ASTM A 472 Standard Specification for Heat Stability of Steam Turbine Shafts and Rotor Forgings

Scope:

ASTM A 472 covers the process for evaluating the steam turbine shaft and rotor forging’s heat stability in order to guarantee operating temperature stability. 

Test procedure:

In this method, the forging initially stresses relived as a part of the heat stability test. When this was completed the stress-relieving temperature is maintained below 50-100ºF final tempering temperature. Then rotated the forgings at 2 to 4 rpm and maintained at stress reliving temperature for 2 h/in of maximum radial thickness, then the temperature was decreased to the specified heat stability test temperature and the test was performed.  

Video 01: lesson 12:avoid expansion differential for steam turbine

Test Specimen:

Forgings are used as specimens in this test. Before the heat stability test, clean the forging’s surface of any grease, oil, dirt, or other foreign matter. A suitable coating can be applied to provide uniform emissivity.

Data:

The forging is acceptable if the movement of its center is not greater than 0.001 inch when determined by the difference between the official hot and the official cold second measurements. This movement is determined for each test band A, B, C, and D. If the forging does not meet the requirements of the test, it may be tested again. 

Conclusion:  

ASTM A 472 gives detailed information regarding the heat stability test of steam turbines shaft and rotor forgings also This specification determines whether a forging will be stable at elevated temperatures and sets go/no go limits for acceptance.