The solutions for common mechanical troubles of grinder

The grinder is one of main feed production equipment for feed plants,the reliability  of grinder operation affects the production efficiency and normal operation of following processes directly, therefore, maintenance and operation personnel should   learn to analyses and dispose common faults of grinder system, solve problems in the short term, restore the production as soon as possible. The grinder system mainly includes grinder and the electric motor. Corresponding faults can be divided into mechanical faults and electrical faults. The following are analyses of vibration, bearing heating and sieve blocking during mechanical faults.
1. The vibration of grinder often uses electric motor to connect grinding device directly. This connection mode is simple and easy for maintenance. But if both are not connected well in the assembly process,causing the overall vibration of grinder.
（1）The rotors of electric motor and grinder are  not concentric. Move electric motor left or right, or add pads under motor feet to adjust the concentrically of the two rotors.
（2）The rotors of grinder are not concentric. Two bearing surfaces which support rotor shaft are not in the same plane. May pad copper strip in the bottom of the supporting bearing seat , or increase the adjustable wedge iron in the bottom of bearing, ensure two shaft heads are concentric.
（3）Some parts of grinding chamber are with bigger vibration.The connection between coupling and rotor is not concentric or the quality of flat hammer in rotor is non-uniform. According to different types of couplings to take the corresponding methods to adjust the connection between coupling and motor.When the hammer quality is non-uniform, must choose and match each group of hammers again, the error of the symmetrical hammer is less than 5G.
（4）The original balance is destroyed. Motor after repair should do the dynamic balance test to ensure the overall balance.
（5）The foundation bolt of grinder system is loose or the foundation is not firm,when installation or maintenance,tighten the foundation bolt evenly,install shock absorber between foundation and grinder to reduce vibration.
（6）Hammers broken or hard sundries in grinding chamber can cause the imbalance of rotor running and vibration of whole pellet mill. Therefore, check badly worn hammers regularly and change them symmetrically. Unusual sound occurs in the operation, must stop machine to check the reason and solve faults timely.
（7）The connection between grinder system and other device is not matched. For example, the improper connection of feeding pipe，discharging pipe cause vibration and noise.Therefore, these connections are not suitable to use hard joints, soft joints are the best.
2.The bearing is overheating. Bearing is a important part for a grinder. Bearing's performance affects the equipment normal operation and production efficiency directly. During operation, users should pay more attention to the bearing temperature rise and noise,deal with the abnormity urgently.
(1) The two bearing seats are uneven, or the rotors of motor and grinder are not concentric,the bearing is overheating under the impact of the extra load. In that case, stop the machine immediately and eliminate faults,avoid the early damage of bearing.                                                                             
（2）Too much or too little lubricating oil in the bearing or ageing are also the main reasons of bearing damage by overheat. Therefore,fill rationing lubricating oil on time according to the instruction book. Generally, lubricating oil occupies 60％－70％ of bearing cavities, too much or too little is not conducive to the bearing lubrication and heat transfer. Extend the useful life of bearing.                          
（3）The bearing cap fits the bearing too tightly,the bearing fits the shaft too tightly or too loosely all can cause bearing overheating, Once this problem occurs, make  friction sounds and clear swing in the operation. Stop the machine to take down the bearing. Repair the friction parts, then re-assembled the bearing as required.
3.The grinder sieve blocking: the sieve blocking is one of common faults in the operation. There may be existing problems of the design of sieve plate, but more is due to improper operation.
(1)The feeding speed is too fast,increasing the load,causing the sieve blocking. In the feeding process, always pay attention to the deflect degree of ammeter indicator, if surpasses the rated current, show the motor is overload, the long time overload will burn the motor. In that case, should diminish or close the feeding gate immediately,or change the feeding way. Through decreasing the feeder to control the feeding quantity. The feeders have manual and automatic types. Users choose appropriate feeders according to the actual situation. Because the grinder with the high rotation speed and high load, the fluctuation of the load is strong.Therefore, the current of operating grinder is usually controlled about 85% of rated current.   
(2)Negative pressure in grinding chamber is not enough, cause powder of grinding chamber  through the sieve is hard discharging or the discharging of wind network pipeline is unsmooth,cause the grinder sieve blocking. There are many reasons for the sieve blocking caused by the wind network system problem, such as the too big or too small diameter of discharging windpipe,the big resistance because of too many windpipe bends,the too low jet pressure of pulse nozzle,the unsuitable air blower, the too long wind network pipeline and the wind network pipeline leakage. Exclude causes one by one to adjust the wind network system. Do daily maintenance well like regular check,clean and replacement of pulse bag, ensure the grinder operates normally.                                                                         
(3)The broken hammer with large wear, the sieve hole is closed and broken. The grinding materials with high moisture content will block the grinder sieve. Replace broken and badly worn hammer regularly, keep the grinder in good working condition and check the sieve regularly. The moisture content of grinding material should be lower than 13％. Not only improve the productivity, but also make the grinder sieve won’t be blocked, enhance the reliability of the grinder operation.