The Science of Heat Fusion Welding
The fundamental of heat fusion welding is to heat two hdpe
pipe surfaces to an appropriate temperature, changing the resin's
molecular structure to an amorphous (pliable state, and then fuse
them together by application of prescribed force until cooling occurs,
returning the material to a crystalline state and creating one homogeneous
pipe.
When fusion pressure is applied at the designated temperature and
prescribed force, the molecules from each pipe surface end mix.
As the joint cools, the molecules return to their crystalline form,
the original interfaces have been removed, and the two pipes have
become one continuous length. The end result is a fusion joint that
is as strong or stronger than the pipe itself, and this creates
the leak-free joint that is one of the amazing strengths of HDPE
pipe.
The Method of HDPE Fusion Welding
Generally speaking, HDPE pipe is Butt fused together using a "fusion
welder". Welding machines vary depending on the Outside Diameter
(OD) of the pipe to be welded. The pipe pieces are held axially
by a clamping device to allow subsequent operations to take place.
Large diameter pipes may require hoisting assistance such as an
excavator or crane. Once the pipe is clamped, the pipe ends are
"faced" with a machining tool to establish clean, parallel mating
surfaces, perpendicular to the centerline of each pipe. A heating
element or heating plate is inserted in between the faced ends,
and the pipe is drawn together against the heating plate. A melt
pattern that penetrates into the pipe ends is formed around both
pipe ends. Once the correct melt temperature is reached, the heating
plate is quickly removed, and the melt ends are drawn together with
a specified force. The specified force on the joint must be continuous,
and held until the joint cools. A small melt bead forms at the joint.
At completion, the fused pipe is removed from the welding machine.
 Availability
of Fusion Welding Equipment.
There are several makes of fusion welding equipment on the market.
Proper fusion equipment must be used to make good
fusion welds. Equipment can be purchased, or rented from various
suppliers. Also, companies which specialize in fusion welding can
be contracted to do the work. Training courses, seminars and operator
certification are available for Contractors who choose to do fusion
welding with their own staff. Training is strongly recommended to
ensure safety and quality. Doing the job right the first time is
the most efficient, safest and quickest way to profitability.
Contact us today by email or our toll free number:
sales@oxfordplasticsinc.com
1.800.263.0502
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