| Abstract | At the request of Ontario Hydro, the Engine Laboratory of the National Research Council is assisting in a program to assess noise levels generated by venting large quantities of high pressure, high temperature steam through drain valves to atmosphere. The program comprises measurement of the noise emitted from the vent pipes of Unit No. 5 and Unit No. 6 at the R.L. Hearn Generating Station in Toronto, both before and after commercially supplied silencers have been installed.
This report describes a preliminary series of tests on the unsilenced vents. Failure of the thermodynamic instrumentation precluded measurement of the steam flow conditions to assure exact compliance of the test conditions with the conditions delineated in the silencer purchase specification. Overall noise levels determined from acoustic data obtained during the preliminary test on Unit 6 agreed approximately with the overall level quoted in the purchase specification, viz. 120 dbA. The noise from Unit 5, however, was considerably lower than the specification level but displayed occasional very loud "surges" inferring violent fluctuations in the nature of the steam flow conditions even after prolonged operation at supposedly fixed conditions.
Also on Unit 5, several transient acoustic phenomena were observed during startup, warmup, and shutdown. It is believed that some of these phenomena are associated with partial throttling of certain steam drain valves.
Further testing of the unsilenced vents is recommended to confirm correct steam flow conditions and to investigate the transient phenomena and instabilities noted during the tests on Unit 5. |
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