About Iplex PocketENGINEER™
Iplex PocketENGINEER™ is a web based portal through which registered users may access free of charge, a suite of reference data and engineering tools relevant to the design of plastics pipelines. The portal was launched by Iplex Pipelines (Australia) Pty Ltd in 2015, with a Flexible Pipe Deflection Tool and Chemical Resistance library and has since expanded to include a library of Plastics Pipe Industry of Australia Technical (POP) Guidelines and a Flange Bolt Torque Calculator. It is intended that the suite will expand to include Polyethylene 3-Point Pressure Decay Test, Hydraulic Friction Loss and Curved Alignment Offset Calculators during 2016. Other tools will follow as demand dictates.
PocketENGINEER™ Flexible Pipe Deflection Tool
The structural design of buried flexible pipe installations in Australia is covered by Australian and New Zealand Standard AS/NZ 2566.1:1998. This Standard, along with a number of other foreign national Standards, uses a mathematical approach based on the Spangler formula to model the behaviour of a pipe with inputs including ring stiffness, depth, pipe material modulus and creep, soil modulus, traffic and other applied loads which aim to predict the pipe’s response and determine long term deflection, strain and risk of buckling. In 1996 The European Plastics Pipe and Fittings Association (TEPPFA) and the Association of Plastics Manufacturers in Europe (APME), in an effort to validate the predicted outcomes of these methods against actual results, invested several million Euro in an expert monitored and reviewed research project looking at the actual performance of flexible non-pressure pipes under various installation conditions. The project concluded that in spite of pretence of accuracy, none of the mathematical design approaches could consistently predict pipe deflection. Further, it determined that ring stiffness, viscoelastic creep, traffic loads and the presence of groundwater all had a minor impact on the pipe installation. The factor of greatest influence was the quality of the installation, specifically the type of embedment material and the degree to which it was compacted under and around the pipe. Based on the actual observed results, a graphical table was produced by TEPPFA to enable designers to easily predict average and maximum immediate deflection of pipes installed under a range of conditions that covered the majority of installation conditions. A consolidation value, based on the standard of installation and embedment type, could then be added to deflection to provide long-term average and maximum deflection estimates. Over the past two decades, this research has been well scrutinised, peer reviewed and accepted to the point where the TEPPFA graphical table and consolidation values are referenced in the latest European Standards for flexible pipe design - CEN/TS 15223:2008 Plastics piping systems - Validated design parameters of buried thermoplastics piping systems and ISO 21138-1:2007 Annex C - Structural Design. The predictions produced by the Iplex PocketENGINEER™ Flexible Pipe Deflection Tool mirror the TEPPFA graphical table and consolidation values. Whilst this approach is applicable in the majority of flexible pipe installation cases, it has not been validated for every possible condition. The conditions under which PocketENGINEER™ ’s deflection predictions have been validated are:
- Pipe Stiffness >2kN/m2 (SN2)
- Depth of cover 0.8m to 6.0m
- Traffic load all cases
- Ground water all cases
- Pipe diameter <DN1100
- Soil types granular to cohesive
- Depth of Cover : Diameter ratio >2
- Installation conditions: Well Compacted, Moderately Compacted and No Compaction
Where a particular installation condition cannot comply with the above criteria, i.e. the conditions for which the CEN/TS 15223:2008 method was validated, an alternate method of structural assessment based on AS/NZS 2566.1 or other recognised design methodology should be utilised.
Flexible Pipe Deflection Tool User Guidance Notes
- Application – “Pressure” versus “Drainage”
Selecting “Pressure” or “Drainage” toggles between ranges of pressure and non-pressure pipes. In instances where pressure pipe is selected, PN rating is used to define pipe class and for drainage pipe, SN rating is used except for polyethylene pipe, which is defined by SDR for drainage applications. Only pipes with a stiffness >2kN/m2 (SN2) have been validated using the TEPPFA research project findings. When the selected pipe possesses a stiffness >16kN/m2, the App returns values based on 16kN/m2 validated results. In instances where “Pressure” is selected, the App considers a potential 80kPa negative pressure situation occurring due to transient surge, to determine the pipe’s risk of buckling. This negative pressure allowance is removed when the “Airvalves” option is selected.
- Minimum Trench Width
The App stipulates a minimum trench width based on 2 x the selected pipe OD. Other widths greater than 2 x OD may be more appropriate, however validation of PocketENGINEER™ is based on a minimum of 2 x OD.
