HIGH SPEED SAVINGS
MACHINING & MACHINERY HIGH-SPEED BALANCING
SULZER
HIGH SPEED SAVINGS
Sulzer investment reduces high-speed balancing time
As one of the only independent highspeed balancing facilities in the UK , there is considerable demand to use Sulzer ' s equipment in Birmingham . Following a recent investment , the typical time to balance a flexible rotor was significantly reduced , meaning that more customers will be able to benefit from this service .
When repairs and refurbishments are completed on large motors and generating equipment it is important to complete a high-speed balancing process to ensure smooth operation . As one of the leading independent repair specialists in the world for rotating equipment , Sulzer uses this facility to complete the final stages of turnkey projects for its customers .
The recent investment has seen the existing equipment upgraded with cutting-edge software from Schenck , experts and leading manufacturer of balancing technology . The new CABFLEX 3 software is complemented by additional hardware that makes the whole package very user friendly and intuitive . This latest development from Schenck offers a high-precision balancing system that will be available to all customers of Sulzer ' s UK high-speed balancing facility .
Critical speed analysis
Flexible rotors that operate at high speed are subjected to considerable forces that cause them to bend . Each rotor has different critical speeds where the amplitude of the bending moment is at its greatest . The purpose of the high-speed balancing process is to minimize the bending of the rotor as well as vibration so that it runs smoothly in normal operation .
To achieve this , the computer system takes the data from the balancing process and uses influence coefficients to calculate a correction response – telling the operator how much weight to add and where to place it .
Flexible turbo-generator rotors are heavily influenced by the first critical speed initially and they often operate close to or above the second critical speed . Each time a rotor passes through these critical speeds the rotor bends and weights are used to counteract the bending moment .
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Precision balancing
In most cases , Sulzer aims to balance a rotor to under 25 µ m peak to peak at running speed and 50 µ m peak to peak through the first critical speed , but specific customer requests can also be accommodated . These measurements equate to balance grades , derived from ISO 1940-1 , with the most common grade being G2.5 , however , Sulzer can achieve grades less than G1.0 if required .
Every rotor has its own set of criteria for balancing and the software makes the calculations based on these criteria to evaluate the best possible application of balance weights . This process can be applied to any high-speed rotor , provided it fits into the generous dimensions of the Birmingham facility , which can handle rotors up to 12 meters ( approx . 39 feet ) in length and 40 tonnes ( approx . 44 US tons ) in weight , with a maximum operating speed of 5 ' 200 rpm .
Once the deflection of the rotor is below the required level , the process moves on to the next critical speed . Previous projects have seen rotors running at operating speed with a peak-to-peak amplitude of 10 µ m .
The new software from Schenck looks at the whole speed range and how the movement changes throughout the range . Using internal calculations , it predicts the influence of placing a certain weight , in a specific plane , in a certain position on the rotor .
Furthermore , it is also able to store information about a rotor including the positions where weight can be added and the locations of existing weights . Less sophisticated software will suggest the addition of weight in a certain plane at a specific location , but in some cases that may be a location where weight cannot be added .
By making the calculations based on all the available data , the final solutions are created much faster and the balancing process is completed sooner .
Time saving technology
Sulzer anticipates this new software will deliver a considerable time-saving in the process of balancing rotors . Previously , it would have taken four days to complete the high-speed and overspeed balancing of a typical generator rotor . In many cases this can now be reduced to just three days – a significant improvement when looking at the annual throughput of the high-speed balancing facility .
The time required to complete the calculations and apply the new weights is greatly reduced . Furthermore , the interface between the balancing data and the operator is much more intuitive , making it much easier to train personnel in the operation of the high-speed balancing facility .
In the UK , there are only a handful of high-speed balancing pits , the majority of which are owned by original equipment manufacturers and not available for maintenance projects . As a result , Sulzer ' s facilities are in constant demand , so the reduction in time to complete the balancing process will enable more customers to benefit from this cutting-edge technology .
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