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<br />001699 <br /> <br />Appendix E . <br />Information for Test Plan and Schedule <br />Navajo Dam Increased Flows <br /> <br />k <br /> <br />Hollow-jet Valves <br />r <br />r ~ Perfo:rm interior inspection after: <br /> <br />5 days of operation in a single valve operated above 1600 c. f.s <br />&" The 5 day requirement should be expected to change with <br />information gained during operations and subsequent inspections. <br />Detailed records of flowrates and the time the valve(s) were exposed <br />should be kept for the inspection. <br /> <br />Yearly for flows less than 1600 c.f.s. <br />&" Perform interior inspection early enough before spring startup to <br />effect repairs if necessary. <br /> <br />. Interior inspection requires closure and lockout of ring follower gates for <br />inspection, but not dewatering of the penstock. <br /> <br />~ Inspection for interior and edge cavitation damage <br />&" If damaged, plans should be made for immediate repair. <br />Cavitation will "jump" downstream and will multiply it's damage <br />rapidly. The valve's casting would be hard to replace and the more <br />welding required, the more likely casting cracking is to occur. <br />~ Inspect the cylinder operator and hydraulic piping integrity. <br />~ Entry to the valve would have to be from boat. The valve's interior cannot <br />be accessed from the chamber surrounding the valves because of the <br />steepness and water depth. Repairs would require draining of penstock and <br />that the tailwater level be below the valve in order to avoid dangerous <br />grounding/shorting of welding machine. <br /> <br />Note: Cavit~'tion of this type of valve is less dependent on flow than any other <br />type of valve. It has happened at lower flows in similar designed valves. The <br />location of t.he damage will change depending on valve plunger position (flowrate). <br />