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Avoiding Pressure Surge Damage in Pipeline Systems Presented by Geoffrey D Stone CP Eng FIE Aust.

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Presentation on theme: "Avoiding Pressure Surge Damage in Pipeline Systems Presented by Geoffrey D Stone CP Eng FIE Aust."— Presentation transcript:

1 Avoiding Pressure Surge Damage in Pipeline Systems Presented by Geoffrey D Stone CP Eng FIE Aust

2 Firstly Quantify the Problem  “In physical science the first essential step in the direction of learning any subject is to find principles of numerical reckoning and practicable methods for measuring some quality connected with it. I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind; it may be the beginning of knowledge, but you have scarcely in your thoughts advanced to the state of Science, whatever the matter may be."  Lord Kelvin [PLA, ]

3 Australian & International Codes & Standards  Pressure Vessel Code AS 1210  Arc Welded Steel Pipe AS 1579  Submarine Pipeline Code AS 1958  Installation of UPVC AS 2032  Installation of PEAS 2033  Buried Flexible Pipelines Design AS 2566  Gas & Liquid Pipeline CodeAS 2885  GRP Pipes for Water & Sewerage AS 3571  Installation of ABS Pipes AS 3690  Pressure Piping Code AS 4041  WSA 01 Polyethylene Pipeline Code  WSA 02 Sewerage Code of Australia  WSA 03 Water Supply Code  WSA 04 Sewage Pumping Stations  PIPA-OP010A:Part 1 Polyethylene Pressure Pipes Design for Dynamic Stresses  Power Piping ASME B31.1  Process Piping ASME B31.3  Pipeline Transportation Systems for Hydrocarbons and other Liquids ASME B31.4  Refrigeration and Heat Transfer Components ASME B31.5  Building Services Piping ASME B31.9  Slurry Transportation Piping Systems ASME B31.11  Glass-reinforced plastics (GRP) piping ISO  Design & Construction of GRP Pipes BS 7159  AWWA Fibreglass Pipe ANSI/AWWA C950

4 There are two categories of damage that arise from surge events  catastrophic failure of the pipeline system or equipment  fatigue failure of the pipeline, supports, instrumentation, equipment and components

5 Equipment and Processes Solutions  Stronger pipework to withstand the pressure surge  Rerouting piping  Change of pipe material to one with a lower modulus (i.e. thermoplastic pipe materials)  Flow control valves  Air/Vacuum Release valves  Intermediate check valves  Non slam check valves  Bypass Valves  Gas accumulators  Liquid accumulators  Surge tanks  Surge shafts  Surge anticipation valves  Relief valves  Bursting discs  Weak pipe sections  Increase diameter of pipeline to reduce average velocity  Variable speed drives  Soft starters  Valve closure and opening times  Increasing the inertia of pumps and motors (i.e. flywheels or by selection)  Minimising resonance hazards and increase reliability by additional supports  Investment in more engineering

6 Selection Process

7 Piping Design Using Stronger Pipe or Re-Routing the Pipeline Use of Stronger Pipework  Increase in capital costs for pipe, fittings, valves and instruments  Increase in velocity and celerity as wall thickness increases  Increase likelihood of fatigue damage and maintenance costs if surge events frequent  Pipe inherently maintenance free compared to other surge devices  Needs to be determined at design stage Re-Routing Pipeline  Increase in capital costs –Land or easement acquisition –Direction drilling –Increased length of pipeline  Hydraulic grade line above the pipeline profile reduces potential for cavitation  Possible increase in energy  Inherently maintenance free  Needs to be determined at design stage

8 Change of Pipe Material to One with a Lower Modulus (i.e. thermoplastic pipe materials)  Capital cost neutral  Not a universal solution because of limited pressure classes available  Thermoplastic pipe materials properties vary with temperature, strain rate and time  Does not protect when column separation occurs  Wall thickness selection to allow for vacuum conditions  Local buckling at above ground supports to be designed  Needs to be determined at design stage

9 Flow Control Valves  Moderate capital cost  Increased maintenance to ensure they remain effective  Can be used for multiple duties and scenarios  Power or instrumentation not necessarily required  Can be retrofitted

10 Air/Vacuum Release Valves  Increased capital costs  Increased maintenance to ensure effective operation  Use requires extensive modelling to ensure operation in all scenarios  Not suitable for hazardous liquids  Primary duty is for line filling and draining and hence location may not be optimal for surge mitigation  Not all air valves are suitable for this purpose due to their original design  Valve pit may be in road causing problems during construction or maintenance  Can be retro fitted easily if reducing tees in pipeline already installed otherwise tee type couplings required to be fitted

11 Modern Design of Air / Vacuum Release Valve-Ventomat

12 Intermediate Check Valves  Increase in capital costs for check valve but reduction in rating of other pipeline components  Effective in splitting the surge pressure rise in two  Degree of increase in maintenance minimal  Protects pumps from highest peak pressure  Non slam check valves preferred  Valve pit may be in road way causing traffic problems during construction or maintenance  Check valves are not considered an adequate form of isolation and hence should be installed with isolation valves  Needs to be determined at design stage otherwise pipeline needs to be out of service for retrofitting check valve

