Laserfiche WebLink
<br />001699 <br /> <br />Appendix E , <br />Information for Test Plan and Schedule <br />Navajo Dam Increased Flows <br /> <br />~: <br /> <br />I Hollow-jet Valves <br />I <br />(~ Perform interior inspection after: <br /> <br />5 days of operation in a single valve operated above 1600 c.f.s <br />Er 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 />Er 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: Cavitation 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 the damage will change depending on valve plunger position (flowrate). <br />