Page 52 - New Supercatalog Color.indd

C-51
Full Face Gaskets
See Flanges.
Gasket Constants
The ASME and ASTM committees are working on a
new system and new set of numbers to be used in the
ASME code calculations for flange design. These new
constants address leak rates at installation and during loss
of compressive load and therefore are meant to help end
users design for a certain leak level. The use of a defined
leak rate will generally generate much higher bolt load
requirements for the flanges, which should improve perfor-
mance of designed joints. For gasket constant values,
see page C-40. Also see M & Y Values and Emissions.
Gasket Grooves
Gaskets installed in grooves or tongue and groove
flanges require one extra consideration: the compressed
height of the gasket must fill the groove. This is typically
important where a highly compressible gasket such as
GYLON® Styles 3545 and 3540 or one of the GRAPH-
LOCK® styles is used to replace a compressed sheet
gasket. The fully compressed thickness, not the original
thickness, must be greater than the groove depth or the
space between the tongue and groove when flanges con-
tact each other. Ideally, the tongue should be at least as
tall as the groove depth.
Gasohol
Gasohol is a blend of gasoline with an alcohol— usu-
ally 15% ethyl alcohol. GYLON® styles are preferred;
nitrile-bound compressed sheet styles should be accept-
able; most rubber gaskets are not recommended.
Installation
Garlock strongly recommends the use of calibrated
torque wrenches to tighten bolts to the correct load. We
have an installation procedure and discussion available
upon request. A video covering the same material is also
available.
Insulation Kits
Customers will occasionally ask for a flange insulation
or isolation kit or gasket to electrically insulate one flange
from the mating flange. Kits are available from a variety of
distributors and include an insulating gasket along with a
sleeve for the bolts and insulating washer to be installed
under the steel washers and nuts.
Garlock does not currently sell kits, but we do offer
many gasket styles with good electrical insulating proper-
ties (see Dielectric Breakdown Voltage).
Jet Fuels
Jet fuels are typically refined petroleum products
similar to kerosene. We recommend our GYLON®, nitrile
bound compressed sheet and GRAPH-LOCK® products.
(See Aviation Gasoline)
Leachable Levels (chemical)
Some pipe specifications call out maximum levels of
"leachables" for gaskets. These limits are usually con-
cerned with leachable chlorides, fluorides, halogens and
sulfur. These ions, or charged particles, are of concern
due to their tendency to promote corrosion of piping
systems. Garlock keeps test results for numerous gasket
styles on file and we will test and certify leachable chlo-
rides, etc., where required. There is a charge for these
tests. Due to the nature of this type of analysis, we publish
"typical" leachables only on certain styles such as our
nuclear grade Style 9920.
"M" and "Y" Values for Flange Design
See page C-40.
Note: Our testing shows an increase in "M" and "Y"
values as gasket thickness increases. This is the opposite
of the trend found in the ASME Code. Fugitive emission
and gasket blowout studies have validated this trend.
Modulus of Elasticity
Some flange programs ask for the modulus of elastic-
ity for the gasket material. This could be erroneous, since
only rubber gaskets are elastic. Other types of gasketing
do not have a true modulus. Garlock Appli-cations Engi-
neering does have compression vs. Ioad curves which can
be inverted to calculate a rough esti-mate for use in these
calculations (see Compression).
Monomers
Monomers are materials, such as styrene and vinyl
chloride, which can combine with themselves and become
polymers, such as polystyrene and polyvinyl chloride. GY-
LON ® Styles 3510 and 3530 are recommended for mono-
mers, since elastomer-bound gaskets are rarely compat-
ible with monomers. Some monomers, under certain
conditions, will penetrate a gasket and polymerize inside
the gasket, causing the gasket to swell and, occasionally,
rupture. This effect is known as "popcorning". This effect
can be reduced or eliminated with additional compressive
load which lowers the void space inherent in a gasket.