Patent Application
20080017251
It should be noted that although
During operation, low pressure steam inlet 30 receives low pressure/intermediate temperature steam 50 from a source, for example, an HP turbine or IP turbine through a cross-over pipe (not shown). The steam 50 is channeled through inlet 30 wherein flow splitter 40 splits the steam flow into two opposite flow paths 52 and 54. More specifically, the steam 50 is routed through LP sections 12 and 14 wherein work is extracted from the steam to rotate rotor shaft 16. The steam exits LP sections 12 and 14 and is routed to a condenser, for example. During operation, a casing drain(s) 108 facilitates removing condensed moisture from an interior of casing 22. Over time casing drain 108 may become obstructed by, for example, sediment collecting within casing drain, which inhibits moisture from being removed from the interior of casing 22. In the exemplary embodiment, turbine 10 includes a drain purge system 100 that facilitates clearing an obstructed or partially obstructed casing drain.
Drain purge system 100 also includes a purge fluid source 128 in flow communication with purge chamber 112. For example, a purge fluid source is high pressure steam or compressed air. Purge fluid flows from purging fluid source 128 through a steam piping manifold 130 to supply purge chamber 112 with a flow of purge fluid. In the exemplary embodiment, steam piping manifold 130 extends from purge fluid source 128 through an exhaust casing 129 to purge chamber 112. In the exemplary embodiment, exhaust casing 129 is fabricated from carbon steel. Alternatively, exhaust casing 129 is fabricated from other suitable materials. In an alternative embodiment, turbine 10 does not include exhaust casing 129. In the exemplary embodiment, purge fluid source 128 is in flow communication with at least some of respective purge chambers 112. More specifically, steam piping manifold 130 includes individual pipes 131 coupled to individual respective purge chambers 112. In the exemplary embodiment, steam piping manifold 130 is a parallel piping arrangement. Alternatively, steam piping manifold 130 uses a piping arrangement wherein purge chambers 112 are coupled together in serial flow communication. When purge chambers 112 are in serial flow communication, steam piping manifold 130 may require various pipe sizes to facilitate equalizing the purge fluid flow to purge chambers 112 and to reduce head losses. In the exemplary embodiment, steam piping manifold 130 is sized to supply purge fluid to respective purge chambers 112 simultaneously. Alternatively, steam piping manifold 130 is sized to supply purge fluid to respective purge chambers 112 individually. When purge fluid is supplied to respective purge chambers 112 simultaneously, steam piping manifold 130 may be sized larger in diameter than when purge chambers 112 are supplied individually to facilitate accounting for head losses due to increased purge fluid flow to purge chambers 112.
Additionally, drain purge system 100 includes a valve 132 configured to initiate purging and to regulate the flow from purge fluid source 128 to purge chamber 112. In the exemplary embodiment, valve 132 is a manually-operated valve. Alternatively, valve 132 is a powered valve that is operated via a signal transmitted to a valve driver, such as, but not limited to, a solenoid, a pneumatic drive, and/or an electric actuator. For example, in one embodiment, valve 132 is a powered valve that receives a signal to initiate purging from a turbine controller or a plant distributed control system.
In one embodiment, drain purge system 100 also includes a sensor 136 configured to detect drain aperture 124 flow. For example, in one embodiment, sensor 136 is a level sensor that monitors the level of purge fluid flow within purge chamber 112. Alternatively, drain purge system 100 does not include sensor 136.
Generally, during operation of steam turbine 10, purge chamber 112 receives drain flow from drain orifice 108, and purge chamber 112 is drained through aperture 124. During operating of steam turbine 10, valve 132 is opened either automatically or manually to initiate purging of drain purge system 100. When valve 132 is open, purge fluid flows through steam piping manifold 130. Purge fluid then flows into individual pipes 131 and into respective purge chambers 112.
After purge fluid has flowed into purge chamber 112, drain aperture 124 maintains a back pressure in purge chamber 112 sufficient to force a reverse flow of purge fluid through drain orifice 108. The reverse flow through drain orifice 108 clears debris and sediments from drain 108 that have collected in drain orifice 108 during operation of steam turbine 10. Clearing debris from drain orifice 108 prevents excessive moisture from remaining in the steam path.
The above-described drain purge system is a cost-effective and highly efficient method for purging a drain orifice in a steam turbine casing to prevent the drain orifice from becoming clogged with deposits. The deposits that have collected in the drain orifices can be removed without shutting down the steam turbine. Drain orifices without deposits enable the drain orifices to continuously flow moisture thereby eliminating the erosion damage to steam path components caused by excessive moisture in the steam.
While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.
