Stabilizing Furnaces

The equipment for steam turbine rotor thermal stability testing has to be understood by this abbreviation. The test is known as HST (heat stability test) and is carried out pursuant to the methodology given by the respective standards, e.g. SEP 1950, ASTM 472-98, etc. The objective is to check the responses – changes in radial runout of the machined turbine rotor forging or weldment under the temperature conditions that reflect the actual conditions in which the turbine is to be run. The equipment can also be used for the stress relief annealing of welded rotors. 

Regarding customer needs, the E-therm Group has developed a testing and stabilizing furnace in quite a new concept, meeting, in all aspects, the requirements of the standards applicable to such equipment. Another result of the company’s own research and development is a sensor used to measure radial runouts of rotors. These measurements are taken during the course of testing one at a time, as specified. Accuracy of measurements is ± 2 μm at the actual temperature in the furnace.

The equipment enables the heat testing of forged and welded turbine rotors. The standard temperature at which the heat stability tests are carried out is 150°C higher than the rotor operating temperature. It will range around 670°C for high-pressure rotors.

The equipment can be used to anneal welded rotors up to 800°C. In the case of heterogeneous weldments, different heat treatment temperatures can be applied to individual parts of such rotors, depending on the steel types and grades from which they are made.

Together with the furnace itself, a fully original radial runout measurement analyzing methodology has been developed as well, applicable also to the thermal stabilization processes. These development efforts have also resulted in new software for the automatic assessment of measurements compliance with the requirements of the individual standards applied to this technological process.

The test running is fully automated, and is also documented automatically, including a certificate drawn up in the setup and format as selected in accordance with the applicable standards.

The quality and high utility value of the newly developed equipment can be confirmed by the fact that a total of eight stabilizing furnace assemblies have already been supplied and hundreds of testing cycles have successfully been carried out on these systems. 

The equipment is mainly comprised of the following components:

• Stabilizing furnace itself, consisting of electrically-fired modules that differ in length, which can be put together to achieve the desired length and arrangement, depending on the dimensions of the tested or heat treated rotor
• Mechanical equipment for precise and reliable bearing of the rotor during testing or annealing and for ensuring its rotation at the desirable speed
• Radial runout meters used to measure the rotor radial runout rates and their changes during the test
• Radial runout meters supporting structure and positioning equipment
• Electrical circuitry used to power the electrical resistance heating system, drives, sensors, and actuators
• Testing and stabilizing equipment operating control system
• Software used to record, process, and analyze measurements and to match them to the requirements of the respective standards

Based on the required range of the tested and/or heat-treated rotors, these systems have been engineered in two sizes.

HST60 stabilizing furnace

• Maximum rotor weight up to 60 tonnes
• Maximum rotor length in furnace 6,000 mm
• Maximum rotor diameter in furnace 1,800 mm
• Maximum furnace operating temperature 700 °C

HST135 stabilizing furnace

• Maximum rotor weight up to 135 tonnes
• Maximum rotor length in furnace 10,000 mm
• Maximum rotor diameter in furnace 2,150 mm
• Maximum furnace operating temperature 800 °C

We are ready to engineer and supply customized stabilizing furnaces and their accessories where different specific requirements/specifications apply.