The App provides the option to select “Airvalves” only when “Pressure” application is selected. Appropriately selected and positioned airvalves will avoid or minimise pipe damage resulting from water hammer and surge conditions due to uncontrolled pump shutdown or rapid closure of valves. Airvalves will minimise the risk of pipes buckling or collapsing due to the effects of topography by permitting air to enter the pipeline during shutdown. Expert advice should be sought on the type and location of airvalves for each application.
- Pipe Material ?
Selecting the “Pipe Material ?” button will open a web browser window of in the Technical Library section of Iplex’s website at the page introducing the pipe type currently selected in the App.
- Bedding and Side Fill Compaction
This criteria has the greatest single impact on the performance of a buried flexible pipe and should be given serious consideration and monitored closely during any subsequent installation.
- “Well with granular embedment” is defined as: Free flowing granular embedment shall be carefully placed in the haunch zone and compacted, then followed by compacted shifts of maximum 30cm depth. The pipe crown shall be covered by 15cm with granular embedment before the trench is filled with native soil and compacted. (Compact granular embedment to achieve at least 70% Density Index.)
- “Moderate with granular embedment” is defined as: Free flowing granular embedment shall be placed in shifts of maximum 30cm depth. The pipe crown shall be covered by 15cm with granular embedment before the trench is filled with native soil and compacted. (Compact granular embedment to at least 60% Density Index.)
- NOTE: In instances where sheet piles or boxes are used to stabilise the trench they must be lifted prior to the compaction, otherwise the installation is to be considered as a “None” condition.
- “None with granular embedment” is defined as: Free flowing granular embedment is placed without compaction, large lumps of dry clay or rock are not permitted to contact the pipe directly. (Free compaction of approximately 50% Density Index is anticipated.)
- “None with cohesive embedment” is defined as: Embedment soil of any type is added without compaction. Large lumps of dry clay or rock are not permitted to contact the pipe directly. (Compaction rates typically 85% Dry Density Ratio are anticipated in cohesive materials.)
- Selecting either of the “None”, i.e. uncompacted installation conditions, in conjunction with pipe stiffness <4kN/m2 will cause the App to return an error message indicating unsuitable bedding and sidefill compaction has been selected.
- Depth of Cover
The validation research conducted by TEPPFA used cover depth ranging from 0.8 to 6.0 metres. The default depth of cover offered by the App is 0.8m. Additionally, a depth of cover : diameter ratio of ≥2 is stipulated. In situations where the selected depth of cover >0.8m but < 2 x OD, the App will return an error message indicating the pipe is too shallow. The TEPPFA research determined that depth of cover up to 6.0m had negligible effect on the deflection of a buried flexible pipe.
- Height of Ground Water
Where ground water above the pipe is selected, the App calculates the pressure exerted on the pipe in its maximum deflected condition to determine the risk of ring buckling. If the pipe is a pressure pipe without airvalves, 80kPa is added to the ground water pressure. If the critical buckling pressure of the deflected pipe is <2.5 x the combined pressure of water and negative surge pressure, then the App with return an error message indicating an unsafe ring buckling condition exists. If ground water height greater than depth of cover is selected, the App will return an error message requesting a check of the input ground water height.
The TEPPFA research project determined that with depths of cover in the range of 0.8m to 6.0m the effect of traffic loads on the final pipe deflection was negligible. Where heavy traffic was present the consolidation of trench fill that was responsible for the transition from short to long term deflection was beneficially reached in less time than installations without traffic. Selecting “Traffic” simply applies a graphic representation of vehicular traffic to the App’s output results.
Selecting the “Back” button allows users to revert to earlier stages within the App to make changes. This feature is particularly useful if an unsatisfactory installation condition (error message) is realised or to change pipe type or class.
- Generate PDF
- Send Email
The “Send Email” button provides users of PocketENGINEER™ with the option to email the single page summary PDF and is especially useful when accessing the App with a smart phone or tablet.
PocketENGINEER™ Flange Bolt Torque Calculator
Flanged joints are commonly used to connect polyethylene (PE) pipelines to valves, pumps and pipes of different material. A flanged PE pipe joint is an engineered assembly consisting of several components, likely to have been manufactured by a variety of companies and from varying plastic and non-plastic materials. The assembled joint must be able to transfer long-term axial forces whilst maintaining essential gasket sealing stress and this requires the use of suitable components, a correct assembly procedure and an appropriate flange bolt force.
