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1 Copyright 2016 American Water Works Association 2016 Webinar Sponsors 2 Please consider the environment before printing. 1

2 Webinar Moderator Alex Gerling ReuseEngineer American Water Works Association Alex Gerling is a Reuse Engineer with the American Water Works Association. Her responsibilities include reviewing, developing, and executing water reuse technical programs and supporting the Divisions and Committees of the Technical and Educational Council. She draws on her utility experience from the Western Virginia Water Authority where she provided technical support for a variety of water quality and reservoir oxygenation projects. She received a M.S. in Biological Sciences from Virginia Tech as well as a B.S. in Geoscience and a B.A. in Environmental Studies from Hobart and William Smith Colleges. 3 Enhance Your Webinar Experience Close Programs Instant messengers Other programs not in use GoToWebinar Support 4 Please consider the environment before printing. 2

3 Webinar Survey Immediately upon closing the webinar Survey window opens Thank you 5 Products or Services The mention of specific products or services in this webinar does not represent AWWA endorsement AWWA does not endorse or approve products or services 6 Please consider the environment before printing. 3

4 Panel of Experts Tom Walski Bentley Fellow, Sr. Product Manager Bentley Systems, Inc. Kevin Laptos Regional Planning Leader Black & Veatch Ferdous Mahmood Senior Hydraulic Engineer Arcadis 7 Agenda I. Hydraulic Transient Basics: An Overview II. Water Hammer Analysis III. Water Hammer / Surge Analysis Case Study for Pressurized Pipe Tom Walski Kevin Laptos Ferdous Mahmood 8 Please consider the environment before printing. 4

5 Ask the Experts Tom Walski Kevin Laptos Ferdous Mahmood Enter your question into the question pane at the lower right hand side of the screen. Please include your name and specify to whom you are addressing the question. 9 Hydraulic Transient Basics: An Overview Tom Walski Bentley Fellow, Sr. Product Manager Bentley Systems, Inc. 10 Please consider the environment before printing. 5

6 Overview What is a transient? Why do we care? How fast does it move? Why does it die-off? What causes it? What is column separation? 11 Learning Objectives At the end of this session you should be able to: Understand the basic characteristics of transients Recognise the risks of transients Learn about the transient calculation methods 12 Please consider the environment before printing. 6

7 Pressure What is a Transient? Shut off New steady state Time 13 Water Hammer Damage! 14 Please consider the environment before printing. 7

8 Water Hammer Damage! 15 Sub-atmospheric Pressure a) Excavated Pipe Section at Leakage Location b) Pipe Joint Jammed by Sand & Dust Residue c) Sample of Failed Pipe Joint 16 Please consider the environment before printing. 8

9 Pressure Wave Properties Transients move as pressure waves a = wave speed The Wave Speed depends on: Fluid Pipe material Joints Presence of dissolved gas Anchoring Time of travel = L/a Characteristic time = 2L/a 17 Pressure Wave Speed Calculation Korteweg equation for wave speed in a pipe: E v = Young's modulus (pipe) E = bulk modulus (liquid) = liquid density = pipe support index = Poisson's ratio D/e = dimension ratio (DR) 18 Please consider the environment before printing. 9

10 19 Pressure Wave Decay Steady friction does not account for all damping mechanisms 250 Steady Quasi-Steady Transient 230 Steady Quasi-steady Head (m) Unsteady (Transient) Time (s) 20 Please consider the environment before printing. 10

11 Characteristic Time: 2L/a Every system has a characteristic time, 2L/a: L is the longest possible path through the system (e.g. from pump to reservoir) a is the pressure wave speed: 300 to 1400 m/s 2L/a is the time required for a pulse to travel to the far end, then return: Fractions of a second for a short suction line Tens of seconds for a forcemain Minutes for long-distance transmission lines 21 System Response to Change Compared to 2L/a, valve movements or pump operations are: 0 = Instantaneous (e.g. phase change) 2L/a = Rapid, requires elastic theory (Method of Characteristics) > 2L/a = Gradual, solvable by rigid-column theory >> 2L/a = Slow, use rigid-column theory (or even Extended Period Simulation) 22 Please consider the environment before printing. 11

