Inertia: Why it is important for buried sewerage infrastructure and why concrete outperforms other pipeline materials.

Posted by & filed under Design.

Wikipedia defines inertia as the resistance of any physical object to any change in its state of motion (this includes changes to its speed, direction or state of rest). It is the tendency of objects to keep moving in a straight line at constant velocity. P08 Pipe Stabilitycropped copy

So, why is inertia important for buried sewerage structures? Without (lots of) inertia, pipes can become more easily dislodged from their intended position during and after installation.

  1. Most sewer pipes are jointed using a push-fit design where an elastomeric seal is compressed between the interlocking ends of two pipes being joined together. If the receiving pipe has low inertia and insufficient resistance to the jointing force applied from the pipe being laid, additional restraint may be required to hold the receiving pipe steady and to maintain the correct position while the pipe being laid is pushed home. This additional effort during installation can increase construction time and means that operatives are working in the trench for longer periods and can be subject to higher safety risk exposure.
  2. Backfilling and compaction. Pipe embedment should be placed and compacted evenly around the pipe to the correct specification. Unbalanced forces acting on each side of the pipe due to uneven backfilling and compaction can lead to a greater tendency for the displacement of pipes with low inertia.
  3. After installation, if the surrounding ground is subject to a high water table or if the ground is saturated, for example during a flood, pipes of low inertia are at greater risk of flotation. Take a look at the video below demonstrating a stunning failure of a corrugated steel culvert in Maine State, USA due to flotation during a flood. In known areas of flood risk or high groundwater levels, resistance to flotation can be designed into the installation for low inertia pipes, at extra cost and requiring a more complex, longer installation time.


Why does concrete outperform other pipeline materials?

Concrete is the Heavyweight Champion of the drainage world. The intrinsic self-weight of concrete provides high inertia to pipeline systems and a natural resistance to being moved out of position during jointing, backfilling, compaction and against flotation.

High inertia concrete pipes are the only sensible choice for a strong, stable, robust and durable wastewater pipeline system.

Comparative Flammability Demonstration in Drainage Pipes

Posted by & filed under Case Studies, Health & Safety.

Have you ever wondered the comparative flammability of different drainage pipes?

 

Polypropylene pipe, reinforced concrete pipe and high density polyethylene pipe. We look which drainage pipe will be crowned champion with this unedited test conducted in October, 2015!

Dry hay is ignited in three 18/18 in pipes and allowed to burn safely. What happens next? Which pipe will survive?!

For more information on concrete pipes please visit the CPSA website in the link to the left.

Structural Design of Buried Pipelines: The American Concrete Pipe Association are direct about being indirect!

Posted by & filed under Design.

In their 2014 Spring newsletter, the American Concrete Pipe Association (ACPA) decided there was the need to publish an abrupt and insightful article rejecting claims that the direct design method provided by the American Association of State Highway and Transportation Officials (AASHTO) should be used to design reinforced concrete pipes. This position may have been initiated by competitors from the HDPE pipe industry making claims that concrete pipes, designed with the indirect design method (also provided by AASHTO) would not sufficiently withstand the loads for which they had been designed. ACPA boldly stated within the article that there was no basis for these claims and that they were being used as a ploy to obscure the long-term proven history of the indirect design method with scare tactics with no technical justification.

The indirect design method is a proof of manufacturing method that has spanned two centuries and is simple to use. It uses a bedding factor which relates the governing moment applied to installed pipe with the moment on a concrete pipe that is tested using a three edge bearing test. The pipes are given strength classes according to the test loads they sustain. The pipes can then be specified for application using the strength class and bedding factors. Since the steel requirements of the pipe produced are dependent on the proof-of-manufacturing test, not directly designed by an engineer, this is called the indirect design method.

The direct design method is based on design coefficients utilising uniform pressure distributions along the sides, tops and bottoms of the pipe; not unlike the pressure distributions that were used for the bedding factors when the indirect method was initially developed. These pressure distributions were considered a rough approximation of the pressures induced on a pipe in its installed condition. The pressure distributions and resulting design coefficients could then be used to develop equations for the moments, shears and thrusts in the concrete pipe wall. Using these values, an engineer can then directly design the steel reinforcing required for the concrete pipe wall. Hence, the term ”direct design”.

The article then went on to inform that HDPE pipes are extremely installation sensitive, no such proof-of-performance test exists and that an extensive design method must be followed to analyse the capability of thermoplastic pipes; along with the post installation inspection program that must follow. It then also implored engineers to base design on sound engineering principles rather than be taken in by the fear tactics of an alternative industry trying to increase market share.

