METSO Barmac B-Series VSI Crushers Frequently asked questions
Over the years we have found that people interested in the Barmac VSI frequently ask the same questions. Below we have provided a list of questions we are frequently asked and provided the answers. Should you have questions that are not answered here or elsewhere on the website we encourage you to contact us or your local representative. We are happy to answer your questions and discuss your application.
1. Is the Barmac VSI dusty in operation?
Under normal conditions the crusher will only emit dust when running empty, this is at startup and stop. In extremely dry conditions or fine crushing duties the crusher may emit dust whilst in operation. This is seldom a great quantity and can be readily controlled by a spray system or dust collection system.
2. Is a high moisture content a problem?
The Barmac VSI crusher is very tolerant of moist feeds. Moisture contents up to 8% are acceptable. Material with greater moisture can be accepted, but may require some minor modification to limit excessive build-up within the crusher.
3. Can the Barmac VSI be operated with a slurry feed?
Metso does not recommend slurry feeds to the machine (except in specialist applications). A slurry feed will result in poor or non existent build-up within the crusher, higher wear and reduced reduction. The Barmac VSI can be modified for slurry operation but is generally limited to a scrubbing duty.
4. Will sticky feed cause a problem?
This is generally related to moisture content, see above questions. Sticky feeds can cause excessive build-up in the rotor, crushing chamber and base. Excessive build-up is not desirable as this can result in increased rotor wear and reduced throughput. Where sticky feed is a problem the introduction of a water spray onto the bottom of the rotor can act to slump out the excess build-up and maintain the normal operation of the crusher. The Barmac VSI is a third or fourth stage crusher – if the feed material does not give problems in crushers or screens before the Barmac VSI, it will not give problems in the Barmac.
5. Is the Barmac VSI noisy in operation?
The Barmac VSI is not a noisy crusher. Sound levels are about 68 to 71 dB one metre from the machine when it is in operation. The rock lining within the crushing chamber is a very effective sound insulator. The electric motor and neighbouring screens are frequently noisier.
6. Does the Barmac VSI vibrate when in operation?
In normal operation there is a slight low amplitude vibration. To restrict any vibration the rotor should always be statically balanced prior to installation in the crusher.
7. Will the rotor go out of balance in normal operation?
No. Wear on the rotor is even and does not affect the balance of the rotor.
8. What happens if the rotor goes out of balance during operation?
Sudden loss of balance of the rotor is normally due to sudden damage of the rotor wear parts, usually caused by foreign material or oversize material entering the rotor. The machine is protected from out of balance operation by a vibration switch which will shut the crusher down. The cause of the vibration should be identified and fixed before attempting to start the crusher again. Prolonged operation in an out-of-balance condition will damage the bearings.
9. What happens if the Barmac VSI receives tramp iron?
Tramp iron entering the rotor can result in broken rotor tips and tip carrier wear plates. This can result in the rotor going out of balance if the wear part is broken free. If in a closed circuit, tramp iron may go through the crusher several times before any damage occurs. Tramp iron is to be avoided and any wear parts damaged beyond their ability to protect the rotor from wear should be immediately replaced.
10. What happens if the Barmac VSI receives oversize material?
Each model has a maximum feed size restriction. Exceeding this can cause accelerated wear of wear parts, damage to wear parts, scouring of the rock build-up or blocking of the rotor feed tube.
11. How long do the rotor tips normally last?
The life of the rotor tips (and all the rotor wear parts) is related to the abrasiveness of the material. Tip life can range from 60 to 70 hours for a highly abrasive material such as Chinese bauxite to over 1500 hours for a virtually non-abrasive limestone.
12. How long does it take to change a rotor?
With overhead lifting equipment and all the required tools available, a rotor change can be performed by one person in 60 minutes.
13. What is the normal life of the bearings?
This depends on how the crusher has been operated. The bearing cartridge is designed with a service life of 15,000 hours. However, abusive operation such as operating with excessive vibration will shorten this.
14. How is the bearing cartridge lubricated?
The bearing cartridge requires regular application of grease to maintain sufficient lubrication. The grease can be applied manually or an optional automatic greasing system can be supplied. When manually applying grease it must be applied every 8-10 hours of operation using a single point grease system.
15. How is the Barmac VSI driven?
The crusher is driven by a belt drive using either one or two electric motors. Rotor speed can then be varied by changing the pulley diameters.
16. Why are two motors used on some Barmac VSIs?
Two motors or dual drive configuration is used to reduce the bearing loads and improve power transmission on high horsepower (greater than 350 HP) machines. Dual drive can also be used where there is a requirement to reduce the starting current draw by starting first one motor (which is only half the required power) then bringing the second motor direct on line.
17. Must both motors on a dual drive operate at the same power draw?
Yes, both motors must operate at the same power draw. When installed, some time may need to be spent balancing the power draw of the motors. Uneven power draw is most often caused by uneven drive belt tension, however mismatched pulley diameter and faulty electrical connections can also be causes.
18. Can the Barmac VSI crush abrasive material?
Yes. In fact the more abrasive the material the more cost effective the Barmac VSI is in comparison with other crushing equipment. This is due to the minimal number of wear parts within the rotor and all of the major wear surfaces being protected by rock build-up. This leads to a machine that is very economical to operate.
19. Is the product grading affected by wear of the wear parts?
No. The product grading does not change as the rotor wear parts wear. This is because the wear parts act to protect the structure of the rotor they are not directly involved in the crushing process.
20. Does the Barmac VSI require a rigid support structure?
No. In fact the crusher must be allowed to vibrate at low amplitude. The use of a rigid support frame leads to premature failure of the bearings and possibly shaft failure. Where the machine is to be mounted on a rigid support structure rubber vibration mounts must be used to isolate the crusher from the support structure and allow the low amplitude vibration.