DNV GL © 2014
Ungraded
30 September 2015 SAFER, SMARTER, GREENERDNV GL © 2014
Ungraded
30 September 2015Mark Grainger
OIL & GAS
Practical Uses of PODDS Discolouration Modelling Capability in Synergi 4.9
1
DNV GL © 2014
Ungraded
30 September 2015
Presentation Objectives
To raise awareness of the new PODDS modelling capability available in Synergi4.9
To show some potential practical examples of how this can be applied to real world problems
2
DNV GL © 2014
Ungraded
30 September 2015
Outline
Turbidity/PODDS overview
Running a turbidity analysis
Practical examples
– Site Re-Design Study
– Effectus 2015
– Trunk Main Conditioning
3
DNV GL © 2014
Ungraded
30 September 2015
PODDS Theory
Discolouration material is held in stable cohesive layers attached to the pipe walls of the systems and that these layers are conditioned by the daily hydraulic regime within the system
The cohesive layers have a defined profile of discolouration potential versus layer strength, with an increase in potential corresponding to a decrease in strength
The strength of the layers is dictated by the shear stress imposed within each pipe at the time of peak daily flow and hence peak daily flow controls the discolouration potential.
4
DNV GL © 2014
Ungraded
30 September 2015
PODDS Theory
The occurrence of disequilibria hydraulic conditions (burst, re-zoning, increased daily flow etc.) is considered to expose the layers to forces in excess of their conditioned cohesive strength and this leads to a mobilisation of the cohesive layers and results in a discolouration event.
5
DNV GL © 2014
Ungraded
30 September 2015
Turbidity Modelling in Synergi
Incorporated into the latest versions of Synergi Water
Two types of turbidity modelling
– Standard method
– Based on PODDS (Prediction Of Discolouration in Distribution Systems)
– Enhanced method
– Based on VCDM (Variable Condition Discolouration Model)
6
DNV GL © 2014
Ungraded
30 September 2015
Standard Model (based on PODDS)
The Standard method is based on the Prediction of Discoloration in Distribution Systems (PODDS) model developed at the University of Sheffield, and helps you model changes in turbidity due to erosion of material attached to pipe walls.
7
DNV GL © 2014
Ungraded
30 September 2015
Enhanced Method (based on VCDM)
The Enhanced method is based on VCDM (Variable Condition Discoloration Model), also developed at the University of Sheffield, and helps you model both erosion and regeneration of material attached to pipe walls, and can give you a better representation of observed turbidity behaviour.
8
DNV GL © 2014
Ungraded
30 September 2015
Process for Running a Turbidity Analysis
9
DNV GL © 2014
Ungraded
30 September 2015
Overview
10
Calibrated Hydraulic Model
Layer Condition Calibration
Event modelling
Prior-to-event Pressure and
Flow data
Event Pressure and Flow data
DNV GL © 2014
Ungraded
30 September 2015
Calibrated Hydraulic Model
11
Will work with any Synergi model
Ideally however, requires a more accurate calibration then a purely hydraulic model
– Calibration usually done using pressures and DMA inlet flow data
Accurate turbidity modelling requires accurate calculations of shear stresses
– Recommended that more flows be included in model calibration to get a more accurate representation of shear stresses and travel times (Boxall, Saul and Skipworth, 2004)
DNV GL © 2014
Ungraded
30 September 2015
Layer Condition Calibration
12
Now the model has been calibrated, the initial layer condition needs to be estimated
– For the standard method, this means estimating/calculating the initial shear strength
– For the enhanced method, this means estimating/calculating the initial shear band condition versus shear strength profiles
For this presentation, I will mostly focus on the standard method
DNV GL © 2014
Ungraded
30 September 2015
Layer Condition Calibration
13
Ensure model is running as in normal operating conditions
– i.e. no special events, bursts etc
– Nothing that will disturb cohesive layers attached to pipe walls
We can now use the peak daily flow from the model to represent initial conditions
– Involves running the model for an extended period, and retaining the shear strengths as new initial conditions for the model
This can now be saved as your PODDS conditioned model, ready for further analysis
DNV GL © 2014
Ungraded
30 September 2015
Layer Condition Calibration
1414
In the Conditioned Model;
Equals Peak Daily Shear
DNV GL © 2014
Ungraded
30 September 2015
Event Turbidity Modelling
15
Using the conditioned model, we can now see any increased turbidity responses for an events we model
– E.g Bursts, re-zones, new-connections, flow reversals etc.
