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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