Pipe Networks Pipeline You are here systems pipe

Pipe Networks äPipeline You are here systems äpipe networks ämeasurements ämanifolds and diffusers äPumps Monroe L. Weber-Shirk School of Civil and Environmental Engineering

Pipeline systems: Pipe networks ä ä ä Water distribution systems for municipalities Multiple sources and multiple sinks connected with an interconnected network of pipes. Computer solutions! ä ä KYpipes Water. CAD Cyber. NET EPANET http: //www. epa. gov/ORD/NRMRL/wswrd/epanet. html

Water Distribution System Assumption ä ä Each point in the system can only have one _______ pressure The pressure change from 1 to 2 by path a must equal the pressure change from 1 to 2 by path b a 1 2 b

Water Distribution System Assumption a Pressure change by path a 1 2 b zero Or sum of head loss around loop is _____. (Need a sign convention) Pipe diameters are constant ä Model withdrawals as occurring at nodes so V is constant ä

Pipes in Parallel ä Find discharge given pressure at A and B ä ______& energy ä add ä flows ____ S-J equation Qtotal A Q 1 Q 2 B Find head loss given the total flow ä assume a discharge Q 1’ through pipe 1 ä solve for head loss using the assumed discharge ä using the calculated head loss to find Q 2’ ä assume that the actual flow is divided in the same _____ proportion as the assumed flow

Networks of Pipes conservation at ä Mass __________ all nodes ä The relationship between head loss and discharge must be maintained for each pipe ä Darcy-Weisbach ä 0. 28 m 3/s equation friction formula _______ Hazen-Williams A ? _______ Swamee-Jain ä Exponential ä 0. 32 m 3/s a 1 2 b

Network Analysis Find the flows in the loop given the inflows and outflows. The pipes are all 25 cm cast iron (e=0. 26 mm). 0. 32 m 3/s A B C D 0. 28 m 3/s 100 m 0. 10 m 3/s 200 m 0. 14 m 3/s

Network Analysis Assign a flow to each pipe link ä Flow into each junction must equal flow out of the junction ä arbitrary 0. 32 m 3/s A 0. 00 0. 10 m 3/s 0. 32 0. 28 m 3/s B 0. 04 C D 0. 10 0. 14 m 3/s

Network Analysis ä Calculate the head loss in each pipe f=0. 02 for Re>200000 Sign convention +CW k 1, k 3=339 k 2, k 4=169 0. 32 m 3/s A 1 B 2 4 0. 10 m 3/s C 0. 28 m 3/s 3 D 0. 14 m 3/s

Network Analysis ä ä The head loss around the loop isn’t zero Need to change the flow around the loop ä ä ä clockwise flow is too great (head loss is the ______ positive) reduce the clockwise flow to reduce the head loss Solution techniques ä ä ä Hardy Cross loop-balancing (______) optimizes correction Use a numeric solver (Solver in Excel) to find a change in flow that will give zero head loss around the loop Use Network Analysis software

Numeric Solver ä ä ä Set up a spreadsheet as shown below. the numbers in bold were entered, the other cells are calculations initially Q is 0 use “solver” to set the sum of the head loss to 0 by changing Q the column Q 0+ Q contains the correct flows

Solution to Loop Problem Q 0+ Q 0. 218 -0. 062 -0. 202 -0. 102 0. 32 m 3/s 1 A 0. 218 4 2 0. 10 m 3/s C 0. 28 m 3/s B 0. 062 0. 202 3 D 0. 14 m 3/s Better solution is software with a GUI showing the pipe network.

Pressure Network Analysis Software: Water. CAD™ reservoir pipe 0. 32 m 3/s junction 1 A 0. 218 4 2 0. 10 m 3/s C 0. 28 m 3/s B 0. 062 0. 202 3 D 0. 14 m 3/s

Network Elements ä Controls ä ä ä ä Check valve (CV) Pressure relief valve Pressure reducing valve (PRV) Pressure sustaining valve (PSV) Flow control valve (FCV) Pumps: need a relationship between flow and head Reservoirs: infinite source, elevation is not affected by demand Tanks: specific geometry, mass conservation applies

Check Valve only allows flow in one direction ä The valve automatically closes when flow begins to reverse ä open closed

Pressure Relief Valve pipeline closed open relief flow Low pipeline pressure High pipeline pressure Valve will begin to open when pressure in exceeds a set pressure the pipeline ____ (determined by force on the spring).

Pressure Regulating Valve sets maximum pressure downstream closed High downstream pressure open Low downstream pressure Valve will begin to open when the pressure less downstream ______ is _____ than the setpoint pressure (determined by the force of the spring).

Pressure Sustaining Valve sets minimum pressure upstream closed Low upstream pressure open High upstream pressure Valve will begin to open when the pressure upstream is _____ greater than the setpoint pressure ____ (determined by the force of the spring). Similar to pressure relief valve

Flow control valve (FCV) Limits the ____ flow rate through the valve to a specified value, in a specified direction ä Commonly used to limit the maximum flow to a value that will not adversely affect the provider’s system ä

Pressure Break Tanks ä ä In the developing world small water supplies in mountainous regions can develop too much pressure for the PVC pipe. They don’t want to use PRVs because they are too expensive and are prone to failure. Pressure break tanks have an inlet, an outlet, and an overflow. Is there a better solution?