Start up of fans
In the first instance the maximum starting moment is about 40% from the nominal value, in the second instance - it is equal to the nominal value. When starting up the large ventilators with the large impellers it is necessary to limit the starting acceleration in order to avoid undue dynamic loads on the impeller blade system.
If the ventilation uses a belt drive one should check the belt tension and pulley alignment. We recommend that you perform the pulley alignment with the laser system BALTECH PA-4000, and to control the belt tension using the BALTECH BC-4000 system. Rotating parts must always have the fences. All the valves and gates must have the initial position. One should make sure that there are no foreign objects in the supply grills and ventilation chambers. Also before starting the fan, make sure that the rotor rotates easily without binding.
Apply a mark on the rotor, rotate the rotor and make sure that the marks don’t coincide, which means that the rotor stops every time at different locations - thus you can check the static balancing of the impeller. If the marks coincide, it means that the rotor has a residual unbalance and the fan impeller stops at the “heavy” spot. In this case before the main start- up of the fan one should perform the in- field balancing using the BALTECH VP-3460 balancing system.
In addition, before starting the fan check the condition of welded and riveted joints, condition of soft inserts, lubricant in the bearings and fan impeller casing and grounding. Before starting the fan, make sure that the motor and fan shafts are properly aligned. We recommend that you perform the alignment of the shafts and couplings using the laser system and calibrated shims BALTECH-23458N.
They should not exceed the vibration levels recommended by the manufacturer in the technical passport of the ventilation system. If after starting- up the fan there are knocking or a high vibration level, it is necessary to tighten the housing bolts and check the correctness of mounting of the impeller on the shaft. If it doesn’t help one should check for unbalance condition and perform dynamic balancing of the fan impeller in their own bearings or perform a natural frequency analysis of the whole ventilation system and analyze the resonant frequency. BALTECH GmbH offers industrial enterprises operating various types of the ventilation systems, a wide range of the equipment for vibration monitoring of bearing assemblies, equipment for dynamic balancing of rotors in their own bearings, equipment for checking and performing the alignment of rotors and pulleys of the belt drives. You can learn a complete list of our equipment on our web- sites, as well as at Reliability technologies seminars which we carry out in Luebeck (Germany).