13 Non Slam Check Valve  Capital cost increase  Fast closing valve reduces surge pressure at pump  Reduces fatigue damage  Increase in maintenance low  Inherently trouble free  Available as short or long pattern  Used extensively in Europe  Can be retrofitted as valves standard lengths

14 Comparison of Check Valve Performance

15 Noreva Annulus Type Non Slam Check Valves

16 Bypass Check Valves  Increase capital cost  Increase maintenance to ensure effective operation  Needs positive pressure upstream to provide energy to fill cavitation voids  Simple and effective for overcoming negative pressures  Does not provide protection for positive pressures  Can be readily retrofitted

17 Bladder Type Gas Accumulator  Increased capitol costs  Maintenance level low for bladder type  Provides secure protection for positive and negative surge pressures  Best located at source of pressure transient event  Overseas design and manufacture  Can be retrofitted  Long lead time

18 Hydro-Pneumatic Accumulator  Increased capital costs  Maintenance level high for hydro pneumatic type  Best located at source of pressure transient event  Provides secure protection for positive and negative surge pressures  Local design and manufacture  Can be retrofitted if branched tees fitted to pipework  Long lead time

19 Liquid accumulators  Increase capital cost  Difficult to model without test data  Inherently maintenance free  Can be retrofitted but generally a long lead time

20 Surge Tanks and Surge Shafts  Commonly used in water transmission systems  Provides protection from negative pressure events but NOT for positive pressures  Inherently maintenance free except for refilling facility of surge tank  Telemetry required for monitoring  Can be retrofitted but generally a long lead time required

21 Surge Anticipation Valves  Moderate capital cost  Complex devices  Require power in the form of electric, hydraulic or pneumatic to operate  Do not cover all surge events in a pipeline systems  High maintenance to ensure that they work when needed  Vendors who perform surge analysis and recommendation are NOT necessarily design engineers and do NOT take responsibility. Often do not have latest, or have limited capability, software.  Can be retrofitted however moderate lead times

22 Relief Valves and Bursting Discs  Increase in capital cost  Conventional devices do not react quickly enough to prevent damage from surge pressure  Do not protect against vacuum conditions  High level of maintenance  Bursting discs require replacement after operation  Need for registration and routine testing per Code  Suitable for lethal and flammable liquids as part of an overall protection strategy  Can be retrofitted however may be moderate lead times

23 Weak Pipe Sections  Capital cost neutral  Reduces celerity in sensitive sections  Reduced surge pressure magnitude  Reduced fatigue damage  Could be damaged by vacuum conditions  Suitable for low pressure systems in the water industry  Inherently maintenance free  Not a universal solution  Needs to be determined at design stage

24 Increase Diameter of Pipeline to Reduce Average Velocity  Reduced celerity and surge pressure  Increase in capital cost of pipe, excavation, valves and instruments  Increased life of the asset  Future augmentation possible  Inherently maintenance free  Reduction in energy of pumping  Settling of solids more likely  Needs to be determined at design stage

25 Variable Speed Drives and Soft Starters  Increase in capital costs and complexity  Low level of maintenance  Increased frequency of replacement and upgrade  Provides NO protection for loss of power scenarios  Soft starters protect power supply more than pipeline; there are NO guarantees they can be set to limit surge pressures  Reduced fatigue issues for normal stop/start  Larger switchroom required to house devices  Needs to be determined at design stage as costly to retrofit and to house in a switchroom

26 Valve Closure and Opening Times  Low capital cost solution  Can be effective in reducing surge pressures  Requires power supply in the form of hydraulic, pneumatic or electrical energy to be totally reliable  Needs uninterruptible power supply for secure operation  Requires extensive modelling to cover all operational scenarios  Requires routine testing to be effective  Can be modified during commissioning or operation if valves are automated and fitted with adjustable opening/closing devices

27 Increasing the Inertia of Pumps and Motors  Modest increase in capital cost  Flywheels increase moment of inertia  Four pole speed motors and pumps have larger moment of inertia and have other benefits over two pole motor driven pumps  Physically larger pump sets and hence buildings may be increased in size  Inherently a low maintenance solution  Needs to be determined at design stage

28 Minimising Resonance Hazards and Increase Stiffness by Additional Supports Minimise Resonance  Increased capital costs  Increased engineering to determine dynamic behaviour of piping  Reduces damage arising from dynamic loading and vibration  Can be retrofitted quickly Improved Stiffness  Increase in capital costs  Reduction in peak pressure due to reduced celerity  Acceptance of high fatigue damage causing increase in maintenance costs  More secure piping system  Inherently maintenance free  Can be readily retrofitted

29 Investment in More Engineering

30 But just a word from Lord Kelvin to temper the quest for an answer: “Large increases in cost with questionable increases in performance can be tolerated only in race horses and fancy women.“ Therefore your investment should be in engineering oooooo-The End - oooooo

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