2015年12月6日星期日

Composite pipes widely used in water and sewage fields

Composite pipes widely used in water and sewage fields now days. As we all know that pipes are everywhere.
Countless miles of them, an essential but low-profile part of the infrastructure of human society. Multitudes of those pipes are associated with water and sewage, a sector that calls up large quantities of them each year.

Water and sewage pipes have variously been made from metals like lead (the word ‘plumbing’ is derived from the Latin word for this), iron and copper, plus concrete, clay, ceramic, plastic and even wood. Today, plastics are bearing a growing share of the load. Often these are unreinforced thermoplastics such as polyvinyl chloride (PVC), polypropylene (PP) and high density polyethylene (HDPE), but fibre reinforced plastics (FRP) play an important role where superior mechanical and corrosion resistance properties are required.

Reinforced plastic pipes have significant advantages. Mechanically, they are stronger and stiffer, for a given size and wall thickness, than unreinforced equivalents. They therefore need fewer supports and resist greater loads from surrounding soil,fiberglass chopped strand mat backfill, surface traffic etc. They can be pushed and drawn into position more forcefully during installation and may be buried deeper. They can be made strong enough to resist seismic loads, structural settlement and high internal surge pressures. A low coefficient of thermal expansion limits pipe movement in environments characterised by high temperature variations. FRP pipes are not damaged by frost.

In contrast to steel, a traditional pipe material, composite pipes do not corrode, taint water, suffer thermal stress or require cathodic protection; nor do they have to be surveyed periodically throughout life. Composites, appropriately formulated, can withstand even the highly acidic and sulphurous sewage environment. Smooth interior pipe surfaces present minimal impedance to flow and burst strength is generally sufficient to enable pipes to withstand pressure from clearing jets when blockages do occur. Jet pressures required to clear smooth-bore composite pipes are less than those needed for concrete and metal pipes.

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