Strong words! It is satisfying to know that the UK use a similar method of design to the indirect design described above. Would you not agree that confidence is gained from using a pipe that has been routinely proven by test? The proven performance throughout the history of indirect design certainly gives assurance regarding design life. So much so that, as up to around 80% of the design strength is inherent within a concrete pipe itself, it can be used in many cases to allow users to choose from a range of bedding solutions requiring less granular embedment thus reducing installation cost, construction time and environmental impact. The use of sound engineering principles using the indirect design method certainly should be recommended.

Written by: Gareth Hughes, Chairman CPSA Technical Committee and Technical Manager at CPSA member company FPMcCann.

Thoughts on sewer jetting

Posted by & filed under Maintenance.

JettingCodePracticeOne of the most common forms of maintenance carried out on wastewater pipelines is high pressure water jetting; a process used to ensure that pipes run free of blockages and to remove accumulated material that would otherwise compromise the hydraulic performance of the system.

In the UK, sewer jetting is a widely used technique for clearing blocked pipelines with comparatively little routine preventive maintenance on sewer networks. As such, it is generally considered an emergency operation and there is a considerable burden on the operative to clear the blockage quickly.

Some pipe materials such as concrete and clay have a very high tolerance to the jetting pressures often required to remove blockages and some water companies already specify 4000psi minimum jetting resilience for sewers, so it would make sense for this to be consistently applied nationwide.

Some may argue that pipelines can be cleared at lower jetting pressures, but the risk remains that higher pressures may sometimes be used to clear stubborn blockages and in these situations some pipes of certain materials, such as thin walled plastic, are vulnerable and may become damaged.

When specifying a pipe with a high jetting resilience such as concrete, an indirect benefit of superior robustness, strength and durability can be achieved. Click here to download the Jetting Factsheet

Newsletter: Autumn 2015

Posted by & filed under eNewsletters & eBlasts.

 

Welcome to the Autumn 2015 issue of Pipelines

In this issue you will find lots of information on sustainable drainage systems (SuDS) including a compelling case study, blogs, reference sources, a Factsheet and a free CPD seminar. Surface water management is entering a new phase and CPSA members are well placed to offer advice and product solutions.

I hope you find this material useful.

Stuart Crisp, Director, CPSA

 

SuDS solution combining Concrete Proprietary Drainage Products with Soft Landscaped Drainage Features.

Susdrain.org has published an excellent case study demonstrating the intelligent combination of vegetated components with proprietary precast concrete SuDS systems to achieve a technically valid sustainable drainage system.

Click here to read more

 

We are a Susdrain Supporter

CPSA joined the impressive cross-sector group of organisations in 2014 dedicated to supporting the www.susdrain.org initiative, further demonstrating growing industry support for widespread delivery of Sustainable Drainage Systems (SuDS).

Over the next two years, it is anticipated that there will be a significant increase and improvement in the delivery of SuDS, with positive change driven by new guidance and the potential implementation of National Standards for Sustainable Drainage. susdrain will help support improvements in SuDS delivery through a range of initiatives including new resources, summaries of the latest guidance, case studies and a series of topical SuDS events.

CPSA is one of 29 organisations including Defra, the Environment Agency and other key industry players involved in the project from September 2014.

Since its launch in 2012, Susdrain has provided a valuable range of resources for those involved in delivering SuDS. Susdrain will continue to support drainage and highways engineers, planners, urban designers, landscape architects, land or housing developers, suppliers, flood risk managers, biodiversity / environment managers and the general public to increase knowledge and confidence in the delivery of SuDS.

 

CPSA Sustainable Drainage Solutions

The use of SuDS drainage systems best management practices should be an integral part of any development’s surface water management strategy. This should provide a basis for replicating the response of a catchment and its surfaces by mimicking, to some extent, the behaviour of surface water on the developed site as if it had remained undeveloped.

CPSA members offer a wide variety of proprietary SuDS components and systems suitable for use within a sustainable drainage system, many of which are listed in the download.

More news on pipeline bedding design

Posted by & filed under Design.

CPD_Certified_Construction_485_CMYKIf our Blog in March and eBlast in May plus social media postings escaped your attention and you haven’t seen our ads and editorial coverage running continuously in the trade press since March, here’s another chance for you to reduce your pipeline installation costs and embodied carbon.

CPSA has produced a new CPD seminar “Optimising Pipeline Bedding Design to Achieve Installed Cost & Carbon Efficiencies”.  The presentation brings CPSA’s total to four seminars independently accredited by the Construction CPD Certification Service and The Chartered Institution of Water and Environmental Management (CIWEM).

This new seminar demonstrates that substantial savings in pipeline installation costs and embodied carbon can be achieved through the effective use of structural design and the resulting selection of an appropriate pipeline embedment detail relevant to the pipe material and strength.