The PocketENGINEER™ Flange Bolt Torque Calculator will estimate a bolt torque suitable to develop the required gasket sealing stress, based on user input conditions, configurations and component dimensions. To ensure meaningful torque values are calculated, it is important that accurate flange and gasket dimensions are entered. This information can generally be found in the applicable flange Standard or from the individual component manufacturers. The estimated torque values do not compensate for temperatures >20° Celsius, applied bending forces, transient pressure surges above the selected maximum operating pressure or other site specific conditions.The output results are not warranted by Iplex Pipelines (Australia) Pty Ltd and for critical applications the advice of a suitably qualified consulting engineer shall be sought.
It is essential that bolt tensioning is achieved by using an appropriate procedure such as that detailed in WSA 109-2011 Appendix E.
The viscoelastic properties of PE will result in compressive creeping of the flange faces that will somewhat reduce the initially developed gasket sealing stress. The greater the initial stress developed, the more creep will result. In the case of stub flanges, there is an additional risk that due to the relatively small bearing surface area between the backing ring and the flange’s shoulder, excessive bolt force will cause compressive yielding. This will be manifest as an apparent loosening of the bolts, so it is essential the nominated bolt loads are not exceeded.
For this reason, the Flange Bolt Torque Calculator does not permit the combination of relatively high sealing stress compressed fibre (CNAF) gaskets and PE Stub End Adaptors. To compensate for the initial PE viscoelastic creep, bolts must be re-tensioned to the estimated torque 24 to 48 hours after initial tensioning.
Furthermore, as it is essential that the bolting force is evenly and accurately applied to the PE flanges via flat steel backing rings with sufficent thickness to avoid cupping. Tensioning of flange bolts to the nominated torque must be achieved utilising a suitable calibrated torque device and selected lubricant shall be applied to all thread and nut contact surfaces prior to tensioning.
In applications where the Maximum Allowable Operating Pressure is up to 16 bar, EDPD or nitrile rubber gaskets are the preferred option, however above that operating pressure the application will default to CNAF gaskets.
The selection of bolt quantity, size and grade is a user input and will ordinarily be determined by reference to a relevant flange product Standard. (For example AS 2129, AS/NZS 4087, ISO 9624 or ANSI B16.5) Provided the correct information is entered by the user, generally where EPDM or nitrile rubber gaskets are selected, grade 4.6 bolts will be adequate. In the case of CNAF gaskets, in most instances it will be necessary to select grade 8.8 bolts.
Once all variables are entered, the application will estimate the necessary gasket sealing stress and allow users to produce a summary sheet in PDF format that details:
- A generic drawing of joint assembly with dimensions
- Maximum allowable test pressure
- Target gasket stress and selected material type
- Number, size and grade of bolts
- Percentage of bolt yield stress
- Type of bolt lubrication
- Estimated bolt torque
You should read the following terms and conditions before using the Iplex PocketENGINEER™ application. Your use of the application is governed by the following terms and conditions. By using the application you agree to comply with, and be bound by, these terms and conditions and assume all risks associated with the use of the application.
- Iplex accepts no responsibility for the completeness or accuracy of the content of the application and makes no representation about its suitability for any particular buried flexible pipe installation.
- Whilst Iplex makes every effort to ensure that the content of the applications is accurate, it does not represent or warrant their accuracy, adequacy or completeness. The content of the applications are only intended as a basic guide to determining predicted deflection of buried flexible pipe and estimating flange bolt torque based on user inputs and do not address the complexities of the particular circumstances of each installation. You should obtain advice from professional engineer specific to your particular circumstances before relying on the deflection estimates and flange bolt torques predicted by the applications or using or purchasing any pipe product offered by Iplex.
- The deflection predictions produced by the application are based on Technical Specification CEN/TS 15223:2008 Plastics piping systems - Validated design parameters of buried thermoplastics piping systems. In critical installations, users of the application shall refer to CEN/TS 15223:2008 to determine the limitations and suitability of this design methodology.
- To the extent permitted by law, Iplex and its directors, officers, employees and consultants exclude all liability for loss or damage whatsoever arising from the use of, or reliance on, the applications or the content of the applications, including damages for loss of profit, lost revenue or loss of opportunity, business interruption, corruption or loss of data and whether or not caused by any negligence on the part of Iplex or its directors, officers, employees and consultants.
Except as permitted under applicable laws, no part of the application may be reproduced, adapted, distributed, displayed, transmitted or otherwise exploited for any commercial purpose without the express written consent of Iplex. You may imprint, copy, download or temporarily store extracts from the applications for your information in relation to Iplex’s flexible pipe products.
These terms and conditions are governed by the laws in force in New South Wales, Australia and any dispute about these terms or the content of the application are subject to the exclusive jurisdiction of the courts of New South Wales and the Courts of appeal from them.