12 What Causes Transients? Any change in momentum that is rapid compared to the characteristic time: 2L/a (usually a few seconds) Power failure Control/component failure Human error Start/Shift/Shut-down Valve operations & air Process changes, heat/cool H.G.L. H.G.L. H.G.L. Sump Pump Check Valve Flow Reservoir Penstock Governor Flow Gate Turbine Generator Tailrace Valve Pump Turbine Valve 23 What is the Impact of Transients? Joukowski s / Allievi equation estimate transient pressure rise due to an instantaneous change in momentum: dh dv a / g where: a = 1000 m/s concrete or a = 300 m/s plastic 1 m/s change (dv) can cause an upsurge (dh) of 100 m or 140 psi! Also be aware of thrust force, oscillations and resonance! 24 Please consider the environment before printing. 12

13 Why Worry About Transients? Positive transients can break pipes Transients can cause pipes to shift Negative transients can collapse pipes Negative transients can suck contaminated water into pipes Injuries or death can occur if staff are present! 25 Assessing System Vulnerability SCADA systems can not usually measure transients fast enough Field data used to calibrate model Modern models make it possible to model an entire system Hammer Modeling (1990 s) Run Hammer TM to find out! SURGE ANALYSIS TOOLS Minutes Days Computer Analysis (1970 s) Months Graphical Analysis (1960 s) Rule of Thumb or Rule of Dumb 26 Please consider the environment before printing. 13

14 Unsteady Pipe Flow Equations Conservation of mass H t H V x 2 a V g x Conservation of momentum (e.g. energy) H 1 V x g t V V x f V 27 Methods to Analyze Transients Arithmetic, e.g. Joukowski equation Makes many assumptions but a useful rule-of-thumb Graphical method and design charts Popularized by Parmakian. Many charts by Fok. Time-consuming. Implicit method (two characteristic equations indexed by time) Linear analysis method Linearize friction to study oscillatory behavior and dampening Wave-plan method (discrete cumulative disturbances) Perturbation method (expands nonlinear friction term) Method of characteristics, e.g. MOC Converts full Navier-Stokes equations to solvable form Very widely-used and thoroughly calibrated/validated 28 Please consider the environment before printing. 14

15 Pressure Envelope Maximum Transient Head Envelopes for a Pumping System Comparison of rigid and elastic theories: Max. Head (Elastic) Max. Head (Rigid) Steady HGL Static HGL Reservoir Min. Head (Rigid) Min. Head (Elastic) Pipeline Reservoir Pump Station + Transient Energy Calculated by Elastic Water Column Theory (EWCT) Transient Energy Calculated by Rigid Water Column Theory (RWCT) 29 Boundary Conditions & Reflections Boundary Conditions Orifices to atmosphere & consumption Dead-ends, reservoirs, and tanks (reflections) Operating equipment such as valves & pumps Changes in Topology Sudden change in diameter Branching Looping 30 Please consider the environment before printing. 15

16 Water Column Separation If pressure < vapor pressure, liquid vaporizes This is called column separation Water column rejoins once the pocket collapse Effect of water column separation 31 What is the Role of Pumps? Surges and Water Hammer happens if pumps start/stop too quickly Variable Speed pumps, soft starts, discharge control valves minimize transients during normal operation Set safe restart delays & ramp times for motor controller or PLC Pre-start safety audits, re-commissioning plans 32 Please consider the environment before printing. 16

17 The End Transients are important - You can model transients to prevent problems 33 Ask the Experts Tom Walski Kevin Laptos Ferdous Mahmood Enter your question into the question pane at the lower right hand side of the screen. Please include your name and specify to whom you are addressing the question. 34 Please consider the environment before printing. 17

18 Water Hammer Analysis Kevin T. Laptos, PE Regional Planning Leader Black & Veatch 35 Rationale An effective approach for Water Hammer Analysis is needed This presentation will provide an approach to model and mitigate water hammer in water systems 36 Please consider the environment before printing. 18

19 Learning Objectives Understand why water hammer analysis is needed Understand how transient models can be used to perform water hammer analysis Understand different methods for mitigating water hammer 37 Agenda Water hammer analysis objectives Model development Model validation Mitigation methods 38 Please consider the environment before printing. 19

20 Water Hammer Analysis Objectives 39 Why is Water Hammer Analysis Needed? Assess the potential for significant pressure transients Help assess the degree of risk in the system Develop and design/implement appropriate mitigation methods 40 Please consider the environment before printing. 20

