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Low-speed balancing process on BVI-03-10T

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Categories: Turbocharger repair

The BVI-03-10T balancer performs low-speed balancing of turbocharger rotor group parts. This process consists of two steps:

  • balancing the “turbocharger shaft”;
  • to balance the same shaft together with the compressor wheel and rotor group parts.
BVI-03-10-T planes 1
BVI-03-10-T planes 2

The correction planes in the first balancing step and in the second balancing step are indicated by Roman numerals. 

Note that some low-cost machines simply cannot technically perform the second step. That’s because in the second step, the center of mass will be to the right outside the supports. Besides, the correction planes will be to the left outside the supports. BVI-03-10T is specially designed to solve this problem.

Preparation

Cleaning

Before starting the low-speed balancing, a small preparation consisting of cleaning the parts to be balanced and making a contrast mark on the surface of the “turbine wheel blade” is carried out. In addition, the “turbocharger shaft” is weighed if the machine operator does not know the permissible residual unbalance of the rotor. To adjust the balancing system, you will need information about the weight of the “shaft” and the diameters of the “turbine wheel”.

The first thing to do before adjusting the machine is to prepare the prism support surfaces on which the “turbocharger shaft” will be mounted for balancing. To do this, the bearing surfaces should be cleaned. If there are signs of wear, they should be removed using a paper knife or a regular knife. The better the prism seating on the surface, the fewer balance errors there will be. It is important to note that no abrasive particles should be present in the contact area between the rotor journals and the prisms. This can cause wear on the bearing surfaces of the shaft.

Setting up the machine

Setting up the machine involves adjusting the position of the supports relative to the bed, adjusting the height of the prisms. As well as to set the “speed sensor” to the desired position relative to the contrast markings on the surface of the shaft. It is also important to correctly adjust the tensioning force of the belt. It will transmit the rotary motion from the machine motor to the workpiece. In this case, it is necessary to determine the “golden mean” in order to eliminate the possibility of belt slippage and over tensioning, because in this case there are errors that affect the quality of the balancing.

The prism height adjustment is performed with the rotor installed and in motion. As in this case, it is possible to center the rotor, taking into account the aerodynamic properties of the product to be balanced. For the convenience of this operation, it is necessary to free the operator’s hands. For this reason, starting and stopping the motor rotation can be done not only by the buttons on the control panel. But also using the foot pedal that comes with the machine.

Setting up balancing system

Running tests

The first step in setting up the balancing system is to enter information about the mass of the rotor and test weight. After that, enter the radii at which it will be positioned on the correction planes. This information will be used by the calculation unit to calculate the magnitude and position of the unbalanced rotor mass.

Three test runs of the rotor are required to adjust the balancing system.

  1. The first start-up is carried out without test weight. Usually at this point, the speed of the turbocharger shaft is adjusted. In addition, the computing unit receives primary information from the vibration sensors and the speed sensor. Further, comparing this information with that which will be received at following two starts. The computing unit, using complex algorithms, can calculate mass and position of unbalanced mass.
  2. A second launch is performed with a test weight installed (at a previously specified radius) at the “0” point of the first correction plane. The point where the weight is placed will be the origin of the coordinates for determining the unbalance angular position.
  3. Finally, the third start is carried out in the same way as the second start. Except that the “test weight” is placed at the same angular position only on the second correction plane. The radius of the load may be different. After calibration of the balancing system, the “test weight” must be removed from the surface of the rotor.

The “turbocharger shaft” balancing process consists of removing material in the two correction planes based on the readings of the “calculation unit”. This will provide the machine operator with accurate information about the angular position and the amount of unbalance.

After assembly

The second balancing step occurs after the turbocharger shaft and rotor group parts are assembled. The shaft, turbine wheel, labyrinth seal bushing, and the nut which holds the assembly together, are all part of the rotor group. Balancing is carried out in the same way as when balancing the turbocharger shaft. But in this case, only the compressor wheel is balanced. As the turbocharger shaft has already been balanced in the previous step. At this point, no metal is removed from the shaft. And all necessary metal is removed from the compressor wheel.

Please also note that when removing metal, nothing should be sawn from the surfaces of the blades. Neither may they be shortened or the shape of one or more blades be changed. The blades themselves must not be sawed in any way at all during low-speed balancing process. This can cause the adjacent parts of the blade to tear off and destroy the turbocharger.

The low-speed balancing is considered finished only when the residual unbalance of the rotor has been reduced to the permissible limits. All parts of the rotor group are then marked in order to remember the angular position of all elements with respect to the “turbocharger shaft”. So that when assembling into the housing you will be sure to assemble everything according to the marks.