INDUSTRIAL KAZAKHSTAN

GUIDE TO MARKET TECHNOLOGIES AND EQUIPMENT No. 6 (102) June 2014 Did you know that ...

Polyethylene pipes and their use for large diameter pipes opens up new possibilities in the construction of pipelines? Traditionally, large diameter pipes are considered as polyethylene pipes with diameter 500-1200 mm. The main application areas of such pipes are storm water and sewer lines, water supply lines and drainage. Market share occupied by polyethylene pipes is quite significant and is very fast growing. According to research, the growth of consumption of large diameter polyethylene pipes in U.S. is expected to reach 4.7% per year and will reach 12.4 thousand km in 2007. PE share will be more than 20% of consumption of large diameter pipes, for which they’ll spent about 440 thousand tons of raw materials.

Increase of polyethylene pipe rate will primarily occur upon construction of new or reconstruction of old or old- fashioned water lines and sewage systems, especially under specific conditions of big cities, broad streets and highways. Concrete pipes still retain their leading position for underground applications. However, polyethylene pipes are going to be serious competitors, due to such benefits as better performance characteristics, faster and easier installation if compared with pipes made of other materials. Good opportunities for utilizing pressure polyethylene pipes in water supply and sewage systems are determined by wear out of current systems and increasing number of such problems as leaks, breaks, ex-filtration, i.e. diffuse penetration of external water in drinking water supply systems because of corrosion and low stability of existing systems to pressure jumps.

Having some perforation damages in walls of discharge pipe or at its connections the water will leak. Therewith, this leaking water dilutes soil around the pipe, which results in soil caving in, basement flooding, and damage to foundations of buildings standing nearby. If there is a leaking drainage the water from the sewage drain washes out soil contaminated with sewage runoffs (including fecal) around the pipeline and can move it further into water- bearing. Outages of water supply effort vacuum in a pipeline that sucks soil close around and ground waters through leakings. And when water supply resumes they are carried by the flow along the pipeline.

Use of polyethylene pipes can significantly reduce failure rate and drinking water contamination hazard; moreover it simplifies installation and allows usage of trenchless technology. Trends of the recent years shows that utility companies of metropolitan cities in different countries pay more attention to the usage of advanced trenchless technology for recovery (curing) and laying of water and drainage pipes, which is defined as technology of laying, replacement, repair, and defect detection in underground utilities with a minimum breaking-up of the ground surface. Currently about 90% of replacement and renewal of underground utilities are carried out by trenchless technology.

One of the most interesting applications of polyethylene pipes is construction of sub water pipelines. Unlike with metal pipes, the entire set of installation works is carried out on -shore, which makes construction incomparably easier and cheaper. After finished pipeline made from polyethylene pipes fitted with ballast weights is ready it is gradually placed underwater.

Advantages of plastic pipes over steel ones:

 Low-cost;  time-proof, guaranteed lifetime - 50 years;  not require cathodic protection, and therefore needs almost no maintenance;  high corrosion and chemical resistance, can easily stand contact with aggressive media;  excludes possibility of calcification of inner surfaces;  low-thermal-conductivity, reducing heat loss and condensation on external surface of the pipe;  reduces possibility of pipeline destruction due to liquid freezing, at such conditions the pipe is not destroyed, it enlarges in diameter, and acquire former size when liquid is melted;  light weight for easy installation, especially in confined areas;  polyethylene pipes are 5-7 times lighter than steel, therefore:  first, shifting movement does not require installation of lifting devices;  secondly, one vehicle ships 5-7 times more plastic pipes than steel ones;  significant reduction of water hammer hazard due to relatively low modulus of elasticity;  reliability of welded connections throughout service life of pipelines;  butt welding of polyethylene pipes is much cost-saving, easier and less time-consuming;  allows multiple remounting at low cost;  low labor costs required for installation;  polyethylene pipes are much longer than metal ones;  polyethylene pipe - is a reliable shield against microorganisms and bacteria since its inner layer does not yield any harmful impurities in water;  Construction and upgrade of water and gas utilities using polyethylene pipes saves up to 40% of expenditures if compared with conventional methods.