Data Sheet

Sliding-Stem Packing Selection
D101986X012
Product Bulletin
59.1:062
December 2012
4
Single PTFE V-Ring Packing
ThesinglePTFEV-ring arrangement uses a coil spring,
as in the easy-e valves, and meets the 100 ppmv
criteria, assuming that the pressure does not exceed
20.7 bar (300 psi) and the temperature is between
-18_Cand93_C(0_Fand200_F). This packing
arrangement offers very good seal performance with
the lowest packing friction.
ENVIRO-SEAL PTFE Packing
The ENVIRO-SEAL PTFE arrangement is suitable for
environmental applicationsonservicesupto51.7bar
and 232_C (750 psi and 450_ F). The sealing capability
is excellent. The ENVIRO-SEAL PTFE packing system is
designed to operate at high stress. This gives the
ENVIRO-SEAL PTFE packing system the ability to
compensate for stem or packing bore imperfections.
The high packing stress design approach also results in
an increase in stem friction. Typically, this slight
increase in stem friction does not cause problems,
such as hysteresis, for actuator sizing or process
control. It is good practice, however, to always verify
actuator sizing whenever you select a different packing
material. Carbon-filled PTFE or glass-filled PTFE adaptor
rings can be selected for process compatibility.
ENVIRO-SEAL Duplex
Packing
ENVIRO-SEAL Duplex packing systems were
developed, utilizing the benefits of both PTFE and
graphite components. These special packing systems
provide the capability of graphite packing along with
low friction advantages of PTFE packing. Thus,
ENVIRO-SEAL Duplex packing s ystems provide a low
friction, low emission, fire-tested solution for
applications with process temperatures below 232_C
(450_F). ENVIRO-SEAL Duplex packing systems were
successfully tested in accordance with API Standard
589, Fire Test Evaluation of Valve Stem Packing, first
edition.
KALREZ with Vespel
CR-6100 Packing
The KALREZ pressure/temperature limits referenced in
this bulletin are for Fisher valve applications only.
DuPont may claim higher limits.
KALREZ packing is available in KVSP-500 (260_C
[500_F] service). The KVSP-500seriesusesDuPont
material called Vespel CR-6100, which is a carbon
fiber-reinforced PTFE.
KALREZ is currently available for Fisher sliding-stem
valves with 9.5, 12.7, 19.1, 25.4, and 31.8 mm (3/8,
1/2, 3/4, 1-,and1-1/4 inch) diameter stems. The
system can be used with many sliding-stem valves, as
shown i n the KALREZ System--Sliding-Stem Valves
instruction manual, D102136X012. KALREZ packing
arrangements are also available for various Fisher
rotary valves (see Fisher bulletin 59.3:042, Packing
Selection Guidelines for Rotary Valves,
D102093X012).
Note that KALREZ packing arrangements require that a
controlled low stress be applied t o t he packing in order
to seal properly and also have a long life. This is
achieved by using the same spring pack as
ENVIRO-SEAL, but with a lower initial loading.
In contrast, the ENVIRO-SEAL PTFE packing system is
designed to operate at high stress (approximately 5
times the KALREZ stress). This gives the ENVIRO-SEAL
PTFE packing system the ability to tolerate
less-than-perfect conditions and continue to seal
reliably. For example, in changing installed valves to
ENVIRO-SEAL PTFE packing, minor imperfections in the
stem finish or packing bore can be tolerated because
of the high stress design of the packing system.