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Tanks, pipework, nozzles, tube fittings
News Release from: Applied Market Information | Subject: Pipes 07 conference
Edited by the Processingtalk Editorial
Team on 04 July 2007
Successful Plastic Pressure Pipes
conference
The Plastic Pressure Pipes 2007 conference was held in Dusseldorf from 25-27 June 2007 and attracted an audience from across the global industry supply chain
The conference featured delegates from the frozen northern countries and from hot climates in the south, which raised a lot of interesting points For example, the PE100 pipe standards stipulate an ambient temperature of 20C - this is not the normal operating temperature in countries such as India and Saudi Arabia
This article was originally published on Processingtalk on 4 Jul 2008 at 8.00am (UK)
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The speakers described the process of material selection - in most cases it is for historical reasons - the material that was first tried in that region of the world is still the material in use now.
Ted Striplin commented that attempts were being made to harmonise international pipe standards but that each country was very protective of their own test methods.
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HDPE pipes have been in use now for over 50 years, as demonstrated by Ulrich Schulte of Basell Polyolefine.
Basell provided pipe for shower blocks for a chemical factory in the 1960s and have been able to remove and analyse pipe samples.
The Markets for Plastic Pressure Pipes in Europe were outlined by Ewan Green (AMI): the principal materials for water pipes are PE (315 kt in 2006) and PVC (145 kt in 2006); PE dominates in the gas sector (134 kt in 2006).
PE100 is widely used - there are higher performance grades but there has not been a great deal of take up.
Molecularly orientated PVC has partly arrested the decline in PVC pipes - an initiative led by the pipe producers Uponor and Seperef.
Money is the limiting factor for market expansion in most areas of the world rather than the need to renew or establish pipes.
Margins are low in utility companies and public funding is limited from Moscow to Philadelphia.
Markets are expanding rapidly in the Middle East and Asia.
Miron Gorilovskiy (Polyplastic, Russia) described the PE pipe markets in Russia, Byelorussia and the Ukraine.
Around 60% of water pipes need replacing.
Overall in Russia there are 530 thousand km of water pipes, 366 of district heating and hot water, and 383 of underground gas pipes.
In the next 10 years he estimated that the need for PE pipes would total: 5070 kt in water, 2000 kt in sewage, 950 kt in district heating and 3110 in gas systems.
Kazanorgsintez and Lukoil-Neftekhim are the two main material suppliers in the region.
Polyplastic is estimated to have around 40% of the pipe production market.
Steven Cianfarini is the 'Dr Plastics' of the Philadelphia Gas Works.
With limited budgets his aim is to find cost-effective ways to replace ageing pipes.
PE has been used since the 1970s.
A typical Philadelphia block is 500 feet long and requires 50 services.
Electrofusion is the joining method for service and branch connections.
In 2007 yellow medium density PE 2406 is used for all mains up to 8 inches (20 cm) in diameter.
These pipes can be inserted in ageing cast iron mains without digging up the pavement and thus reducing costs.
He is considering 12 inch (30 cm) pipes in a test installation, probably of PE100 but the cost of the fittings is prohibitive.
Chicago has already installed some 18 inch (45 cm) plastic pipes.
PA 11 is being considered for higher pressure pipes (up to 150 psig).
Australia has been using PA 11 in gas pipes since the mid 1970s as described by Jim Mason (Arkema).
It has been in trials in the US since 1992 and 10 and 15 cm pipe has been developed and tested: to set up a trial a Department of Transport waiver has to be organised and a range of trial sites established.
It is currently awaiting US government approval to commercialise.
Polyamide 12 is being tested in North America for high pressure natural gas distribution by the Gas Technology Institute.
Richard Wolf (UBE Industries) gave details of the field trials.
It has higher maximum operating pressures than PA 11 (18 bar at SDR 11 at 20C, compared to 16 bar for PA 11).
In weathering testing there was no deterioration in tensile properties after 4320 hours in a xenon arc chamber.
Degussa has been running tests with Ruhrgas.
PA 12 is a candidate for replacing medium pressure ageing metal gas pipe.
Frans Scholten (Kiwa Gastec Technology) presented the results of lab experiments to test methane gas permeability of PE100, PE mixed with 10% polyamide, and PA 12.
Permeated gas can flow away from a pipeline and accumulate generating a flammable or explosive mixture.
This will be even more important when hydrogen is mixed with natural gas.
Under pressure the gas dissolves in the pipe wall and then diffuses out.
PA 12 was the most impermeable, and PE 100 failed at around 40 days (explosive levels of gas are reached outside the pipe).
Adding long chain PA greatly improved the barrier properties of PE100.
Whole life costing is important in pipe specification as discussed by Christoph Salles (Borealis).
This has been studied in large diameter mains with water companies in Europe.
Currently PE accounts for only 20% of mains in excess of 300 mm (12 inch).
Low sag grades have been developed for thick wall pipes.
PE has the smoothest surface to improve water flow; it is usually jointed above ground; it can often be installed by trenchless methods.
All of these factors reduce costs and make PE an attractive alternative.
Frank Schemm (Basell) described the benefits of polybutylene in pipes - it was discovered in the 1950s and first used in the mid 1960s in pressure pipe applications.
225 mm pipes are on the market and can be joined by a variety of methods.