Turbidity (measured in NTUs) becomes an attribute that can be viewed on any pipe in the model, at any time during the analysis period
DNV GL © 2014
Ungraded
30 September 2015
Practical Usage – Site Re-design Study
16
DNV GL © 2014
Ungraded
30 September 2015
Site Re-design Study
17
Site-specific study from early 2015
Due to increased demand over the last few years, low pressures were observed in a tower block
DNVGL were asked to investigate the area, and suggest potential improvements to the network
DNV GL © 2014
Ungraded
30 September 2015
Recommendations
18
Required pressures could be achieved by changing the metering and valvingconfiguration of the network as shown below
Valves opened
Valves closed
Meter relocated
Cross-connection installed and meter
relocated
DNV GL © 2014
Ungraded
30 September 2015
PODDS Analysis
19
The proposed changes were made and the model re-run to highlight the areas of the network likely to experience an increase in Shear Stress and therefore be potentially subject to discolouration.
DNV GL © 2014
Ungraded
30 September 2015
PODDS Analysis
20
The model shear stresses before any changes have been made
DNV GL © 2014
Ungraded
30 September 2015
PODDS Analysis
21
After the proposed changes have been modelled
Increased shear
DNV GL © 2014
Ungraded
30 September 2015
PODDS Analysis
22
Predicted turbidity response
DNV GL © 2014
Ungraded
30 September 2015
PODDS Analysis
23
It was recommended that robust flushing or mains conditioning of these sections was incorporated as part of the reconfiguration works.
Undertake over a period of several days to ensure the network is conditioned to the increasing flows gradually, in order to keep the turbidity response low
DNV GL © 2014
Ungraded
30 September 2015
Practical Usage - Effectus
24
DNV GL © 2014
Ungraded
30 September 2015
Effectus 2014
25
Systemised outage analysis of every modelled asset including; pipes, pumps, tanks, and sources
• Identifies areas affected by;
– Low pressure (DG2)
– Supply interruption (DG3)
– Discolouration potential (based on shear stress increases and flow/velocity changes
• Outputs Include;
– Pipes affected by DG2/3 and discolouration
– Number of customers affected in each case
– List of valves and pipes forming isolated section
– Valves proximity data & Drain-down time analysis
DNV GL © 2014
Ungraded
30 September 2015
Effectus 2014
26
DNV GL © 2014
Ungraded
30 September 2015
Effectus 2015
Now expanded to include
– DMA rezoning
– Open DMA boundary valves
– Hydrant flushing
– Simulate hydrant operation
– Burst main analysis
– Simulate a burst at each main
Every applicable analysis for Effectus 2015 will also include a PODDS turbidity simulation
The above analyses have been carried out on a test DMA model
27
DNV GL © 2014
Ungraded
30 September 2015
Effectus 2015 - Rezoning
Simulate DMA inlet failure
Trace all DMA boundary valves
Sequentially open valve meeting a certain criteria in turn on report on the consequences
Report on consequences (pressures, flows, turbidity etc.)
