FIELD: check of radial clearances of turbines. SUBSTANCE: radial clearance is checked during operation of turbine between its casing and shaft or between turbine casing and blade. To ensure constant and accurate result of measurement of radial clearances, measuring datum mark is provided on at least one blade and/or on surface of turbine shaft; this mark is made from non-oxidizing material for reflecting light from light fiber probe. EFFECT: enhanced reliability and accuracy of check of radial clearance. 10 cl, 3 dwg
