RotaTip: Blade Clearance Measurement System
Technical Details.
| Resolution: | 0.01mm (0.0004”) | |
| Repeatability: | +/- 0.05 mm (0.002”) | |
| Maximum Machine Speed: | In excess of 50,000 rpm. | |
| Minimum Machine Speed: | No minimum when operating with an acceptable tachometer signal input. (a) 1,000 rpm (with external software control) |
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| Power Supply: | 110/240v, 50/60Hz | |
| Mounting: | 19” rack or desktop cabinet. |
The Probe Cartridge. Probe Cartridge attached to Actuator.
The probe cartridge has a coaxial construction with a central extendable touch wire insulated from an
external casing. Cartridges are available in various standard sizes but can be designed for specific
applications if required.
The Actuator.
The actuator is configured in standard and miniature sizes, for all applications. Principally it is used to carry the stepper motor, which drives the probe in and out of the rig, turbine or test vehicle. It also contains the circuit, which generates the high voltage ‘touch’ supply and detects the ‘touch’ with the rotor blade. The actuator has a purge air-cooling connection but in installations with a particularly hot mounting arrangement air or water cooled casings can be fitted to protect the internal circuits from radiated heat. A “miniature” probe cartridge and actuator combination is available for use where installation space is restricted or allowable engine casing loadings are low.
The Upper Probe Assembly.
The short probe extension, known as an upper probe assembly, is used to connect the central touch wire in the probe cartridge with the stepper motor mechanism in the actuator. This is standard for all installations.
The Mounting Tower.
Probe/actuator assemblies are attached to the rig, turbine, or test vehicle via a mounting tower. Usually the tower is a standard design with a connection for cooling/purge air, which vents into the rig, turbine or test vehicle through the probe tip. This keeps the probe tip clean and ensures that any hot gases do not escape through the RotaTip installation. Probes are sprung loaded into the tower to allow for thermal growth between the probe tip seating and the actuator mounting flange.
The Control Unit.
A standard Rotadata microprocessor based electronic controller is used. Operating from the normal 120/240v, 50/60 Hz mains supply, the controller consists of separate control and power supply modules, mounted together in a single 19” instrumentation rack. Up to 2 channels can be mounted into this 3U high configuration. Alternatively cabinets are available where multiple systems are required. These are suitable for single, twin and four channels of RotaTip. The control unit carries all controls necessary for manual operation. A 4-digit indicator displays the distance between datum and ‘touch’, which may be displayed in inches to an accuracy of +/- 0.05mm (0.002”).
Cables.
There is a 19-core cable between the control unit and the actuator. This low loss construction has each core separately screened and the ends plotted to avoid failures. Ranges of standard lengths up to 50 metres are available, suitable for operation in temperatures up to either 80°C or 150°C. A second cable links the controller with the rig, turbine or test vehicle tachometer generator to permit the control of the dwell between probe advancements. The single channel RotaTip (RCMS4) system is the basic unit and comes configured as a single channel, a twin channel or a four channel installation.
Diagram above: A Single Channel RotaTip (RCMS4) System
A Four Channel RotaTip (RCMS4) System
The system is used for blade tip clearance
measurement on the compressor and
turbine stages of a gas turbine engine.
One channel of RotaTip is usually
installed on each of the selected
compressor and turbine stages.
Typical Scope of Supply for a Four Channel RotaTip Package.
- four actuators with a choice of either “miniature” or “standard” actuators.
- four probe cartridges with a choice of either “miniature” or “standard” cartridges.
- four mounting towers and four upper probe assemblies.
- two dual channel ground station controllers.
- four 19-way cables and two RS232 cables.
- one actuator setting tool.
- PC or laptop complete with control and display software.
- One user manual in the English language and two days user training at Rotadata Limited Derby factory for up to three of customers engineers.
- Customer to agree all cable lengths required prior to order placement. The 19-way cables are suitable for use up to 150°C.
- A double skinned, actuator air-cooled, environmental cover for use up to 200°C is available as an optional extra.
Examples of RotaTip Display Screens.