21 4-Step Analysis Approach Step 4: Step 1: Develop transient hydraulic model of system Step 2: Identify and analyze key transient scenarios Step 3: Develop and evaluate mitigation strategies for excessive pressure transients Develop design criteria for selected mitigation strategies 41 Model Development 42 Please consider the environment before printing. 21

22 How are Transient Models Different than Steady-State and EPS Models? Simulate the propagation of pressure waves and resulting flow and pressure conditions due to transient causing events Additional system information is needed 43 Transient Model Development Add transient control equipment (i.e. air valves) Pump Station Reservoir Combination Air Valves Reservoir 44 Please consider the environment before printing. 22

23 Transient Model Development Add transient control equipment (i.e. air valves) Surge tanks Pump Station Reservoir Surge Tank at Pump Station Reservoir 45 Transient Model Development Add transient control equipment (i.e. air valves) Surge tanks Pipeline wave speeds Pump Station Reservoir Reservoir 46 Please consider the environment before printing. 23

24 Transient Model Development Add transient control equipment (i.e. air valves) Surge tanks Pipeline wave speeds Additional pump (inertia, specific speed) and valve characteristics Pump Station % of Maximum C v Reservoir Reservoir Valve Opening (%) 47 Model Validation 48 Please consider the environment before printing. 24

25 Surge Tank Air Volume (ft 3 ) How can we Ensure Transient Models are Accurate? As with steady-state and EPS models.calibration/validation is important However, challenges exist with transient models: Instrumentation sample rate and data storage Reluctance to purposely cause a significant transient event 49 Example 1: Model Validation Field Data Pump #1 ON Pump #2 ON Pump #2 OFF Pump #1 OFF Modeled Surge Tank Air Volume ft Time (sec) Manual collection of surge tank volume and timing data 50 Please consider the environment before printing. 25

26 Flow (mgd) / Surge Tank Water Level (in) / Pressure (psi) PS Discharge Pressure (psi) Example 2: Model Validation 160 PS Discharge Pressure (psi) +3 psi psi 120 Field Data Pump #2 OFF Pump #2 ON Pump #5 ON Pump #4 ON Pump #4 OFF Pump #5 OFF Pump #2 OFF 60 Surge Tank Water Level (in) +5% PS Flow Flow (mgd) +5% -5% -5% Time (sec) Collection of field data using existing instrumentation at PS 51 Example 3: Model Calibration PS Power Loss Field Recorded Pressure Model Predicted Pressure Time (sec) Collection of field data using RADCOM pressure transient logger Adjusted pump control valve closing speed to best match logger data Validated pump/motor inertia 52 Please consider the environment before printing. 26

27 PS Discharge Pressure (psi) Example 4: Model Calibration 160 Pump #1 ON Pump #2 ON Pump #3 ON PS Power Loss Field Recorded Pressure Model Predicted Pressure Time (sec) Collection of field data using RADCOM pressure transient logger Adjusted pump startup sequencing and VFD settings to best match logger data 53 Mitigation Methods 54 Please consider the environment before printing. 27

28 Manually Operated Equipment Hydrants and isolation valves Slow closing and opening Operator awareness and training are key 55 Automated Equipment & Facilities Pump stations and control valves Proper analysis and design of transient control equipment is key 56 Please consider the environment before printing. 28

29 Transient Control Methods for Pumping Stations Normal (i.e. hourly/daily) pump startup and shutdown Variable speed drives Pump control valves for constant speed pumps Pump control procedures (PLC) Only start/stop one pump at a time Delay between consecutive pump starts/stops 57 Transient Control Methods for Pumping Stations Emergency (i.e. power loss) pump shutdown High pressure control Surge relief valves Surge anticipator valves Surge tanks Low pressure control Air valves Surge tanks 58 Please consider the environment before printing. 29

30 Summary 59 Summary Numerous causes of water hammer in water systems Also numerous risks associated with both high and low pressure transients Transient models are indispensable for: Assessing the potential for significant pressure transients Helping to assess the degree of risk in the system Developing and designing/implementing appropriate mitigation methods 60 Please consider the environment before printing. 30

