Workshop «Shaft alignment and dynamic balancing»
We invite technical specialists to participate in the training course on the topic «Shaft alignment and dynamic balancing» which will take place on 04-05 April, 2019 in Germany (Lubeck). The workshop is arranged for specialists in quality, service engineers, mechanics and power engineers who are responsible for the reliability of machines and industrial equipment.

Kronsforder Allee 45,
23560 Lübeck
Tel: +49 (0) 451-370-87-700
Articles -- Oher

Start up of fans

Trouble-free and efficient operation of ventilation systems of industrial enterprises is defined not only by timely performance of condition monitoring testing, carrying out preventive maintenance of the ventilation systems, arranging of efficient operation, but also a by a clear sequence of actions during the pre-start activities. The setup procedure of the ventilation systems is specified in the operating instructions, approved by the enterprise administrative authorities. The guides also describe the special requirements to premises where the ventilation systems are installed, nature of production processes, mode of ventilation systems and responsibilities of operating and maintenance personnel. During the start up of the fan the gate that controls the cross section of the suction pipe must be closed. To achieve a mode which corresponds to the nominal load of the drive electric motor one should increase the cross section of the inlet fitting little by little and control its electrical parameters. The start up of the ventilation systems can be performed in two ways: when the ventilation system is unloaded and when the ventilation system is operating normally.

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.

To do this use the devices to ensure a smooth start- up of the drive motor, a phased increase of the electric motor speed up to the working speed as well as schemes with an auxiliary accelerating engine. Before you start up the ventilation system it is necessary to ensure that the doors and manholes of an air handling plant and exhaust chambers are closed. The housings of the ventilation and electric motor must be installed on the foundations properly.

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.

After starting - up the fan one should check if the rotation direction corresponds to the defined one. After 10-15 minutes of the fan operation it is necessary to control the temperature and relative humidity of the supplied air. The start-up time and the air parameters should be recorded in the daily log book. After 1-2 hours of the fan operation check the vibration level of the bearings of electric motor and impeller of the fan.

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).