Chapter 5 – Surge Protection
Surge Analysis and the Wave Plan Method
Supplementary Material: Example Problems and Solutions
Chapter 5 – Problem 5.11
5.11 A 100 m3 one-way surge tank was proposed to protect a pipeline from extreme low-pressure conditions. The preliminary surge protection design recommended a 10m long 1m diameter connecting pipe between the main transmission line and the one-way surge tank. The connecting pipe resistance was computed assuming there will be one 90° elbow, one 1000 mm butterfly isolation valve, and one 1000 mm swing check valve within the connecting pipe. At the time of construction, the one-way surge tank had to be shifted to a new location roughly 25m away from the previous location because of the land acquisition problems. The new connecting pipe is 30m long and has three 90° elbows.
a. Compute the new diameter for the connecting pipe to maintain the same resistance used for sizing the one-way surge tank.
b. Would you recommend increasing the diameter of the check valve and the isolation valve within the connecting pipe to match the new connecting pipe diameter? What are the positive and negative effects of increasing the check valve and isolation valve sizes? Remember, the check valve within the connecting pipe of a one-way surge tank is generally designed to open almost instantaneously when the hydraulic gradeline at the connection point drops below the water surface elevation in the one-way surge tank. As a further consideration, the check valve should stay closed drip-tight during the steady state operations.
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