31 Ask the Experts Tom Walski Kevin Laptos Ferdous Mahmood Enter your question into the question pane at the lower right hand side of the screen. Please include your name and specify to whom you are addressing the question. 61 Water Hammer / Surge Analysis Case Study for Pressurized Pipe Ferdous Mahmood Senior Hydraulic Engineer Arcadis 62 Please consider the environment before printing. 31

32 Modeling Pressurized Pipes Steady state models master planning system improvements control valve settings Extended period models storage/production needs energy optimization operational improvements water age / disinfectant decay Surge models controlling high and low pressures 63 Water Hammer in Pressurized Pipes Surge / Transient analysis Sudden changes in pressures Propagates through system until dampened Damages system equipment (pumps, valves, pipes) Damage may not be sudden but develop over time due to repeated surge or transient episodes 64 Please consider the environment before printing. 32

33 Causes of Surge Pump operation startup, shutdown or power failure Valve operation rapid opening or closure Tank operation loss of service Pipe filling and draining air release Pipe breaks rapid changes in demands Hydrant testing rapid changes in demands 65 Preventing Pipeline Surge Proper selection of surge control components during design Proper operation of surge control devices and other components of system Proper maintenance of surge control devices Surge / transient modeling 66 Please consider the environment before printing. 33

34 Elevation (m) Volume (L) Pump Station 4 duty, 1 stand-by pumps Each pump 5,400 m3/hr, discharges to 30-inch line Valve opening and closing time controlled Pipeline 21.9 km (13.6 miles) pressurized pipe Standpipe on high ground Case Study 28.4 km (17.6 miles) gravity flow to WTP 67 Scenario 1 No Check/Control Valves or Surge Prevention Devices Maximum hydraulic grade Steady state hydraulic grade Minimum hydraulic grade Pipe profile Distance (m) 68 Please consider the environment before printing. 34

35 Pressure (psi) Flow (m3/hr) Pressure (psi) Scenario 1 No Check/Control Valves or Surge Prevention Devices Maximum transient pressure Steady state pressure Minimum transient pressure Water Vapor pressure Distance (m) 69 Scenario 1 No Check/Control Valves or Surge Prevention Devices Time (sec) 70 Please consider the environment before printing. 35

36 Elevation (m) Volume (L) Pressure (psi) Scenario 2 Check/Control Valves Closes in 2 Minutes Maximum hydraulic grade Steady state hydraulic grade Minimum hydraulic grade Pipe profile Distance (m) 71 Scenario 2 Check/Control Valves Closes in 2 Minutes Maximum transient pressure Steady state pressure Minimum transient pressure Water Vapor pressure Distance (m) 72 Please consider the environment before printing. 36

37 Flow (m3/hr) Pressure (psi) Flow (m3/hr) Pressure (psi) Scenario 2 Check/Control Valves Closes in 2 Minutes Time (sec) 73 Scenario 4 Check/Control Valve Closes in 5 sec; 24 Surge Relief Valve Time (sec) 74 Please consider the environment before printing. 37

38 Flow (m3/hr) Pressure (psi) Pressure (psi) Scenario 4 Check/Control Valve Closes in 5 sec; 24 Surge Relief Valve Maximum transient pressure Steady state pressure Minimum transient pressure Water Vapor pressure Distance (m) 75 Scenario 4 Check/Control Valve Closes in 5 sec; 24 Surge Relief Valve Time (sec) 76 Please consider the environment before printing. 38

39 Elevation (m) Volume (L) Pressure (psi) Scenario 5 Check/Control Valve Closes in 5 sec; 24 Surge Relief Valve Two 150,000 gal Hydro Pneumatic Tanks Maximum hydraulic grade Steady state hydraulic grade Minimum hydraulic grade Pipe profile Distance (m) 77 Scenario 5 Check/Control Valve Closes in 5 sec; 24 Surge Relief Valve Two 150,000 gal Hydro Pneumatic Tanks Maximum transient pressure Steady state pressure Minimum transient pressure Water Vapor pressure Distance (m) 78 Please consider the environment before printing. 39

40 Flow (m3/hr) Pressure (psi) Pressure (psi) Volume (L) Scenario 5 Check/Control Valve Closes in 5 sec; 24 Surge Relief Valve Two 150,000 gal Hydro Pneumatic Tanks Time (sec) 79 Scenario 7 Check/Control Valve Closes in 5 sec; 24 Surge Relief Valve Four 120,000 gal Hydro Pneumatic Tanks Maximum hydraulic grade Steady state hydraulic grade Minimum hydraulic grade Pipe profile Distance (m) 80 Please consider the environment before printing. 40

