COOLING STEAM TURBINE ASSEMBLY BY PASSING COOLING MEDIUM TO LOW PRESSURE TURBINES
Publication Date: 2013-Apr-22
The IP.com Prior Art Database
AbstractThe present invention proposes a technique of connecting to a low pressure (LP) turbine to introduce cooling medium there through during cooling of turbines, after steam turbine shutdown. The technique includes a flow control skid connected to a LP admission line. A cooling medium is supplied by the flow control skid to the LP admission line. Addition of the cooling medium into the LP turbine dilutes the exhaust gas from the IP in order to maintain LP metal temperatures within limits. .
The present invention relates generally to steam turbines, and more particularly to a technique of cooling steam turbines after shutdown.
Steam turbines include a high-pressure (HP) turbine, an intermediate-pressure (IP) turbine and a low-pressure (LP) turbine. The HP turbine and the IP turbine are connected to each other through a common shaft or through two shafts.
Steam generated in a boiler passes to the HP turbine through an inlet conduit having a stop valve. The steam is then exhausted through a steam outlet portion into a HP outlet line. The steam exhausted into the HP outlet line is heated by a re-heater and the reheated steam is subsequently supplied to the IP turbine. The reheated steam enters the IP turbine through a reheated steam inlet conduit having a control valve. The steam from the IP turbine is exhausted to a cross-over line through a steam outlet portion of the IP turbine and supplied into the LP turbine. Steam is subsequently passed to a condenser from the LP turbine.
Further, the assembly of steam turbine as mentioned above is periodically dismantled due to a failure or for maintenance. The steam turbine is therefore, required to be shutdown. The highly heated portions of the steam turbine need to be cooled down to ambient temperature for steam turbine outage disassembly. Usually, the heated steam turbine portions require a long time to cool down after the steam turbine is shutdown. The inefficiency of cooling down the steam turbine after shutdown results in a substantial production loss and associated expenses annually for a given power generating unit based on steam turbines.
Several conventional techniques are for cooling of steam turbine after shutdown.
One conventional technique includes a forced-air cooling apparatus for a steam turbine. The apparatus includes an outer casing, an inner casing disposed inside the outer casing and a rotor coaxially disposed inside the inner casing. Coaxial placement forms two cooling passages, one passage between the inner casing and the rotor and another passage between the outer casing and the inner casing for flow of steam. An external cooling air is charged into the cooling passages during steam turbine shutdown process. After achieving the cooling of turbines, cool air is discharged to ambience.
Another conventional technique includes steam turbine having a vacuum pump that creates suction. The turbines are cooled by suction driven air. Another conventional technique includes a flow of nitrogen from a nitrogen pump through a single piping header to a flow control station installed under the turbine. This stat...