Identifies DMAs where the network flexibility exists to allow feasible rezones options
Identifies DMAs where no viable rezone exists. Risk of supply interruptions are unmitigated
Identifies discolouration risks associated with each viable rezone. Highlights excess shear pipes and the parts of the network likely to experience a turbidity response
28
DNV GL © 2014
Ungraded
30 September 201529
SummaryEffectus 2015 – Rezoning ExampleEffectus Analysis Process
DMA shear stress values at peak demand time
Inlet
DNV GL © 2014
Ungraded
30 September 201530
SummaryEffectus 2015 – Rezoning ExampleEffectus Analysis Process
Predicted turbidity response from conditioned model
DNV GL © 2014
Ungraded
30 September 201531
SummaryEffectus 2015 – Rezoning ExampleEffectus Analysis Process
Shear stresses with inlet closed, and valve opened to re-zone DMA
Inlet closed
Boundary valve opened
DNV GL © 2014
Ungraded
30 September 201532
SummaryEffectus 2015 – Rezoning ExampleEffectus Analysis Process
Predicted turbidity response from re-zone (maximum over 24 hours)
DNV GL © 2014
Ungraded
30 September 2015
Effectus 2015 – Hydrant Operation
Create a stand pipe element
Simulate each hydrant operation running through the stand pipe
Report on consequences (pressures, flows, turbidity etc.)
Identifies hydrants which do not achieve a predetermined set of flushing criteria
Identifies pipes associated with each hydrant operation that experience an increase in shear stress above an agreed threshold
33
DNV GL © 2014
Ungraded
30 September 201534
SummaryEffectus 2015 – Hydrant Operation ExampleEffectus Analysis Process
Max Shear = 0.00413
Max Shear = 0.2174Max Shear = 0.02526
Max Shear = 0.05821
DNV GL © 2014
Ungraded
30 September 201535
SummaryEffectus 2015 – Hydrant Operation ExampleEffectus Analysis Process
Max Shear = 0.06212
Max Shear = 0.68372
Max Shear = 0.36874
Max Shear = 0.18939Hydrant Flushed
DNV GL © 2014
Ungraded
30 September 201536
SummaryEffectus 2015 – Hydrant Operation ExampleEffectus Analysis Process
Max Turbidity Response
DNV GL © 2014
Ungraded
30 September 2015
Effectus 2015 – Burst
Analyse all mains in the network
Simulate a burst main
Report on consequences (pressures, flows, turbidity etc.)
37
DNV GL © 2014
Ungraded
30 September 201538
SummaryEffectus 2015 – Burst Main ExampleEffectus Analysis Process
DMA shear stress values at peak demand time
Inlet
DNV GL © 2014
Ungraded
30 September 201539
SummaryEffectus 2015 – Burst Main ExampleEffectus Analysis Process
Predicted turbidity response from conditioned model
DNV GL © 2014
Ungraded
30 September 201540
SummaryEffectus 2015 – Burst Main ExampleEffectus Analysis Process
Burst main simulated
Burst
DNV GL © 2014
Ungraded
30 September 2015
Summary
41
Effectus 2015 – Burst Main ExampleEffectus Analysis Process
Predicted turbidity response from conditioned model
DNV GL © 2014
Ungraded
30 September 2015
Practical Usage – Trunk Main Conditioning
42
DNV GL © 2014
Ungraded
30 September 201543
Trunk Main ConditioningEffectus Analysis Process
TM Contingency Planning
Sweetening Flow around 1-2 Ml/d
Emergency Demand Flows around 50 Ml/d
Required to maintain regional supplies during critical asset outage
DNV GL © 2014
Ungraded
30 September 201544
Trunk Main ConditioningProcess
TM Model Conditioned to turnover flow
Emergency demand applied and Turbidity response predicted
Turbidity at 12 NTU
DNV GL © 2014
Ungraded
30 September 201545
Trunk Main ConditioningEffectus Analysis Process
Incremental Increases of 1 Ml/d enabled STW to achieve the Emergency flow rate whilst keeping the turbidity response below 2 NTU
DNV GL © 2014
Ungraded
30 September 201546
Trunk Main ConditioningEffectus Analysis Process
Trunk main conditioned to 50Ml/d
Confidence that trunk main is in a state of readiness for any emergency flows
DNV GL © 2014
Ungraded
30 September 2015
Summary
Turbidity/PODDS now available in Synergi software
– Version 4.9 onwards
Easy to implement
– Only requires a calibrated model
– Minimal set up time
We plan to use this functionality more going forward in our work
47
DNV GL © 2014
Ungraded
30 September 2015
SAFER, SMARTER, GREENER
www.dnvgl.com
48
Mark [email protected]