41 Flow (m3/hr) Pressure (psi) Pressure (psi) Volume (L) Scenario 7 Check/Control Valve Closes in 5 sec; 24 Surge Relief Valve Four 120,000 gal Hydro Pneumatic Tanks Maximum transient pressure Steady state pressure Minimum transient pressure Water Vapor pressure Distance (m) 81 Scenario 7 Check/Control Valve Closes in 5 sec; 24 Surge Relief Valve Four 120,000 gal Hydro Pneumatic Tanks Time (sec) 82 Please consider the environment before printing. 41

42 Pressure (psi) Volume (L) Pressure (psi) Volume (L) Scenario 8 Check/Control Valve Closes in 5 sec; 24 Surge Relief Valve Six 120,000 gal Hydro Pneumatic Tanks Maximum hydraulic grade Steady state hydraulic grade Minimum hydraulic grade Pipe profile Distance (m) 83 Scenario 8 Check/Control Valve Closes in 5 sec; 24 Surge Relief Valve Six 120,000 gal Hydro Pneumatic Tanks Maximum transient pressure Steady state pressure Minimum transient pressure Water Vapor pressure Distance (m) 84 Please consider the environment before printing. 42

43 Flow (m3/hr) Pressure (psi) Volume (L) Pressure (psi) Scenario 8 Check/Control Valve Closes in 5 sec; 24 Surge Relief Valve Six 120,000 gal Hydro Pneumatic Tanks Time (sec) 85 Scenario 9 Check/Control Valve Closes in 5 sec; 24 Surge Relief Valve Six 120,000 gal Hydro Pneumatic Tanks with 4 by-pass Maximum hydraulic grade Steady state hydraulic grade Minimum hydraulic grade Pipe profile Distance (m) 86 Please consider the environment before printing. 43

44 Flow (m3/hr) Pressure (psi) Pressure (psi) Volume (L) Scenario 9 Check/Control Valve Closes in 5 sec; 24 Surge Relief Valve Six 120,000 gal Hydro Pneumatic Tanks with 4 by-pass Maximum transient pressure Steady state pressure Minimum transient pressure Water Vapor pressure Distance (m) 87 Scenario 9 Check/Control Valve Closes in 5 sec; 24 Surge Relief Valve Six 120,000 gal Hydro Pneumatic Tanks with 4 by-pass Time (sec) 88 Please consider the environment before printing. 44

45 Pressure (psi) Volume (L) Pressure (psi) Volume (L) Scenario 13 Check/Control Valve Closes in 5 sec; 24 Surge Relief Valve Five 120,000 gal Hydro Pneumatic Tanks with 4 by-pass Maximum hydraulic grade Steady state hydraulic grade Minimum hydraulic grade Pipe profile Distance (m) 89 Scenario 13 Check/Control Valve Closes in 5 sec; 24 Surge Relief Valve Five 120,000 gal Hydro Pneumatic Tanks with 4 by-pass Maximum transient pressure Steady state pressure Minimum transient pressure Water Vapor pressure Distance (m) 90 Please consider the environment before printing. 45

46 Elevation (ft) Volume Case Study 2 Pump Station 2 duty, 1 stand-by pumps Each pump 3 mgd, discharges to 10-inch line Valve opening and closing time controlled Pipeline 9,500 feet pressurized pipe 3 MG storage tank 91 Scenario A - Four 2-inch Air Valves Only with Pump Check Valve Closing Immediately Existing four 2-inch air valves only with pump check valve closing immediately 92 Please consider the environment before printing. 46

47 Hydraulic Grade (ft) Flow (m3/hr) Air Vapor Volume (gal) Elevation (ft) Volume Scenario A - Four 2-inch Air Valves Only with Pump Check Valve Closing Immediately Time (sec) 93 Scenario B - Existing Four 4-inch Air Valves and 8-inch Surge Relief Valve 94 Please consider the environment before printing. 47

