Plastic Pipes Conference Association # 1985 York
Alferink, Blom, Venema, Wolters
Joints in PE casings of district heating pipelines are made by extrusion welding, butt welding or sleeves in which sealing is obtained by an adhesive. To set up guidelines for making these joints a lot of research has been performed, part of which is described in this paper.
Joints of a good quality are obtained if extrusion and butt welding are performed under the prescribed conditions using good equipment. In some tests in which the effects of soil conditions on the joint are simulated, welded joints proved to be better than joints containing an adhesive.
District heating is a system by which the required heat for room heating and hot the generation of electrical energy, industrial processes, incineration of domestic waste, and central combustion of fuels. The heat is usually transported and distributed in steel carrier pipes at temperatures between 100 and 140 “Cc and pressures of 10-16 bar. To avoid excessive heat losses this steel pipe must be insulated. There are several ways to install the system either above ground or underground. In the Netherlands normally underground systems are used.
To ensure reliable distribution with a buried pipe system attention should be paid to protection of the insulation against mechanical damage and water ingress. This is often done by means of a PE casing pipe. In most of the systems polyurethane rigid foam (insulation) bonded to a PE casing pipe is used. The system is built up of prefabricated pipe lengths of 6, 12 or 16 metres each, and fittings like bends and branches.
For the straight pipe lengths an uninterrupted casing is used. But for the fittings the casing is mostly composed of several parts (segments) jointed by butt welding prefabricated in the factory.
To connect the prefabricated pipe sections and fittings steel welds are used for the carrier pipes, while the outer casing pipes are often jointed by means of sleeves and tightened by welding or using an adhesive.
By direct burial of the bonded steel - PUR - PE system, the soil friction is used to reduce the thermal expansion of the pipe system. Small parts of the system still move in the ground. To withstand these movements jointed casing pipes shall have sufficient strength to resist axial movements and water pressure.
To obtain a watertight and strong PE joint, butt welding is normally used for fittings while extrusion welding is used for the connection of the prefabricated parts.
This paper reports on research carried out to define the conditions by which acceptable butt welds in fittings and extrusion welds in joints are obtained.
In extrusion welding a distinction is made between fillet welds using a sleeve and V-shaped groove welds (Fig. 1).
The aim of the investigations performed was to set up a standardized procedure for making butt welds in fittings and extrusion welds in joints.
Related papers
Author(s) : Anders Andtbacka, Frans Alferink, Peter Sejersen
The behavior of buried plastic pipes is already well described in standards and technical specifications and as well as proven in real life conditions. Plastics pipes in diameters up to around 400 mm are already in use for more than 60 years and pipes with larger diameters for more than 20 years now. All with good...
Author(s) : Frans Alferink
PVC pipes for buried applications for water, sewer and gas, has developed an excellent track record. PVC is very inert, has a high resistance against permeation of soil contaminations and gas components and meanwhile has a long proven lifetime. Next to that, the lifecycle costs of buried PVC pipe systems are amongst...
Author(s) : André Nijland, Frans Alferink
PVC-U is used around the globe for potable water supply and sewer applications. This is due to its strength and stiffness as well as to its excellent flow properties. PVC-U shows an excellent performance in protecting the potable water quality. And it is registered that failure rates of PVCU pipelines are very low....
Author(s) : Emiel Drenth, Ton Bor, Roy Visser and Mannes Wolters
Various non-destructive methods, based on different physical principles, were investigated for their ability to differentiate between uPVC pipes having various levels of gelation. It was found that the micro-hardness method was not able to differentiate between uPVC samples of different levels of gelation. A possible...
Author(s) : Frans Alferink and Jos Oosterik
PVC-O pipes were already introduced in the mid-seventies, but why did it take until the beginning of this century before this high quality pipe product really expanded successfully into the water markets? The second part of this paper will present an answer to that question. Feedback from various pipe markets around...
Author(s) : Frans Scholten and Mannes Wolters
PA11, PA12 and plasticized PA6.12 pipes are interesting candidates for gas transport and distribution pipelines at 16 bars pressure, which is beyond the maximum pressure for PE100 pipeline systems (10 bars). However, PA pipelines are not meant as an alternative to PE pipelines, but to steel pipelines. Therefore,...
