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Home My WebLink About9 Water System Piping Design Agenda Item # Memorandum To: Board of Directors From: Jessica Kosfiszer, Associate Water System Engineer Date: September 16, 2005 Subject: Discussion of Design Criteria for Water System Piping. 1. WHY THIS MATTER IS BEFORE THE BOARD Informational presentation for Design Criteria for water system pipe sizing. 2. HISTORY The water system has experienced major growth in water usage. Many of the transmission main lines were sized for the usage twenty to thirty years ago. 3. NEW INFORMATION The impact of growth is requiring that additional flows be pumped to all areas of the District. Many of the pipelines are under sized to accommodate the higher flows. New pipelines need to be designed to accommodate the higher flows. 4. RECOMMENDATION No action required. Design riteria for Water System Piping TDPUD Regular Meeting September 21 , 2005 .. ., [ Design Criteria for 1 Water System Piping � ■ Pipe Sizing ■ Power Costs ■ Illustration : Power Costs to pump from Airport & Martis Wells to Northside Tank ■ Illustration : Power Costs to pump from Innsbruck Tank to Stockholm Tank z Design Criteria for ..... [Water System Piping ■ Pipe Sizing (size & velocity) ■ Power Costs ■ Illustration : Power Costs to pump from Airport & Martis Wells to Northside Tank ■ Illustration : Power Costs to pump from Innsbruck Tank to Stockholm Tank 3 Area of a Circle , A ■ Area = Pi x radius2 ■ Pi is the ratio of the circumference of a circle to its diameter (twice the radius) or approximately 3 . 14 Ex: Area of 8-inch pipe is 3.14 x 42, 40 which equals 50 square inches. Divide by 144 square inches per square foot to get 0.35 square feet. 4 s L6 'tb LOL 9ZZ OE V L 06 Z9tb tbtb L tbZ 0tb' L We 99 9 L LO' L tb9 L 6t tb L 6L '0 6 L L 9E Z L 9600 09 9 L 8 Wool) (zs040ui) (say:)ui) (sayoul) adid 10 eaad paaenbS aaiewela Jeuo1139S ssoa3 snipeH edl.d adid adind 10 eaad IBu01as SSOJOI r Velocity v ■ Distance water travels through the pipe over a period of time , D/t ■ Measured in feet per second , (fps) ■ Not dependent on pipe size velocity D 6 System Planning Criteria Description Criteria Maximum Pipeline Velocity 12-inches and smaller 5 fps 14-inches and larger 3 fps Fire Flow and Emergency Conditions 10 fps From Table 2-1 of Water Master Plan Fl,,wJ Q ■ Volume of water passing through the pipe over a period of time , Q = A x v 46 X velocity ■ Measured in cubic feet per second , (cfs) or in gallons per minute , (gpm) or in million gallons per day, (mgd) ■ 1 . 55 cfs = 694 gpm = 1 mgd 8 Velocity vs . Flow Cross Pipe Sectional Flow when Flow when Flow when Diameter Area of Pipe Velocity - 3 fps Velocity - 5 fps Velocity - 10 fps (inches) (square feet) (cfs) (gpm) (cfs) (gpm) (cfs) (gpm) 8 0.35 1 .1 469 1 .8 782 3.5 1 ,563 12 0.79 2.4 19055 3.9 1 ,758 7.9 39517 14 1 .07 3.2 11436 5.4 21393 10.7 41786 16 1 .40 4.2 11876 7.0 31126 14.0 6,252 24 3.14 9.4 41220 15.7 71033 31 .4 14,066 30 4.91 14.7 61594 24.5 10,989 49.1 21 ,978 Carrying Capacity ■ A 24-inch pipeline has 4 times the carrying capacity of a 12-inch pipeline , not just twice as much . 