High Speed Balancing and Spin Test Facilities

High-speed balancing and spinning systems are used for balancing so-called flexible, i.e. shaft-elastic rotors. With such rotors, one or more critical speeds occur in the run-up and run-down to the operating speed. In the vicinity of the critical speeds, the rotors bend in a typical way (inherent shape), which leads to the emergence of new imbalances that are speed-dependent.

Typical Rotors That Require High-Speed Balancing

High-speed pumps and compressors
Steam and gas turbines for industrial applications
Power station turbines
Generator rotors
Engine components and engine turbines

Typical Areas of Application Are

Investigations on operating bearings
Low-speed (in rigid condition) pre-balancing
High-speed balancing at operating speed
Overspeed testing by spinning for strength testing
Research and development

Mechanical Structure of the Facility

Due to the high speeds and weights of the rotors, it is essential to erect a sufficiently dimensioned protective structure. Together with the control room, this protective structure forms the core of the plant. In our HighProtect plant concept, we have paid particular attention to keeping foundation work to a minimum.​

A special feature here is that the use of state-of-the-art oil supply technology means that the oil tanks and pumping stations are not installed underfloor, which saves time, material and resources in the execution required on site. Optimized installation of the individual system components through modularization and pre-assembly further reduces the on-site assembly and commissioning times.​


The Class D protective structure is always designed specifically for the customer and adapted to the rotor spectrum. It must reliably protect the environment against detached parts of the rotor or, in extreme cases, against a complete rotor bursting. Depending on the size of the system, this is achieved by several layers of steel and, if necessary, additional special concrete with appropriate reinforcement.​

Bearing Pedestals

When balancing elastic rotors, it is important that the stiffnesses of the operating bearing arrangement and the bearing arrangement in the pedestals of the balancing system are similar. Only then the critical speeds and, above all, the bending mode shapes of the rotors under test in the different bearing arrangements match well.​

Thus, exactly those modal unbalances are identified and corrected in the pedestals of the balancing system that would cause the rotor to vibrate during operation. When running through critical speeds, high vibrations and high dynamic bearing forces occur. Rotors can settle at higher speeds which can lead to an unbalance change. The bearing pedestals of a balancing system must therefore be designed in such a way that possible critical operating conditions are safely controlled.​

Measuring System for Low and High Speed Balancing of Elastic Rotors

Quasar 2 is an innovative unbalance measuring system from Hofmann Mess- und Auswuchttechnik, which is designed for the economical balancing of elastic rotors in practice. For the first time, it combines low-speed and high-speed balancing in one unbalance measuring system. The software supports high-speed balancing in many ways. For example, the unbalance of the rotor in the rigid state can already be distributed over several planes. This also reduces the modal unbalance of the rotor in the flexible state and thus the overall effort. The influence coefficient method implemented in Quasar 2 can work with single weights or – to increase effectiveness – with modal weight sets. When calculating the unbalance correction for several balancing planes, unbalance and/or vibration limits can be specified. This avoids large correction weights in a correction plane.​

In addition to vibrations, process values (pressures, temperatures, etc.) can be recorded to obtain an overall picture of the balancing process of a rotor.​

Quasar 2 offers the option to work offline, this allows to prepare data for an upcoming balancing project or to perform further analysis and create protocols after a project has been completed.​

Quasar 2 can be easily retrofitted into existing high-speed balancing systems of any type.