95TH Annual Conference | November 20015 | Raleigh Convention Center, Raleigh, NC

Optimizing Operations of Finished Water Pumps and Protecting the Distribution System with Transient Modeling

95TH Annual Conference | November 2015 | Raleigh Convention Center, Raleigh, NC

Crystal Broadbent, Hazen and Sawyer

Kelvin Creech, Town of Cary

Michael Wang, Hazen and Sawyer

AuthorsOutlineProject BackgroundSurge ModelingField WorkModel CalibrationAir Release Valve AnalysisEconomic AnalysisRecommendationsSummary

Surge Model used to identify problems affecting operations of finished water pumps, WTP, and distribution system PurposeOptimize operationsReduce O&M costProtect critical infrastructureBackgroundStaff suspect finished water pumps were adversely affected by entrained air left in the transmission mainBackgroundThe WTP:40 mgd WTP9 finished water pumps42-inch transmission mainThe challenges:After maintenance, unable to purge all air out of transmission mainHigh-pitch sound emanating from existing air release valves

Surge Model

Surge Model2010 MDDPumps Operating at MDDTwo 1000 hp One 450 hpQ= 24.3 mgdPressure = 161.4 psi

High Service Pump Detail

High Service Pumps in Surge Model

Surge Relief ValveFWP-7FWP-6FWP-5FWP-3FWP-4FWP-8ADAMS Control Valve, typ.42-inch Transmission Line Profile

HSPCPZ ZoneField Test

Field Test Logger LocationBetween pumps and ADAMS valvesVenturi VaultGreen Level Church RdJenks & Apex Hwy 55Field Test Work performed April 18th, 2013Evaluated a series of pump on and off configurationsPump 6 startPump 5 start while Pump 6 operatingPump 6 off while Pump 5 operatingPump 3 on while Pump 4 operatingPump 3 off while Pump 4 operatingMeasured pressures at hydrants

Pump 6 StartSCADA does not capture the pressure waveSCADA does not capture the pump start up

Pump 5 StartPump 6 OperatingA 25 psi difference between Pump 5 and Pump 6 & WTP Meter. This indicates that the ADAMS valve in front of Pump 5 is throttling flow and energy is being consumed.25 psi difference

Pump 6 OffPump 5 Operating

Pressures are the same for Pump 4, Pump 3 and WTP Meter, as would be expectedPump 3 OnPump 4 Operating

29 second closing: 62 psi pressure increaseSCADA does not capture the pressure wave Pump 3 OffPump 4 OperatingModel CalibrationSurge Model Calibration to Field Test ResultsAnalyzed two scenariosPump 6 onPump 6 turns off while Pump 5 remains on GraphField test results: dashed linesSurge model results: solid linesDifferent color for each location

Model Matches Loggers

Model Matches LoggersAir Valve EvaluationBasic Purposes of Air ValvesThe Basic PremiseAllow air and gases to be released from a pipeAllow air into a pipe under negative pressure conditions

Behavior of AirAir & Its Impact on a Water and Wastewater System, Val-Matic; Air Valves Bulletin 1500; issue 3 volume 52 p 37-44

Installation GuidelinesAir valve connection to the pipe needs to be correctly sized and located to capture the small air bubbles as well as larger pockets.For air-release valves this is particularly important, since their function is to release these small bubbles and pockets.Ideal (but not generally practiced in the U.S.):Connection to Pipe (d) Ratio to Pipe Diameter (D):d = D for D 12 inchd = 0.6D for D inch < D 60 inchd = 0.35D for > 60 inch

Orifice Sizing: Air-release ValveDifficult to predict quantity of air/gases that will come out of solution

Assume 2% solubility of air in water under standard conditions

Less is known about dissolved air properties in wastewater

Choked orifice, or sonic flow occurs when the ratio of low pressure (absolute) to high pressure (absolute) < 0.528 (for vacuum, avoid internal pressures below -5 psi gauge)Ask Crystal about sonic flow.28Orifice Sizing: Air/Vacuum ValvePipeline FillingFill rate 1ft./sec. Exhaust air at a rate = pumping rate or the design fill rateTypically vented to atmosphere a differential pressure of < 2 psi.Valves with anti-slam or slow-closing may have a differential pressure of 5 psi

Air enters Orifice (3), travels through the annular space between the cylindrical floats (4), (5), and (6) and the valve Chamber Barrel (2) and discharges from the Large Orifice (1) into atmosphereOrifice Sizing: Air/Vacuum Valve, cont.Pipeline DrainingGravity flow based on pipe slope or drain valveDetermine maximum allowable negative pressure (usually -5 psi)

CautionImproper design of orifice size for an air/vacuum valve = Release air too fast air slam31

Singlestage2 stage31Air Valves for Burst and Draining

4344488443Each manufacturer uses its own set of calculations and some provide free sizing programs

Existing Air Valves are 2 times too Small

Velocity: 3-3.3 fpsCurrent Size Air Valves would be for ONLY a 16 to 24 inch pipeFor 42 inch pipe Air Valve size is between a 4 and 6 inchEconomic AnalysisEconomic AnalysisEvaluated current operations for taking 42 offline and returning it to serviceDetermined effectiveness of existing air valves Using model and field test Determined existing restrictions in 42 transmission mainEnergy cost due to restrictions in 42 transmission main