48 Hydraulic Grade (ft) Flow (m3/hr) Air Vapor Volume (gal) Elevation (ft) Volume Scenario B - Existing Four 4-inch Air Valves and 8-inch Surge Relief Valve Time (sec) 95 Scenario C - Two 2-inch Air Valves and Four 4- inch Air Valves AND 5000 gal Surge Tank with 12 Inlet 96 Please consider the environment before printing. 48

49 Hydraulic Grade (ft) Hydraulic Grade (ft) Flow (m3/hr) Flow (m3/hr) Air Vapor Volume (gal) Air Vapor Volume (gal) Scenario C - Two 2-inch Air Valves and Four 4- inch Air Valves AND 5000 gal Surge Tank with 12 Inlet Time (sec) 97 Scenario C - Two 2-inch Air Valves and Four 4-inch Air Valves AND 5000 gal Surge Tank with 12 Inlet Time (sec) 98 Please consider the environment before printing. 49

50 Surge Analysis Summary for Pressurized Pipes 99 Options for Surge Prevention Design / install surge protection devices Surge tanks, pump control valves, pump flywheel, air release valves and vacuum breakers, pressure relief valves, others Modify pump and valve operation set points, timing Reduce pipe velocity larger diameter pipe Reduce wave speed different pipe material Increase pump inertia flywheel Increase pipe pressure rating higher class pipe Provide additional pressure relief pump bypass line Reduce elevations changes pipe re-routing 100 Please consider the environment before printing. 50

51 Surge / Transient Pressure Modeling Analyze existing transient pressures for specific operational events Mitigate transients using appropriate devices such as: Surge tanks, pump control valves, pump flywheel, air release valves and vacuum breakers, pressure relief valves, others Conduct detailed surge analysis Hand calculations and charts Transient computer models (Hammer, Infosurge, CFD models can be used but time consuming) Observe hydraulic behavior of each component and their interaction 101 Ask the Experts Tom Walski Kevin Laptos Ferdous Mahmood Enter your question into the question pane at the lower right hand side of the screen. Please include your name and specify to whom you are addressing the question. 102 Please consider the environment before printing. 51

52 Upcoming Webinars May 4 Practical Examples of Delivering Cyber Security at a Water Utility May 11 Preparing for Cyanotoxin Events: Learning from Recent Utility and State Experiences May 18 Advancing the Capital Improvement Planning Strategy for Your Utility Register for a 2016 Webinar Bundle Individual Full Year Group Full Year Upcoming Conferences Register Online at: Please consider the environment before printing. 52

53 Thank You for Joining AWWA s Webinar As part of your registration, you are entitled to an additional 30-day archive access of today s program. Until next time, keep the water safe and secure. 105 Presenter Biography Information Tom Walski has 40 years of experience in water and wastewater design and operation. He is currently senior product manager for Bentley Systems and has previously served as civil engineer for the Army Corps of Engineers, distribution system manager for the City of Austin, Tex., executive director the Wyoming Valley Sanitary Authority, and engineering manager for Pennsylvania American Water. He has written several books and hundreds of journal and conference papers on many aspects of water distribution systems. Based in Charlotte, NC. Specializes in planning and modeling of water distribution and wastewater collection systems and hydraulic transient analysis. 26 years of experience in engineering practice and management involving the planning, design, construction, operation, and rehabilitation, of water and wastewater systems. Mr. Mahmood is a senior hydraulics engineer at Arcadis specializing in hydraulics and water quality modeling of distribution systems and treatment plants. He conducts various types of modeling - hydraulics, computational fluid dynamics (CFD), surge, and water quality for master planning of water distribution systems and for evaluating and optimizing design of treatment plants. Mr. Mahmood assisted USEPA with the development of the Initial Distribution System Evaluation (IDSE) Guidance Manual, and is a co-author for AWWA M32 Manual on Computer Modeling of Distribution Systems. 106 Please consider the environment before printing. 53

54 CE Credits (CEUs) and Professional Development Hours (PDHs) AWWA awards webinar attendees CEUs. If you wish to take advantage of the opportunity to earn CEUs, visit Certificates will be available within 30 days of the webinar 107 How To Print Your CEU Certificate of Completion Within 30 days of the webinar, login to or register on the website. If you are having problems, please Once logged in, go to: My Account My Transcript Information To print your official transcript, click Print list To print certificates, click Download certificate 108 Please consider the environment before printing. 54

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