The seminar aims to provide the delegate with an awareness of the structural design fundamentals for buried pipelines and the main industry reference sources available.  The presentation should lead to an appreciation of the importance of combining structural integrity with minimum installation costs and lower embodied carbon and how this can be achieved through an understanding and effective use of structural design.

To arrange a free CPD seminar, please visit http://www.concretepipes.co.uk/page/cpsa-accredited-cpd-programme

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How to make your product’s carbon footprint look good

Posted by & filed under Sustainability.

Will there ever be an end to the relentless series of claims by product manufacturers that their product has superior carbon footprint credentials compared with competitors’, only to be followed by those same competitors claiming superiority based on yet another set of studies?

And how do specifiers decide who to believe?

By way of an example, the concrete pipeline industry is fighting its own battle with plastic. In 2010 CPSA published a detailed report based on the most comprehensive study of its type ever undertaken, providing embodied carbon footprints for precast concrete pipes, manhole rings and cover slabs. This study was then used to produce two further reports providing carbon footprint comparisons between concrete pipes and plastic pipes and between alternative manhole construction methods.

The pipe comparison study indicates that concrete pipes have up to 35% lower cradle-to-site embodied carbon when compared with HDPE pipe using the same full granular (Class S) bedding design. However, rigid concrete pipes can often be used with alternative bedding designs using less imported granular material, whereas standard stiffness plastic pipes will invariably require Class S. The result of which is that the potential carbon (and installed cost) saving with concrete pipes can be even higher.

After several years silence, the plastic pipe industry responded. Using the embodied carbon values for concrete pipes from the CPSA study, an alternative set of values were presented for plastic pipes. These values were based on a much older “generic” study using Bath University’s Inventory of Carbon and Energy, taking an average across a wide spectrum of products and geographical sources; unlike the CPSA study for precast concrete pipes, there was no new study based specifically on the manufacturer’s own plastic pipe products. And the comparison did not include impacts for alternative bedding designs.

Using this generic data, the results of the study indicated a lower carbon footprint for plastic pipes.

But is this riposte valid? Is it right to use data specific to a single product type (CPSA concrete pipe study) and compare it with generic data across a wide spectrum that does not represent the manufacturer’s own product? Different accounting methods will lead to different results. Does it make sense to make a comparison where the results were derived by separate methodologies with different rules and boundary conditions?

Almost all UK carbon databases and calculators use data for plastic pipes that trail back to data for resins from a study in 2005 by TNO for Plastics Europe. Recently, the integrity of this data has been questioned as the allocations to distillate products used in the Plastics Europe study do not appear to comply with the rules set out in the construction industry’s most recognised methodology, EN 15804. The Plastics Europe study assumes that the plastic pipe manufacturer is located 100km from the source of the resin. For a UK plastic pipe manufacturer, this is extremely unlikely. Resin supplied from further afield, such as the Middle East and Asia will significantly increase the carbon footprint of plastic pipes manufactured in the UK due to higher emissions from grid electricity plus emissions associated with transport.

Be aware. The plastic pipe industry has not embraced EN15804, the main Standard for carbon accounting in Europe for construction products. Instead, they have elected to follow an alternative route via Product Environmental Footprints (PEFs). Maybe the numbers work out more favourable for plastic using PEF rather than EN15804?

Concrete pipes Vs Plastic Pipes. Which has the lower carbon footprint? Whose claims do you believe?

Newsletter: Summer 2015

Posted by & filed under eNewsletters & eBlasts.

Welcome to the Summer 2015 issue of Pipelines

The popularity of precast manhole base systems is rising as users appreciate the many benefits they offer. However, there are still many installers, developers, specifiers and clients missing out.

If you are interested in reducing risk on site, cutting installation time and costs, improving quality and eliminating leakage and you are not using CPSA members’ precast manhole base systems, it’s time you took a closer look…

Stuart Crisp, Director, CPSA

Concrete manhole system, packed with many benefits that will satisfy designers, contractors and operators alike

Traditionally, manhole construction has required the base to be formed in-situ where building of the channel, connections and benching occurs in the trench, often in confined spaces that can present a safety hazard for operatives frequently encountering wet and unpleasant conditions.

The process can take around 40 hours per manhole to complete and is not always successful, particularly in terms of water-tightness, where egress of waste water can lead to contaminated groundwater and where ingress can contribute to overloaded sewer networks plus increased energy usage, carbon emissions and running costs at treatment works and pumping stations.