It has very good flexibility, a property that has given it 90% market share in the shipbuilding markets and that makes it easy to install.
It is in use for water, geothermal pipelines, radiator connections, etc.
The global market size in 2007 is estimated at 300-350 thousand km.
Chlorinated PVC (PVC-C) is fire resistant and has good chemical resistance - properties that make it useful in the chemical industry.
Bob Newby (Lubrizol) looked at the benefits and compounding of this material.
It has a 30-year history of transporting hot, corrosive liquids and is suitable for acids, bases and aliphatic (but not aromatic) chemicals.
Tangentially (spiral) extruded PE100 pipes have a 40 year history as outlined by Stephan Fuellgrabe (Frank and Krah Wickelrohr).
The material has to be dried before processing and quality standards are kept high.
In this method pipes cool down slowly with laminar air flow resulting in lower internal stresses.
Multilayer structures have been developed and fibre reinforced solid pipes.
One application for very large diameter pipe was sea outlet pipes in New Zealand.
It has been challenging to build test rigs for these wide structures.
Marco Gulminelli (Sica SpA) showed an experimental method of jointing.
One HDPE pipe end is thermoenlarged using IR heating in a belling machine, forming a socket.
This requires improved bimodal PE100 to meet the standards.
PVC pipes can be joined by a variety of methods and the advantages and disadvantages were described by Joel Fumire (Solvin).
Solvin has carried out trials on double walled pipes where the outer layer is laser transparent allowing the laser to be used to weld the layers together.
Gluing is suitable for small diameters and limited pressures, but uneven for larger diameter pipes.
External fittings with rubber seals form fast connections and are water tight, but a full range is required and they are not resistant to pulling forces.
An external coupler is tensile resistant.
Butt welding takes a long time (over 45 minutes for 250 mm diameter).
Ted Striplin (McElroy Manufacturing) has looked at fusing PE pipes at higher interfacial pressures.
The theory is that higher pressure would expel more melted material from the joint interface and thus remove surface contaminants from the joint.
It also reduces cooling time considerably, allowing more joints to be made per day.
Long term performance is critical in utility applications.
Failure in PE pipes usually occurs due to slow crack growth.
Markus Haager of Agru Kunststoffetechnik has studied the link between slow crack growth resistance and the long term performance of electro fusion fittings (E-sockets and tapping saddles).
In tensile tests, fittings failed due to slow crack growth initiating at the end of the welding zone and material selection was critical for long-term integrity.
Ken Oliphant (Jana Laboratories) also looked at slow crack growth testing.
This has been accelerated by injection moulding samples to increase the internal stresses in work carried out with Ernest Lever of Central Plastics.
Pascale Godon (Ineos Polyolefins Europe) highlighted the benefits of new high stress crack PE100 materials.
During installation HDPE pipe is subject to surface scratching and point loading.
Pipes from the new material can be laid without a sand bed and using trenchless methods saving time and money.
Both water and gas compounds are available.
Total Petrochemicals has developed a low sag PE100 for thick wall pressure pipes.
This material resists flowing under gravity, which is important in retaining pipe structure after extrusion.
For UV exposure pipes must be protected using additives such as carbon black.
Steve Dougherty of Cabot Corporation outlined the properties of new specialty P-type carbon blacks.
Particle size and dispersion are critical.
The new grades disperse well; show low moisture absorption (trapped water can expand and cause blisters when welding plastic pipe); and are low in aromatics, sulphur (which affects organoleptic properties) and inorganics (a focus for stress cracking).
Johan De Witte (3M Belgium) looked at the advantages of adding fluoropolymer processing additives to reduce melt fracture and die lip build up when manufacturing HDPE pipe.
There are new developments in pipe production methods.
Rob Spekreijse of Rollepaal estimated that uptime is often as low as 60% which wastes money.
Issues with dies include thicker wall distribution 'giving away' material; centering is hard with large diameter pipes; colour changes can take a long time (24 h) and temperature rises can degrade the material.
They have developed a new RPD die to address these issues.
Crosslinked PE (PEX) is mainly used in small diameter pipes.
Josef Dobrowsky (Cincinnati Extrusion) described work to manufacture larger diameters.
The production line starts with gravimetric dosing and an extruder, via a Teflon coated die to an IR oven where the crosslinking takes place by peroxide curing.
If temperature is too high there is premature crosslinking, if it is too low there are visible flow lines in the pipe.
Traditional machines have an output of a few kg/h, the new machines are estimated to extrude at a much higher rate.
Daniel Lachhammer of KraussMaffei described an innovative reinforced thermoplastic pipe (RTP) production system.
This line has been sold into China.
Typically the inner pipe comprises PE100 to seal off fluids and support the tape.
In the middle is a wound tape layer (typically aramid, polyester, glass or carbon fibre) to carry axial loads and bear internal pressure.
The outer layer of PE80 protects against damage, weather and provides stiffness.
These pipes can withstand pressures up to 600 bar, giving an operating pressure of 200 bar (a 3-fold safety factor).
Delegates at Plastic Pressure Pipes 2007 enjoyed the international nature of the conference and the global business and technology opportunities.
AMI is organising further pipe conferences including Plastic Pipe Fittings and Joints from 10-12 December in Cologne, Germany.
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