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Emissions
There is certainly a great deal of interest in limiting
emissions of the numerous chemicals and other sub-
stances regulated under the Clean Air Act. Garlock has
performed testing in this area and our report, available on
request, covers the effects of gasket type, compressive
load, internal pressure and flange finish on relative emis-
sions levels. The use of heavier flanges where possible
and the selection of premium gasket materials with good
sealability numbers are the easiest ways to reduce emis-
sions.
FDA
Style 3500 (Fawn) and Style 3510 (Off-White) comply
with FDA regulation 21CFR177.1550. They meet ingredi-
ent and extract requirements. The fillers are also accept-
able under 21CFR177.2600 and coloring agents (where
used) under 21CFR178.3297. The branding ink complies
with 21CFR175.300. Style 3500 (Fawn) has USDA ap-
proval for direct contact in meat and poultry applications.
Style 3504 (Blue), Style 3565 (ENVELON® ), Style
3591 (Gold), and Style 3594 (Green) comply with FDA
regulation 21CFR177.1550. They meet the ingredient
and extract requirements. The filler is listed in the Food
Chemicals Codex (FCC 3rd Edition) and is considered
GRAS (generally recognized as safe – 21CFR170.30).
The branding ink complies with 21CFR175.300.
Style 3522 (Clear) complies with FDA regulation
21CFR177.1550.
The ingredients for Style 3540 (Microcellular)
and Style 3545 (Microcellular with Rigid Core) comply
with FDA regulations 21CFR177.1550, 21CFR182.1,
21CFR182.1217, and 21CFR175.300. The branding ink
complies with 21CFR175.300.
The PTFE resins used in Style 3535 PTFE joint
sealant comply with FDA regulation 21CFR177.1550. The
PSA tape used to hold the joint sealant material in place
meets 21CFR175.105.
Fire Tests
Garlock has developed a Fire Test Standard modeled
after industry fire tests API 589 and 607. Styles G-9900,
9800, 9850, ST-706, IFG® 5500 and GRAPH-LOCK®
styles have all passed this fire test. Test procedures and
results are available upon request.
Flanges
Flanges come in all shapes and sizes, and the type of
flange used in a service has a large impact on the type of
gasketing material recommended. Standard ANSI raised
face flanges are best suited for use with compressed fiber
and GYLON ® gaskets. Elastomer (rubber) gaskets may be
crushed in these flanges.
Flat faced non-metallic flanges seal best with elas-
tomeric (rubber) gaskets, such as the various STRESS
SAVER ® gasket styles. GYLON® Style 3545 may also
be suitable for some applications. Compressed fiber and
standard GYLON ® are frequently used in flat-faced carbon
steel flanges, but the compressive stress available in
these flanges is well below our minimums. The result is
that the gaskets are compressed very little; if there is a
significant flange irregularity present, the gasket may not
seal. Since leakage rates of gaskets depend on the avail-
able compressive stress, the joint may not be as tight as
the customer would like.
Glass-lined flanges are found in many chemical
applications. Due to the inherent "waviness" created
when these flanges are fired to apply the glass, the softer
GYLON® styles such as Styles 3545, 3565, and 3504 are
preferred. The gap between the flanges, when placed
together empty, must be measured before the gasket is
ordered. Gasket thickness should be four to five times the
maximum gap observed.
Stainless steel (SS) flanges are common in many
plants for chemical service, and often utilize low strength
SS bolts. Due to the chemicals present and the low com-
pressive stress generated by the bolts, Styles 3545, 3565,
and 3504 are often recommended. We do prefer, however,
the use of high strength, strain-hardened stainless steel
bolts.
Flange Finish
We recommend the flange finish conform, whenever
possible, to 30-55 serrations per inch, in a concentric or
spiral pattern, cut with a 1/16" radius, round-nosed tool.
This finish is usually difficult or impossible to create in
non-circular flanges. We recommend that machined sur-
faces which can not be serrated have a surface finish with
a multi-directional lay and roughness of 125-250 micro-
inch RMS.
Fuel Additives
The chemical MTBE (methyl t-butyl ether) has be-
come a very common fuel additive and gasketing com-
patibility inquiries on this material are frequent. Garlock
in-house testing has shown GYLON ® gasketing to be
unaffected by MTBE. We have also found compressed
sheet Styles 9850 and 3000 to be suitable for MTBE ser-
vice. These materials are recommended for MTBE alone
or mixed with gasoline.
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