10 ;Design Criteria for Water System .. Piping ■ Pipe Sizing ■ Power Costs ■ Illustration : Power Costs to pump from Airport & Martis to Northside Tank ■ Illustration : Power Costs to pump from Innsbruck Tank to Stockholm Tank Horse Power of a Pump , hp ■ From the Water Master Plan , page 2-6, installed horsepower can be calculated as : h _ Q x TDH p 3 , 960 x E Where: Q = flow, gallons per minute TDH = total dynamic head, feet E = pump efficiency, assumed to be 75% 12 [Total Dynamic Head , TDH ■ The energy added to water by system wells and pumps to send it uphill . ■ For a pump raising water from one open reservoir to another, the total dynamic head TDH consists of the total static head or elevation rise Hs and the friction head losses HF in the suction and discharge pipelines . TDH = Hs + HF 13 Total Dynamic Head (con 't) ---------------------- ------ HF ---------------------- ------- -------------------------------------------------------------- HS Discharge Suction Pipeline Pipeline 14 Friction Head, HF ■ Loss of energy in water as it flows through a pipe due to friction ■ The greater the flow, the greater the energy lost to frictional forces Friction Head Loss ■ The Hazen-Williams equation defines energy loss due to friction per 1 ,000 feet of pipe as : H F _ 10, x 500 Q 1 .85 _ 11000 p 4.87 C Where: Hp = dynamic head loss, feet D = pipe diameter, inches Q = flow, gallons per minute C = coefficient of pipe friction for ductile iron pipe, C = 100 16 Friction Head Loss Per 1 ,000 Feet of Pipe Pipe Head Loss (ft) for Head Loss (ft) for Head Loss (ft) for Diameter Velocity = 3 fps Velocity = 5 fps Velocity = 10 fps (inches) C=100 C=100 C=100 8 7.3 18.8 67.9 12 4.6 11 .7 42.3 14 3.8 9.8 35.3 16 3.3 8.4 30.2 24 2.0 5.2 18.8 30 1 .6 4.0 14.5 17 Notes on Friction Head Loss ■ A 24-inch pipeline has less than half the friction head loss of a 12-inch pipeline given the same pipe material and water velocity 18 Returning to Horse Power, hp ■ The horse power equation can be rewritten as: Qx (Hs + HF) hp = 3 , 960 x E ■ Qualitative Observations: o To provide more flow, more horse power is required o As static head or friction losses increase, more horse power is required o As pump efficiency increases, less horse power is required 19 .... [ Cost of Pumping ■ To convert from horsepower to kilowatts: 1 hp = 0 . 75kW ■ Then multiply kW by the hours the pump or well is used . ■ Currently, the TDPUD charges 11 . 40/kW-hour. 20 [ Design Criteria for Water System. Piping ■ Pipe Sizing ■ Power Costs ■ Illustration : Power Costs to pump from Airport & Martis Wells to Northside Tank ■ Illustration : Power Costs to pump from Innsbruck Tank to Stockholm Tank 21 Illustration : Airport & Martis t Northside Tank ■ Airport Pump Station and Martis Well to the Northside Tank via 11 , 000 feet of pipeline ■ HS = 6027 ft - 5906 ft = 121 ft Airport Tank EL 6027 EL 5906 Northside Tank `'Airport PS 22 yy 01 Z +may}{�+ yp)y�,]pp(�q l4 .. ,. AYt U Y' �t... ... 4 Ufi.34 .