Current 42 OperationNormally: 42 feeds CPZ (641); 30 feeds WPZ (540)Operate valves to switch 30 from WPZ to CPZDrain 42 through blow off valvesSupply WPZ through PRVs from CPZ Supply CPZ using 3 WPZ pumps 400hp; 5.5 mgd @ 305 ft1 Swing pump 1000 hp; 9 mgd @ 450 ftSupplement with Durham water24-72 hrs to refill 42 MainRefill from NC 55 & Old Jenks Rd30 Main still providing supply to CPZOperate valves to switch 30 from CPZ to WPZFlush through hydrantsReturn 42 Main to service

Placing back into service

Taking out of serviceHydraulic Model Analysis* Evaluating 30 TM Supplying WPZ (typical operation)Average Day Demand for WPZ: 3.4 mgd1 WPZ Pump: 3 hrs a day6.3 MGD @ 271 ft; 78%Calculated HP: 384Davis Drive & Waldo Rood Blvd PRV between CPZ and WPZ2.7 mgd Setting 78 psiSupplying CPZ (when 42 offline)Average Day Demand CPZ: 16.2 mgdSwing Pump: operates 2 to 3 times a day: ~ 14hrs each day9.6 MGD @ 424 ft; 85%Calculated HP: 840WPZ Pumps operating: 1, 2 and 9 operates continuouslyEach: 4.2 mgd @ 380 ft; 78%Calculated HP: 359 per pumpTogether, the WPZ pumps and swing pump can continue to meet average day demands

* hydraulic model received from CH2Ms

WPZ PumpPumping to WPZPumping to CPZCost Difference Between Supplying CPZ with 42 vs. 30: Average Day Demand30 Supply CPZ3 WPZ pumps each: 359hp, 24hrs/day, 30days/monthSwing Pump: 840 hp, 14hrs/day, 30days/monthTotal : 841,000 kwh/month

42 Supply CPZPump 3: 384 hp, 8.4hrs/day, 30days/monthPump 5: 835 hp, 9.4hrs/day, 30days/month; 827 hp, 14.6hrs/day, 30days/monthPump 6: 835 hp, 9.4hrs/day, 30days/monthTotal : 720,000 kwh/month

Difference 121,000 kwh/monthkWh cost$0.0535/kwh for all over 140,000 kWh per month, per kWh (duke energy)Cost for using 30 verses 42 to supply CPZ$1,600 cost/week $6,500 cost/month

Effectiveness of Existing Air ValvesSurge model power loss result: Existing valves let in a greater volume of air and take longer to expel it than the proposed valves.

Larger volume of air is directly proportional to the headloss.

Comparing Field Test to ModelPumps are operating below the 20.2 inch impeller curve (shown in the next slides)Field Pump 6Model-Without RestrictionsFlow, mgd10.7510.75*Discharge Pressure, psi148140Discharge HGL, ft656637Suction HGL Range, ft290290TDH, ft366347Efficiency, %8080Calculated HP862818* Forcing the model to provide the exact flow as the field test41Pump 6

Field TestModel

Possible Restrictions:Throttled valveAir pocketCorrosion buildup*Biofilm**City staff confirmed this is not the caseReduction of Pump Capacity Air PocketAir pockets in the pipeline add additional head loss and restrict flowHead loss is directly proportional to the size of air pocketAs high as 16% additional head lossExtremely difficult to predict exact head lossDetermine entrained air by comparing the design capacity and actual capacity Another way is to determine the actual friction value through field work and then recalculate capacity with new friction value to see if entrained air is an issue

S J van Vuuren, M van Dijka and J N Steenkamp, Quantifying the Influence of Air on the Capacity of Large Diameter Water Pipelines and Developing Provisional Guidelines for Effective De-aeration. WRC Report No. 1177/2/03Potential Energy Savings: One Pump Evaluation818 hp, 24hrs/day, 30days/month

439,000 kwh/month

862 hp, 24hrs/day, 30days/month

463,000 kwh/month

24,000 kwh/month difference

Savings$15,400 saving/yr

DifferenceModel with No RestrictionsField Test$0.0535/kwh for all over 140,000 kWh per month, per kWh (duke energy)

45RecommendationSuggested Sizing for 15 and 20 MGDfrom Manufacture Software

43/6 & 344488443New LocationsHazen Recommendation

434466443New LocationsRemains the sameVarious Construction Cost Estimate for Valve UpgradeItemDescriptionTotal CostAir ValveTee Connection (42x20)$110,000Tapping Saddle (42 x 12)$18,000Existing Tapping Saddle (42x8)$13,000

New ManholeTee (42x20)$120,000New ManholeTapping Saddle(42 x 12)$29,000Recommended Modifying Pump Control ValvesReplace Actuators

More control of open/close times

Reduce operational cost by removing headloss through malfunctioning valve

50ADAMS ValveSummarySummary

Calibrated Surge Model Optimized OperationsImproved Air Release Protected Critical InfrastructureReduces O&M Cost

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