Hydro Plant Risk Assessment Guide

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Drift Test -- suspend the working load for one hour on a hydraulically isolated piston and determined the hydraulic fluid leaked through piston rings. The following performance estimates are rules of thumb: or where N = V/(πDt) in terms of volume leaked [units = ml/(cm-h) = cm 2 /h] N = LD/(4t) in terms of length drifted [units = ml/(cm-h) = cm 2 /h] N = piston drift number V = fluid volume leaked (1 ml = 1 cm 3 ) D = internal piston stroke diameter (cm) t = test time (hours) L = length of drift (cm) Note: 11.64 ml/(cm-h) = 1 oz/(in-h) For resilient piston rings, leakage for a properly working piston should be very small [N < 2 ml/(cm-h)]; for cast iron rings, leakage is much more, on the order of N ≈ 40 ml/(cm-h). For multistage cylinders, the piston drift number applies to each stage individually; e.g., a 3-stage, telescoping cylinder with cast iron piston rings will have an allowable leakage limit of N = 3 times ≈ 40 ml/(cm-h) ≈ 120 ml/(cm-h) of cylinder drift. Table 28 – Pistons Results Good – Normal internal leakage, N < 40 ml/(cm-h) for cast iron piston rings, N < 2 ml/(cm-h) for resilient piston rings and packing. No noticeable scoring, cracking, or chipping on piston rods, corrosion minimal. No external leakage into a sensitive environment. Moderate – Some internal leakage, N ≥ 40 and < 200 ml/(cm-h) for cast iron piston rings and packing, N ≥ 2 and < 10 ml/(cm-h) for resilient piston rings. Some piston rod wear with no external leakage into a sensitive environment. Severe – Large volume of internal leakage N ≥ 200 ml/(cm-h) for cast iron piston rings and packing, N ≥ 10 ml/(cm-h) for resilient piston rings and packing. Significant piston rod wear and danger of failure or significant external leakage into a sensitive environment. Adjustment to Condition Index Score Add 0.5 No Change Subtract 0.5 Test T2.3.7: Hydraulic Operators – Hydraulic Systems This rating adjustment applies to the entire hydraulic system other than the pistons themselves. Since hydraulic systems can be relatively simple or fairly complex, the rater must use their best judgment to rate the overall condition of the hydraulic system. E11-26
Table 29 – Hydraulic Systems Results Good – Overall condition indicates the need for little or no attention, leakage is minimal; valves, solenoids relays, and heat exchangers are in working condition. Fittings, lines and hoses are in good condition. Hydraulic fluid is clean and uncontaminated. Replacement parts are in stock or readily available. Moderate – Some attention required but system in service able condition. Some hoses and fittings worn and/or leaking. Some components are not working optimally. Hydraulic fluid is dirty. Replacement parts are hard to obtain. Severe – System frequently needs repair; spare parts unavailable or very hard to find. Major leakage. Dirty or contaminated fluid. Overall condition poor. Adjustment to Condition Index Score Add 0.5 No Change Subtract 0.5 Test T2.3.8: Hydraulic Operators – Electric Motors Motors powering hydraulic systems may be tested in accordance with IEEE 112 if the motors a suspected of being deficient. IEEE 112 contains a multitude of tests, some which may not need to be performed. If the motor(s) is not tested, the score will not be adjusted. Table 30 – Electric Motors Results Good – Performance passes given performance tests. Moderate – Some non-critical performance tests are failed (e.g., efficiency) but motor is in still serviceable condition. Severe – Motor fails one or more critical test. Is deemed not serviceable and in need of repair or replacement. Adjustment to Condition Index Score No Change Subtract 0.5 Subtract 1.0 E11-27
Page 1 and 2: September 2006 Hydro Plant Risk Ass
Page 3 and 4: qualified personnel that are compet
Page 5 and 6: Condition Indicator 2 - Physical Co
Page 7 and 8: Table 3 - Valve Physical Condition
Page 9 and 10: power supply, inspections, exercisi
Page 11 and 12: Table 6 - Intake Valve Operator (Hy
Page 13 and 14: E11.11 TIER 1 - EMERGENCY CLOSURE S
Page 15 and 16: • Miscellaneous Damage or Other C
Page 17 and 18: Note: If the gate performs unaccept
Page 19 and 20: Test T2.2: Valves Valves - Structur
Page 21 and 22: Valves - Functional Operation Test
Page 23 and 24: Test T2.3: Gates and Valves Operato
Page 25: Table 26 - Improper Field Repair an
Page 29 and 30: Table 32 - Actuation Performance Re
Page 31 and 32: extensive wearing. Extreme - Brake
Page 33 and 34: Table 39 - Gearboxes, External Gear
Page 35 and 36: Table 43 - Maintenance Escalation R
Page 37 and 38: EMERGENCY CLOSURE GATES & VALVES TI
Page 39 and 40: EMERGENCY CLOSURE SYSTEM TIER 2 CON
Page 47 and 48: Part II: Calculate the Net Emergenc
Page 49 and 50: Porosity Crack at flange diaphragm
Page 51: Weld performed by nonqualified weld

Hydro Plant Risk Assessment Guide

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