Main steam inlet sleeves on steam turbines: External ultrasonic test and external sleeve replacement (closed HP-IP casing)

Conference · Tue Dec 31 04:00:00 EST 1996

OSTI ID:549971

Lauro, M; Arrighi, L; Gaibazzi, I

ENEL has gained extensive experience on turbines with bell seals in relation to defect diagnosis and the conducting of on-site repairs on the main steam inlet sleeves. Several cases of cracking in the trepan radius area, and of retainer nut breakage, on this type of sleeve have caused very significant levels of turbine downtime that have demanded costly unscheduled work in order to open the HP-IP housing. These are related phenomena which were initially diagnosed by using temperature sensing at the IP turbine exhaust. As a consequence of the above, a technique was developed for detecting defects from outside the turbine by using non-destructive ultrasonic inspection (UT). A procedure for replacing the sleeves while the casing is closed was developed in conjunction with the manufacturer. The time required and the scope of operation are both of a limited nature. Initial trials were held with inspections carried out on an open turbine when there was a planned outage and then on a real case. Since completing these trials, periodic UT inspections have been made on (all) the sleeves and this check is being carried out on a continuing basis. Any changes in relevant indications are noted during these inspections, thereby allowing any replacement operation to be planned on site and at any time.

• OSTI ID: 549971
• Report Number(s): CONF-961006--; ISBN 0-7918-1796-2
• Country of Publication: United States
• Language: English

Related Subjects

20 FOSSIL-FUELED POWER PLANTS
CRACKS
IN-SERVICE INSPECTION
STEAM TURBINES
TENSILE PROPERTIES
ULTRASONIC TESTING