Case Study Metropolitan Water Board & Siewert Equipment Centrifugal Water Pump Repair MWB Eastern Pump Station Bruce Collins NY Service Manager Siewert Equipment Barry Erickson, Ph.D Pump Improvement Engineer Siewert Equipment David D Angelo Water System Manager Metropolitan Water Board
Case Study Efficiency and Operational Benefits with Large Water Pump Repairs This case study is presented in cooperation with, Metropolitan Water Board.
Metropolitan Water Board County water district Created by Onondaga County in 1962 Develop Lake Ontario as a supplementary supply 3
Lake Ontario Intake Intake Constructed by City of Oswego (1957) 6,250 feet offshore and in 50 feet depth of water Tunnel in bedrock 8 + diameter, Crib covering West of Oswego River discharge Intake capacity 125 mgd NYSDEC permitted 62.5 mgd Consistent raw water quality 4
Raw Water Pumping Station Water physically screened, bar rack, traveling screens KmnO 4 applied seasonally for zebra mussel control CO 2 added seasonally for ph optimization (7.6-7.8) Pumps lift water approximately 153 and 3 miles distance to Treatment Plant 5
Water Treatment & Clear Water Pumping Station Filtration & Clear Water PS Direct filtration; Max 66MGD. Chemical feeds: Pre and post Sodium Hypochlorite, Polyaluminum Chloride, Sodium Hydroxide, Hydrofluorsilicic Acid, etc. Clear water pumped ~24 miles to the Terminal Reservoir. 6
Eastern & Western Stations Western Station Eastern Station Eastern 50 million gallons New 20 & 30 mg closed tanks. Western - 20 million gallons New 20 mg closed tank. Both stations at 610 feet elevation 7
Eastern Pump Station Eastern Pump Station Built in 1972 8
Eastern Pump Station #1 #3 Three identical pumps Rated 6.6 mgd each #2 9
Eastern Pump Station Worthington 10LNH-18: Split-case pumps 400 HP motors Manufactured in 1972 35+ years old at time of 1 st repair 10
Eastern Pump Station Operational Sequence: Pump #1 lead pump Pump #3 lag pump Pump #2 backup Historically #1 could satisfy typical demand In dry weather a 2 nd pumps is required to supplement #1 #1 has 50% more operating hours 11
Pump History System demand: Averages 6.0 mgd Peaks 6.6 mgd Each pump originally rated for 6.6 mgd It became necessary to run two pumps to maintain tank level. Significant impact on both energy usage, and energy demand charges. 12
Pump Removal Pump #2 (1 st pump to be repaired): 13
Inspection Findings As Received (1 of 3): 14
Inspection Findings As Received (2 of 3): 15
Inspection Findings As Received (3 of 3): 16
Inspection Findings Pump #2 repair assessment: Lower Casing Rotating Assembly 17
Inspection Findings Rotating Assembly: 18
Inspection Findings Shaft Sleeves: Sleeve wear Sleeve & sleeve nuts seized to shaft 19
Inspection Findings Impeller condition: Exceptional for 35+ year old impeller! 20
Inspection Findings Inspections findings: Packing glands & hardware corroded. Shaft sleeves worn & sleeve nuts seized, requiring repair or replacement. Concern with ability to remove shaft sleeves without damaging shafts. Wear ring clearance 10 times OEM specification & out-of-round. Overall good integrity of major components. 21
Repair Recommendations Repair Recommendations: Replace casing & impeller wear rings to restore OEM clearances. Shaft sleeves: Machine 0.020 under and flame spray coat with Chrome Oxide-Silica using Metco 9MC plasma spray system and diamond polish ground to RMS 20 micro inches AA finish. Impeller dynamically balanced to ISO 1940 G 1.0 tolerance (OEM spec. G 6.3) 22
Repair Internal/External Sandblast / Prime: 23
Repair Rotating Element: Shaft Sleeve Repair Chrome Oxide-Silica coated & polished without removing or disrupting sleeve nuts or impeller. 24
Repair Rotating Element: New casing & impeller wear rings, restoring OEM clearances. 25
Repair Rotating Element: Impeller & rotating element assembled & dynamically balanced in accordance with ISO 1940 G 1.0 tolerance. 26
Repair Rotating Element: As Found As Built 27
Repair Rotating Element: As Received: As Built: 28
Repair Following reinstallation: a. Installation inspection b. Precision laser shaft alignment of pump & driver c. Start-up commissioning Simultaneously, the 400 HP electric motor was also rebuilt. 29
Pump 2 Results Pump #2 hydraulic performance returned to as new. Performance was monitored for several months and verified to remain as new. MWB made decision to repair all pumps. 30
