Ningbo Fangli Technology Co., Ltd. is a
mechanical equipment manufacturer with nearly 30 years’ experiences of plastic
pipe extrusion equipment, new environmental protection and new materials
equipment. Since its establishment Fangli has been developed based on user’s
demands. Through continuous improvement, independent R&D on the core
technology and digestion & absorption of advanced technology and other means,
we have developed PVC pipe extrusion line, PP-R pipe extrusion line, PE water
supply / gas pipe extrusion line, which was recommended by the Chinese Ministry
of Construction to replace imported products. We have gained the title of
“First-class Brand in Zhejiang Province”.
Polyethylene (PE) pipe was first
commercially made in the 1940s, after World War II. Today, it is the second
most widely used plastic pipe material, after polyvinyl chloride (PVC). These
two materials account for over 90 percent of all currently produced plastic
PE is a non-conductor and therefore not
susceptible to galvanic or electrochemical corrosion —the mechanism that limits
the durability of buried metallic pipes. It is also unaffected by most acids,
alkalis, and corrosive salts.
Its excellent toughness and flexibility
distinguish PE. It is very resistant to damage by impact, even at lower
temperatures. It is a ductile material that does not shatter even if punctured
or cut regardless of service temperature. It withstands the effects of cyclic or
repeated stressing (such as by water pressure surging). Its greater flexibility
permits the coiling of smaller diameter pipes, which reduces fitting
requirements and facilitates installation. PE pipe’s toughness allows it to resist
failure under the expansive action of freezing water.
To protect PE pipe during extended outdoor
storage against the effects of the sun’s ultraviolet (UV) radiation — which
over time can damage most plastics – PE pipe compositions include additives
that either physically screen or chemically absorb UV rays. The commonly used
UV screen is finely divided carbon black, hence the black color of many PE
pipes. Black PE pipe has excellent weathering resistance. Pipe made to other
colors relies on stabilizers to absorb UV rays.
Of course, once installed underground or
away from sunlight, UV protection is no longer needed.
While PE pipe has sufficient strength,
toughness, and chemical resistance for water service pressure piping in common
with other plastics, it has certain limitations on its performance just as any
other engineering material. These limitations include the following, which must
be recognized and addressed to ensure a proper and durable installation:
• Mechanical properties are temperature sensitive. As temperature
increases, PE becomes less strong and less stiff. For continuous use where the
pipe temperature exceeds 80°F, the pipe pressure rating should be appropriately reduced.
• The coefficient of thermal expansion/contraction is higher than
metal. For the same change in temperature, unconstrained PE pipe expands about
8 times as much as metallic pipe. Installation must prevent the development of
excessive pipe contraction forces which, while normally not damaging to the
pipe, can produce higher than desirable pull-out and bending loadings at the
point the pipe connects with a rigidly held fitting.
• Shear strength is relatively low. Installation must avoid the
development of high shear stressing, which can occur in a flexible pipe subject
to overburden from above while connected to a fixed, immovable structure, such
as a service tap on a water main.
• Kinking can compromise mechanical properties. Pipe should not be
bent so tightly that it kinks either during handling or while in service.
• Mechanical properties can also be compromised by gouging, cutting,
and excessive abrasion. PE pipe should be handled and installed to prevent the
possibility of excessive damage.
• Certain solvents can permeate the pipe wall. Plastic water service pipe,
like most piping materials in general, should not be installed in soils which
are contaminated, or can be subject to contamination, by organic solvents.
Chlorine used as a disinfectant must not exceed
the requirements of ANSI/AWWA C 651, Standard for Disinfecting Water Mains. For
potable water systems using chlorine as a disinfectant, the recommendation
limits chlorine dosage to 25mg/l free chlorine with a residual of 10 mg/l at
the end of a 24-hour stand. Daily amounts of chlorine should not exceed 3 ppm
at temperatures in excess of 75°F.
Additional Information. PE piping is widely
used for many other applications, including municipal water distribution
systems; drop piping for submersible pumps; ground coupled heating/cooling
systems; gas distribution; oil and gas production; gathering gas generated by land-fills;
conveying corrosive fluids; conveying slurries, sewerage, and drainage; and