Cutter Sizes for Taps
For line-size branch outlets, the proper
cutter diameter for HDPE taps is accepted to be as large as 75%
to 90% of the inside diameter of the pipe main. Note: The cutter
must fit through the branch. It is acceptable to use a hole-cutter
whose metal OD is up to at least 75% of the ID of the HDPE main
pipe, but no larger than 90% of the HDPE main ID. Obviously, the
cutter can be smaller for smaller branch-outlets.
Some users want the "maximum"
diameter opening, thinking that it will maximize the water volume
throughput and minimize the pressure loss through the fitting. A
detailed examination of the numbers reveals the following:
Using a portal outlet cutter hole diameter
that is nominally 87% of the ID of the pipe main, a detailed examination
of the pressure loss through the "orifice" of the cut
hole was done. The pressure loss was equal to about 3 diameters
of extra pipe length.
The
pressure loss was less than 0.010 psi ... 1/100th of one psi.
A full
copy of the detailed report is available upon request.
Using the cutter size range of up to
75% to 90% of the HDPE main pipe ID, the user can choose
a cutter diameter that fits thru the branch to provide good flow
at minimum pressure loss and avoid tapping problems.
Note: When using line-size metal
tapping sleeves, the cutter OD should be smaller, usually about
75% of the pipe main inside diameter to avoid cutting through the
spring line of the HDPE pipe main and not allowing the removal of
the HDPE pipe coupon. The cutter OD should not be as large as the
ID of the HDPE pipe main so that when the coupon is removed, it
will retract freely within the cutter.
In all cases, the cutter OD must
be slightly smaller in diameter than the HDPE pipe- main ID!!
Many
other self tapping tees are available including larger outlets,
other radius and "high volume self tapping tees".
Contact
us today by email or our toll
free number:
sales@oxfordplasticsinc.com
1.800.263.0502
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