2015 HDR, all rights reserved.

Transcription

1 2015 HDR, all rights reserved.

2 Upgrades for a Critical Wastewater Pump Station Northeast Ohio Regional Sewer District (NEORSD) Second Stage Lift Station, Southerly WWTC Cleveland, OH Robin Rupe (NEORSD) Rich Atoulikian (HDR) 2015 HDR, all rights reserved.

3 Project Objectives & Overview Background Evaluations Recommendations Summary Questions

4 01 Project Objectives & Challenges Second Stage Lift Station

5 Project Objectives Evaluate the pump station for long-term reliable service under alternative operating conditions Review operating efficiency of the pumps and motors Identify rehabilitation improvements Extend service life

6 Project Challenges 1. Verify Pump Condition for Long Term, Reliable Performance 2. Existing Pumps/Drives Cannot Respond to Rapid Flow Changes 3. Existing Pumps Have an Insufficient Operating Range to Respond to Current Conditions 4. Upgraded Pumps Must be able to Respond to Different Future Operating Conditions 5. Confirm Inlet Well Configuration for Future Wet Weather Operating Conditions

7 02 Background

8 NEORSD Background Political subdivision of Ohio Created in 1972 by Court Order o Code of Regulations o Governed by seven Trustees Wastewater Service to Cleveland & 61 communities o 1 million customers o 90+ billion gallons treated each year o 200 MGD average daily flow treated

9 NEORSD has 3 Treatment Plants Westerly WWTC Southerly WWTC Easterly WWTC

10 Southerly has the Largest Average Day Flow Capacity of the Three Plants Two-stage nitrification facility Discharges to Cuyahoga R Population served: 530,000 Flows: o Average Day 120mgd o Full Treatment: 400 MGD Design Capacity: o Preliminary/Primary: being upgraded to 735 MGD o Future full treatment: 615 MGD

11 Flow Path to the Second Stage Pump Station

12 The Existing Pumps Cannot Keep Up With Rapid Flow Changes Liquid Rheostat Drives Can t Respond Quickly Enough, Causing Rapid Wetwell Level Fluctuations Rapid Level Fluctuations Cause Excessive Lag Pump Cycling Due to Small Wetwell Volume Motor Life Is Reduced

13 Second Stage Lift Station Flow Schematic

14 SSLS Overview Existing Conditions Component Description & Notes Inlet Wet Well One Wet Well with no redundancy Stop logs can be inserted to partition wetwell Tight Operating Band: 40-inches, typical Pump Suction 60 Diameter Independent, parallel suction pipes Pumps Firm Capacity: 450 MGD 6 Pumps at 90 MGD, 38.5 feet THD Pump Model: Worthington 42 MC-1 Non-clog centrifugal, 7 Sphere Motors/Drives 3 C/S: Synchronous RPM 3 V/S Liquid Rheostat/Wound Rotor-278/350 RPM Horsepower: 800 HP Pump Discharge 60 Diameter Independent, parallel discharge piping Effluent Wet Wells Two wet separately isolatable wells

15 Second Stage Lift Station Section View Effluent Wet Well 40 Operating Range, 200,000 Gal Inlet Wet Well 1. The liquid rheostat s have reached the end of their useful life. 2. The existing pumps are not able to meet the required operating range 3. The inlet wetwell s small operating band between LWL and HWL adversely impacts pump control

16 03 Evaluations

17 Multiple Evaluations Were Conducted to Ensure Future Pump System Reliability Pump Testing (by Mechanical Solutions, Inc.) o Experimental Model Analysis (EMA) o Operational Deflection Shape (ODS) o Pump Performance Test on one VSP Desktop Pump Performance and VFD Evaluation Pump Inspection CFD Modeling

18 Pump Performance Evaluation: Pump Testing Experimental Modal Analysis (EMA) Operational Deflection Shape (ODS) Pump Performance Challenge 1 Verify Pump Condition for Long Term, Reliable Performance Challenge 2 Existing Pumps/Drives Cannot Respond to Rapid Flow Changes (Impacts Associated With Application of VFDs)

19 Baseline Testing Goals o Monitor Vibration o Identify pump structural natural frequencies o Assess overall performance & health of pumps Testing Program o Experimental Modal Analysis (EMA) motor, motor stand, bearing tower, volute, and concrete supports o Operational Deflection Shape (ODS) o Pump Performance

20 Pump Testing: Experimental Mode Analysis Top of Pump Overall Vibration Amplitude (in/s RMS) Directions in Relation to Discharge Source: MSI There was low overall vibration amplitude at the top of the bearing tower, meeting ANSI/HI spec of 0.34 in/s RMS. The highest measured value is ~0.08 in/s RMS was during speed fluctuations.