Author(s) : Wolters, Wikkerink
The use of plastic pipeline materials in gas distribution systems is still increasing. Presently PE and high impact PVC are the dominating materials in gas distribution networks up to 4 bar. Most of these networks operate at these pressures, only a limited part of the network operates at higher pressures, up to 10 to...
Author(s) : Alferink
Plastics pipes products are more and more appreciated in sewer schemes throughout the world. The advantages of thermoplastics, like the good resistance against sewer environments and the possibility to built complete tight systems are many times the drivers to use thermoplastic pipes and chambers. Plastics chambers...
Author(s) : Janson, Alferink, Wolters
This paper presents the results of work that was performed at the request of TEPPFA , The European Plastics Pipes and Fittings Association, on the issue of “Combined loading” (external and internal loading) of buried thermoplastics pressure pipes. The work is of great importance for users and designers of...
Author(s) : Meijering, Wolters, Hermkens
One of the options for a low-pressure gas distribution system is the use of ductile PVC pipes and joints. The long-term performance of ductile PVC pipes has been reported in a number of previous studies. In this paper the long-term performance of the socket joints, in which elastomeric (NBR) sealing rings are used, is...
Author(s) : Alferink
When starting with the application of buried thermoplastics pipes in the fifties, Wavin started to gain a lot of experimental experience with these pipes, which later formed a solid base for the correct application of thermoplastics pipes. In analogy, a lot of experimental experience is gained now with buried manholes...
Author(s) : Alferink
Two papers dealing with the intermediate results of the TEPPFA / APME project on design of thermoplastics pipes has been published at the 10th Plastics Pipes Conference in Gothenburg in 1998 by Alferink et al.1, 2 Meanwhile the study has been almost completed and the results discussed with several experts. Pipe...
Author(s) : Alferink, Janson, Olliff
Extensive field trials are being performed in a project sponsored by TEPPFA and APME,to obtain well documented information about the behaviour of buried thermoplastics pipes. as outlined in the paper by Alferink, Bjorklund and Kallioinen (Ref 1). This information is of vital importance to obtain a workable design...
Author(s) : Wikkerink, Wolters, van den Berg, Huppes
Environmental aspects tend to be increasingly important in designing gas distribution systems and in selecting gas distribution materials. Therefore the environmental aspects of various materials options for gas distribution networks were analyzed by means of a quantitative life cycle assessment. This paper describes...
Author(s) : Wolters
In the Netherlands, rigid PVC and impact-modified PVC pipes have been used in gas distribution systems for dozens of years. In general, these pipes have performed excellently. Some years ago, however. questions were raised about the resistance of these materials to certain gas constituents. An extensive research...
Author(s) : Alferink, Bjoerklund, Kallioinen
Over the last 15 years several attempts have been undertaken to establish a design method for plastics pipes (IS0 TC138 WG13) and over the last ten years to establish an unified design method for all buried pipes (CEN TC1641165 JWGI). Several national methods are available and it is shown over the last ten years that...
Author(s) : Scholten, Wolters
An investigation has been carried out into butt welding and electrofusion welding of PEX pipes, which had been crosslinked using the peroxide, silane and electron beam processes (PEXa, PEXb and PEXc respectively). A new hypothesis was set-up to explain the good weld quality of PEXa pipes electrowelded with regular...
Author(s) : Alferink, Guldback, Grootook
Wavin gained a lot of experience with operational PVC sewer pipes by monitoring installations and measuring pipe deflections over a period of about 35 years, as reflected in the database "PiPer". Some of the oldest pipes have been measured and dug up now to study the durability of these pipes. Furthermore the results...
Author(s) : Alferink, Wolters
Results of deformation measurements carried out on buried plastics pipes installed at six different tests sites are discussed in this paper. The results show that the deflection of buried pipes is usually rather small and the time dependence is limited to a few years after installation. Traffic loading does not result...
Author(s) : Rijpkema, Wolters
In the Netherlands about 20,000 km of uPVC (unplasticized PolyVinylChloride) gas pipes are in use. The oldest uPVC pipes have been in operation for over 30 years now. These systems were usually designed for a period of between 30 and 50 years. Probably, however, the actual service life will turn out to be much...
Members of the Association
