Data Sheet

Sliding-Stem Packing Selection
D101986X012
Product Bulletin
59.1:062
December 2012
6
ENVIRO-SEAL Graphite ULF
ENVIRO-SEAL graphite ULF packing is designed
primarily for environmental applications at elevated
temperatures in excess of 232_C(450_F). It has a full
temperature rating of -7_Cto316_C(20_Fto600_F)
and still maintains the 100 ppmv leakage criteria. For
best performance the service temperature should be a
least 149_C(300_F). At temperatures below 149_C
(300_F), packing wear may be accelerated compared
to higher temperatures.
Compared to PTFE packing systems, graphite packing
systems operate at higher stress levels and have higher
friction values for a given level of sealing. To combat
this, most graphite systems incorporate a small
amount of PTFE which acts primarily as a lubricant.
The ULF packing system, however, incorporates very
thinPTFElayersinsidethepackingringsaswellasthin
PTFE washers placed on each side of the packing rings.
This strategic placement of PTFE material minimizes
control problems (such as slip-stick action), reduces
friction, promotes sealing, and extends the cycle life of
the packing set. (With slip-stick action, packing friction
prevents the valve stem from moving until stem force
increases enough to make the stem move suddenly.)
While the PTFE components of the ULF packing set are
critical to the overall performance of the packing set,
they make up a very small volumetric percentage of
the ULF packing set and therefore do not require
additional follower travel. The ULF packing system has
remarkably low stem friction at elevated
temperatures, compared to other graphite packing
systems. ENVIRO-SEAL Graphite ULF packing systems
were successfully tested in accordance with API
Standard 589, Fire Test Evaluation of Valve Stem
Packing, second edition.
HIGH-SEAL Graphite ULF
The HIGH-SEAL graphite ULF packing system is
identical to the ENVIRO-SEAL graphite ULF packing
system below the packing follower. The primary
advantage of the HIGH-SEAL packing system i s the use
of large diameter Belleville springs. These heavy duty
springs offer additional follower travel and can be
calibrated with a load scale. The load scale provides a
visual indication of packingloadaswellaspacking
wear, making it easier for you to determine when
additional torquing might be required.
For ENVIRO-SEAL or HIGH-SEAL graphite ULF packing,
the service life is very long, compared to other
graphite packing arrangements. Both offer excellent
seal performance. The ULF packing system has
remarkably low stem friction at elevated
temperatures, compared to other graphite packing
systems.
Nonenvironmental
Services
For the nonenvironmental pressure/temperature
guidelines, service life can be extended by using
ENVIRO-SEAL and HIGH-SEAL packing systems. As
service pressures and temperatures increase, the
ENVIRO-SEAL packing systems provide a significant
step change in performance, compared to the
traditional single PTFE V-ring or braided graphite
filament arrangements. For example, a CL1500 (HP
valve) application at 137 bar and 93_C (2000 psi and
200_F) frequently required packing maintenance. The
HIGH-SEAL packing system with PTFE washers was
installed, significantly reducing maintenance
requirements. This system is rated to 290 bar and
371_C (4200 psi and 700_F). The ENVIRO-SEAL
packing system or compact Belleville spring
arrangement is rated to 207 bar and 371_C (3000 psi
and 700_F).
HIGH-SEAL packing systems have a disadvantage, from
an installation perspective. The disadvantage is that
the actuator cannot be removed from the valve
without removing the Belleville springs. You must
release process pressure from the valve before
removing the Belleville springs.
Table 1 shows that the braided graphite filament
arrangement is limited to 103 bar (1500 psi). Due to its
construction, braided graphite filament cannot sustain
high packing stress levels. Over time, the braided
graphite filament will break down and compress, and
sealing force will be lost. Due to these characteristics,
braided graphite filament will not provide the required
seal performance for environmental services. The
braided graphite filament arrangement is also
susceptible to stick-slip action, which might cause
process control deviations.