Ovalizing ventinox – DuraVent Ovalizing Flexible Liners User Manual
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cAuTION
wear gloves and eye protection when
handling/cutting any liners.
essential, as it pulls the inner layer of steel 
against the corrugated layer of FasNSeal Flex, 
producing a clean cut across both layers.
3. Drill a 1/4" where the center of the 
Universal Take-off will be located in the liner.
4. Position the rubber guard of the Circle 
cutting guide into the 1/4" hole. See Figure 4
5. Turn on the Angle Grinder and begin 
cutting the liner in a clockwise direction. 
Keep the angle Grinder perpendicular to the 
liner at all times. You do not need to apply 
much pressure - let the drill bit do the cutting 
for you. See Figure 5a, 5b, and 5c
OVALIZING VENTINOX
Sizing a chimney system properly is an 
important decision the installer must make 
when bidding a job. It is often impossible 
to insert round liners into chimneys with 
rectangular shapes and still maintain the 
proper cross sectional area to vent the 
appliance and the required insulation 
thickness around the liner. Ventinox liners 
can be reshaped to feature oval or nearly 
rectangular cross sections. Ventinox 
distributors have the VOV612 Ovalizing 
Machine at their locations and can 
accomplish this task to your specifications. 
Before ordering "ovalized" liners, refer to 
Table A, and find the cross sectional areas 
created when round liners are reshaped. 
This is important for matching the venting 
requirements of an appliance.
Table A shows the cross sectional areas in 
square inches, when liners are ovalized from 
round to 4"-11" on the minor dimensions. 
Example: when a 9" VENTINOX liner is 
ovalized so that its minor dimension 
measures 6", the cross section area is reduced 
from 65 sq. in to 53 sq. in.
Table B shows the major dimensions when 
liners are ovalized from round to 4"-11" on 
the minor dimensions. Example: When a 9" 
wARNING
when the outside diameter of any thing
walled liner is reduced beyond a certain
point, it tends to develop "crinkles" on
the major Od. The same is true when
ovalizing FasNSeal Flex and duraFlex Sw,
it only looks different: the inner layer may
begin to "pucker". See Figure 1. while this
does not reduce the structural stability
of the liner, you should be aware of this
possibility.
cuTTING ANd OVALIZING
FASNSEAL FLEX ANd
duRAFLEX Sw
Due to its smooth inner layer not being 
mechanically fastened on the downward 
side, traditional cutting methods are not 
usually successful. By using an Angle Grinder, 
a clean cut can easily be achieved. 
INSTRucTIONS
1. Set up the 90o Angle Grinder with the 
masonry wheel. Make a cut across the 
liner's corrugations, first, then follow the 
corrugations all the way around the liner. See 
Figure 2a and 2b
While cutting, rotate the liner away from you 
and with the direction of the wheel's rotation. 
This method produces a nice, clean cut across 
both layers of FasNSeal Flex and DuraFlex SW 
greatly increases the lifetime of the Masonry 
wheel. 
2. Set up the Angle Grinder with an Up-Cut 
Mill bit and the Circle Cutting Guide. Set 
the guide for the desired hole diameter. See 
Figure 3a and 3b.
NOTE: The use of the Up-Cut Mill Bit is