Pump 3 Results Pump #3 repairs complete with similar results. MWB proceeded with plan to repair the final pump, Pump #1. Pump #1 had ~90,000 hours compared to ~60,000 hours on #2&3. 31
Pump 1: Inspection Findings Pump #1 As Received: How does it compare to #2 & 3? 32
Pump 1: Inspection Findings Pump #1 As Received : Impeller vane tips, rear shroud, & wear rings 33
Pump 1: Inspection Findings Pump #1 As Received : Impeller vane tips & impeller shroud 34
Pump 1: Inspection Findings Pump #1 As Received : Impeller vane leading edge 35
Pump #1 As Received: Casing erosion Pump 1: Inspection Findings Stuffing box Wear Ring shoulder 36
Pump 1: Assessment Impeller Damage Assessment: Damage observed is typical of hydraulic cavitation or operation at low flow rates. As the last pump to be rebuilt it likely had been run in parallel with repaired pumps. Operating a repaired pump in parallel with a deteriorated pump will cause the deteriorated pump to operate far left on the curve. To restore hydraulic performance, the impeller will need to be repaired or replaced. 37
Pump 1: Repair Options Repair Considerations: Leave it as is. Performance would never be comparable to pumps #2 & #3. Further damage would occur. 1. Repair the impeller. 2. Purchase new impeller. 3. Purchase new pump. 38
Pump 1: Repair Options Repair considerations: A repaired impeller would deliver hydraulic performance comparable to the other pumps. Would it last? An extended life rebuilding grade metallic polymer would last many years so long as the pump was not operated at low flows. Good with erosion but not with cavitation. 39
Pump 1: Repair Options Repair Options: Recommend same repairs as #2 & 3, except impeller issue: Pump is 40 years old and is non-current product. Three impeller options: 1. Impeller Repair ($$) 2. New OEM Impeller ($$ x 6) 3. New OEM Pump ($$ x 30) MWB chose option 1 Impeller Repair at a fraction of the cost compared to other options. 40
Impeller Repair Belzona 1311 Ceramic R- metal: Designed for rebuilding and protection of metal components damaged by erosion-corrosion. Non-machinable grade twocomponent composite that can be applied by hand to repair & protect damaged metallic components. 41
Pump 1: Repair Impeller repair: Leading edge of impeller vanes 42
Pump 1: Repair Pump #1 Impeller Leading Edge: 43 As Found As Built
Pump 1: Repair Pump #1 Impeller Vane tips & Shroud: 44 As Found As Built
Pump 1: Repair Pump #1 Casing Erosion Repair: Stuffing Box repair Wear Ring shoulder repair 45
Pump 1: Repair Pump 1 Repaired impeller & new wear rings prior to balance & assembly. 46
47 Repair Complete
Results EASTERN PUMP STATION HYDRAULICS 350 300 OEM PUMP CURVE 250 TDH - FT 200 150 100 CURRENT SYSTEM CURVE CURRENT OPERATING POINT - 6.9 MGD 50 0 0 1000 2000 3000 4000 5000 6000 7000 FLOW RATE - GPM 48 All pumps perform as new and a single pump now is able to meet the demand. Lag pump never runs!
Results DATE BEFORE REBUILD STATION DEMAND KW AVG PUMP FLOW - MGD GAL/KWH MAR 2009 568.8 6.07 809 APR 2009 547.2 5.16 717 MAY 2009 309.6 4.97 864 JUNE 2009 511.2 5.49 879 AVERAGE 484.2 5.42 817 49
Results AVERAGE PUMP FLOW - MGD 7.0 6.0 5.0 MGD 4.0 3.0 2.0 1.0 BEFORE # 1 AFTER # 2 AFTER # 3 AFTER 0.0
Results ENERGY UTILIZATION GAL/KWH 1000 950 900 850 800 750 700 BEFORE # 1 AFTER # 2 AFTER # 3 AFTER 51
Energy Demand Charge Usage Charge: Charge for the actual electrical energy used ~ $0.02 - $0.10 /kwh Demand Charge: Charge for ability to provide temporary peak energy Based on the maximum power consumption over a 15 or 30 minute period ~ $10 - $20 / kw
Energy Demand Charge Example: 300 kw motor runs 20 hours / day 180000 kwh Second 300 kw motor runs 15 minutes / month 75 kwh Usage charge (180000 + 75) kwh x $0.02 /kwh $3602 Demand Charge 600 kw x $15 / kw $9000 Compare usage & demand charge for 2 nd pump?
Results ENERGY DEMAND 600 500 400 KW 300 200 BEFORE # 1 AFTER # 2 AFTER # 3 AFTER 100 0 54
Final Analysis 55 Energy Utilization Reduction 13% Demand Reduction 17% Payback 1.28 YEARS (INCLUDES ALL THREE PUMPS)
Special Thanks To Metropolitan Water Board, for providing detailed data from this project and allowing this information to be available today.
Case Study Metropolitan Water Board & Siewert Equipment Centrifugal Water Pump Repair MWB Eastern Pump Station Bruce Collins NY Service Manager Siewert Equipment Barry Erickson, Ph.D Pump Improvement Engineer Siewert Equipment David D Angelo Water System Manager Metropolitan Water Board