21 Pump Testing: Experimental Mode Analysis (EMA) & Operational Deflection Shape (ODS) Testing Parallel Response with Parallel Impacts Rocking Mode 11.5 Hz Source: MSI

22 Pump Testing: EMA & ODS Source: MSI Pump 5 Bearing Tower and Stuffing box Running Speed 285 rpm 4.75 Hz

23 Pump Performance Testing: On Site Head vs. Flow Note: TDH Deteriorated by 10 to 15% from original pump curves in 1980 Source: MSI

24 Testing Conclusions Vibration Test Results: o The pump casings were sound o No adverse harmonic or operation effects when increasing pump speed Soft foot was discovered under certain supports Pump Test Results: o TDH deteriorated 10 to 15%

25 Pump Performance Evaluation Desktop Analysis Challenge 3 The Existing Pumps Have an Insufficient Operating Range to Respond to Current Conditions

26 Desktop Pump Performance Evaluation Existing Conditions Liquid rheostat pumps vary between 278 and 350 RPM Original design operating point: 90 MGD at 345 RPM

27 Desktop Pump Performance Evaluation Existing Condition Existing Condition Current Operating Range Existing AOR Existing POR Lead - V 188 Lag 1 - V Lag 2 - C Lag 3 - C Lag 4 - C Lead - V Lag 5 - V 50 Lag 1 - V Lag 2 - C Lag 3 - C Lag 4 - C Lead - V Lag 5 - V 59 Lag - V Lag 2 - C Lag 3 - C Lag 4 - C 388 Lag 5 - V 447 Firm Capacity Total Capacity Flow (MGD)

28 04 Recommendations

29 Use Full Size Impellers Challenge 4 Under Wet Weather Mode, Future Pumping Conditions Will Be Different (Higher Flows May Occur)

30 Recommendations Proposed Pump/System Curves RPM Head (ft) RPM 250 RPM Flow (MGD) AOR & POR (360 RPM) AOR & POR (250 RPM)

31 Recommendations Effect of increased impeller diameter with VFDs Alternative AOR Alternative POR 105 Lead - V Lag 1 - V Lag 2 - C 176 Lag 3 - C Lead - V Lag 1 - V Lag 2 - C 198 Lag 3 - C Lag 4 - C Lag 4 - C Firm Capacity 480 Lag 5 -V 468 Lag 5 - V 567 Total Capacity Flow (MGD) Existing Conditions: Existing AOR Existing POR g Lead - V Lag 5 - V 50 Lag 1 - V Lag 2 - C Lag 3 - C Lag 4 - C Lead - V Lag 5 - V 59 Lag - V Lag 2 - C Lag 3 - C Lag 4 - C 388 Lag 5 - V Flow (MGD)

32 Provide Baffling in Inlet Wet Well For Future Condition Challenge 5 Confirm Inlet Well Configuration under Wet Weather Operating Conditions

33 Development of a CFD Model Starts With A 3D Model

34 Model Scenario: 400 MGD, Flow from Two Sides

35 Model Scenario: 480 MGD, Flow From One Side From PSTs

36 Model Scenario: Three-foot Curved Wedge Baffle 480 MGD

37 06 Summary

38 Summary Objective 1 Evaluate Pump Station for Long Term Reliable Service o o o o Inspect/Evaluate Existing Pumping Equipment Evaluate Pump Ranges to Preferred and Acceptable Operating Ranges (AOR and POR) Consider VFDs for Liquid Rheostat Replacement Consider impacts of more rapid VFD speed changes on rotating equipment (improves wetwell level control) Objective 2 Review Operating Efficiency of Pumps and Motors o Improve System Operating Efficiency Through Proper Equipment Selection Pumps (Maximum Impeller Size), Motors and VFDs Objective 3 - Identify Rehabilitation Improvements o o o Building Envelop Upgrades Ferric System Electrical and I&C Upgrades Objective 4 Extend Service Life o o o Replace pump rotating assemblies Design pumping system for current and future conditions Maximize Operating Time within POR and AOR ranges

39 Questions? Robin Rupe, PE (NEORSD) Rich Atoulikian, PMP, PE (HDR) The authors wish to thank: Kevin Zebrowski (NEORSD) Kathryn Crestani (NEORSD) Christy Wood (NEORSD) Dan Wiglusz (NEORSD Tom Seiter (NEORSD) Paul Kopchak (NEORSD) Gary Hoffman (Retired NEORSD) Jennie Celik, (HDR) Doug Mohn (HDR) Kim Kennedy (HDR) David Watson (HDR) Dino Angelopoulos (HDR) John Koch (HDR) The Team From Mechanical Solutions, Inc. and Flowserve Pumps

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