| Budget Amount *help |
¥1,700,000 (Direct Cost: ¥1,700,000)
Fiscal Year 1987: ¥200,000 (Direct Cost: ¥200,000)
Fiscal Year 1986: ¥1,500,000 (Direct Cost: ¥1,500,000)
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| Research Abstract |
In this study the perfect prevention of waterhammer by a simply constructed check valve of quick-shutoff type, equipped with a subvalve of the slow closure type, is investigated over a wide range of the closing moment of the primary valve, the length of the pipeline, the actual head, the flow rate, and the subvalve bore. Furthermore the displacement response of the primary valve is measured and the drag coeffiecient C_d is calculated. The results obtained are summarized as follows:
1. When the length of the pipeline is long, waterhammer due to the time delay of valve closing is not ready to occur, since the time interval from the cutoff of the electric power to the occurrence of the reverse flow is long. However, minimum pressure head becomes lower and the occurrence of large waterhammer is unavoidable even if the valve is closed in an ideal manner without any time delay after the flow rate is zero.
2. When the closing moment is large, the eliminating effect of waterhammer is remarkable, but head loss becomes large. Therefore it is needed to choose suitable closing moment.
3. The size of the subvalve bore has to be chosen to satisfy conditions of thelength of the pipeline, the actual head, and so on.
4. Waterhammer is completely eliminated by providing the check valve equipped with a subvalve which bore is 8 mm in the case which ID of the pipe is 53.45 mm and the length of the pipeline is 47.0 m.
5. The drag coefficients of the valve agree well between the case when the valve is closing and stationary state if the displacement of the valve is small, but they differ entirely if the displacement is large.
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