The Restoration of Main Turbine Barring Gear Stoppage Issue in Thermal Power Station
Journal Title: International Journal of Mechanical and Production Engineering Research and Development (IJMPERD ) - Year 2019, Vol 9, Issue 4
Abstract
Barring gear (or "turning gear") is the mechanism providing to rotate the Turbine Generator shaft at a very low speed after unit stoppages. Once the unit is "tripped" (i.e., the steam inlet valve is closing), the turbine coasts down from 3000 rpm to Barring Gear speed of 75-80 rpm and runs at Barring Gear speed until next rolling or towards standstill after sufficient cooling of Turbine casing. There are two cases of particularly which this condition must be filled. However it is always true that turbine should be on barring gear. CASE 1: COLD START (TURBINE STARTING IN COLD CONDITION) Rotor is big enough in length and is supported at two bearings at extreme ends. It acts like simply supported beam. Rotor is bound to sag in this condition and if it is rolled at higher rpm in this condition, turbine will encounter with high vibration. To remove this sagging it is must that turbine must be on barring gear before rolling that too at least 8 hours. CASE 2: HOT START UP TURBINE STARTING IN HOT CONDITION) When turbine has tripped and again started within 6 hours. In this condition top casing is generally hotter than bottom casing as hot air tends to move up due to less density. If turbine is not rolled on barring gear, the upper part of rotor will be subjected to higher temperature that the lower part of it. By rolling shaft at slower rpm, it is ensured that no uneven expansion happens. Any issue in Turning of Barring Gear results in halting of Turbine Generator shaft until HP Turbine Shaft Temperature reaches 100 Deg C, which usually takes 4-5 Days and thus results in loss of Generation.
Authors and Affiliations
S. Murugesan, J. Manikandan
Keywords
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- EP ID EP656940
- DOI 10.24247/ ijmperdaug2019127
- Views 89
- Downloads 0
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