water distribution systems, network systems ce 3372 water systems design
TRANSCRIPT
Water Distribution Systems, Network Systems
CE 3372 WATER SYSTEMS DESIGN
OUTLINE
Review of Lecture 3Water Distribution Systems
Network Systems
Define HydraulicsWhat is the Energy EquationName some assumptions of the Energy EquationDifference in EGL and HGL2 Main types of Head Loss3 types of head loss models
REVIEW
Water Supply System Includes water supply Treatment Facilities Pumping facilities Transmission lines Local distribution network
WATER DISTRIBUTION
Distribution network - Consists of items designed to convey potable water at adequate pressures and discharges Pipes Fittings Valves Other appurtenances
WATER SUPPLY SYSTEM
Who? Personnel within the water company Engineers / Consultants
Design Requirements? Pressure Fire Flow Potable water Cost Effi cient $$
Design parameters and regulations? State board of health Local city/county health departments EPA, AWWA, ANSI
DESIGN
Pressures Must be high enough to..
overcome head losses in the system. But not too high to...
prevent damage to fittings and other appurtenances.
Pressure Zones – Set pressurized areas (min and max) within the system by storage, boosters, or pressure control valves. Can also be due to varying pipe size and topography May be generated to ensure reliability in meeting fluctuation
demands.
System pressures are adapted to requirements. Hilly areas – booster pumping Minimum pressures vary state to state Established by the state’s Health Department / other agency Fire Marshall may establish additional requirements.
PRESSURE
Fire Flow Parameters Each municipality establishes own parameters based on
local cond. Insurance Services Offi ces (ISO) - Most used
“Guide for Determination of Required Fire Flow” Recommends criteria for
Establishing insurance rates Classifying mun. with reference to their fire defenses and physical cond.
F = required fi re fl ow in gpmC = coeffi cient related to the type of constructionA = total fl oor area in ft2 (excludes basements)
FIRE FLOW
Hydraulic Characteristics Pressures and discharges are a functions of HC Length Size Condition of pipe
Service Characteristics Demand as it relates to:
Present and projected population Economic base Fire flow Climate
WATER SUPPLY SYSTEM
Water utility company …who is responsible for the water quality and operation of
the distribution system.
Companies exist in two forms public entity that
..“exists for the health, safety, and welfare of the public” privately owned utility that ..provides water for profit
WATER UTILITY
WATER SUPPLY SYSTEM
Gravity Dependable Source of supply must be located well above the city High-pressure demand for fire-fighting may require pumper
trucks
Pump Least Desirable Pressures vary substantially with variations in flow Provides no reserve if power failure
Pump with Storage Most common Water supplied at approximately uniform rate Flow in excess of consumption stored in elevated tanks
PIPE SYSTEM
Primary Mains (Arterial Mains) Form basic structure of the system Carry flow from pumping station to elevated storage tanks Carry flow from elevated storage tanks to service areas
Laid out in interlocking loops Mains not more than 1 km (3000 ft) apart
Valved at intervals of not more than 1.5 km (1 mile) Smaller lines connecting to them are valved
PIPE SYSTEM
Secondary Lines Form smaller loops within the primary main system Run from one primary line to another
Spacings of 2 to 4 blocks Provide large amounts of water for fire fighting with out
excessive pressure loss
PIPE SYSTEM
Small distribution lines Form a grid over the entire service area Supply water to every user and fire hydrants –Connected to
primary, secondary, or other small mains at both ends Valved so the system can be shut down for repairs Size may be dictated by fire flow except in residential areas with
very large lots
Water source (Main Supply)• Lake• River• Aquifer
Treatment Facility• Treats and disinfects water• Meet water quality standards• Potable water
Transmission Lines• Convey water from
source – treatment facility facility – network
Pumping Facilities• Provide energy to move water
Intermediate Storage Facilities• Stabilize line pressures• Reserve for peak demand periods
• Provide storage for fire flow req.
Distribution Lines• Convey water from
storage – service areas
• Looped(grid) and Branched Layouts
Appurtenances• Fire Hydrants. Valves, auxiliary pumps, fittings
WATER SUPPLY SYSTEM
WATER USE SYSTEMS
Spatial and temporal distribution in support of human habitation Water supply/treatment/distribution Waste water collection/treatment/discharge
Capacity is based on POPULATION served hydraulic dominated designs
WATER USE AND DEMAND
Water Use Consumptive
Municipal Agricultural Industrial Mining
Non-consumptive Hydropower Transportation Recreation
Water Demand Quantity that consumers use per unit of time Ex: Mgpd Depends on population, climate, industry and economic
factors
WATER DEMAND
Residential Single-family, multi-family (apartments) Water for drinking, landscape, swimming, fires,
street cleaning, etc. Usually two demand peaks (morning and evening)
Commercial Motels, hotels, offi ces, shopping centers Usually less peak demand and less varied than
residential
Industrial Chemical plants, food processing plants, mines Water for fabrication, cooling, petroleum refining,
etc. Water use depends on type of industr.
ASSIGNING DEMAND
Assign demand using network models (links and nodes)
Network models contain nodes that represent a multitude of actual connections .
While conceptually possible to model to every single connection,it is discouraged because Model is hard to maintain Small errors may go unnoticed The operation of any single connection is not well known.
NETWORK TYPES
Branch No circulation Has terminals and dead-ends
Water in dead-ends is stagnant Disinfection residual Corrosion
NETWORK TYPES
Grid/Loop Furnishes supply from more than one direction
Water circulates Disinfection is more effective. Water “age” in system is younger (fresher).
In case of water main break, fewer people are inconvenienced
NETWORK TYPES
Loop vs. Branch during network failure Every link in a branch system is a single point of failure
that isolates all downstream nodes. Not with loop, only main supply line is failed
Distribution networks are multi-path pipelines
Node Inflow =
Outflow Energy is
unique valueLinks
Head loss occurs along line path
BRANCHED SYSTEM
BRANCHED SYSTEM
Continuity at the node
BRANCHED SYSTEM
Head loss in each pipe
Common head at the node
4 Equations, 4 unknownsNon-linear – solve by
Newton-Raphson/Quasi-Linearization
Quadratic unknown – can find solution in iterations
BRANCHED SYSTEM
TWO RESERVOIR EXAMPLE – Refer to spreadsheet
BRANCHED SYSTEM
Looped system is an extension of branching where one or more pipes rejoin at a diff erent node.
LOOPED SYSTEM
Nodes: Inflow = Outflow Energy Unique
Links Head loss along pipe Head loss in any loop is zero
LOOPED SYSTEM
LOOP