High-speed balancing installations and systems for high-speed balancing of flexible rotors; runout testing systems for the exact measurement of radial and axial runout.
Steam turbines, gas turbines, turbo generators and turbo compressors are machines whose rotors usually run beyond at least one critical speed. Therefore, they are balanced as flexible rotors. The HS type high-speed balancing and spin testing installations meet all requirements for balancing and spinning flexible rotors with multiple correction planes and multiple speeds. Flexible concepts – for example for propulsion and safety structures – enable Hofmann to optimally adapt the high-speed balancing and spin testing installations to specific project requirements, or to provide them as turn-key solutions.
In addition to balancing, rotors from turbomachines undergo further special tests.
For example, the field winding of a turbo generator is supplied with electric current in order to evaluate the influence of rotor heating on the balancing result. Magnetic field and electric impedance measurements are performed on the rotating rotor to determine the electrical properties and detect winding defects.
With many rotors from turbomachines, the runout testing must meet specific requirements. Hofmann’s type UHR runout testing machines measure all important runout values (total, mechanical, electrical) with the rotor set in V-blocks. To check on-site runout, the RO 7000 portable runout testing system is used.
Type HS 16 - 34
The high-speed balancing and over-speed testing installations are used to balance flexible rotors under operational conditions and to perform spin tests at over-speed. Hofmann HS installations cover rotor weights from just a few kilograms up to 100 tons.
Hofmann’s UHR Runout-Testing Machines measure the radial and axial runout of rotors in multiple axial planes. A rotor is placed on pedestals with V-blocks for runout measurement and is driven jolt-free using an end-drive. The runout sensors are mounted to a measuring stand, which is positioned along the rotor axis. The sensors point to the rotor under a set angle and can be radially adjusted according to the rotor diameter to be measured. The signals of the runout sensors and encoder (connected to the drive system) are acquired and evaluated by the runout measuring software Orbistar 2.
Orbistar 2 enables setup of a specific measuring task, acquires and displays the measuring data, provides tools for data analysis and generates reports. This software can also compensate for the systematic measuring errors of the V-blocks and for shaft movement by using a reference sensor. The runout measurement results are used to compare actual values with target values and to perform corrections, when necessary.
A special feature of Orbistar 2 is its ability to measure electrical runout simultaneously with a tactile (mechanical runout) and an eddy current senor (total runout). The electrical runout is the difference between the total runout and the mechanical runout, i.e. the systematic measurement error of the eddy current sensor. This measuring value is useful when inspecting traces used for shaft vibration measurements.
Type RO 7000
Hofmann’s Portable Runout Inspection System RO 7000 provides a solution to measure radial and axial runout of rotors and other cylindrical parts in multiple axial planes. During a measurement a rotor will be supported for example in a lathe, in V-blocks or on rollers. Rotors may be rotated by a motorized drive or manually. The system consists of a measuring controller to be hooked-up to a PC, a sensor set and the measuring software Orbistar 2.
Orbistar 2 helps to setup a specific measuring task, acquires and displays the measuring data, provides tools for data analysis and generates reports. This software can also compensate for systematic measuring errors of typical rotor bearings like V-blocks and for the shaft movement using a reference sensor.
Runout will be measured using proximity sensors which provide adaptors with interfaces to standard magnetic bases. The angular position will be captured with an encoder wheel which is driven by the rotor surface or by a speed sensor.
A special feature of RO 7000 is its capability to measure electrical runout simultaneously with a tactile (mechanical runout) and an eddy current senor (total runout). The electrical runout is the difference between the total and the mechanical runout, i.e. the systematic measurement error of the eddy current sensor. This measuring value is useful when inspecting traces used for shaft vibration measurements.