criticality analysis – assessing vulnerability: the
TRANSCRIPT
Criticality Analysis – Assessing Vulnerability: The Important Pipes Below
Joe Foote, PE PNWS AWWA Kennewick WA May 2017
Contents • Overview/Purpose of
Criticality Analysis
• Criticality Analysis • Facility • Pipe • Valve
• Summary
Purpose of Criticality Analysis • Consequences of failure
• Strength of the system with components off-line • Impacts to pressure and supply • Distribution network redundancy
• Valve criticality and isolation
• Prioritization of identified projects
• Supply and boosting facility “firm” capacity
Two-part Approach • Mass balance
• Source • Pump station • Storage
• Hydraulic modeling • Pipe Criticality: Strength of the pipeline network • Valve Criticality: Availability of valves to isolate breaks, or failed valves
Mass Balance Approach
Part of master planning • Supply redundancy
• Pump station redundancy
• Availability of storage
Hydraulic Model Approach - Pipelines Pipe Criticality – the importance of any single pipe segment in the network
• Closes each pipe in the system and evaluates the results • Finds “Functional” dead-ends, needed looping • Needed tie-ins • Service to critical customers
Hydraulic Model Approach - Valves
Valve Criticality • Evaluates consequences if a
valve fails to close • Isolates each valve in the
system and reports number of valves required, demand isolated
• Indicates difficulty of isolating a valve in the field
Criticality Process – Criticality Goals
Identify level of desired resiliency • Extent of evaluation
• Single component • Entire facility • Analysis of dead-ends
• Context of decisions • Age of facilities • Capital project prioritization • Operational flexibility
Redundancy
Cost
Criticality Process – Hydraulic Criteria • Develop hydraulic performance criteria
• Identify the target demand scenario(s) • Average day, Maximum day, Peak hour • Fire flow
• Pressure criteria • 20 to 30 psi
• Extent of pressure drop or disconnection • Pressure loss: Service pressure drops below criteria limits • Disconnection: The pipeline that has no looping
• Number of customers impacted • Amount of demand
Criticality Process – Valve Criteria • Number of valves required to isolate a failed valve
• Valve on distribution main • Valve on transmission main
• Demand isolated by valve closure
• Impact of critical customer to isolate failed valve
Software Tools • Protector and VCM extension - Innovyze • WaterCAD/WaterGEMS - Bently • OptiCritical - Optimatics
• EPA Net-based
• Data intensive • Data requirements for hydraulic models
• Calibrated GIS based model • GIS data for the location of system valves • GIS data for the location of critical customers
• Data streamlining • Skeletonizing or phased analysis
Model Development • Develop a GIS based
calibrated hydraulic model
• Skeletonize the model (as required)
• Validate the skeletonized model (as required)
• Create criticality scenarios
Streamline Data
40,000 pipes
8,000 pipes
Criticality Modeling – Pipes • Define location of critical customers
• Locate simple dead ends
• Group results • Categorize: disconnection or low pressure • Group pipe segments in series
• Rank the importance of critical pipe groups
• Validate project criticality with full model
Pipe Criticality Results Disconnection
Pipeline Criticality Scoring Maximum Pressure Violation – worst case pressure loss
Scoring Basis Critical Pressure Loss Pipeline Disconnection Pipeline
Critical Customer Score (number of critical customers with criteria violation)
10 points per critical customer, multiplied by the pressure violation
10 points per critical customer
General Customer Score (customers with criteria violation)
1 point per 100 equivalent people, multiplied by pressure violation score
1 point per 100 equivalent people
Pressure Violation Score (Magnitude of pressure loss)
1 point per 10 psi pressure violation, round up as long as the pressure violation is 10 psi or greater
N/A
Ranked Critical Pipes
• Prioritization of any existing improvement
• Development of improvements
Rank Projects
• Critical Customer Score = 10 points per critical customer below criteria pressure multiplied by the pressure violation
• General Customer Score = 1 point per 100 customers, multiplied by the pressure violation score
• Pressure Violation Score = 1 point per 10 psi below criteria, round up if over 10 psi
• Total Score = Critical Customer Score + General Customer Score + Pressure Violation Score
Group ID
Max Pressure Violation
Pressure Violation
Score
Critical Customers
Equivalent People
Customer Score
Total Score Rank
NH4A 40 4 - 8,990 360 364 1
NH51 5 0 5 2,217 250 250 2
H27B 21 3 - 3,579 107 110 3
NH86 19 2 - 1,235 25 27 4
L500 24 3 - 410 12 15 5
T33A 14 2 - 544 11 13 6
NT52 10 1 - 97 1 2 7
Secondary Prioritization • Secondary ranking criteria
• Areas with limited capacity • Headloss (2ft/1000 ft, 6ft/1000 ft) • Velocity 5ft/sec
• Age/Material • Identified growth areas
• Hydraulic capacity results may inform the improvement alternative process
Criticality Modeling – Valves • Skeletonized model (as required)
• GIS valves • Spatially located on model pipes • Relocate valves on junctions
• Run valve criticality
Red and yellow valves are required to isolate the black and yellow valve
Valve Criticality • Valves that require a large
number of other valves to isolate
• Valves that would impact critical customers
• Valves that impact large customer demand
• The addition of a few valves may reduce the criticality of many valves
Valve Criticality Results
• Transmission: Red valves require 11 or more valves to isolate
• Distribution: Yellow valves require 7 or more to isolate
Critical Valve Information • Operational Value
• Resource requirements • Prioritize valve maintenance
program • Identifying system improvements
• Limitations • Complexity based on size of
system • Limited tools for operator
reference
Summary • Mass balance
• Critical pipes • Pressure loss • Disconnection • Prioritization
• Valve criticality • Valves to isolate
(manpower) • Projects, maintenance
priority
A Special Thanks to • City of Spokane
• Dawn Wirz, Murraysmith
Questions?
Contact: Joe Foote, PE
Murraysmith
M: 421 W Riverside Ave, Suite 762
Spokane, Washington 99201
P: 509.321.0340