99/01509 Diagnostics based on thermodynamic analysis of performance of steam turbines: case histories : Tirone, G. et al. PWR (Am. Soc. Mech. Eng.), 1996, 30, (2), 415–421

Abstract

The purpose of this paper is to describe some types of failures which have occurred with the ENEL stock of fossil-fuel steam turbines over the last 5--7 years. This paper also presents the corresponding thermodynamic analysis of turbine parameters which permitted failure diagnosis and pre-scheduled opening of the turbine. The examined failures concern: (1) in-service rupture of the bell seal retainer nut between a SH steam inlet sleeve and the inner HP/IP cylinder, on turbines with a main steam inlet system with bell seals; (2) incorrect assembly of pressure seal rings between steam inlet sleeves and the inner cylinder on turbines with a main steam inlet system with pressure seal rings during a scheduled outage; (3) steam flow path restriction in IP turbine inlet; (4) steam flow path restriction in 1st HP turbine stage nozzles; and (5) steam flow path restriction in 2nd HP turbine stage vanes. Thermodynamic failure analysis and the subsequent analysis of turbine damage (mechanical and financial) enabled condition-based maintenance operations to be carried out.