• y t a tis Y RdY{WWy Well i North side Tank Airport Well and Tank Illustration: Airport & Martis Wells to Northside Tank Illustration (con 't) : Airport & Martis to Northside , Q = 4 , 000 gpm Pipe Diameter Velocity HF POWER Cost to Pump (inches) (fps) (feet) (hp) (M) for One Day 8 25.6 41250 51886 4,415 $12,072 12 11 .4 590 957 718 $1 ,968 14 8.4 279 538 404 $1 ,104 16 6.4 145 358 269 $744 24 2.8 20 190 143 $384 30 1 .8 7 172 129 $360 Given: HS = 121 ft, E = 75%, C = 100, and 11 ,000 ft of pipe 24 Illustration (con 't) : Airport & Martis Wells to Northside Tank -- ------------------------- 279 feet (145y) 20 feet (24") -------------------- ---- ----------------- --- -- ------------------------------------------------- 121 feet Northside Tank Airport Tank Airport PS 25 [ Design Criteria for Water System Piping ■ Pipe Sizing ■ Power Costs ■ Illustration : Power Costs to pump from Airport Tank to Northside Tank ■ Illustration : Power Costs to pump from Innsbruck Tank to Stockholm Tank 26 Illustration : Innsbruck Tank to Stockholm Tank ■ Innsbruck Pump Station pumps water from the Innsbruck Tank to the Stockholm Tank via 10,000 feet of pipeline ■ Hs = 6708 ft — 6493 ft = 215 ft Innsbruck Tank EL 6708 EL 6493 Stockholm Tank '~'Innsbruck PS 27 Stockholm Tank t t 4 4 ( 1 J4`*'` r t rt�� Ei1r r✓ x ,� � ter its h t r� yv�Qit�; '��i�E�� r � �'Y�siy 3{�s v7 �� ✓b$th r ti Y. � J �f�� h,✓ .fit'�s% !"3�$ �`� r r s y,��rzi,� 2S� �,*� >✓+e�,1 iz S r SK s F r a y, .i1 �liliaudl�le,�. .,. ✓v>„.� � ,ro°,' LL t Xyµ,: 3 ', `°' ! `. Innsbruck Tank and Dump Station Illustration: Innsbruck Tank to Stockholm Tank Illustration (con 't) : Innsbruck to Stockholm , Q = 2 , 500 gpm Pipe Diameter Velocity HF POWER Cost to Pump (inches) (fps) (feet) (hp) (M for One Day 8 16.0 1 ,619 11544 1 ,158 $3,168 12 7.1 225 370 278 $786 14 5.2 106 270 203 $552 16 4.0 55 228 171 $456 24 1 .8 8 187 141 $384 30 1 .1 3 183 137 $384 Given: Hs = 215 ft, E = 75%, C = 100, and 10,000 ft of pipe 29 Illustration (con 't) : Innsbruck Tank to Stockholm Tank ---- - ------------------------ fi 225 feet 55 feet (2 x 8") (16") ---------------- 1 ---- 215 feet Stockholm Tank it --1w Innsbruck Tank Innsbruck PS 30 bc-) o toW OL cooz 0 OT El Z i5l, oz LOT 0 0 ooz a 666L 06 j IZ ot s qluoN jad seaI wals lelol. Illustration (con 't) : # 1 Airport Tank to Northside Tank H F _ 10 , X 500 Q 1 .85 _ 1 ,000 ft D 4.87 C ■ D = 24 inches ■ Q = 4,000 gpm ■ C = 100 o HF = 1 .8 ft of friction loss per 1 ,000 ft of 24-inch pipe 1 . 8 ft x 11 , 000 ft = 20.2 ft 1 , 000 ft 32 [ Illustration (con 't) : #2 Airport Tank to Northside Tank hp _ Q x TDH 3, 960 x E ■ Q = 4, 000 gpm ■ TDH = HS + HF = 121 ft + 20 .2ft ■ E = 75% _ 4, 000 x 141 . 2 hp 3 , 960 x 75% - 190 . 1 hp 33 [ Illustration (con 't) : #3 Airport Tank to Northside Tank kW = 190 . 1 hpx0 . 75kW = 142 . 6kW 1 hp Cost = 142 . 6 kW X 1 hour X 11 .4¢ kW-hr Cost . $ 16. 26 Illustration (con 't) : # 1 Innsbruck Tank to Stockholm Tank H F 10, 500 x Q 1 .85 = 1 , 000 ft D 4.87 C ■ D = 8 inches ■ Q = 2,500 gpm ■ C = 100 o HF = 161 .9 ft of friction loss per 1 ,000 ft of 8-inch pipe 161 . 9 ft 1 , 000 ft x 101000 ft = 1 , 619 ft 35 ..., [ Illustration (con 't) : #2 Innsbruck Tank to Stockholm Tank hp _ Q x TDH 3 , 960 x E ■ Q = 2 , 500 gpm ■ TDH = HS + HF = 215ft + 1 , 619 . 3ft ■ E = 75% _ 2 , 500 x 1834 hp 3 , 960 x 75% - 1 � 544 hp 36 [ Illustration (con 't) : #3 Innsbruck Tank", to Stockholm Tank kW = 1 , 544hpx0 . 75 kW = 1 , 158kW 1 hp Cost = 1 , 158 kW X 1 hour X 11 . 40 kW-hr Cost = $ 132 . 01 37