusher and surrounding process equipment.
2.	Make sure all personnel working on the crusher or responsible for its operation and maintenance are fully aware of all safety procedures and maintenance requirements of the machine.
3.	Install crusher on proper legs or support structure anchored to concrete pad and/or skid. Be sure crusher is level. Refer to Installation Section of manual. If installation is not on REMco supplied support legs, contact REMco for review and guidance of the intended crusher support structure.
4.	Install magnets or metal detectors to remove tramp uncrushables from rock feed. Provide all appropriate electrical inter-locks between crusher and feed and discharge conveyors.
5.	Make sure discharge chutes and conveyors are properly designed, amply sized and installed to prevent build-up and plugging under the crusher. Keep crusher discharge clear of roots, trash and other debris.
6.	Make sure that the feed conveyor or feed chute direct the incoming feed into the center of the receiving hopper and onto the feed diverter device. Install feed conveyor or chute to allow service clearance for removal of feed hopper and rotor.
7.	Make sure all walkways, access platforms, railings, etc., are free of trip points, tools, accumulated rock, debris and protect personnel from falling.
8.	Install all necessary dust suppression and collection equipment to ensure a safe environment for plant personnel and compliance with local air quality regulations.
9.	Install all electrical supply lines for vibration switch, hydraulic pump, auto lube and any other accessories to be installed. Make sure installation is suitable for crushing plant environment. Before start up, make sure the electric motors, vibration switch and lube system are correctly wired. Each drive motor is to have its own ammeter. All electrical connections and wiring should be made only by trained and qualified electricians.
10.	All welding connections and assemblies should be made by appropriately certified and qualified welders who are familiar with the machinery they are working on. Torque all bolts to correct tightness specifications.
11.	Check the planned operating circuit for the crusher to see that it complies with REMco's recommendations as regards to material flow, size and type of supporting equipment, feed size and specification, etc.

Operations

1.	Prepare desired crusher feed by eliminating all excess moisture, fines, dirt or other contaminants before feeding to crusher.
2.	On new machine start ups or whenever a clean rotor is installed, be sure to pre-line rotor and rock chamber by feeding the crusher 2 to 3 tons of minus 1/2" fine aggregate or sand. This may be introduced by shoveling it manually into the top of the crusher after the first 30 minutes of break in no-load operation.
3.	The crusher operator should become familiar with the expected performance, feed size, feed rate and desired product size expected from the crusher.
4.	The feed rate to the crusher should be the amount and size intended for the application of the machine. Over feeding or under feeding the crusher will cause erratic operation and damage to the machine and may lead to accelerated wear of crusher components or over loading of drives and drive motors.
5.	REMco VSI crushers achieve their best fine crushing performance when fed a well graded feed and operating in a closed circuit with a properly sized vibrating screen. Make sure screen capacity is adequate for the expected crusher discharge and finished product rate.
6.	Avoid extended no-load/no-feed/low feed operation. This will cause erosion of the rock lining exposing the chamber components to accelerated wear and may cause dust emission from the crusher.
7.	Feed moisture should never exceed approximately 5% by weight. Avoid feeding the crusher free running waster or feeds that contain free running water. This will wash out the chamber and lead to faster chamber and rotor wear.
8.	Monitor all incidents of excess vibration and note this in the operating record provided with the crusher. Advise maintenance or management personnel if vibration is judged to be excessive.
9.	Keep the crusher and operator's platform clean of mud, accumulated dust build up, rock spillage, grease and other undesirable debris.
10.	Periodically check that the crusher's operating support systems, such as auto lube, service monitor or vibration switch are functioning properly.
11.	Clear all packed fines and mud build up from feed diverter plate and feed hopper to assure proper feed flow into the crusher. When cleaning this area, be sure the crusher is turned off and locked out.
12.	Operate the crusher such that the motor power draw is steady. The higher the power, the greater the crushing action. Typically, power demands of 80 to 90% of the full motor amp rating produce the best product. Avoid feed interruptions and severe power fluctuations. Use automation controls when they are part of the crusher installation.

