DIFFERENTIAL EXPANSION

• It is prohibited to raise the speed of turbine rotor or the load if the relative expansion (+) or contraction (-) of the rotor reaches the maximum permissible values as per given by original equipment manufacturer.
• If HP rotor expands quicker than the HPT casing, steam supply for heating flanges and studs should be increased, but pressure in header supplying steam for heating should not exceed 2 kg/cm².
• If HP rotor contracts quicker than the HP casing , stop supply of heating steam to flanges and studs, increase temperature of live steam and increase load or supply fresh steam to the front sealing of HPT and the entry of leak-off steam into the gland steam condenser.
• If IP rotor expands quicker than the IP cylinder, stop the increase the temperature of steam after reheat or lower its temperature. If these measures are not sufficient, stop the increase in load too.
• If IP rotor contracts quicker than the IP casing , increase temperature of steam after reheater and increase load or supply fresh steam to the front sealing of IPT and the entry of leak-off steam into heater no. 4.
• If LP rotor expands quicker than the LPT cylinder, worsen the vacuum and stop re-circulation of condensate in the condenser.
• If LP rotor contracts quicker than the LP casing, improve vacuum in the condenser.

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