These issues can be avoided by using the new circular precast concrete manhole base systems available from all CPSA members. They comprise a circular precast concrete base unit, complete with channel and benching with predetermined / bespoke combinations of inlet(s) and outlet and new chamber rings with watertight flexible joints and no lifting holes, thereby removing points of possible leakage.

Base units and chamber rings are made with thicker, stronger walls. The robust design means that the requirement for a concrete surround is eliminated in most cases, considerably reducing the total volume of concrete required and resulting in up to 43% lower(*) embodied carbon for the installation. The excavation is backfilled sooner and there is less need for men to work in confined spaces. This reduces time spent in the excavation, further improving site safety and reducing installation time and costs.

(*)CPSA Manhole Systems Comparison Report

The manhole system the drainage industry has been waiting for

Precast Concrete Manhole Installation

Installation of the whole system is speedy and efficient. Take a look at CPSA members’ demonstration videos

CPMs Perfect Manhole Installation

Fast, Safe and Efficient Installation of FP McCann’s Easi Manhole Unit

Stanton Bonna The Perfect Manhole System

Enviromental Advantages

Less concrete is used, there is less waste and less excavated material disposed to landfill. An estimated UK annual saving of over 22,000 tonnes of CO2e could be achieved if all traditional manhole components manufactured by members of CPSA changed to the new precast base system.

All systems are manufactured under factory conditions by third party certified companies to ISO 9001 quality management system. Products are Kitemarked to BS EN 1917:2002 and BS 5911-3 and tested under laboratory conditions.

The precast manhole revolution: safer, higher quality, faster, cheaper – are you missing out?

Posted by & filed under Pipes & Manholes.

Traditionally, manhole construction has required the base to be formed in-situ where building of the channel, connections and benching occurs in the trench, often in confined spaces that can present a safety hazard for operatives frequently encountering wet and unpleasant conditions.

The process can take around 40 hours per manhole to complete and is not always successful, particularly in terms of water-tightness, where egress of waste water can lead to contaminated groundwater and where ingress can contribute to overloaded sewer networks plus increased energy usage, carbon emissions and running costs at treatment works and pumping stations.

These issues can be avoided by using the new circular precast concrete manhole base systems, which are available from all CPSA members. They comprise a circular precast concrete base unit, complete with channel and benching with predetermined/bespoke combinations of inlet(s) and outlet and new chamber rings with watertight flexible joints and no lifting holes, thereby removing points of possible leakage.

Base units and chamber rings are made with thicker, stronger walls. The robust design means that the requirement for a concrete surround is eliminated in most cases, considerably reducing the total volume of concrete required and resulting in up to 43% lower(*) embodied carbon for the installation. The excavation is backfilled sooner and there is less need for men to work in confined spaces. This reduces time spent in the excavation, further improving site safety and reducing installation time and costs

Benefits of the Precast Manhole
• Improved safety on site
• Reduced construction time; c50% (min 20%)
• Decreased installation cost; c30% (min 15%)
• Superior quality; factory made in a controlled environment
• Watertight; reduced leakage = reduced energy consumption, operational carbon emissions and running costs at treatment works and pumping stations
• Typically, no concrete backfill/surround required
• Reduced embodied carbon; up to 43% per manhole

(*) CPSA Manhole Systems Comparison Report

The Concrete Pipe Lifter: Safer, Easier, Faster, Cheaper

Posted by & filed under Construction, Health & Safety, Innovation.

The Concrete Pipe Lifter is a cost effective, simple-to-use system, which has been introduced to the UK by CPSA. It is a chance to improve safety, reduce costs and increase productivity.
The Concrete Pipe Lifter is a collaboration across all members of the CPSA who are working to reduce risks and to increase efficiency during deliveries, offloading and installation of sewer pipes in open cut trenches.

Concrete Pipe Lifters connect to an excavator via a quick hitch attachment and have no motorized parts making it easier to maintain. The lifting arm is inserted horizontally into the barrel of the pipe and raised to make contact with the internal crown of the pipe. The clamp arm will press down onto the top of the pipe at the socket end and hold it in position.

The concrete pipe is lifted without using slings or chains and without the need for an operative working at height on the bed of a lorry during offloading. The Pipe Lifter can be used to install the pipe with no-one in the trench and to push the pipe home to ensure formation of the correct joint gap.. The pipe may also be tilted up to 30 degrees from horizontal and manoeuvred between struts on trench support systems.

The Concrete Pipe Lifter is suitable for standard UK specification BS EN1916 concrete pipes from DN 300 to DN 1200 and the Type 2 lifter is designed for larger pipes DN1350 to DN2000.
Concrete Pipe Lifters make handling and installing concrete pipes safer, faster, easier and cheaper.

For more information and videos on The Concrete Pipe Lifter visit us today.