Maintenance

1.	Use all personnel safety devices including eye protection, hard hats, hard-toed shoes, work gloves, etc., whenever servicing the crusher.
2.	Make sure the lifting devices are amply rated for the weights being lifted.
3.	All rotor service is to be done in a suitable workshop area. Not in the dirt and dusty environment adjacent to the crusher.
4.	Follow recommended inspection intervals and procedures as outlined in this manual. Record all maintenance in the operating record for the crusher.
5.	Do not force anything that does not come apart readily. Check procedures per the manual. If difficulties persist or the procedure is not understood, contact REMco.
6.	After all maintenance work, close all doors, replace all guards with all bolts, replace safety pins, locks and other safety devices. Put away all tools.
7.	Do not torch cut or otherwise alter any part of the crusher or its support structure. This will interfere with the design integrity of the machine and may lead to operating difficulties or unexpected failures. Re-tighten support leg bolts after initial operation. Check periodically.
8.	Use all factory approved parts and fasteners to ensure continued, reliable performance from the crusher.
9.	Purchase and maintain a reasonable quantity of replacement wear parts on site to make sure crusher operation will not be interrupted due to lack of parts.
10.	Check and lubricate drive motors per the motor manufacturer’s recommended interval for severe duty. If in doubt, lubricate motor every 500 hours of use.

Advice to the Wise

REMco VSI crushers have become popular because they are economical machines to buy, install and operate. They also are capable of large reduction ratios at high tonnages and produce cubical products of high quality. However, it requires knowledge and experience to get the optimum performance from REMco machines. It also requires a willingness to learn and a desire to understand the finer points of VSI application and usage. We pass on the following suggestions in the hope that it will save the new VSI owner time, money and aggravation.

1.	The most important thing is safety before installation, operation and maintenance. All safety requirements must be known and met. Safety is a production activity. Without safety, the plant will stop.
2.	Just because you know and have experience with jaw crushers, cone crushers and other types of crushers, do not assume that the same rules apply to a REMco VSI. Every crusher manufacturer provides information on their machine. Become familiar with the requirements and differences between crushers that are operated in the same plant.
3.	Take the time to understand your circuit, not only the crusher but also the importance of the screens and feed control used to feed the machine. The crusher is totally dependent on them to produce the desired product. The best product comes from best feed. The best feed is produced by a proper circuit.
4.	Do not ignore the requirement of regular, visual inspection of the crusher. This is but a few minutes invested every day which will keep all problems as little problems that are quickly and easily fixed. The big problems are the ones you don't know about until it's too late.
5.	If you don't know or don't understand it, don't guess. Look it up, check it out, call and ask. Guessing is dangerous.
6.	Operating the crusher with extended, excessive vibration which goes unattended will destroy the machine. Believe it. Make sure the vibration switch is installed and operating. Never bypass or defeat a vibration switch.
7.	Know what your crusher is producing. Take test samples and gradings regularly. Learn how to measure tonnage on a conveyor belt. True crusher performance is measured as an average of several tests. A single test tells you very little.
8.	Clean up. A plant that has good housekeeping will produce more and better material than a plant which is littered with debris, junk and trash.
9.	All crushing plants are subject to variations in the material which is being processed. Whether it is a stone plant, gravel pit or mine, the nature of rock is such that its crushing characteristics can vary measurably depending on depth of the deposit, side of the pit, percent moisture content and fines to coarse ratio. The plant and the crushers will react accordingly.
10.	Crushing is work. All crushers consume energy and dissipate it through heat generation, air movement, noise and broken rock. The harder the stone, the greater the amount of energy that is required per ton produced. The finer the product, the greater the amount of energy that is required. Thus, hard stone crushed to a fine product is the toughest job.
11.	Do not ignore the lessons of multiple stage crushing. Do not attempt to operate a single crusher at its maximum reduction ratio capability in an attempt to do the job of two. Two crushers in stages will be more productive, produce a better product and be less costly to operate than a single overworked crusher.
12.	Closed circuit operation provides greater control over the final product. Closed circuit operation should be used for producing all specification materials, sands, etc. All REMco VSI crushers are designed for closed circuit operation as the primary method of use.
13.	Second shift operation of a plant will always produce less than first shift. Third shift operation will always produce less than the second shift. Thus, do as much as possible in the first shift.
14.	Train the people. All crushing plants are dependent on the expertise of the people which operate them. The best equipment will perform poorly if operated by untrained, inexperienced personnel.
15.	Plant operating people depend on their leadership. The leaders must be willing to recognize that they may not know all that is needed. Train yourself.
16.	Use automation-Modern automation systems can increase plant and crusher productivity by 10 to 20%. Automation is essential for optimum fine crushing and consistent gradings.
17.	Maintenance is a production activity. Without maintenance, the plant will stop.